University of Nigeria Research Publications

SAMUEL, Baba Onoja

Aut

hor

PG/M Eng/89/5409

Title

University of Nigeria Nsukka (UNN)

Wastewater as Irrigation Water Source: Its Suitability and its Effects on Soil and Crop

Facu

lty

Agriculture

Dep

artm

ent

Agricultural Engineering

Dat

e

November, 1989

Sign

atur

e

Sa-nuel 3359 Onoja , a P o s t g r a a u a c e scuaeac i n s n e

Depar txen t of A g r i c u l t u r a l Z n g i n ~ e r i n g an? with

the Reg. 210 PG/:d.3ng/37/5409 has sa t i s f a z t o r i l y

c o n p l e t e 4 the r e q u i r e z e n t s f o r the coursa and

r e s e a r c h work f o r t h e degree o f Xastar of

and has n o t Seen su5nittzd in c z r t o r fall f2r m y

o t h e r di?lorna o r d a g r s e o f t h i s o r any otisr

Supervisor Superv I ' s o r

E x t e r n a l Exan ine r

D Z D I C A T I O N

The o n l y x i s ? God;

tat he^, Son and 3oly S p i r i t . r

Ynom to Zear i s x i sdoa

indeed.

iii.

I acknowledge t h e i n c e n s e c o n t r i b u t i o n of m y s u p e r v i s o r s :

Zngr (Dr ) 7.1. I d i k e and D r . G.O. Ch-dwuca f o r a p p r o g r i a t e

a d v i c e , encouragement and s u g ? o r t th rov~ghout t h e c o u r s e o f

t h i s work. I acknowledge t h e i n t e r - d e p a r t m e n t a l c ~ m n ~ i c a t i o n

acd a l s o t k a d i f f e r e n t c o n t r i h l t l o n s f r z a a n u b a r of t h e

acadein ic , t e c h n i c a l and a d o i n i s t r a t i v e s t a f i o f t h e Dep2r tnan t .

The i n t ? r - d i s c i p l i n a r y ~ s t u r 9 of t3is study made it

' c a n n o t be a a n t i o n e d h s r e . I ackro:tledga the a p g r e v a l g r a n t e d - -

n e by t h e Heads o f D e ? a r t n e n t s o f C i v i l S n g i n o e r i n g , S o i l

S c i e n c e and Crop S c i e n c e f o r t h e use of their l a b o r a t o r i e s .

I a m g r a t e f u l t o D r s B.N. Mbah, B.B. Fakae , 0. Onof iok and

C.P.E. Ornaliko f o r t h e i r i n d i v i d u a l c o n t r i b u t i o n s . I

acknowledge t h e c o - o p e r a t i o n and a s s i s t a n c e o f Mr. Ongeokoro

a n d h i s t e a n of staff a t the U n i v e r s i t y of N i g e r i a , Nsukka

Sewage T r e a t m e n t works; the l a b o r a t o r y and f i e l d a s s i s t a n c e o f

Messrs N. 'dogu, E. Udea la , S.E. Ani, C.J. O n y i r i o h a , U. Umeh,

C.E.O. ~ e b o ; E.O. E l e r i , M.O. Agbahiwe and A. Ezernah and t h e . .

good t y p i n g work done by Mrs Nkechi Okpala.

iv.

I am e q u a l l y i n d e b t e d t o a number of r e l a t i o n s , f r i e n d s

and c h r i s t i a n b r e t h r e n f o r mora l , f i n a n c i a l and p r a y e r

s u p p o r t . I a l s o acknov ledgs t h e f i n a n c i a l a s s i s t a n c e from

s p s c i f i c i n d i v i d u a l s l o r t h e p u r p o s e of t h e e n t i r e programs.

l i n a l l ~ , I a c ! m o v l a d ~ a and a p p r e c i a t e t h e f u l l s u g s o r t

of 3y w i f e Xr3 2ode 3ab3 Ooojs and t h e p a t i e n c e of t h e f a z i l y

f o r t h e p e r i o d c f t h i s X a s t e r I s d?grae progranme.

T h a n k s and m y God reward yo11 a l l , .Anzn.

U n i v e r s i t y o f N i g e r i a , Nsukka (UN, Nsukka Campus) w a s t e w a t e r

t r e a t m e n t works as i r r i g a t i o n w a t e r s o u r c e . F i e l d and

\

l a b o r a t o r y e x a m i n a t i o n s were c a r r i e d o u t t o e v a l u a t e t h e

w a s t e w a t e r c h a r a c t e r i s t i c s , t h e p h y s i c a l and c h e m i c a l p r o p e r -

t i e s of t h e s o i l a n d t h e m i n e r a l c o m p o s i t i o n o f wal3tcwater

i r r i g a t e d a m a r a n t h u s SPP.

The r e s u l t s o f t h e s t u d y show t h a t w h i l e w a s t e w a t e r f rom

pond 2 o f t h e t r e a t m e n t works is s u i t a b l e for i r r i g a t i o n , t he

i n f l u c n t and the w a s t e w a t e r i n pond I n r e t o o p o l l u t c d t o s e r v e

as i r r i g a t i o n w a t e r s o u r c e . Wastewater i r r i g a t i o n i n t h e s t u d y

s i t e improved t h e w a t e r h o l d i n g c a p a c i t y of t h e s o i l a n d

i n c r e a s e d i t s c h e m i c a l p r o p e r t i e s i n t h e o r d e r of o v e r 200% f o r

E-Ce 'and 1 3 ~ ; o v e r 100Y f o r N , P a n d Ca, 92% f o r CEC, 45% f a r K

and 675 f a r Na; b u t d e c r e a s e d t h e s a i l pH, SAR and ESP by 5%,

17.5; a n d ~87.? r c s p e c t i v e l y . Wastewntcr a p p l i e d an i r r i g a t i o n

w a t e r was a l s o found t o c o n t r i b u t e e s s e n t i n l m i n e r a l s n o t o n l y

t o t h e s o i l b u t a l s o to t h e c rop . C o n s e q u e n t l y t h e p r a c t i c e ,of

w a s t e v g t c r i r r i g a t i o n is recommended as a s o i l improvement

p r a c t i c e .

Rased on t h e r e s u l t s o f t h e s t u d y , recommendat ions f o r

f u r t h e r s t u d i e s and f o r t h e management a n d u s e o f w a s t e w a t e r as

i r r i g a t i o n w a t e r i n t h e g e n e r a l l o c a l i t y o f t h e s t u d y s i t e a r e

p r e s e n t e d ,

Content P a g e

CHAPT3R 111: ?!ATERIALS AND METHODS - w e o

I : The Zxper imenta l Area .a. . e O - . o

2 2 v s l u a t i o n of w a s t e x a t e r c k a r a c t e r i s t i c s . . 3.2: Sam?ling positions and f requency ... ... 3.2.2: L z j o r a t o r y T a s t s ... .-. -.. 3 . 3 Z v a l u a t i n g the E f f e c t o f v a s t e w a t e r

I r r i g a t i o n o n s a i l progert i e s . S O ... 3.4: 3raLsating t h e E f f e c t o f w a s t e x a t e r

Irrigation on t h e I r r i g a t e d vege tab le (Xx3ranthus SP?. ) ... ... ..,

3.4.1 : San?linq ... ... . . - ... t ,.-r.2: n. bile " i c e r a l Inal;7sis cf v e s e t s j l s s a 3 ? l e s ,

Vas5exa te r c h a r a c t e r i s t i c s .-a ... 61 S o i l g r o g e r t i e s ... ... . . . 6 9

The p h y s i c a l p r o p e r t i e s o f t h e s o i l .ma 69 ... C t e z t c s l - - ~ r o z e r t i e s of t h e s a i l ... '7 3 T?--5 ninersl coa?osition of leaves of ... Xca~c..Stus S?? . I . 6.e .-- 73

'3 : DISSCSS I C Y ... ... . . . 77 -.-

5.1: m & u a l i t y o f t h e University o f ' l lgeria, P7sukka (UE?;) !Jaaterater for I r r i g a t i o n ... 7 7 &'ze e f f ~ c t s 5.2: o f wastewater I r r i g a t i o n 02 s o i l p r o p e r t i e s .-. ... ... 33

5.2.1: E f f e c t s on t h e P h y s i c a l p r o p e r t i s s o f t h e s o i l .-• o . . ..- - 0 - 83

5.2.2: E f f e c t s o n t h e chemical p r o p e r t i e s of t h e s o i l . a m . - . a = . ... 85

- 5.3: E f f e c t of wastewater on some of the mineral constituents of Amaranthus SPP. v e g e t a b l e l e a v e s ... ... ... 88

.CHAPTYR V I : CONCLUSION AND RECOMMENDATIONS ... 91

S e f e r e n c e s ... ..a .-• ..- 97

v i i i .

LIST OF TABLES

Table

Recommended maximum c o n c e n t r a t i o n s o f t r a c e ... e l e m e n t s i n i r r i g a t i o n water ... . o m

C o n d i t i o n s f o r s a l i n e , s a l i n e - a l k a l i and ... a l k a l i s o i l s ... ... ... ... Limi ' ts o f boron i n i r r i g a t i o n w n t o r For s e n s i t i v e , s e m i - t a l c r a n t a n d t o l e r a n t s p e c i e s based on t o x i c i t y symptoms o b s e r v e d on p l a n t s grown i n s a n d c u l t u r e .,, . . 0 . . ..*

Physical, Chemical and B i o l o g i c a l c h a r a c t e r i s t i c s of vrastevrat e r ..* .-• ... ...

\

T y p i c a l s a n i t a r y c h e m i c i l ? a n a l y s i s o f sewage ... ( Q u a l i t y o f domes t i c w a s t e ) . . . . . C a l i f o r n i a S t a t e Department o f R e n l t h s t a n d a r d s f o r t h e s a fe and d i r e c t u s e o f r e c l a i m e d waste- water f a r i r r i g a t i o n and r e c r e a t i o n a l ... impoundments -., ... . . . ... VIIO s u ~ g e s t e d t r e a t m e n t p r o c e s s e s t o meet t h e givcn h e a l t h c r i t e r i a f o r was tewate r r e u s e

l-lcthods for the examina t ion of was tewate r samples ... . . . - 1 0 ... Sampling s c h e d u l e o f t h e w a s t e w a t e r f a r examinat i o n ... ... ... . . . Site s e l e c t i o n f o r s o i l a n a l y s i s ... 1~Icthod.s used f o r t h e d c t c r m i n a t i o n o f s o i l p r o p e r t i c s . . ... ... . rn Methbds used f o r t h e chemical a n a l y s i s o f hnrnrnnthus SPP, leaves a * e m e ,

P a g e

12

t a l s o l i d s of een Cecenber 1988 * 0 . . . . ..a

P-- ~ - - , - , - ~ s l 5-: ,- propertils of soil f r o 3 e i g h t l o c a t i o n s i r r i z a t e d w i t h wastewater compared w i t h IX soil smp133 f r c n an a 2 j a c e n t a r e a ... . .. Xean a ~ d s t a c d a r d d e v i a t i o s of s o i l c h e n i c a l p r o p e r t i s s a s influezced 37 sewage t r e a t a e n t .., X i n e r a l c o n t e n t s o f l e a v e s of amaranthus SP? grown on soils i r r i g a t e d with t h e wastewater and with ordinary water . .. . m e ... o m -

Ths e f f e c t of treatment was teua te r l o c a t i o n and tap water on t h e chenica l composit ion of =aranthus l eaves , DXTIRT . .* @ . 0 . .

B l e ~ e n t s with statistical differences between t a p wate r and t h e d i f f e r e n t l o c a t i o n s o f wastewater ... a * - -.. 0 . . .-. ~ o a c e n t r a t i o n s of t h e e s s e n t i a l macro- a u t r i e n t a o f t h e wastewater i r r i g a t e d and n o n - i r r i g a t s d a r e a s . . . ... . . . ...

X.

LIST OF FIGUXS

1. .Concent ra t io .? o f i r r i p t i o n w a t e r s r e l a t e d t o c o n d u c t i v i t y ... . -. ...

2 . U53X c l a s s e s of S a l i n i t y and Sodiun h a z a r d f o r I r r i g a t i o n water . . . ...

3. S c h ? n s t i c d i a g r a n o f s ampl ing ? o i n t s o r l o c a t i o n s f a r w a s t e w a t e r , s o i l aad c r 0 ? ... ... . . . ... ...

4. P r e p a r e d c o ~ r u g a t i o r i s resdy f o r a n a r m t b n s s e e d l i n g ... . . . . . ...

Sa & b Viexs o f s i t e d u r i n g t h e psak p e r i o d of amaran ths3 c u i t i v a t i o n ... . . . . ..

6a & ?I Vieus of s i t e a t t h e o n z e t o f r a i n y s e a s a c c r a g ~ i z g . . . ... ...

7. :locoi;raa f o r d e t e r n i n i x g t h e SX?, v a l u e of I r r i p t i o n v a t e r and f o r e s t i m a t i n g t h e c o r r e s p o n d i z g ZSP v a l u e o f a s o i l e q u i l i b r a t e d w i t 3 t h i s w a t e r . . . ... . . . 54

8. Aaarai i thca 522 grown i n t h e study a r e a and i r r i g a t e d w i t h o n l y p o t a b l e ta? w a t e r . .. 59

-. x i .

SPP

5 d a y b i o c h e n i c a l oxygen denand

Calc i urn

C a t i o a exchange c a ~ a c i t y

Duncan 3ew N u l t i p l e Ban35 Test

E l 2 c t r i c a l C o n d x c t i 7 l t y

3xc3aagsaSle sodium p e r c e n t age

P i e l d c a p s c i t y

P o t a s s i m

X a p e s s i u a

Xi t r o g l n

Sodium

Phosshorus

S o d i u Adsorp t ion ratio

S p e c i e s

p r o d u c t i o n i; s u p p l i e d a r t i f i c i a l l y . It i s scg?lexeatal

ar- $0 3e 7roduced t o z k e t . m n ' s n e e d f o r f o o d a n d f i b r e .

persons 324 5" ecro? prodxczd as i f e l l as

' L using it 1s irrigation

f u n c t j o n o f climatic f a c t o r s ; quantity o f v 8 t e r uzed Sy t h e

c o n s i d s r z i l l y redaced. The e f f l u e z t f r o a t h e s t a b i l i z a t i o n

?or .h 1; s - ~ ~ - z s s e d A - t o Se s a f e f o r d i s 2 3 s s l acd t h e f i c a l

long t h b e f f l u e n t c o u r s e d u r i n q t h e d r y s e a s o n (::oveab.2r - Februarg/>!nrch) . No d i s c r i m i n a t i o n is made a s t o xhnt saints

o f t h e p o n d s s h o u l d be u s e d as i r r i g a t i o n w a t e r . The m a j o r

c r o p i r r i g a t e d d u r i n g t h i s s e a s o n i s t h e v e g e t a b l e ,

a m a r a n t h u s s p e c i e s .

T h i s s t u d y i s aimed a t a s s e s s i n g t h e c u r r e n t u s e o f t h e

U n i v e r s i t y o f N i g e r i a , Nsukka (U.N.N.) w a s t e v a t e r a s i r r i g a t i o n

w a t e r s o u r c e a n d g e n e r a t i n g p e r t i n e n t i n f o r m a t i o n o n ,waste-

w a t e r i r r i g a t i o n i n Nsukka a n d i n a r e a s w i t h s i m i l a r c o n d i t i o n s

and f a c i l i t i e s . The s p e c i f i c o b j e c t i v e s o f t h e s t u d y i n c l u d e

(i) To i n v e s t i g a t e t h e s u i t a b i l i t y o f t h e

U n i v e r s i t y o f N i g ; r i a , Nsukka w a s t e w a t e r

as i r r i g a t i o n w a t e r ,

( i i ) To d e t e r m i n e t h e e f f e c t s o f p r o l o n g e d

w a s t e w a t e r i r r i g a t i o n on t h e p h y s i c a l and

c h e m i c a l p r o p e r t i e s o f t h e s o i l , and

( i i i ) To d e t e r m i n e t h e e f f e c t s o f w a s t e w a t e r

' i r r i g a t i o n o n t h e n i n e r a l c o m p o s i t i o n o f

i r r i g a t e d a m a r a n t h u s spp . v e g e t a b l e .

p r o d u c t i o n .

2. 2 C ','.2?7E!

2.2.1 S o u r c e s a n d q u a l i t y .

The comnonly a v a i l a b l e s o u r c e s o f water f a r irrigation

l i ! n i t o l , i n c ~ e a s e d u s e is b e i n 3 zade of in! a r i o r quality i r r i g a t i o n

for C It io only t h r o u g h ? r o p e r nacnge "11t b a s e d on i k c

-;..:: . 7 . . . bnductivity (rnicromhos per cm., E.C. X 106, at 25' C)

rig 1: C c s c e c t r a t i o n of i r r i g a t i o n w a t e r s r e l a t e d t o c o n d u c t i v i t y .

. S o u r c e : - I s r a e l s e n a n d 3 a n s e n ( 1 9 6 2 ) .

EC X 10' = Conductivity micrornhos/cm at 25°C

C-1 C-2 C-3 C-4

Low Medium High Very high u I I I I

Salinity hazard

F i g 2 : USDA c l a s s e s o f s a l i n i t y a n d s o d i l n h a z a r d f o r i r r i g a t i o n w a t e r .

b

S o u r c e : - T r o e h e t a1 ( 1 9 8 ~ ) .

Table I. Recommended naximun c o n c e n t r a t i o n s of t r a c e

e l emen t s i n I r r i g a t i o n water 1

Aluminium

Arsen ic

B e r y l l i m

Boron

Cadmium

C h r o z i m

Co5al t

Copper

F l o u r i n e

I r o n

Lead

Li th ium

Manganese

Molybdenum

?lickel

S e l e n i u n

Vanadium

Zinc

F o r w a t e r s used c o n t i n u o u s l y on a l l s o i l ( ~ g / l i t e r )

For use up t o 20 y e a r s on f i n e - t e x t u r e d s o i l s a t pH 6.0 t o 8.5

( m a / l i t e r )

20.0

1. These l e v e l s w i l l n o t normal ly nave an a d v e r s e e f f e c t on ~ l a n t s o r s o i l s . No d a t a a v a i l a b l e f o r mercury, s i l v e r , - . t i n , t i t a n i u m , t u n g s t e r .

2. Recommended maximum c o n c e n t r a t i o n s f o r c i t r u s is 0.75mg/ l i t e r .

3 Only f o r f i n e - t e x t u r e d a c i d s o i l s , o r a c i d s o i l s v i t h I!elat ively h i g h c o n t e c t of I r o n oxide.

Source : S h a i n b e r g and 0 s t e r ( 1978).

13.

2.2.2. E f f e c t s of I r r i g a t i o n 'da ter Q u a l i t y on S o i l P r o p e r t i e s .

The q u a l i t y of i r r i g a t i o n wa te r can adverzzly a f f e c t

s o i l p r o p e r t i e s depending on t h e c o n c e n t r a t i o n s of i t s con-

s t i t u e n t s . G e n e r a l l y , t h e major conce rn i n e v a l u a t i n g

i r r i g a t i o n wa te r i s t h e p o s s i b l e n e g a t i v e e f f e c t s t h a t may

be caused by s a l i n i t y and s o d i c i t y problems. The main f a c t o r s

a r e c o n c e n t r a t i o n of s a l t s i n t h e s o i l s o l u t i o n and t h e n a t u r e

and degree of exchangesble c a t i o n s (Michael , 1978). The

p h y s i c a l and chemical ' p r o p e r t i e s of i r r i g a t e d s o i l s depend

l a r g e l y on t h e chemical compos i t ion of t h e i r r i g a t i o n wa te r ,

s o i l t y p e , d r a i n a g e c h a r a c t e r i s t i c s and t h e c l i m a t i c c o n d i t i o n s .

A s o i l may be s a l i n e , s a l i n e - a l k a l i o r a l k a l i ( s o d i c ) depending

on t h e l e v e l of c o n c e n t r a t i o n of sal t i n the s o i l ( t a b l e 2) .

S a l t c o n c e n t r a t i o n i n t h e s o i l may be caused by t h e q u a l i t y of

i r r i g a t i o n water .

The e f f e c t s of s a l t s on t h e chemica l p r o p e r t i e s of t h e s o i l

i n c l u d e among o t h e r s :

( i ) S a l i n i t y haza rd a s r e c o g n i s e d i n s o i l by t h e

p r e s e n c e of w h i t e s u r f a c e c r u s t s and caused by

e x c e s s i v e s a l t c o n c e n t r a t i o n .

( i i ) . Inc reased exchangeably sodium pe rcen tage caused

by i n c r e a s e i n SAR of i r r i g a t i o n water .

T a b l e 2: C o n d i t i o n s f o r S a l i n e , S a l i n e - A l k a l i a n d A l k a l i

s o i l s .

S a l t Index : - I a l k a l i I I I

A l k a l i ( s o d i c )

B l a c k a l k a l i L

C o n d u c t i v i t y o f S a t u r a t i o n E x t r a c t i n m i l l i m h o r p e r cm

S a l i n e - A l k a l i S a l t C o n d i t i o n

Common Term

Sodium Index :

S a l i n e

' d h i t e

Exchangeab le Sodium p e r c e n t a g e

1

Bydrogen I o n 1ndex :

Reclamat i o n Leach ing

3 e n e r a l l y a b o u t 8 -5

g e n e r a l l y between 8.5 - 10.0

L e a c h i n g n e c e s s a r y and p o s s i b l e , b u t as s a l t s a r e r e - ma-led t h e s o d i u n must be r e p l a c e d t o p r e v e n t d i s - p e r s i o n o f s o i l p a r t i c l e s and r e d u c t i o n o f p e r m e a b i l i t y

Low p e r m e a b i l i t y due t o d i s p e r s i o n o f s o i l by t h e sodium r e q u i r e s r e p l a c i n g t ?e sodium t o i . ? rove t h e p e r m e a b i l i t y s o t h a t l e a c h i n g c a n proceed .

S i n c e a pH of 7.0 i s n e u t r a l , pH v a l u e s l e s s t h a n 7.0 i n d i c a t e a n a:id s o i l which is common i n n o n - a r i d r e g i o n s . Note t h a t t h e l a r g e r t h e pH, t h e l e s s t h e c o n c e n t r a t i o n o f hydrogen i o n s , s i n c e pH i s t h e l o g a r i t h m of t h e r e c i p r o c a l o f t h e hydrogen i o n c o n c e n t r a t i on .

A b l a c k c r u s t fo rms o n t h e s u r f a c e o f Sn a l k a l i s o i l o n l y i f o r g a n i c m a t t e r i s p r e s e n t . Hencz, t h e t e r m may be m i s l e a d i n g i n s o i l s o f low o r g a n i c m a t t e r .

Source : I s r a e l s e n and Hansen (1962).

( i i i ) D e t e r i o r ~ t i o n of s o i l s t r u c t u r e c a u s e d when

more magnessium t h s n c a l c i u m is p r e s e n t i n

i r r i g a t i o n w a t e r . Such i r r i g a t i o n w a t e r may

l i k e l y d e c r e a s e s o i l p r o d u c t i b i t y .

The p h y s i c a l p r o p e r t i e s of s o i l may be a f f e c t e d

p o s i t i v e l y o r a d v e r s e l y i n t h e p r e s e n c e o f s a l t s depend ing

upon t h e n a t u r e a n d amount o f sa l ts , t h e r e a c t i o n p r o d u c t and

t h e i n i t i a l p h y s i c a l and c h e m i c a l c o n d i t i o n s of t h e s o i l . The

main p h y s i c a l p r o p e r t i e s i n f l u e n c i n g t h e a i r - w a t e r r e l a t i o n -

c l a y p a r t i c l e s and p e r m e a b i l i t y of t h e s o i l ( ~ i c h a e l , 1978).

These t x o p r o p e r t i e s a r e a f f e c t e d by s a l t s i n t h e f o l l o w i n g

ways:

( i ) The d e g r e e o f d i s p e r s i o n i n c r e a s e s i n t h e

p r e s e n c e o f e a s i l y d i s p e r s i b l e c l a y w i t h

i n c r e a s e i n sodium s a t u r a t i o n , and d e c r e a s e s

w i t h t h e p r e s e n c e of c e a e n t i n g a g e n t s and s a l t s .

( i i ) The p e r m e a b i l i t y o f s o i l d e c r e a s e s w i t h t h e

i n c r e a s e o f d i s p e r s i b i l i t y and exchangeab l e

sodium p e r c e n t a g e o f t h e s o i l .

I n o t h e r t o p r e d i c t t h e s u c c e s s o f i r r i g a t i o n i n a

p a r t i c u l a r s i t u a t i o n , i t i s e s s e n t i a l t o have a d e q u a t e i n f o r m a t i o n

on t h e q u a l i t y o f i r r i g a t i o n w a t e r , i t s e f f e c t s o n t h e p h y s i c a l

and c h e m i c a l p r o p e r t i e s of t h e s o i l , w a t e r t r a n s m i s s i o n

c h a r a c t e r i s t i c s o f t h e s o i l and sa l t b u i l d - u p i n t h e s o i l .

2.2.3. E f f e c t s o f I r r i g a t i o n ' d a t e r ( q u a l i t y On Croas .

w a t e r The q u a l i t y o f i r r i g a t i o n L c a n a f f e c t c r o p s i n t h e

f o l l o w i n g ways ( X i c h a e l 1978 S h a i n b e r g a n d o s t e r 1978 ) 1

( a ) I n c r e a s e i n o s m o t i c p r e s s u r e i n a s a l i n e s o i l

t h a t c a n r e s u l t f rom t h e u s e o f s a l i n e i r r i g a t i o n

w a t e r and which i n t u r n d e c r e a s e s t h e o s m o t i c

a c t i v i t y o f p l a n t t h e r e b y r e d u c i n g t h e u p t a k e o f

w a t e r and n u t r i e n t s f rom t h e s o i l .

( b ) Accumula t ion o f i o n s i n t o x i c c o n c e n t r a t i o n i n

t h e p l a n t t i s s u e r e s u l t i n g f rom h i g h c o n c e n t r a -

t i o n s o f such i o n s i n t h e s o i l s o l u t i o n . T h i s

c a n d e p r e s s c r o p groswth and y i e l d .

( c ) Accumula t ion o f one o r more n u t r i e n t s i n e x c e s s

amounts which may be a t t r i b u t a b l e t o t h e i r r i g a -

t i o n w a t e r , i n h i b i t s t h e u p t a k e o f o t h 2 r e s s e n t i a l

n u t r i e n t s . T h i s c3n a l t e r t h e p l a n t ' s m i n e r a l

n u t r i t i o n a l c h a r a c t e r i s t i c s .

( d ) Aeavy m e t a l s i n i r r i g n t i o n w a t e r t h o u g h immob i l i z ed

i n t h e s o i l can be t a k e n up by t h e p l l n t s . They

a r e o f t e n t o x i c t o t h e p l a n t s , and c a n have t o x i c

e f f e c t on t h e human consune r . D i f f e r e n t c r o p s ,

however have d i f f e r e n t t o l e r a n c e s t o t h e heavy

m e t a l s as known i n t h e c a s e o f b o r a n ( t a b l e 3)

A 1 1 o f t h e above e f f e c t s a r e g e n e r a l l y m a n i f e s t 2 d i n poor

s t a n d s o f c r o p , s t u n t e d growth and r e d u c e d y i e l d . O t h e r e f f e c t s

may i n c l u d e l e a v e b u r n s a l o n g t h e marg in o r t i p i n some c r o p s

T a b l e 3: L i a i t s of boron i n i r r i g a t i o n w a t e r f o r

s e n s i t i v e , s e a i - t o l e r a n t and t o l e r a n t s 2 a c i e s

b ~ s e d on t o x i c i t y symptoms o b s e r v e d on p l m t s

grown i n s a n d c u l t u r e .

S e n s i t i v e 0.3 - I pprn b o r o n - -

C i t r u s

Avocado

A p r i c o t

P e a c h

C h e r r y

Persimmon

F i g

Grape

Apple

P e a r

P l u a

Navy be a n

J e r u s a l e m a r t i c h o n e

Yalnu t

Semi - t o l e r a n t 1 - 2 ppm b o r o n

Lima bean

Sweet p o t a t o

B e l l p e 9 p e r

Cat

Milo

Corn

'dhe a t

B a r l e y

O l i v e

F i e l d pea

Radish

Tomato

C o t t o n

P o t a t o

Sunf l o u e r

T o l e r a n t 2 - 4 ppm bo ron

C a r r o t

L e t t u c e

Cabbage

T u r n i p

Onion

Bread bean

A l f a l f a

Garden b e e t

Mange1

S u g a r b e e t

Palm

Aspa ragus

I n each g r o u p t h e c r o p s a r e arran;e? i n d e s c e n d i n g

o r d e r of t o l e r a n c e w i t h i n t h e r a n g e i n d i c a t e d .

S o u r c e : S h a i n b e r g a n d O s t e r ( 1978).

and deep b l u e g reen c o l o u r s i n o t h e r s . I n some c a a z s

symptoms of e x c e s s i v e s a l t s a r e s i m i l a r t o t h o s e of drought

o r low f e r t i l i t y s t a t u s . S o i l s a l i n i t y c a u s e s a dec rease

i n t h e s i z e and v i g o u r of t h e p l a n t . The ge rmina t ion of

s e e d s c a n be d e l a y e d and r e t a r d e d and t h e c r o p growth p e r i o d

may a l s o be s l i g h t l y reduced. Herbaceaus c r o p s such as

maize, cowpea and amaranthus growing on s a l i n e s o i l s may have

b a r r e n s p o t s , s t u n t e d g r o w t h and deep-blu ish-green f o l i a g e .

E a c r o s i s and dcf ~liaticn z r a also ind4 A b a b l v e --' ' of s a l i n i t y . A

r e d u c t i o n i n y i e l d may occur wi thou t any v i s i b l e symptoms of

s a l t i n j u r y s u c h a s r o o t c rops . T h i s is a l s o t r u e where a

s u l p h a t e - i n d u c e d ca l c ium d e f i c i e n c y may cause t o t a l c rop

f a i l u r e i n toma toes due t o blossom-end r o t , and i r . l e t t u c e due

t o i n t e r n a l brawning.

19

2 .3 W A S T Z ' d X T i R .

I S o u r c c s and c h a r z c t e r i s t i c s of 'dzistewater.

Yas t ewa te r a l s o c a l l e d sewage is s p e n t w a t e r supp ly

from a coinmunity ( P f a f f l i n and Z i e g l e r , 1976) S c a t e t a 1

(1981) d e f i n e was t ewa te r a s t h e wa te r s u p p l y from a community

a f t e r i t h a s been used, Uas tewater i s 99.95% wa te r and

0.05% waskes ( P f a f f l i n and Z i e g l e r , 1976). Although s o u r c e s

of was t ewa te r a r e a s v a r i e d a s t h e u s e s o f w a s t e v a t e r , t h e

major s o u r c e s nag be c l s s s i f i z d 2 s :

( i ) Dumestic was tewater which i n c l u d e s t h o s e from

t h s k i t c h e n , t o i l e t , b a t h , l a u n d r y , e t c .

( i i ) I n c u s t r i a l was tewater from b o t t l i n g companies ,

b r e . ~ e r i e s , chemica l i n d u s t r i e s e t c .

( i i i ) A g r i c u l t u r a l w a s t e v a t e r such as unused i r r i g a t i o n

w a t e r , a g r i c u l t u r a l l a n d r u n o f f .

( i v ) Urban s torm r u n o f f .

' dha tever t h e s o u r c e , was tewater c o n t a i n t h e was te of a

c i t y and i t s i n h a b i t a n t s . By v i r t u e o f h a v i n g been used ,

was t ewa te r h a s p h y s i c a l , chemica l and b i o l o g i c a l c h a r a c t e r i s t i c s

o r compos i t i on t h a t a r e d i f f e r e n t from t h o s e o f t h e o r i g i n a l

~ o k t a b l e w a t e r . The c o n t e n t s of w a s t e ~ a t e r depend main ly on

t h e compos i t i on of t h e water s u p p l y , t h e use t o which t h e wa te r

w a s pu t and t h e method of c o l l e c t i o n . The c o n c e n t r a t i o n s of

t h e different c s n s t i t u e n t a depend on t h e amount of w a t e r

used p e r capita and t h i s z a o u n t is u s u a l l y s m a l l e r i n - _ d e v e l o p i n g c o u n t r i e s a n d i n a r i d and semi -a r id c l i m a t e s

( S h u v a l e t a l , 1986). T a b l e 4 g i v e s t h e p h y s i c a l , chemica l

and b i o l o g i c a l c h a r a c t e r i s t i c s o f was tewater . Depending on - -

t h e compos i t i on o f t h e s e c h a r a c t e r i s t i c s , was tewater can be

c l a s s i f i e d as s t r o n g , medium o r weak ( t a b l e 5 ) f o r t h e c a s e

of domes t i c sewage.

The c o n s t i t u e n t s - , - of domes t i c and i n d u s t r i a l waste-

w a t e r s t h a t a r e s i g n i f i c a n t i n w a t e r p o l l u t i o n c o n t r o l ,

d i s p o s a l and r e u s e i n c l u d e :

(a) S o l u b l e o r g a n i c m a t e r i a l s r e s u l t i n g i n d i s s o l v e d

oxygen d e p l e t i o n i n s t r e a m s , and e s t u a r i e s and o r

c a u s i n g t a s t e a n d odour , i n

( b ) Organ ic suspended s o l i d s r e s u l t i n g / d i s s o l v e d - oxygen d e p l e t i o n ,

( c ) i n e r t suspended s o l i d s c a u s i n g t u r b i d i t y and

r e s u l t i n g i n s e d i m e n t s ,

( d ) t o x i c s u b s t a n c e s and heavy m e t a l i o n s ,

( e ) o i l and f l o a t i n g m a t e r i a l s ,

- ( f ) k c i d s and a l k a l i s and . .

(g) d i s s o l v e d sal ts .

a t e r Source Phys ica l

S o l i d s Carr iage water,. domeetic and i n d u s t r i a l waster

Temperature Domestie and i n d u s t r i a l wastes

Color Domestic and i n d u s t r i a l wastea % Odor Decbnpostng aewage, i n d u e t r i a l wastes

Chemical

O i ~ d n i c : -

P r a t s i n o Domestic and comme~-of a 1 das tes

Carbohydrates DCmestic and commercial wastes

F a t s , o i l r , and greqse Domestic, commercial, and i n d a s t r i a l wastes

Surfactnnts Domestic and i n d u s t r i a l n a s t s e

Phenols I n d u s t r i a l vaa tes

p e s t i c i d m Agr iau l to ra l waster

Inorganicr

PI( I n d u s t r i a l wastes Chlorides Carr iage water, domestic wamtes, ground

water i n f i l t r a t i o n

Alka l in i ty Domestit wastes, ca r r iagu water, ground water i n f i l t r a t i o n

d i t rogen Domeatilr and e g r i e u l t u r a l v a s t e r

Phosvhorue Domestic and indnstr iml vaatea.

Table 5 : T y p i c a l s a n i t a r y chemical a n a l y s i s of sewage.

( Q u a l i t y of Domestic Wastes) ,

CONSTITUENTS

Salf dfi, Tot a 1

CVdlat i l e

Fixed

Suspended s o l i d s , T o t a l

V o l a t i l e

Fixed

Dissolved S o l i d s , T o t a l

V o l a t i l e

Fixed

S e t t l e a b l e s o l i d s

BOD (5 day 2 0 ' ~ ) ..-

Oxygzn consumed

Dissolved Oxygen

Nitrogen, t o t a l

0 r gan i c

Pree Ammonia

N i t r a t e (3NO ) 3

C h l o r i d e s

A l k a l i n i t y ( a s CaCO ) 3

F a t s

HZD I U M ( ~ g / l )

500

350

150

300

250

5 0 200

100

100

8

200

75 0

5 0 2 0

3 0 0 005

0.20

100

100

20

- Source: Bond and S t r a u b : (1974).

b

23.

Generally, biochemical oxygen demand (30D) is t h e rnlasure

of t he pol lut ional load of was t ewa te r on t h e oxygen r e s o u r c e s

of the receiving water w h i l e e s c h e r i c h i a c o l i f o r m (3. C o l i )

is used as an i n d i c a t i o n o f p o l l u t i o n a l l o a d i n g due t o

human i n t e s t i n a l t r a c t . ( P f a f f l i n a n d Z i e g l e r , 1976).

2.3.2. Y a s t e v a t e r Trea tment .

h sys tem of c e n t r a l c o l l e c t i o n , t r e a t m e n t and d i s p o s a l

i s a c h a r a c t e r i s t i c of u r b a n i s a t i o n where o n - s i t e t r e a t m e n t

of sewage is no l o n g e r p o s s i b l e because o f i n c r e a s i n g volume

o f wa te r u s e and s h o r t a g e o f l a n d f o r s u c h purposes . C e n t r a l

c o l l e c t i o n o f was t ewa te r n e c e s s i t a t e s c e n t r a l t r e a t m e n t

because decay ing o r g a n i c m a t t e r i s obnox ious and h a r b o u r s

d i s e a s e .,

The .?rimarg r e a s o n f o r t z g a t i n g any was t ewa te r is t h e need

f o r a v o i d i n g n u i s a n c e and dange rous c o n d i t i o n s i n t h e e n v i r o n -

ment. The re i s t h e need t o e n s u r e t h a t u n d e s i r a b l e c o n d i t i o n s

do n o t d e v e l o p i n t h e w a t e r body r e c e i v i n g t h e t r e a t e d was t e -

w a t e r e f f l u s n t ( P f a f f l i n and Z i e g l e r , 1976) . A c o n v e n t i o n a l

sewage t r e a t m e n t work c o n s i s t s of t h e f o l l o w i n g s t a g e s ( ' d h i t e ,

P r e l i m i n a r y Trea tment : s c r e e n s , g r i t s e t t l i n g t a n k s ,

s to rm t a n k s o r b a l a n c i n g t a n k s i n p a r a l l e l wi th

p r i e a r y s e d i m e n t a t i o n t a n k s , s torm-or ba l anc ing -

t a n k emptying pumps.

S ludge Trea tment : P h y s i c a l o r b i o l o g i c a l de-water ing

p r o c e s s e s . T r a n s p o r t o f s l u d g e from s i t e f o r

d i s p o s a l o r i n c i n e r a t i o n .

- Secondsry Trea tment : B i o l o g i c a l o r i n c i n e r a t i o n f i l t r a t i o n - . ' ' *

o r a c t i v a t e d s l u d g e , o c c a s i o n a l l y i n combinat ion.

I n a d d i t i o n t h e t r e a t n e n t works may i n c l u d e t e r t i a r y

t r e a t m e n t which c o n s i s t s of m i c r o - s t r a i n e r s o r sand f i l t e r s

L

t o improve t h e e f f l u e n t by removing f u r t h e r suspended o r g a n i c

- mat te r . - . - .

Metcalf and Eddy Inc , (1972) c l a s s i f i e d t h e s e s t a g e s

i n t o p h y s i c a l u n i t o p e r a t i o n s , chemical u n i t p r o c e s s e s and

b i o l o g i c a l u n i t p r o c e s s e s , The means of t r e ~ t m e n t i n which

t h e a p p l i c a t i o n of p h y s i c a l f o r c e s predominate a r e known a s

u n i t o p e r a t i o n s e,g, s c r e e n i n g , f l o c u l a t i o n , s e d i m e n t a t i o n ,

f l o a t a t i o n , vacuum f i l t r a t i o n , d ry ing e t c . While u n i t p r o c e s s e s

a r e means o f t r e a t m e n t i n which t h e removal of contaminants i s

brought about by a d d i t i o n of chemicals (chemical p r o c e s s e s )

o r by b i o l o g i c a l a c t i v i t y ( b i o l o g i c a l p rocesses ) such a s

chemical p r e c i p i t a t i o n , d i s i n f e c t i o n , b i o l o g i c a l o x i d a t i o n , e t c .

Treatment is s a i d t o be primary i f i t is without b i o l o g i c a l

b a s i s . I f t r e a t m e n t i n c l u d e s on ly s c r e e n i n g , sed imenta t ion ,

and c h l o r i n a t i o n of e f f l u e n t , t h e t r ea tmen t is c l a s s e d a s

pr imary ( P f a f f l i n and Z i e g l e r , 1976). Primary t r e a t m e n t is

b e t t e r t h a n no t r e a t m e n t a t a l l , Secondary t r ea tmen t i s g e n e r a l l y

, . accep ted as b i o l o g i c a l t r ea tmen t ( P f a f f l i n and Z i e g l e r , 1976).

-- I n b i o l o g i c a l t r e a t m e n t of wastewater , t h e o b j e c t i v e s a r e

t o c o a g u l a t e and remove n o n s e t t l e a b l e c o l l o i d a l s o l i d s and t o

s t a b i l i e e t h e o r g a n i c ma t t e r . For domestic wastewater t h e

o b j e c t i v e i s t o r e d u c e t h e o r g a n i c c o n t e n t ( Y e t c a l f and

Eddy Inc. 1972).

Secondary o r b i o l o g i c a l t r e a t m e n t is t h e most i m p o r t a n t

s t a g e of was t ewa te r t r e a t m e n t i n o r d e r t o achi.eve t h e pu rpose

o f v a s t e w a t e r t r e a t m e n t . The d i f f e r e n t methods f o r s econda ry

t r e a t m e n t i n c l u d e

( i ) a c t i v a t e d - s l u d g e

( i i ) t r i c k l i n g o r p e r c o l a t i n g f i l t e r s

and ( i i i ) l a g o o n s ( a e r o b i c , a n a e r o b i c and f a c u l t q t i v e ponds).

The a c t i v a t e d - s l u d g e p r o c e s s i s used a lmos t e x c l u s i v e l y i n 8

l a r ' g e c i t i e s . T r i c k l i n g f i l t e r s a r e o f t e n used i n s m a l l e r

c i t i e s and f o r h i g h - s t r e n g t h i n d u s t r i a l was t e s . Lagoons a r e

u sed f o r small c i t i e s where l a r g e l a n d a r e a i s a v a i l a ' 3 l e - ( N e t c a l f and Eddy Inc . 1972) . S t a b i l i z a t i o n pond method i s

a c o n d i t i o n where sewage is e f f e c t i v e l y t r e a t e d mere ly by

s t o r a g e i n r e l a t i v e l y s h a l l a w open ponds f o r p e r i o d s r a n g i n g

from a few d a y s t o a few weeks depending on c l i m a t i c c o n d i t i o n s

a n d t h e deghee of t r e a t m e n t d e s i r e d .

Whatever t h e method o f t r e a t m e n t , t r e a t m e n t works u s u a l l y

have a f i n a l p r o d u c t r e f e r r e d t o as e f f l u e n t , which u s u a l l y . . o f n e e d s t o be disposed{, U l t i m a t e d i s p o s a l o f was tewater e f f l u e n t -

- c a n be by d i l u t i o n i n t h e r e c i e v i n g body of wa te r ; by d i s c h a r g e

on l a n d ; o r i n some c a s e s sucn as i n d z s c r t ~ 1 2 s by

e v a p o r s t i o n i n t o t h e a tmosphere as wel l aa seepage i n t o t h e

- ground. Dispo;al by d i l u t i o n ( n f t e r p r e l i n i n a r y o r b i o l o g i c a l

\ '

t r e a t m e n t ) i n l a r g e r b o d i e s of w a t e r , such a s l a k e s , r i v e r s ,

e s t u a r i e s o r oceans i s by f a r t h e most common method ( ~ e t c a l f

and Eddy I n c , , 1972) . R e g a r d l e s s of t h e d i s p o s a l method t h e r e

a r e r e q u i r e d q u a l i t y s t a n d a r d s f o r t h e e f f l u e n t based on

d e s i r a b l e p h y s i c a l c h e m i c a l and b i o l o g i c a l c o n . ; t i t u e n t s ,

2 , i f a s t e w a t e r I r r i g a t i o n ,

d a s t e w a t e r i r r i g a t i o n i s t h e a p p l i c a t i o n o f was tewater and

- o r i t s e f f l u e n t on t h e l a n d f o r p u r p o s e s of c r o p p roduc t ion .

The r e c y c l i n g of human w a s t e s t o add n u t r i e n t s t o and improve

t h e p h y s i c a l q u a l i t y of t h e s o i l had been p r a c t i c e c i n a n c i e n t

t ims i n China and i n o t h e r a r e a s o f Xsia, The e a r l i e s t raw

sewage f a rms documented i n l i t e r a t u r e appea r t o be t h o s e o f

Banz lau , Germany which were i n o p e r a t i o n i n 1531 and t h o s e o f

. . Zdingurgh , S c o t l a n d which were a c t i v e a round 1050 (Shuva l

e t al, 1986) - T h e r e a f t e r t h e p r a c t i c e s p r e a d a c c r o s s Europe ,

- t h e Un i t ed S t a t e s and Mexico, A f t e r sometime t h e p r a c t i c e

d e c l i n e d f o r l a c k o f l a n d due t o t h e enchroachnent of urban

deve?oprnent. O t h e r f a c t o r s r e s p o n s i b l e f o r t h e d e c l i n e i n raw

, w a s t e w a t e r i r r i g a t i o n i n c l u d t h e problems of odour and t h e

c o n c e r n s abou t p u b l i c h e a l t h ( o a r t i c u l a r l y t h a t o f t h e

p o s s i b l e t r a n s m i s s i o n o f d i s e a s e s from v e g e t a b l e c r o p s

i r r i g a t e d w i t h raw sewage) a n d t h e d i s c o v e r y o f b i o l o g i c a l

p r o c e s s e s of t r e a t i n g was t ewa te r t h a t r e q u i r e d much l e s s l a n d

t h a n r a w sewage fa rms , : t h e

C u r r e n t l y , t h e m i s renewed i n t e r e s t fn L p r a c t i c e o f

was tewater i r r i g a t i o n i n many c o u n t r i e s o f t h e wor ld i n c l u d i n g

u n i t e d ~ i n g d o m , U.S.X., I s r a e l , I n d i a , F e d e r a l Repub l i c o f

Germany, Sou th A f r i c a , J apan , USSA', ' China , A u s t r a l i a as w e l l

as L a t i n American, Nor th A f r i c a n , Middle E a s t e r n a n d Sou th

3ast Asian c o u n t r i e s (Shuva l e t a l , 7986). No d e t a i l e d i n f o r -

mat ion is a v a i l a b l e on was t ewa te r r e u s e i n t h e l a r g e r p a r t o f

A f r i c a . There is t h e p o s s i b i l i t y t h a t as more c e n t r a l sewage

c o l l e c t i o n and t r e a t m e n t s y s t e m s a r e a d o p t e d i n A f r i c a , waste-

wa te r r e u s e i n a g r i c u l t u r e may s p r e a d i n t h e c o n t i n e n t .

The b e n e f i t s o f was t ewa te r i r r i g a t i o n a r e nunerous. It h a s

become an i m p o r t a n t s t r a t e g y f o r c o n s e r v i n g w a t e r r e s o u r c e s i n

a r i d and semi -a r id a r e a s of . t h e wor ld , Sven i n humid a r e a s

where t h e r e a r e r e g u l a r p e r i o d s o f d r o u g h t , t h e r e a r e d e f i n i t e

a d v a n t a g e s of was tewater i r r i g a t i o n , The f e r t i l i z e r v a l u e o f

- t h e n u t r i e n t s i n was tewater are a d d i t i o n a l economic i n c e n t i v e s ,

p a r t i c u l a r l y f o r d e v e l o p i n g c o u n t r i e s where t h e c o s t o f impor t ed

c h e n i c s l f e r t i l i z e r s makes i t d i f f i c u l t t o m a i n t a i n h i g h

l e v e l s of a g r i c u l t u r a l p r o d u c t i v i t y ( S h u v a l e t a l , 1986) .

Sewage i r r i g a t i o n c o u l d c o n t r i b u t e i n maximizing t h e e f f i c i e n t

t u s e of l i m i t e d l a n d r e s o u r c e s f o r t h e p r o d u c t i o n o f food and

+ f i b r e . Resources p r e s e n t i n was t ewa te r c a n be r e c o v e r e d when

u s e d on l a n d , and t he o t h e r w i s e d i s c h a r g e o f p o l l u t a n t s o f

wa te r b o d i e s and c o u r s e s e l l i m i n a t e d t h e r e b y improving t h e

w a t e r q u a l i t y o f such b o d i e s of w a t e r ( A r a r , 1987).

2.3.4. H e a l t h I n p l i c a t i o n s o f Wastewater I r r i g a t i o n .

Although was t ewa te r ( raw and t r e a t e d ) h a s been used as

i r r i g a t i o n w a t e r s o u r c e s i n c e a n c i e n t t i m e s , t h e n e g a t i v e

- h e a l t h i m p l i c a t i o n s were n o t d i s c o v e r e d u n t i l t h e t u r n of t h i s

c e n t u r y . Beginning i n 1912, numerous h e a l t h r i s k s a s s o c i a t e d

w i t h was t ewa te r i r r i g a t i o n have been r e v e a l e d . These r e v e l a t i o n s

a r e based on q u a n t i f i a b l e r e s e a r c h works , a few of which a r e

mentioned below as rev iewed by S h u v a l e t a l , (1986).

K h a l i l (1931) d i s c o v e r e d c a s e s o f a s c a r i a s i s and t r i c h u r i a s i s

among i n m a t e s of T a r a p r i s o n i n Egypt who consumed v e g e t a b l e s

from t h e sewage farm a t t a c h e d t o t h e p r i s o n . Baumhogger (1949)

' r e ~ o r t e d . t ha t a number of major e p i d e m i c s o f a s c a r i a s i s t o o k . .

p l a c e i n Dorrnstadt, Germany between I908 and 1909, d u r i n g 1921,

and b a t m e n 1945 and 1943. I n e a c h c a s e , t h e e p i d e x i c \vas

a s s o c i a t e d w i t h s e v e r e economic d i s l o c a t i o n s and food

s h o r t a g e s , The v e g e t a b l e s and s a l a d c r o p s grown on t h e -

Darmstadt sewage f a rms o b v i o u s l y made up a n impor t an t p a r t -.-

of t h e f o o d s u p p l y o f t h e p o p u l a t i o n of t h e c i t y d u r i n g

t h o s e p e r i o d s . A number o f s t u d i e s between 1923 and 1970

showed e v i d e n c e o f he lmin th t r a n s m i s s i o n by v e g e t a b l e s i r r i g a t e d

w i t h was te7vater i n Jerusa lem. 4 c h o l e r a o u t b r e a k i n J e r u s a l e m

i i i 7972 :;as found t o be a s s o c i a t e d w i t h t h e consumption o f

, , , a s t e~>~a te r i r r i g a t e d vege tab lz - . I n S a n t i a g o , C h i l e , i t w2s

d i s c o v e r e d b e t x e e n 1982 and 1984 th rough a nunber o f f i n d i n g s

t h a t typhod f e v e r was a s s o c i a t e d w i t h sewage i r r i g a t i o n . The

c s s e s o f typhod f e v e r were more s i g n i f i c a n t d u r i n g t 3 e d r y

e f f e c t s o f was t ewa te r i r r l , : s t i o n on peop le i n v o l v e d i n s e v a e e

f a rming as w e l l as c o n s u a e r s o f t h e p r o d u c t s of s u c h fa rms i n

U.S.A., I n d i a , Mexico, e t c (Shuval , e t a l , 1986).

I n many d e v e l o p i n g c o u n t r i e s where h e l m i n t h d i s e a s e s a r e

endemic, p r i o r i t y pa thogens a s s o c i a t e d w i t h d i s e a s e t r ansmi -

s s i o n 5y was tewa te r i r r i g a t i o n can be r anked i n d e c r e a s i n g

o r d e r of r i s k a s f o l l o i l s (Shuval e t a l , 1336) : - 1. High r i s k - h e h i n t h s

2. Lower r i s k - e n t e r i c h s c t e r i a acd pro tozoan

7. L e a s t r i s k - e n t e r i c v i r u s e s

Samsboye (1986) n o t e d t b a t wate r borne e n t e r i c d i s e a s e s

such as typhad f e v e r , b a c i l l a r y d y s e n t r y , a s i a t i c c h o l e r a

and i n f e c t i v e h e p a t i t i s can b e t r a c n d t o wa te r p o l l u t i o n of

faecal o r i g i n . Apar t from e n t e r i c d i s e a s e s , f i l a r i a s i s

and s c h i s t o s o r n i a s i s c a n be t r a c e d t o w a t e r p o l l u t i o n i n

some t r o p i c a l a r e a s . The d i s a d v a n t a g e s o f was t ewa te r

i r r i g a t i o n which a r e e s s e n t i a l l y h e a l t h based can be

sumnar ised as

(i) t ~ a n s m i s s i o n o f c o r n ~ u n i c a b l e d i s e a s e s t o

s u s c e p t i b l e sewage f a r m e r s and t h e g e n e r a l

p u b l i c who consume produce f r o a s u c h f a r m

a n d

(ii) p o l l u t i o n t o s u r f a c e w a t e r and groundwater

w i t h p a t h o g e n i c microorganisms and chemica l s

c a r r i s d by t h e wastewater . ,

2.3.5. P u b l i c H e a l t h based Requirements and Q u a l i t y

S t a n d a r d s o f Yas t ewa te r f o r I r r i g a t i o n .

G e n e r a l l y a c c e p t a b l e w a t e r q u a l i t y s t a n d a r d s f o r

i r r i g a t i o n have been c o n s i d e r e d e a r l i e r i n s e c t i o n 2.2.1.

I n a d d i t i o n , because o f t h e p e r c u l i a r i t i e s of was tewater , - .

o t h e r r e q u i r e m e n t s a r e n e c e s s a r y f o r c o n s i d e r a t i o n b e f o r e

any was t ewa te r can be used f o r i r r i g s t i o n . The p r a c t i c e o f

( d l M e t c a l f a n d Eddy Inc . (1972) s u g g e s t

t h a t p r e l i m i n a r i l y t r e a t e d sewage and/

o r u n d i s i n f e c t e d sewage e f f l u e n t c o u l d

b e a p p l i e d t o f i e l d c r o p s , such as c o t t o n ,

s u g a r b e e t s and v e g e t a b l e s grown f o r s e e d

p r o d u c t i o n .

( e ) The s t a t e o f C a l i f o r n i a and t h e !qorld S e a l t h

O r g a n i s a t i o n haye s u g g e s t e d t r e a t m e n t

r e q u i r e m e n t s and q u a l i t y s t a n d a r d s f o r

i r r i g a t i o n p u r p o s e s a s shown i n t a b l e s 6

a n d 7 r e s p e c t i v e l y (Shuva l , e t a l , (1986).

(f) The e f f l u e n t g u i d e l i n e s t h a t S h u v a l , e t a 1

(1986) recornxiended f o r u se i n u n r e s t r i c t e d

x a s t e x a t z r i r r i g a t i o a o f ali c r o 2 a i n c l u d i n g

v e g t t a t l s s a r l

( i ) Mot s o r e t 5 a n 1 v i a j l e c e z s t o d s

( h e l a i n t h ) egg ( a s c o r i s , t r i c h ~ r i s ,

hookxorn) p e r l i t e r .

California Stete Dcpar~ment of tiealth'standarda Tor thi: onfe . and direct use of reclai-d vaeteuvter for irr:gation and recreational i m p o u n ~ n t e

Description of minimum required vasteuater characteristics

-- Secondary coagulet eC Colilorm

Secondary filtered - b' ' M~N1100 ml and and median . Use of reclaimed uasteuarzr ~rimar~?' disinfected di sinfecred (daily ramp1 ing)

a. Effluent not containing more than 1.0 ml/liter/hr settlable solids. b. Effluent not containing more than 10 turbidity units.

I ! 1

Irrigation Fodder crops x No requirement Fiber crops x No requirement

Source: Af ter Ongerth and Jopl iug i n Shuva l et a1 (1986).

Seed crops x Produce eaten raw, surface irrigated x Produce eaten raw, spray irrigated

No requirement 2.2

x 2.2 Processed produce, surface irrigated x No requirement Processed produce, spray irrigated x 2 3

Landscapes, parks, etc. x ! 2 3 Creation of impoundments Lakes (aesthetic enjoyment or.? y) x 23

I Restricted recreational lc!:es x 2.2 . Nonrestricted recreational lakes x 2.2

Table 7

r '.Suggested t reehmnt processes t o m e t the given hea l th c r l t e r l e f o r res tare tar reuse

. I r r i g a t i o n Racraatlon -- uunic-ifal.p e U X

Crops not Crops eaten fo r d l r e c t ccoked; Crops

human f l s h eaten Ho Industrial Nan

e ~ s u m p t Ion c u l t u r e re. contact Contact reuse potable Potable

Primary t r ee fmn t e e e e.0 0.0 e.0 e e e e e e *em om.

Secondary treatment e.0 eoe ee. 0 . e.. em*

Second f i l t r a t i o n o r equlvalant w ison ing methods

Hi tri f i c a t i ~ t

-!hn k t r H i c a t i i m

Chemcal ' c la r l f l ca t i on

Ion exchange or other H e n s o f removing I m s . .

- ... ee. *.. e..

b a l t h c r i t r r i a :

A - Fr- f r a gross so l ids ; r l g n l t l c a n t r-vel o f paras l ta qys. B - As A, plus r l g n l f l c a n t r r r o v a l o f bacteria.. C - As A, p lus -0 r f f r c t l v r r w v a l o f baet r r la , p l u r saw ramoval o f v l ruras. 0 - Not Iwr than 100 c o l l f o c r org8nloc.s per 100 m1 I n IK) porcrn t of r w p l r r . E - No fecal c o l l f w m o r g a n l v s i n 100 ml. p l u r no v l r u r p a r t l c l o s i n 1OOO mI. p lus no t o x l c r f f u t s on man and other

dr ink ing r a t e r c r l t r r l a , . F - tb c h c l c a l s t ha t lead t o undesirable rosldues I n crops or f lsh.

G - M , c h m l c a l r t ha t lead t o lrrl t a t i o n o f mucous u r b r a n e r md rkln. . ..

I n w d e r to mt the glvan hea l t h c r l t r r l a , processes narke4 l l l .Ill k r s w n t l r l . I n eddl t ion, one w more processes rarked r l l l a lso k r r s o n t l a l , and f u r t h u p r o c r s u r marked 0 M y Sawtlmr k requlrod.

Free chlar ina a f t e r I hour.

Source: W30 in Shuval et a1 (1986) .

a n d ( i i ) a g e o m e t r i c mean n o t g r e a t e r t h a n -

1,000 f a e c a l c o l i f o r m b a c t e r i a p e r 100 m l , t h e y

In a d d i t i o n t o t h e above recommendation, ' L s u g g e s t

t h z t brhere was t ewa te r e f f l u e n t s z r e known t o c o n t a i n

pa thogens , t h e i r u s e f o r i r r i g a t i o n o f mzrke t v e g e t a b l e s

s h o u l d be p r o h i b i t e d .

a l s o s u g g e s t t h a t t h e f o l l o w i n g c r i t e r i a f o r t r e a t m e n t

of was t ewa te r f o r i r r i g a t i o n shou ld be met

( 1 ) Kwdnum r e ~ o v a l o f h e l m i n t h s

( 2 ) E f f e c t i v e r e d u c t i o n i n S a c t e r i a l and v i r a l

pz thogens

3 The p r o d u c t i o n o f n u i s a n c e - f r e e a n d odour - f r e e '

e f f l u e n t (i .e. BOD is e f f e c t i v e l y r educed) .

?e s t a b i l i z z t i o n pond cen c e e t t h e t h r e e c r i t e r i a . Well

d e s i g n e d and w e l l o p e r a t e d s e r i e s of s t a b i l i z z t i o n ponds

czn a c h i e v e z l z o s t t o t a l removal of h e l m i n t h s w h i l e 20 - day

s t 5 b i l i z a t i o n ~ o z d s c s n renove e lmos t a l l b a c t e r i a and v i r u s e s .

370

2.4 CRO? PRODUCTION W1Ti-I YASXYATER IRSIGATION.

2.4.1. E f f e c t s o n s o i l p r o p e r t i e s

Although sewage f a rming cou ld have a d v a n t a g e s due t o

r e c y c l i r g o f n u t r i e n t s and o r g s n i c n a t t e r t o t h e s o i l

( S a b e r , 19%) , w a s t e w a t e r as i r r i g a t i o n x a t e r , l i k e conven-

t i o n a l i r r i g a t i o n w a t e r f r o a e i t h e r s u r f a c e o r s u b s u r f a c e

s o u r c e s , may a f f e c t t h e s o i l p h y s i c a l , c h e n i c a l and b i o l c g i c a l

p r o p e r t i e s depend ing o n t h e c o n c e n t r a t i o n o f t h e c h a r a c t e r i s t i c

c o n s t i t u e n t s o f t h e i r r i g a t i o n was t eda te r . The e f f e c t s of

t o t a l s a l t 7 c o n c e n t r a t i o n 3 t k e r e l a t i v e c o n c e n t r a t i o n o f

s o i i u z i o r s t o o t h e r c a t i o n s and o t i e r s p e c i f i c i o n i c e f f e c t s

' . a s w e l l z s t u r h i d i t y i n x a a t e w z t e r SR s o i l p r o g e r t i e s a r e - - s i n i l a r t o t h e i r e f f e c t s when i n h i g h c o n c e n t r a t i o n s i n t h e

c o n v e n t i o n a l i r r i g a t i o n w a t e r a s d i s c u s s e d e a r l i e r i n s e c t i o n

2.2.2. Some o l t h e documented e f f e c t s o f was t ewa te r i r r i g a t i o n

o n s o i l are b r i e f l y g r e s e n t e d below:

In Gabel e l A s f a r sewage fa rm i n Ca i ro (Sabe r , 19861,

where t h e o n l y s o u r c e o f i r r i g a t i o n is d e c a n t e d sewage s i n c e

1925, seuage f a r m i n g t e n d e d t o b u i l d up m i c r o b i a l p o p u l a t i o n

a n d t o t a l b a c t e r i a c o u n t s as w e l l as t h e promot ion o f the

p r o l i f e r a t i o n -- o f p h y s i o l o g i c a l groups. T h i s p o p u l a t i o n h a s

a c c e l e r a t e d t h e o x i d a t i o n o f o r g a n i c m a t t e r t o a v a i l a b l e

n u t r i e n t s , It a l s o r e s u l t e d i n a h i g h i n c r e a s e i n n i t r o g e n ,

phosphorus , m i c r o - n u t r i e n t s , o r g a n i c c a r b o n and r a i s e d t h e

w a t e r h o l d i n g c a p a c i t y and exchangeab le c a t i o n s . The b a l a n c e

o f n u t r i e n t s i n s o i l appea red t o have been d i s t u r b e d as t h e

p9 s h i f t e d towards a c i d i t y . The f a e c a l 2. C o l i , which is

a n i n d i c a t o r o f t h e p re sence o f e n t e r i c pa thogens was found

i n a l l ae-.qaged s o i l s ,

I n as 8 - ~ % r sewage e f f l u s n t i r r i g a t i o n e x p e r i a e n t ,

3 e c n e t t s t a 1 (19731, e s t a ' d i s h o d t h a t t h e e f f l u e n t i n c r o 2 s e d

p?ms?horus, sodium, s 0 l u 3 l e s a l t s and p5 i n t h e s o i l ( a t 1;;

l e v e l o f s t a t i s t i c a l s i z n i f i c a n c e ) , P e r c i v a l (1984) obse rved -.-

t h a t t h z h i g h sodium c o n c e n t r a t i o 3 i n t 3 e K r 2 f t p u l p m i l l

e f f l u e n t u s e d as i r r i g a t i o n w a t e r s o u r c e i n t h e c e n t r a l ?Jorth

I s l a n d i n :law Zea land cou ld c a u s e s o i l d 'eflocul.at ' ion a f t e r

s e v e r a l years. C r o ~ e r e t a 1 (1984) e s t a 5 l i s h e d t h a t i r r i g a t i n g

w i t h s a l i n e was t ewa te r produced s u b s t a n t i a l i n c r e a s e s i n

exchangeab le s e d i u a and po ta s s ium, e x t r a c t a b l e phosphorus, pX

and t h e e l e c t r i c a l c o n d u c t i v i t y o f t h e s o i l and t h a t n i t r o g e n

remained l a r g e l y i n t h e o r g a n i c farm, Wastewater i r r i g a t i o n

c a n c a u s e o r i z c r e a s e heavy m e t a l b u i l d up i n t h e s o i l ,

39

S c h i r a d o e t a1 (1986) have shown t h a t u n t r e a t e d w a s t e w a t e r - i n c r e a s e d t h e l e v e l s o f e x t r a c t a b l e Cadaium, Coba l t , Copper ,

Manganese, n i c k e l and z i n c i n t h e c u l t i v a t e d l a y e r o f t h e

s o i l when compared t o t h e u n d i s t u r b e d lower l a y e r s . However

p o t e n t i a l heavy m e t a l h a z a r d i s l e s s i n h i g h exchange c a p a c i t y

s o i l s .

a '

r. 4.2. 3 f f e c t s o n Crops.

was t ewa te r i r r i g a t i o n of food and f i b r e c r o p s h a s been

known t o produce d i f f e r e n t r e s p o n s e s on d i f f e r e n t c r o p s .

" o r t e n e t a1 (1980) have e s t a b l i s h e d t h a t p e r e n i a l f a r a z e

g r a s s s s az? z a i z e y i e l C v e l l and e f f i c i e n t l y r eaovs l a r g e

amouafs o f n i t r o g e n from w a s t e v a t s r e f f l u e n t on w e l l manaqed

a c d p e r a e a b l e s o i l s . I n a g reen3ous3 e x p e r i z e n t x i t h d i f f a r e ~ t

t r e a t m e n t l e v e l s o f w a s t e w a t e r , 3aogSoye (19%) r e p o r t e d t h a t

sewaze e f f l u e n t t r e a t e d w i t h one h a l f t h e dosage o f f e r t i l i z e r

. r e q u i r e m e n t produced t h e h i g h e s t g r a i n y i e l d i n c o r n p r o d u c t i o n .

T e s t e r and P a r r (9982) r e p o r t e d t h a t was t ewa te r i r r i g a t i o n

- i n c r e a s e d y i i l d and q u a l i t y o f v e g e t a b l e s (cabbage , t oma toes

and caul i f lo : . , e r ) . I n a c o m p a r a t i v e s t u d y on c o t t o n i r r i g a t e d

w i t h w a s t e ~ ~ a t e r and p o r t a b l e w a t e r , Day e t a 1 (1981) n o t e d .. .

t h a t c o t t o n i r r i g a t e d w i t h a m i x t u r e o f was t ewa te r and p o r t a b l e

watlr hzd more v e g e t a t i v e growth a a d s t o o d h i g h e r t h a n

c o t t o n i r r i g a t e d w i t h o n l y p o r t a 5 l a water . It was a l s o

obse rved t h a t t h e y i e l d o f s e e d c o t t o n and l i n t c o t t o n

were b o t h h i g h e r i n t h e c a s e o f a mix tu re o f v s s t e w a t e r and

p o r t a b l e water . The L i n t c o t t o n q u s l i t y was hoxever t h e

sams f o r t h e two d i f f e r e n t t r e a t n o ~ t s . The above f i n d i c g s

x o u l d i n d i c a t e t h s t rnunic ina l w a s t e v a t e r can be a n e f f e c t i v e

i r r l g x f i o n !:12tor so2 r " as a e l l a s a sou rcd o f p l s c t n u t r i a n t s

i n co t5on p r o d u c t i o n i n Ar izoca , U . S . A . , where t h e s t u d y was

c a r r i o d o u t .

n i t r o g e n c o n t a n t a n d n s t s k e b j f o d d e r , maize and s p i n a c h

were i n c r e a s e d by a p p l y i n g i ~ c r e a s i - g n i t r o g e n r a t e s (0 - 153

kg/ha), f a r n y a r d manure o r t owr r e f u s e . S i m i l a r i n c r e a s e s

mix tu re o f sewage watsr and c a n a l m t z r c o q o s e d wi th c a n a l

w a t e r aLone.

- 2.5, CBOP SZLECTION FOR WSTZ-JATER IRRIGATION

.-

S h u v a l . e t a 1 (1986) has s u g g e s t e d t h r e e c o n s i d e r a t i o n s f o r

s a l e c t i n g c r a p s t o b e srot,qn undzr v a s t e w s t e r i r r i g a t i o n .

1. S u i t a b i l i t y o f c r o p t o t h e g e n e r a l agronomic

c o n d i t i o n s of t h e s i t e w i t h r e s p e c t t o c l i m a t e ,

s o i l t g p t s , a v a i l a S i l i t y of marke t , e t c . I n

ge9era1, any c r o p u s u a l l y grown by l o c a l f a r x r s

undor i r r i g s t i o n i n a given l o c s t i o n shou ld

s a t i s f y t h e c r i t e r i o n .

2. C o ~ s t r a i n t s on c r o p groxth .

T k s e c o n s t r a i n t s a r e due p r i n c i p a l l y t o t h e

s i l i n i t y o f e f f l u e n t which l i n i t s c r o p growth

aid c a u s e s t k e d e t e r i o r a t i o n of some o f t h e

p k j s i c a l a n d chemica l p r o 7 e r t i a s o f t h e s o i l

as w e l l a s t h e t o x i c e f f e c t o f s p e c i f i c i o n s

t o c e r t a i n c rops .

3. P u b l i c H e a l t h C o n s t r a i n t s .

These a r e c o n s t r a i n t s on c r o p u t i l i z a t i o n

o r m a r k e t i n g imposed by p u b l i c h e a l t h

c o n s i d e r a t i o n s o r r e g u l a t i o n s r e s u l t i n g f r o a

b o t h p a t h o g e n s and t o x i c chemica l c o n t e n t s o f

t h e w a s t e w a t e r t h a t can con tamina te t h e c rop .

The r a t i o n a l e o f c o n s i d e r i n g pa thogen c o n t a m i n a t i o n i n

s e l e c t i n g c r o p s t o 5 e i r r i g a t e d by was t ewa te r s t ems from t h e

obv ious - p ~ s s i b i l i t g o f t h e c o n t a m i n a t i o n o f t h e p l a n t p a r t s

d e s t i n e d f o r human consumption d i r e c t l y o r i n d i r e c t l y

w i t h i n a s h o r t p e r i o d a f t e r con tamina t ion and w i t h o u t %

-& f u r t h e r p r o c e s s i c g . The s u i t a b i l i t y o f c r o p s f o r was te-

w a t e r i r r i g a t i o n b a s e d on p o s s i b l e c o n t a a i n a t i o n 5y pa thogens

is g i ~ e n Selow i n d e s c e n d i c g o r d e r o f s u i t a b i l i t y :

( i ) Crops n o t grown f o r food such a s wood and

f i 5 r e c r o p s anong which c o t t o n i s by f a r t h e

n o s t i m p o r t a n t world ;#idem

( i i ) Ta l l -g rowing f ~ u i t and cnt t r e e s i r r i g a t e d

by s u r f a c e o r d r i p system o r low t r a j e c t o r y

s p r i n k l e r s .

( i i i ) B r a i n c r o p s and f r u i t c roFs f o r which

i r ~ i g a t i o n c o u l d be t e r ~ i n a t e d s e v e r 2 1

weeks b e f o r e h a r v e s t i n g and f r u i t s t h a t a r e

no rma l ly vashed and t r e 3 t e d b e f o r e consuap-

t i o n ( c i t r u s , o l i v e s , avocados e t c ) .

( i v ) Low-growing b u t e r e c t p l a n t s , grown i n t h e

r idge -and- fu r row s y s t e ~ and no t i r r i g a t e d by

s p r i n k l i n g . Such c r o p s i n c l u d e t a b l e g r a p e s

and t o m a t o e s grown o n t r e l l i s e s , swee t c o r n ,

peppe r , egg p l a n t , e t c .

(v) Crops t h a t a r e l e a s t s u i t a b l e f o r e f f l u e n t

i r r i g a t i o n a r e t h o s e w i t h s u p i n e growth h a b i t

s u c h a s Squash , Cucumbers, some tomato v a r i e t i e s ,

s t r a w b e r r i e s , p e a s , beans , r o o t c r o p s e a t e n

.. raid ( c a r r o t s , r a d d i s h ) a s w e l l a s a s p a r a g u s ,

p o t a t o e s , b e e t s , o n i o n s e t c .

The degree of t r e a t m e n t t o which t h e e f f l u e n t i s L

- s u b j e c t e d as w e l l a s t h e i r r i g a t i o n method used w i l l i n f l u e n c e

t h e s e v e r i t y o f t h e l i m i t a t i o n ,

The c h o i c e of a n m a n t h u s SPP. c r o p f o r t h e m i n e r a l a n a l y s i s

d e r i v e s from t h e f a c t t h a t i t i s t h e crop under waste-

water i r r i g a t i o n a t t h e s i t e under s tudy, Amaranthus i s a

v3ge tab le c r o o wi th nany s p e c i e s , soxe of ~dh ich a r e w i l d ,

Ar thur (1965). r e f e r s t o t h e v e g e t a b l e c r o p a s a l a r g e

group of quick-growing sp inach p l a n t s and i t i s connonly

r e f e r s d t o a s African a ~ i n a c i ,

Anaranthua i s an e a s i l y grown l e a f v e g e t a b l e v i t h a high

d i e t e t i c va lue . During t h e e a r l y r a i n s when t h e r e is s h o r t a g e . - C

of g reen v e g e t a b l e s , i t g i v e s an abuadance of g reen l e a f

( G r e e n s i l l , 7964). I n Niger i a , i t i s grown p - i n s i l y f o r i t s

g reen v e g e t a b l e supply.

Vege tab les a r e ve ry impor tant t o poor peop le i n many under-

developed c o u n t r i e s i n c l u d i n g N i g e r i a s i n c e t h e s e poor people

cannot a f f o r d enough meat o r f i s h and must depend on v e g e t a b l e s

- f o r much o f t h e f l a v o u r and t h e p r o t e i n r equ i rement i n t h e i r

food ( A r t h u r , 1965). Most v e g e t a b l e s need l a r g e amounts o f wa te r

and hence y a t e r supp ly i s o f t e n a l i m i t i n g f a c t o r i n v e g e t a b l e

farming. Consequent ly , i r r i g a t e d v e g e t a b l e f a rming is becoming

popular and common world wide,

HXT39I.iLS A';iD i1IE'THOrSS - - The g e n e r a l g u i d e l i n e s or r e q u i r s e c c c s f o r i r r i g d c l o n

% a t e ? azd t h e s g e c i Z i c r e q u i r e m o n t s f o r was tewater f o r

i r r i g a t i o n were c o n s i d e r e d i n t h e e x e c u t i o n of t h i s r e s e a r c h

work. These c o n s i d e r a t i o n s l e d t o t h e i d e n t i f i c a t i o n of t h e

f o l l o w i n g p a r a a e t e r s f o r e x m i n a t i o n .

S s v e n t e e n c n a r s c t e r i s t i c s o f was t ewa te r were c o n s i d e r e d

f o r e v s l u a t i o n i n ths l x b o r s t o r y ( t a 5 1 s 8 ) . S o i l a n a l y s i s

invol-:ed a c o n b i n a t i o n o f f i e l d and l a b o r a t o r y t e s t a f o r t h e

d e t e r m i n a t i o n of t h e ohgsical c h a r a c t e r i s t i c s ( f i e l d

t h e s o i l . C:hez ica l ~ a i g s i s o f t h e s o i l i n c l u d e d

l a b o r s t o r y e v a l u s t i o n o f 23, e l e c t r i c a l c o n d u c t i v i t y , c a t i o n

exchange c a p a c i t y , n i t r o g e n , phosphorus as !#ell as potassium,

sodium, ca l c ium a2d nagnessium. The v e g e t a b l e ( amaran thus SPP)

s a n p l e s were a n a l y s e d i n t h e l a b o r a t o r y f o r n i t r o g e n , phosphorus ,

. po t a s s ium, c a l c i u n , magnassium a a d s o d i u a c o n c e n t r a t i o n s .

The l a b o r a t o r y f a c i l i t i e s used f o r t h e l a b o r a t o r y work

of t h i s s t u d y - . i n c l u d e t h o s e of t h e f o l l o w i n g d e p a r t m e n t s / u n i t s

o f t h e U n i v e r s i t y of N i g e r i a , Nsukka campus:- C i v i l E n g i n e e r i n g

( p u b l i c ~ e a l t h ) , A g r i c u l t u r a l E n g i n e e r i n g , Geology, V e t e r i n a r y .

Table 8: Methods f o r t h e examinat ion o f wastewater

Refe rences

sample s .

American P u b l i c H e a l t h A s s o c i a t i o n e t a 1 (1971) f o r t e s t s 4 t o 11 and 13.

* * Vogel, A.1. (1972) - For t e s t 12

M E T H O D O L O G Y

Thermometer

E l e c t r i c a l C o n d u c t i v i t y me te r

pH meter

Gravimet r i c

S t a n d a r d Method

S t a n d a r d P l a t e count

Phenodisulphunic a c i d method

Stannous Chlo r ide

T u r b i d i m e t r i c method

Argentometr ic T i t r a t i o n

D o T A. T i t r a t i o n

E. D. To A. T i t r a t i o n

E- D - T. A - T i t r a t i o n

Flame Photometer

Flame Photometer

F l o a t a t i o n Method

F l o a t a t i o n Method

*** S h a p i r o and Branock, (1962)- For t e s t s 14 and 15

CHARACTZRISTIC

Temperature

E l e c t r i c a l Conduc- t i v i t y

PH T o t a l s o l i d s

BOD 5

B a c t e r i a l Densi ty

N i t r a t e

Phosphate

Su lpha t e

C h l o r i d e

Calc i um

Magnessium

Hardness

Potass ium

Sodium

Helminth egg count

P r o t o z o a

.-

L

8

8

- ** *

* * * 8 *

* * * * M i n i s t r y of A g r i c u l t u r e , Food and F i s h e r i e s London (1977). For t e s t 16 and 17,

S/NO. I

1.

2.

3 0

4 . 5. 6.

70 8 . 9.

10.

11.

12.

13.

14,

P a r a s i t o l o g y , Crop S c i e n c e a l d S o i l Sc i ence .

The e x p e r i n e n t a l area is t h e U n i ~ s r s i t y of S i g e r i a ,

wor!<s, l o c s t z d a t t h e S o u t h - a s s t e r n end o f Xsukka c a a p u s

soms 500 c z t r e s f r o a t h e j u i o r s t a f f q u a r t a r s , compr i s s a

z a t i o n ponds.

d s s c e v a t e r i r r i g s t i o n i z t h e area a round t h e t r a a t m z t

( 5 , 1 . The l a i i d undzr c a l t i v a t i o n s x t a a d s u? t o - -

tLs bun& of t h e ponds and c o v e r s l a n d a l o o g t h ? e f f l u e z t

c o u r s e s . The t o t a l a r e a under c u l t i v a t i o n i s e s t i m a t e d as 4 - 6

The sys tem o f i r r i g a t i o n a d o y t e d i s t h s c o r r u g a t i o n

v e r s i o n o f fu r row i r r i g a t i o n (F ig . 4). Wastewater is conveyed

- from t h e t r e a t m e n t works t o t h e c o r r u g a t i o n by g r a v i t y t h rough

temporary d i v e r s i o n s and by d i r e c t l i f t i n g o f was t ewa te r from

,he s o u r c e J i t h b u c k e t s . The main c r o p grown d u r i n g t h e s e a s o n

is amaranthus SPP. which is p o p u l a r l y known as ' g r e e n t . O t h e r

Wastewater Sampling p t ~

Soil Sampl ing P t s

V e g e t a b l e Sampling Pts

XO* are approximate Pts

lntormediate 11 1 effluent

S T A B 1 L I Z A T I O N ' = 3

P O N D 2

=I

=2

I FIG. 3'- SCHEMATIC DIAGRAM OF SAMPLING POINTS '

Fig 4: P r q a r e d c o r r u g z t i o n s rssdg f o r a n s r s n f h s s

seedlings.

v e g e t a j l e c r o p s gro ra are garden egg and f l u t e d punpkin

( t e l f a i r i a o c c i d e n t a l i s ) . Figures 5a a n d 5 b s h o w viesrs of

d i f f e r a n t s tages of a n a r a n t h u s p r o d u c t i o n a t t h e site d u r i r 3

t h e seak c u l t i v a t i o r p e r i o d . Oth2r food c r o p s s ~ c h as

c a s s x v a , yams, inel lon, etc. are c u l t i v a t e d in the r a i n y

s e a s o n at t h 2 sit; x i t h o - ~ t i r r i z a t i o n ( f i g ~ r ~ s 5 a m d b),

C1' A::? 2zsa m<;r st:?: is t . ; $ r z f ~ r e uzdar l c t i -72 c ~ o ? pro?uct!.o?

a l l y e a r rc~und.

F i g 5b:- L Xrjar,,,,ds c u l t i v a t i o n on t h e bund-of the ponds. O n t h e r i g h t i s Treatment Pond 1; on t h e l e f t i s T r e a t a e n t Pond 2. A t t h s f o r e g o m d i s a s e x e r d i s c h a r g i s g t h e i n t e r m e d i a t e e fT luen t from Fond 1 t o Poad 2.

F i g 6b.-

52

3.2. EVALUATIOH OF ;iASTEdATER CHARACTERISTICS

3.2.1. Sampling P o s i t i o n s and Frequsncy.

The sampl ing p o s i t i o n s f o r t h e wastewater examinat ion

a r e shown i n f i g u r e 3. The f i r s t sampl ing p o s i t i o n (I) is

a t t h e e n t r a n c e i n t o t h e f i r s t s t a b i l i z a t i o n pond where t h e

wastewater from t h e pr imary t r e a t m e n t ( : h e r e a f t e r r e f e r e d

t o a s t h e i n f l u e n t t o t h e s t a b i l i z a t i o n t r e a t m e n t sys tem)

i s r e c e i v e d i n t o , the f i r s t s t a b i l i z a t i o n pond (Pond 1 ) f o r

t h e secondary t r ea tmen t . The second sampl ing p o s i t i o n (11)

i s t h e e f f l u e n t from Pond I t o Pond 2 : h e r e a f t e r r e f e r e d t o

as t h e i n t e r m e d i a t e e f f l u e n t , wh i l e t h e t h i r d sampling

p o s i t i o n (111) r e p r e s e n t s t h e ou t f low from pond 2 which is

a l s o t h e f i n a l e f f l u e n t from t h e t r e a t m e n t ponds unto farm

l a n d s . The f o u r t h sampl ing p o s i t i o n (IV) is a t t h e o f f i c e o f

t h e s t a f f o f t h e t r e a t m e n t works and is t h e w a t e r ( t a p wa te r )

from t h e w a t e r d i s t r i b u t i o n system of t h e campus. The sampling

d a t e s and f requency a r e shown i n t a b l e 9

T A B U 9 sampl ing schedu le of t h e wastewater f o r examinat ion

DATS OF s AMPLING

7 - 1 2 - 88 18 - 1 - 89

b

27 - 2 - 8 9

16 - 3 - 89

TIME OF SAMPLING

9.00 - 10.o0 a.m.

9.00 - 10.00 a.m.

9.00 - 10.00 a.m.

9.00 - 10.00 a.m.

DATd OF COMMENCEMdNT

OF TESTS

7 - 12 - 88 18 - 1 - 89

2 7 - 2 - 89

1 6 - 3 - 89

DATE OF COMPLETION OF TZSTS

13 - I - 89

6 - 3 - 8 9

21 - 3 - 8 9

3.2.2. Laboratory Tests .

The l abo ra to ry t e s t s c a r r i e d out i n t h e s tudy a s we l l

as t h e procedures adopted f o r t h e t e s t s a r e i n d i c a t e d i n

t a b l e 8, A l l samples were preserved i n t h e r e f r i g e r a t o r

dur ing each examinat i o n period.

The temperature read ings f o r January were t aken a f t e r

t h e samples had s t ayed over n igh t i n t h e r e f r i g e r a t o r .

Consequently o n l y - t h e February and March 1989 va lues were

accep ted f o r ana ly s i s . The s tandard p l a t e count t e s t s were

0 on ly approximates because t h e i ncuba to r temperature was 37 C

i n s t e a d of 35 + 0.5'~ and t h e i n c u b a t o r s used d i d not f unc t i on

very well. The t o t a l s a l t concen t r a t i ons i n p a r t s per m i l l i o n

(ppm o r mg/l) were r e a d from f i g u r e I us ing t h e e l e c t r i c a l

c o n d u c t i v i t y values. The sodium adso rp t i on r a t i o (SAR) and

t h e exchangeable s o d i m percentage were determined from F i g 7, ++ us ing t h e concen t r a t i ons of Calcium and Magnessium (Ca + ~ g + + )

and t hose o f sodium.

Figure '7 . Noniogro~n for clctcr~iii~ii~ig, tlir SAR value of irri- gatio~i watcr micl for cstilnating the corrcspollclilig ESP valuc of a soil

. cquilibratcd with this watcr.

Source : S h a i n b e r g and O s t e r (1978).

55

3.3. EVXLUI\T~HG T 33 ZFFECT OF '/IABT"LUATER IRRIGATION

ON SOIL P30P32TIES.

Both f i e l d a n d l a b o r a t o r y t e s t s were c a r r i e d o u t t o

e v a l u a t e t h e e f f e c t o f was t ewa te r i r r i g a t i o n o n t h e s o i l . The

t e s t s were c a r r i e d o u t between A p r i l arid June I989 e x c e p t f o r

s i t e I on which t h e tests of t h e p h y s i c a l p r o p e r t i e s had been

c a r r i e d o u t e a r l i e r i n J m u a r y 1989.

Sampl ing po i r i t s were s e l e c t e d i n such a way t h a t t h e y

were f a i r l y d i s t r i b u t e d a c r o s s t h e a r e a under s t u d y . They were

e i g h t (8) s i t e s s e l e c t e d from ' the a r e a under was t ewa te r i r r i g a -

t i o n and two o t h e r s i t e s ( s i t e s 9 and 10) s e l e c t e d from a n a r e a

n o t s u b j e c t e d t o v a s t e u a t e r i r r i g a t i o n but w i t h i n t h e g e n e r a l

a r e a of t h e s t u d y . l h a s e two s i t e s were s e l e c t e d t o s e r v e as

c o n t r o l s t o t h e p o s s i b l e e f f e c t s was tewater i r r i g a t i o n h a s on

t h o s e p o r t i o n s o f t be a r e a s u b j e c t e d t o i r r i g a t i o n . T a b l e 10

g i v e s t h e d e t a i l s of t i e s i t e s s e l e c t e d f o r t h e s o i l t e s t s . While

t a b l e 1 1 g i v e s a f u l l d o c u m c n t a t l ~ ~ r ~ . "11 $>-: t o ~ ' , ~ c a r r i e d o u t

and t h e p rocedure adop ted f o r each.

Fd C 0 + 0 0 Y 0 rn'd + u +ti r n h ( D P

m I r-

57.

T a b l e 11: Methods used f o r t h e D e t e r m i n a t i o n of s o i l

p r o p e r t i e s .

PROPERTY

F i e l d C a p a c i t y

Pry Bulk 3 e n s i t y

P o r o s i t y

T e x t u r e

I n f i l t r a t i o n

E l e c t r i c a l c o n d u c t i v i t y

C a t i o n Exchange c a p a c i t y

N i t r o g e n

Phosphorus

Po ta s s ium

S o d i urn

Calc i um

Magnessium

S A R

E S P

NATURE OF PROPL3Tl

P h i s i c a l

p h y s i c a l

P h y s i c a l

P h y s i c a l

P h y s i c a l

Chemical

Chemical

Chemical

Chemical

Chemical

Chemical

Chemical

Chemical

Chemical

Chemical

Chemical

PIGTHODOLOGY

G r a v i m e t r i c method

G r a v i m e t r i c method

G r a v i m e t r i c

Bouyocus method

Double r i n g k n f i l t r o m e t e r

pH me te r

C o n d u c t i v i t y me te r

Ammonium s a t u r a t i o n n e t hod

K j e l d a h l method

Vanadomolybdate a e t h o d

Flame photometry

Flame photometry

Complexometric T i t r a t i o n

Complexometric T i t r a t i o n

From Nomogram

From Nomogram

3.4 EVALUATING THE EFFECT OF 'iIASTE'AXTZil IRRIGATION

ON TAYE IXIIGATED VZGiiTABLE ( MIA:IANTHUS SPP . ) The e v a l u a t i o n and a n a l y s i s o f t h e e f f e c t o f was te-

w a t e r on i r r i g a t e d v e g e t a b l e c o n s i d e r e d ma in ly t h e e f f e c t

of i r r i g a t i o n was t ewa te r on t h e m i n e r a l compos i t i on o f

a m a r a n t h u s SPP.

3.4.7. Sampl ing

Twelve samples o f amaranthus SPP v e g e t a b l e were o b t a i n e d

f o r t h e a n a l y s i s . Nine samples were o b t a i n e d from p r o d u c t s

grown under was t ewa te r t r e a t m e n t i n t h e g e n e r a l a r e a o f t h e

t r e a t m e n t works ( f i g 3 ) , t h r e e from e a c h of t h e t h r e e l o c a t i o n s

%..

o f w a s t e w a t e r 2onds e v a l u a t e d . The r ema in ing t h r e e samples

were o b t a i n e d from v e g e t a b l e grown w i t h p o t a b l e w a t e r , farm

y a r d manure and/or f e r t i l i z e r a t l o c a t i o n s d i f f e r e n t from t h e

s t u d y a r e a b u t w i t h i n t h e U n i v e r s i t y town o f Nsukka. I n

a d d i t i o n , v e g e t a b l e ( amaran thus SPP) was grown i n t h e s t u d y

- a r e a and i r r i g a t e d w i t h p o t a b l e t a p w a t e r ( f i g 8 ) . A l l s amples

were o b t a i n e d from t h e f i r s t c u t t i n g of t h e l u s c i o u s s t a n d s

(March - May 1989). Vege tab le s amples were o b t a i n e d w i t h i n a

p e r i o d of one veek and t h e sampl ing t i m e was u s u a l l y between

7.00 a.m. and 8.00 a.m.

b

Fig 8: Amaranthus SPP grown in the study area

and irrigated with only potable tap

water.

3.4.2. The Mineral A n a l y s i s of

The samples ob ta ined were I

s ampl ing a t a tempera ture o f 60

60 . Vegetable Samples.

d r i e d i n t h e oven a f t e r each

+ 4 ' ~ f o r a p e r i o d of - approx imate ly twelve hours . T h e r e a f t e r t h e samples were

m i l l e d i n a hammer m i l l i n t o f i n e powdery form. Tab le 12

g i v e s t h e e l ements a n a l y s e d and t h e procedure adopted f o r

each.

Tab le 12:- Methods used f o r t h e m i n e r a l a n a l y s i s o f

amaranthus SPP. samples.

Element

Ni t rogen

Phosphorus

Potassium

C a l c i urn

Nagnessium

Methodology -- - - - - - -

K j e l d a h l Method

Phosphorus - Molybdate Method

Flame Photometry

3. D. T. A . Method

E o D. T. A . Method

Sodium I Flame Photometry sir.

CHXPTZR FOUR

R X S U L T S .

CHARACTZ3ISTICS.

The t e m p e r a t u r e , p 3 and t o t a l s o l i d s of t h e was t ewa te r

sampled a t t h r e e l o c a t i o n s a l o n g t h e t r e a t m e n t gonds and o f

t h e t a p wa te r f o r t h e s t u d y e a r i o d ( ~ e c e r n b e r 1988 t o March

1989) are shown i n t a b l e 13. Tempera tu re was lowes t i n

J anua ry b u t d i d n o t v a r y be tween l e b r u a r y and March. The

i n f l u e n t t e m p e r a t u r e was c o n s i s t e n t l y ( t h o u g h s l i g h t l y ) h i g h e r

t h a n t h o s e a t t h e o t h e r two l o c a t i o n s . The was tewater pH was

c o n s i s t e n t l y h i g h e r t h a n t h a t o f t h e t a p water . There were

d i f f e r e n c e s i n p a among t h e l o c a t i o n s f o r e a c h month b u t t h e r e

was no c o n s i s t e n t p a t t e r n . T o t a l s o l i d s was h i g h e s t i n t h e

i n f l u e n t i n a l l t h e months , w h i l e t h e i n t e r m e d i a t e and f i n a l

e f f l u e n t s d i d n o t d i f f e r much e x c e p t i n Feb rua ry when t h e f i n a l

e f f l u e n t was v e r y h igh . Compared w i t h t h e t a p w a t e r , average

of t o t a l s o l i d s of w a s t e w a t e r . was f o u r t e e n f o l d s h i g h e r ,

Four b i o l o g i c a l c h a r a c t e r i s t i c s o f was t ewa te r a r e shown

i n t a b l e 14. The BOD 5

months,. Though on t h e

e f f l u e n t and t h e f i n a l

w a s h i g h s s t i n t h e i n f l u e n t f o r a l l t h e

a v e r a g e , t h e BOD . f o r t h e i n t e r m e d i a t e 5

e f f l u e n t were t h e same, t h e y v a r i e d on

t ' t ' 0 0 n o P w n CT t'. I-. C 0 P P

I-. I 0

a

0 n : 2 m m 1 CI a FI I-. m e e m I-. P pl . CT

m

m -2 b P c

2 rt -. S w CT r . 0 P

1-1

111:

1

''1 F..

e w I-

m b -2

P c e * -.

I-. 0

P

n I::

monthly b a s i s wi thou t any c o n s i s t e n t t r e n d . The BOD f o r 5

t a p water f o r ~ e c e m b b r was much h i g h e r than f o r January and

Narch which were very smal l . On t h e whole, t h e BOD f o r 5 . t h e wastewater was h i g h e r t h a n f o r t h e t a p water . The

s t a n d a r d p l a t e count f o r t h e wastewater was h i g h e r t h a n t h a t

f o r t h e t a p wa te r throughout t h e per iod . There was however

no c o n s i s t e n t t r e n d w i t h t h e wastewater l o c a t i o n s . Helminth

e g g s were c o n s i s t e n t l y p r e s e n t on ly i n t h e i n f l u e n t waste-

w a t e r i n c o n c e n t r a t i o n s r a n g i n g from 20 p e r l i t r e t o 60 p e r

l i t r e . P ro tozoa o o c y s t s were found i n two out o f t h e f o u r

sampl ing times i n c o n c e n t r a t i o n s of 20 p e r l i t r e each t ime

and only i n t h e i n f l u e n t .

The chemical c h a r a c t e r i s t i c s of t h e samples w i t h i n t h e

p e r i o d a r e shown i n t a b l e 15. The e l e c t r i c a l c o n d u c t i v i t y

(LC.), from which t h e t o t a l s a l t was determined, was con-

s i s t e n t l y h i g h e r i n t h e wastewater t h a n i n t h e t a p wa te r and

c o n s i s t e n t l y h i g h e s t i n t h e i n f l u e n t wastewater . The Z.C. f o r

- t h e i n t e r m e d i a t e and f i n a l e f f l u e n t s were s i m i l a r excep t f o r

February when t h e f i n a l e f f l u e n t w a s much higher . On t h e

a v e r a g e , t h e n i t r a t e c o n t e n t of t a p wa te r was h i g h e r t h a n t h o s e

of t h e wastewater . J anuary and February n i t r a t e c o n c e n t r a t i o n s

2

2 2 0 UI 05 c . ~ ; ? $ ~ p p \ . n p p g g .l \,a .F - m . F - m ca N 0 V l o 0 Vl O N - 03 &- &-

W

0 N O 3 - Oa L - C U l O N W O O E m

W W a 2 m 2 A 2 V l N V l N N w a p p V l U ) . . . . . 0 I I$ o m o c - O ' > b L ; I w u l o o o w w W . I O O \ i l " m

o f t a p water were t h e same. The n i t r a ~ e concencrabAun

of t h e i n f l u e n t was c o n s i s t e n t l y h i g h e r t h a n t h o s e o f t h e

- i n t e r m e d i a t e and f i n a l e f f l u e n t . Phospha te c o n c e n t r a t i o n

\

i n t h e w a s t e w a t e r was c o n s i s t e n t l y h i g h e r t h a n t h a t o f

t h e t a p wa te r . Phosphate was h i g h e s t i n t h e i n f l u e n t

-- -- s l igh t ly_-decreas ing- f rom- i - n f l u e n t - - t o -- -- f i n a l -- --- - . e f f l u e n t --- .- f o r t h e -. -

months o f J a n u a r y , F e b r u a r y a n d Narch. The r e v e r s e was t h e

c a s e f o r December 1988, C h l o r i d e c o n c e n t r a t i o n w a s h i g h e s t

among t h e a n i o n s i n t h e was t ewa te r and i t s v a l u e s were

a p p r o x i m a t e l y similar f o r t h e t h r e e l o c a t i o n s . The c h l o r i d e

i n t h e was t ewa te r was on t h e a v e r a g e 27 t i m e s t h a t i n t h e

t a p wa te r . The c a t i o n s - ca l c ium, Magnessium, Sodium and

Po ta s s ium - were c o n s i s t e n t l y very low i n t h e t a p wa te r , They

were however h i g h i n t h e w a s t e w a t e r w i t h t h e i n f l u e n t

h a v i n g t h e h i g h e s t . Magnessium d e c r e a s e d from t h e i n f l u e n t t o w h i l e

t h e f i n a l e f f l u e n t L ~ a l c i u m , Sodium a n d Potass ium d i d n o t show

any c o n s i s t e n t t r e n d . Among t h e c a t i o n s i n t h e was t ewa te r t h e

- c o n c e n t r a t i o n o f sodium was h i g h e s t . The SAR and ESP were

c o n s i s t e n t l y low wi thou t any t r e n d among t h e l o c a t i o n s .

T a b l e 16 shows a compara t ive a n a l y s i s o f t h e cha rac -

t e r i s t i c s o f t h e was t ewa te r o f t h e t h r e e l o c a t i o n s i n t h e

t r e a t m e n t works w i t h t h o s e f o r t a p wa te r . Except f o r t h e L

n i t r a t e c o n c e n t r a t i o n , a l l t h e o t h e r c h a r a c t e r i s t i c s were

h i g h e r f o r a l l t h e l e v e l s o f was t ewa te r t h a n t h o s e f o r t a p

wa te r .

T a b l e 17 is t h e Duncan New ~ u l t i p l e Range T e s t a n a l y s i s

o f t h e c h a r a c t e r i s t i c s by l o c a t i o n s . Except f o r n i t r a t e a n d

s u l p h a t e , t h e r e were s i g n i f i c a n t d i f f e r e n c e s between t h e

means o f t h e t a p water and a t l e a s t one o f t h e l o c a t i o n s of

,, t h e was t ewa te r f o r a l l t h e o t h e r c h a r a c t e r i s t i c s . The BOD 5

a n d t h e E.C. f o r t h e i n f l u e n t were s t a t i s t i c a l l y s i g n i f i c a n t l y

d i f f e r e n t from t h o s e o f t h e i n t e r m e d i a t e e f f l u e n t and t h e

f i n a l e f f l u e n t . The i n f l u e n t t o t a l s o l i d s was s i g n i f i c a n t l y

d i f f e r e n t from t h a t o f t h e i n t e r m e d i a t e e f f l u e n t bu t was t h e

same w i t h t h a t f o r t h e f i n a l e f f l u e n t . The pH, phospha te , . c h l o r i d e , h a r d n e s s , t h e c a t i o n s and t h e SAR had means t h a t

were s t a t i s t i c a l l y t h e same f o r t h e t h r e e l o c a t i o n s o f t h e

was t ewa te r .

T a b l e 16: Comparat ive A n a l y s i s of the Means of Wastewater

c h a r a c t e r i s t i c s w i t h Tap Ya te r .

C h a r a c t e r i s t i c

Tempera ture

pH

T o t a l s o l i d s -- -

S t a n d a r d p l a t e coun t

Helminth e g g

P r o t o z o a c y s t

E l e c t r i c a l Conduct i v l - t y

T o t a l s a l t

N i t r a t e

Phospha te

S u l p h a t e

C h l o r i d e

Calcium

Magnessiurn

Hardness

Po ta s s ium

S o d i urn

S A R

Zornparative v a l u e s o f * L o c a t i o n s k

I -- - -

1.025

1.479

17 653 . -

12.549

594.49 Very l a r g e

Very l a r g e

25.271

14

0 553 12.301

27 5F3 29.896

2 725 4.070

2.788

21.109

25.110

6.000

h t a p us

TT

0 995 7.422

I I -281 . -..- -

7 707

562.99 0

0

19.271 11

0 375 6.781

74.767

26.434

2.339

3.423

3.151 18.609

20.83

5.600

*The v a l u e s f o r l o c a t i o n s I , TT and ,IT? were d i v i d e d by t h e

c o r r e s p o n d i n g v a l u e s f o r l o c a t i o n I V ( t a p w a t e r ) t o g e t t h e

v a l u e s i n t h e t a b l e . b

68.

FsS

le

17: Y

ean

se

pa

ratio

n o

f la

ste

wa

ter a

nd

Tap

wa

ter

ch

ab

ac

teris

tics

by lo

ca

tion

__

__

---

-- by

the

D

un

can's

New

M

ultip

le ra

ns

e

tes

t at 5%

lev

el,

.

m

Hean

s

' T.S. (33%

o f th

e

Ele

me

nts.

- Z

.yo4

so2; PO';

c1-

ca ~g

Ha

rdn

ess

Lo

ca

tion

I

- In

flue

nt

I I -

- In

term

ed

iate

efflu

en

t

I11 -

- F

ina

l efflu

en

t

Tap

:d

ater

:lean

s fo

llow

ed

by

the

same

lette

r a

re

sta

tistic

ally

the

same,

wh

ile

ne

an

s follo

we

d b

y

diffe

ren

t lette

rs

are

sta

tistic

ally

sig

nific

an

tly

a

diffs

nt a

t 5% le

ve

l of

pro

ba

bility

as

by

th

e DNHRT.

4.2. SOIL PBOP~RTIZS

4.2.7, The P h y s i c a l : P r o p e r t i e s

- Table 18 shows t h e p h y s i c a l

of t h e S o i l .

p r o p e r t i e s of t h e s o i l from

t h e v a r i o u s sample l o c a t i o n s .

The mean of t h e f i e l d c a p a c i t y (F.C.) f o r IOcrn, 20cm,

and 40cm d e p t h s f o r t h e i r r i g a t e d a r e a were co r respond ing ly

h i g h e r t h a n t h o s e from t h e c e n t r a l a r e a , The h i g h e s t va lue

f o r t h e IOcm d e p t h of 16.22% from s i t e 5 was approx imate ly

t w i c e t h e lowes t of 7.89% from s i t e I . A t t h e 2Ocm and 40cm

d e p t h s t h e h i g h e s t F.C. were bo th from s i t e 7 whi le t h e lowest

were b o t h from s i t e 3. For t h e c o n t r o l l o c a t i o n s s i t e 9 had

= c o n s i s t e n t l y h i g h e r v a l u e s of F.C. t h a n s i t e 10 f o r t h e t h r e e

dep ths . The b u l k d e n s i t i e s a t 0 - I5cm and 20 - 35cm d e p t s

were lower f o r t h e i r r i g a t e d a r e a t h a n t h e c o n t r o l a rea . The

p o r o s i t i e s were h i g h e r a t b o t h d e p t h s (0 - I5cm and 20 - 35 cm)

f o r t h e i r r i g a t e d a r e a ,

The t . e x t u r a 1 c l a s s i f i c a t i o n of t h e a r e a i s predominant ly

- s a n d y , r a n g i n g from s a n d , loamy sand , sandy loam t o sandy c l a y

loam. The c o n s t a n t i n f i l t r a t i o n r a t e r e s u l t s d i d not show any

c o n s i s t e n t t r e n d . The i n f i l t r a t i o n r a t e s were i n g e n e r a l very

h i g h and o n l y r e s u l t s of t e s t s t h a t l a s t e d up t o 90 minutes o r

4,2.2, Chemical P r o p e r t i e s o f t h e s o i l .

Tab le 19 g i v e s t h e chemical a n a l y s i s of t h e s o i l proper-

t i e s examined. A 1 1 t h e chemical p r o p e r t i e s examined, except

t h e pH, were h i g h e r i n t h e i r r i g a t e d a r e a t h a n t h e non-

i r r i g a t e d c o n t r o l a r e a . Tab le 20 g i v e s t h e mean and t h e

s t a n d a r d d e v i a t i o n of t h e s o i l chemical p r o p e r t i e s as i n f l u e n c e d - - . - - - - -

by sewage t r ea tmen t . The pe rcen tage d i f f e r e n c e s i n d i c a t e

i n c r e a s e s of t h e s e p r o p e r t i e s i n t h e i r r i g a t e d a r e a compared

t o t h e c o n t r o l but a d j a c e n t a rea . Of t h e s i x e l ements d e t e r -

mined, t h e c o n c e n t r a t i o n o f n i t r o g e n was t h e h i g h e s t , i n both

t h e i r r i g a t e d and i n t h e c o n t r o l b u t a d j a c e n t a r e a whi le t o t a l

phosphorus was t h e lowes t .

From t h e chemical a n a l y s i s , l o c a t i o n 5 had t h e h i g h e s t

c o n c e n t r a t i o n o f most o f t h e e l ements examined fo l lowed by

l o c a t i o n 4. The lowes t i n t h e i r r i g a t e d a r e a was from l o c a t i o n

12.37 113-21

12.56 j 12-98

10.20 1?.88

1,420 1.238

1.518 1.371

46.4 51.0

42.7 48.3

84-16 84.0

;.o 0

15.82 16.0

sandy S

an

dy

loam loam

4.545

43.6 41.8 84.56 1.44

14.00 toady

sand

90

1 7-59

45.5 42.0

-88.72 0

11.28

mam

y sa

nd

Percen

t1

Percen

ts

Percen

tc

Overall

Con

stant

ramre

~y

:

cn

em

ca

L p

ro-p

erries or soils

rrom ergnt

rae

atlo

ns

irr

iga

ted

w

ith Y

asteu

ater

comp

ared w

ith

-,

two

so

il samples from

ra

ad

jacen

t rrer.

Prop

erty -3-11

t Locations

wit1

1 I

sd area

5 3.20

150 8.750

105-996 0.2648 5.344

6

0.717b 0.925 o.3E3 7 .O

. .

PE

4.60 E

lbtttita

l Co

nd

uctiv

ity

Um

hos#cm

85

Ca

tion

Exch

ange

Capacity

Meg/100g 3.775

W

3';.1;75 ,

It

0.058~

1 . p r o p e r t i e s as i n f l u e n c e d by sewage t r ea tmen t .

P r o p e r t y

N i t r o g e n

Phosphorus

Potass ium

Sodium

Calcium

Magnessium

S A R

ESP.

Mean

3.76

188

5.065

51.615

0.1138

0.2620

0.4947

1.011

0.363

0.825

0.186

C o n t r o l 1 S t d

e v i a t i o n

0

0.41

0.2298

0.3528

0

0.0152

0.01 70

0.0615

3.0792

0

0

' pe rcen tage Di f fe rence

L - 4.8 251

92

122

135

45

6

110

205

-17.5

-38

+Percen tage d i f f e r e n c e i n t h e means i s c a l c u l a t e d by

t h e equa t ion .

%D = (Treatment Mean - C o n t r o l mean) x 100% . . . . (2) C o n t r o l Mean

P o s i t i v e v a l u e s of p e r c e n t a g e d i f f e r e n c e show i n c r e a s e d

e f f e c f w h i l e n e ~ a t i v e v a l u e s show decreased e f f e c t due

t o wastewater t r e a t m e n t .

73 . . 4*3* TI-B HINZRAL CONPOSITION OF LEXVZS OF MARANTHUS SPP.

- The p e r f o r m m c e of . t h e v e g e t a b l e grown i n t h e s t u d y

- a r e a and i r r i g a t e d w i t h p o t a b l e t a p w a t e r was ve ry poor .

More t h a n h a l f of t h e p l a n t s , e i t h e r d i d n o t s u r v i v e t h e

t r a n s p l a n t i n g o r d i d n o t deve lop more t h a n t h e i r s e e d l i n g

s i z e s . Most of t i e s u r v i v o r s s t a r t e d f l o w e r i n g and f r u i t i n g

much e a r l i e r t h a n e x p e c t e d w i t h o u t t h e f u l l development o f

t h e v e g e t a b l e l e a v e s , Consequen t ly no d e t a i l e d m i n e r a l

a n a l y s i s o f t h e p r o d u c t s from t h i s c r o p p i n g was c a r r i e d o u t

b e c a u s e o f t h e growth performance.

The m i n e r a l compos i t i on o f t h e s a n p l e s a r e shown i n

t a b l e 21. Xnaranchus SPP l e a v e s sampled from o u t s i d e t h e s t u d y

a r e a have h i g h e r c o n c e n t r a t i o n s o f t h e p r o p e r t i e s examined

t h a n a l l t h e s a r n ~ l e s o b t a i n e d from t h e was t ewa te r i r r i g a t e d

a r e a , Except f o r ca l c ium t h a t showed s i g n i f i c a n t l y h i g h e r

c o n c e n t r a t i o n f o r two o f t h e t h r e e samples i r r i g a t e d w i t h t h e

i n f l u e n t , most of t h e c o n c e n t r a t i o n s o f t h e o t h e r ? r o p e r t i e s

' were s i m i l a r f o r a l l t h e samples from t h e i r r i g a t e d a r e a ,

T a b l e 22 g i v s s t h e Duncan New 1 4 u l t i p l e Range T e s t a n a l y s i s

f o r t h e m i n e r a l compos i t i on o f amaran thus SPP v e g e t a b l e by

l o c a t i o n w h i l e t a j l e 23 b r i n g s o u t t h e e l e m e n t s t h a t a r e

7.4.

T a b l e 21: M i n e r a l C o n t e n t s o f l e a v e s of amaranthus S p e c i e s

TREATMEN

I

I n f l u e n t

I1 - I n t e r - m e d i a t e

e f f l u e n t

I I1 - F i n a l

e f f l u e n t

grown on s o i l s i r r i g a t e d w i t h t h e was tewater

( i n f l u e n t ; . i n t e r m e d i a t e e f f l u e n t and f i n a l

e f f l u e n t ) and w i t h o r d i n a r y water .

SAMPUS

1

2

3

Nean

1

2

3

Mean

1

2

3

Ne a n

1

2

3 Mean

~~- -

PHOS- PHOaUS

%

0 75 0.63

0.55

0.643

0.66

0.63

0 59

0.627

0.59

0 53 0.31

0 . 477 0.70 0.63

0.70

0 677

POTASSIUM

%

1.5 1.4

1.4.

1 e43

1.2

1.6

1.2

1.33

1.5

1-3 1.5

1.43

1.8 2.4

1.4

2.03

MAGNESS I U P

L 0.24 0.18

0.15

0.19

0.24

0.30

0.30

0.28

0.58

0.18

0.15

0.303

0.30

0.37 0.46

0 . 377

75

T a j l e 22: The e f f e c t o f t r e a t m e n t

Yastewater l o c a t i o n and t a p wa te r on t h e

chemica l composi t ion of Amaranthus l e a v e s ,

Mean s e p a r a t i o n i n columns by Duncan's new

m u l t i p l e range t e s t 5% l e v e l ,

I = I n f l u e n t , ,I1 = I n t e r m e d i a t e e f f l u e n t , T I 1 . . = F i n a l e f f l u e n t

-- IS = Tap-water - - ( p l u s p o u l t r y manure and/or f e r t i l i z e r ) z -L

- -- . - Means f o l l o w e d by t h e sane a l p h a b e t a r e s t a t i s t i c a l l y the - -

s a n e , whi l e means fo l lowed by d i f f e r e n t a l p h a b e t s a r e

s t a t i s t i c a l l y d i f f e r e n t a t 5% l e v e l of p r o b a b i l i t y as by

Table 23: Elements and s t a t i s t i c a l D i f f e r e n c e s between t a p

wa te r and t h e d i f f e r e n t l o c a t i o n s ( t r e a t m e n t s ) o f wastewater .

Treatment

I n f l u e n t

I n t e r m e d i a t e -I-- ar I l u e n t

F i n a l E f f l u e n t

Minera l s t h a t show s t a t i s t i c a l d i f f e r e n c e between t h e treatmenk means.

N , Ca i N, P , C a , Na

s t a t i s t i c a l l y d i f f e r e n t between t h e t a p water t reatment

and d i f f . e ren t t r e a t h e n t s of t h e wastewater. The means of

a l l t h e p r o p e r t i e s examined a r e s t a t i ' s t i c a l l y t h e same

b f o r t h e t h r e e l o c a t i o n s of wastewater used.

CHAPTER FIVE

D I S C U ~ S I O N ,

5.1 T83 QUALITY OF TI33 UNIVERSITY OF NIGZRIA,

NSL'KKX 'XXSTX';JATE3 FOR IRRIGATION.

Zxzep t f o r n i t r a t e , t h e d i f f e r e n t c o n s t i t u e n t s o f t h e

w a s t e w a t e r f r o n t h e U n i v e r s i t y of N i g e r i a , J sukka t r e a t m e n t

ponds were found t o be c o n s i s t e n t l y h i g h e r t h a n t h o s e o f t h e

t a p w a t a r ( t a b l e A3 - 15) . The m u l t i p l e r a n g e t e s t ( t a b l e 17 )

shows t h a t f o r most o f t h e c h a r a c t e r i s t i c s , t h e r e is s i g n i f i c a n t

d i f f e r e x e be tween t h e was t ewa te r l o c a t i o n s and t h e t a p w a t e r

examined. 3 a s e d on t h e above r e s u l t s and t h e f a c t t h a t t h e

t a p watlr a n a l y s e d i n t h i s s t u d y is c o n s i d e r e d p o t a b l e , t h e

was t ewafe r f r o n t h e U n i v e r s i t y t r e a t m e n t ponds is no t p o t a b l e . -F

The n o s t i m p o r t a n t c r i t e r i a f o r e v a l u a t i n g q u a l i t y o f

w a t e r f 3 r . i r r i g a t i o n p u r p o s e s a r e t h e s a l i n i t y and s o d i c i t y

l e v e l s . The a n a l y s i s o f t h e t h r e e l o c a t i o n s o f was tewater

i n t h i s s t u d y showed h i g h s a l i n i t y l e v e l a t t h e t h r e e l o c a -

t i o n s , T h i s means t h a t t h e p r o b a b i l i t y f o r s a l i n i t y h a z a r d

* is h igh . The u s e of t h i s s o u r c e of w a s t e w a t e r f o r i r r i g a t i o n

i s l i k e l y t o i n c r e a s e t h e sa l t c o n c e n t r a t i o n i n t h e s o i l

s o l u t i o n . T h i s i s s u p p o r t e d by t h e r e s u l t o f t h e chemica l

a n a l y s i s of t h e s o i l s i n t h e i r r i g a t e d a r e a ( t a b l e 1 9 ) which

shoved c o n s i s t e n t l y h i g h e r s a l t c o n c e n t r a t i o n a t t h e l o c a t i o n s

b

78

of was t ewa te r t r e a t m e n t even though t h e s a l t c o n c e n t r a t i o n s

a r e n o t a t t o x i c l e v e l . S a l i n i t y problem from i r r i g a t i o n

w a t e r be s i g n i f i c a n t i n a r e a s where t h e w a t e r t a b l e i s h i g h ,

o r where t h e s o i l i s a l r e a d y s a l i n e o r i n a r i d r e g i o n s . I n

t h e s t u d y a r e a as i n most p a r t s o f Msukka, t h e w a t e r t a b l e

is very low ( o v e r 1CO x e t r e s below t h e ground) ; t h e low pH

a n d e l e c t r i c a l c o n d u c t i v i t y v a l u e s o f t h e s o i l o f t h e s t u d y

area show t h a t t h e s o i l s a r e n o t s a l i n e ; and t h e a r e a under

s t u d y i s n e i t h e r a r i d n o r s emi -a r id . Consequent ly , a l t h o u g h

t h e i n f l u e n t / e f f l u e n t s o f t h e U n i v e r s i t y o f N i g e r i a , Nsukka

was t ewa te r t r e a t n e n t x o r k s nay be c o n s i d e r e d s a l i n e , t h e

e f f e c t i v e s a l i n i t y hazard due t o i ts use a s i r r i g a t i o n w a t e r

i s low.

The s o d i c i t g l e v e l s i n d i c a t e d by t h e sodium a d s o r p t i o n

r a t i o (SAR) were low f o r t h e t h r e e l o c a t i o n s of t h e was tewater .

The p r o b a b i l i t y of sodium h a z a r d as a r e s u l t o f t h e a p p l i c a t i o n

of t h i s was t ewa te r f o r i r r i g a t i o n is t h e r e f o r e low. The s o i l

t e x t u r e i n t h e s t u d y a r e a h a s a low c o n t e n t o f c l a y which

- makes t h e d e f l o c u l a t i o n e f f e c t o f sodium c o n c e n t r a t i o n

n e g l i ' g i b l e . The combined e f f e c t of s a l i n i t y h a z a r d and.

sodium h a z a r d as r e f l e c t e d i n f i g . 2 shows t h a t t h e Un ive r s i t y

of N i g e r i a , 8 sukka wastev.gater i s s u i t a b l e f o r i r r i g a t i o n b

p u r p o s e s i n t h i s r e g a r d .

The most i m o o r t a n t c r i t e r i a f o r t h e d e t e r m i n a t i o n of

t h e s u i t a b i l i t y o f w a s t e x a t e r f o r i r r i g a t i o n depend on t h e

c o m p o s i t i o n o f v i a b l e p a t h c g e n i c o rgan i sms i n t h e was t ewa te r

( S h u v a l e t a1 1986). Thzse o rgan i sms i n c l u d e b a c t e r i a ,

v i r u s e s , h e l m i n t h s and 2,-otazoa v h i c h a r e o f t e n r e s p o n s i b l e

f o r t h e t r a n s m i s s i o n of d i f f e r e n t d i s e a s e s on ep idemic s c a l e .

S h u v a l e t a1 (1986) recommended t h a t was tewater f o r un res -

t r i c t e d i r r i g a t i o n s h o u l d not c o n t a i n more t h a n 'one v i a b l e - .

h e l m i n t h e g g ( a s c a r i s , t r i c h u r i s , hookworm) p e r l i t r e and n o t

g r e a t e r t h a n 1,000 f a e c a l Co l i fo rm (3 ~ o l i ) b a c t e r i a p e r

'100~1. The i n f l u e n t was t eVd3 te r c o n s i s t e n t l y had a high

c o n c e n t r a t i o n o f he l rn in th e z g s r a n g i n g from 20 t o 60 p e r l i t r e

d u r i n g t h e s t u d y p e r i o d . T h i s i s 2000 - 6000% above a l l o w a b l e

naxinun. E x c r e t e d h e l n i n t h s a c c o r d i ~ g t o Shuva l e t a1 (1986)

c a n be c l a s s i f i e d i n t o s e v e n t e e n t y p e s a l l o f which have man

as one o r t h e o n l y h o s t . D i s e a s e s c a u s e d by h e l m i n t h s a r e as

many as t h e i r t y 2 e s and i n c l u d e a s c a r i a s i s , hookworm,

t r i c h u r i a s i s , s t r o n g y l o i d i a s i s , e t c , These d i s e a s e s o c c u r

i n . t h e f o r m s of mechan ica l o b s t r u c t i o n -by round worms, anaemia

by hookworms, abdominal p a i z s , damage t o l i v e r o r l u n g s , e t c

( S h u v a l e t a l , 1986) . Of a i l t h e pa thogens , h e l m i n t h s

b

c o n s t i t u t e t h e h i g h e s t r i s k i n w a s t e w a t e r i r r i g a t i o n , The

i n f l u e n t was t ewa te r i n t o pond I i s t h e r e f o r e a dangerous

s o u r c e of w a t e r f o r i r r i g a t i o n . The p r o b a b i l i t y of t h i s

i n f l u e n t t r s n s a i t t i n g h e l m i n t h d i s e a s e s when used as i r r i g a -

t i o n w a t e r i s ve ry high. C u r r e n t l y , t h e p r a c t i c e i n t h e

s t u d y a r e a is t o l i f t was t ewa te r f o r i r r i g a t i o n from t h e

n e a r e s t p a r t of t h e ponds ( i n c l u d i n g t h i s i n f l u e z t ) t o t h e

i r r i g a t e d l a n d .

The i n t e r ~ e d i a t e e f f l u e n t and t h e f i n a l e f f l u e n t were

o n t h e o t h e r hand c o n s i s t e n t l y f r e e o f any h e l m i n t h egg f o r

t h e p e r i o d o f t h e s tudy . T h i s means t h a t t h e t r e a t m e n t i n

Pond 1 a c c o n p i i s h e d comple te removal of n e l m i n t h eggs. Hence

t h e u s e of t h e was t ewa te r i n Pond 2 and t h e f i n a l e f f l u e n t

f o r i r r i g a t i o n is s a f e w h i l e t h e was t ewa te r i n Pond I i s no t

s u i t a b l e a s i r r i g a t i o n w a t e r i n t h i s r ega rd . I f t h e was tewater

i n pond 1 must be used as i r r i g a t i o n w a t e r it s h o u l d be used

f o r i r r i g a t i n g s u c h c r o p s as c o t t o n a n d v e g e t a b l e s f o r s e e d

p r o d u c t i o n ( H e t c a l f and Eddy I n c , 1972).

Al though t h e p r o t o z o a c o n c e n t r a t i o n i s n o t a c r i t e r i o n

i n S h u v a l l s recommendations ( ~ h u v a l e t a1 1986) f o r was t ewa te r

f o r f r r b g s t i o n , t h e a n a l y s i s c a r r i e d o u t i n t h i s s t u d y showed

20 c y s t s p e r l i t r e a t t h e i n f l u e n t l o c a t i o n ( I ) . P a t h o g e n i c

p r o t o z o a s r e kaovn t o cause s i c k n e s s e s l i k e d i a r r h o e a d y s e n t r y ,

l i v e r a b s c e s s a n d m a l a b s o r p t i o n ( S h u v a l e t a l , 1986) . T h i s

f i n d i n g t h e r e f o r e a l s o s u p p r t s t h e f a c t t h a t t h e i n f l u e n t

was t ewa te r is u n f i t f o r i r r i g a t i o n . The s t a n d a r d b a c t e r i o l o -

g i c a l c r i t e r i o n f o r d e c i d i n g t h e s u i t a b i l i t y of was tewater

f o r i r r i g a t i o n is t h e d e t e m i n a t i o n o f t h e f e a c a l c a l i f o r m ,

E s c h e r i c h i a Coliforrn ( 3 C o l i ) and n o t t h e s t a n d a r d p l a t e count

de t e rmined i n t h i s a n a l y s i s . Bovever , Agus iobi (1976)was of

t h e o p i n i o n t h a t t h e b a c t e r i a removal was n o t good enough f o r

t h e w a s t e w a t e r t o 5 e * x e d f o r i r r i g a t i o n . Shuva l e t sl (1986)

a l s o s u g g e s t e d t h a t where w a s t e x a t e r e f f l u e n t s a r e known t o

c o n t a i n p a t h o g e n s , t h e i r us? f o r i r r i g a t i o n o f marke t v e g e t a b l e s - - - . -

s h o u l d be p r o h i b i t e d . Pa thogen ic j a c t e r i a a r e known t o

t r a n s m i t d i s e a s e s s u c h as d i a r r h o e a typhod f e v e r , c h o l e r a ,

b a c i l l a r y d y s e n t r y , e t c ( ~ h . l v a l e t a l , 1986). A p r o p e r examina-

t i o n f o r t h e f e a c a l c o l i f o r z ( E . C o l i ) b a c t e r i a a t t h e t h r e e

was t ewa te r l o c a t i o n s x i l -1 be n e c e s s a r y t o d e t e r m i n e t h e e x t e n t

o f c o n t a m i n a t i o n and t h u s s g e c i f j t h e e x t e n t o f 2 o s s i b l e u s e

o f t h e w a s t e u a t e r f o r i r r i g a t i o n g e n e r a l l y and f o r i r r i g a t i o n

- o f v e g e t a b l e s i n p a r t i c u l a r ,

Values o f b i o c h e m i c a l oxygen demand (BOD ) r a n g i n g from 5

100mg/l t o 300 mg/l a r e c o n s i d e r e d a c c e p t a b l e (Agus iob i , 1976).

Consequen t ly t h e 3OD v a l u e s ( a v e r a g e o f 191 mg/l) o f t h e 5

i n t e r a e d i a t e and f i n a l e f f l u e n t s a r e a c c e ~ t a b l e , n u i s a n c e - f r e e a n d o d o u r - f r e e and s u i t a b l e as i r r i g a t i o n wa te r . The

f a c t t h a t t h e r e i s s i g n i f i c a n t d i f f e r e n c e i n BOD between t h e

i n f l u e n t a n d t h e e f f l u e n t s show t h a t t h e deg ree o f p o l l u t i o n

i s s i g n i f i c a n t l y reduced .

The c h m i c a l a n a l y s i s of t h e t h r e e l o c a t i o n s o f was te-

[ i a t e r showed s i g n i f i c a n t d i f f e r e n c e s be tween t h e i r means on

t h e one hand and t h a t o f t h e o r d i n a r y w a t e r on t h e o t h e r

e x c e p t f o r n i t r a t e and s u l p h a t e ( T a b l e 17) . However t h e r e

were no s i g n i f i c a n t d i f f e r e n c e s o f t h e means of t h e t h r e e

d i f f e r e n t l o c a t i o n s of ? fas t enrtter fop- ;no&-of-f he- chsaica1.- - -

p r o p z r t i e s . :{~st of t h e s e c h e n i c a l s - o r l n i n e r a l s a r e e s s e n t i a l

m a c r o - n u t r i e n t s f o r c rop p r o d u c t i o n . The u t i l i z a t i o n of t h i s

was t ewa te r f o r i r r i s a t i o n w i l l t h e r e f o r e s u p p l y needed n u t r i e n t s

f o r c r o p p r o d u c t i o n ;dhich i s one of t h e a d v a n t a g e s o f was te- - - .

w a t e r i r r i g a t i o n ( ~ h u v a l e t a l , 1986). The was t ewa te r i n

Pond 2 c a n t h e r e f o r e be s e e n as a r e s e r v o i r of b o t h w a t e r

and n u t r i e n t s f o r c r o p p roduc t ion . The s i g n i f i c a n c e o f t h i s

i s o b v i o u s i n 4 i g e r i a v h e r e c h e m i c a l f e r t i l i z e r s a r e expens ive

and somet imes n o t a v a i l a b l e . It lwould appea r t h a t t h i s was te-

w a t e r n u t r i e n t s o u r c e h a s c o n t r i b u t e d immensely t o c r o p produc-

t i o n Yn t h e s t u d y a rea . During t h e i r r i g a t i o n s e a s o n ( d r y

s e a s o n ) t h e s e n u t r i e n t s a r e d i r e c t l y s u p p l i e d from t h e a p p l i e d

8 3.

w a s t e w a t e r , During t h e r a i n - f e d , c r o p a i n g s e a s o n ( r a i n y

s e a s o n ) , t h e r e s i d u a l e f f e c t of t h e d ry s e a s o n a g p l i c a t i o n

s u s t a i n s t h e c r o p s grown i n t h e a r e a w i t h o u t t h e need t o

a p p l y chemica l f e r t i l i z e r . Although t h e was t ewa te r i n pond 1

a l s o c o n t a i n s t h e s e n u t r i e n t s ; o t h e r c r i t e r i a a l r z a d g -

d i s c u s s e d p r o h i b i t i t s use a s i r r i g a t i o u w a t e r .

5.2, T S ElTIECTS OF JASTEJATER IRRIGATIOiI ON SOIL

PROPZRTIZS.

5.2.1. E f f e c t on t h e p h y s i c a l p r o p e r t i e s of t h e s o i l .

F i e l d Capac i ty . - --.-- -.

Three dep ths : IOcm, 20cm and 40cn were c o n s i d e r e d f o r

t h e d e t e r m i n a t i o n of t h e f i e l d c a p a c i t y . The r e s u l t s shoved P

t h a t t h e mean v a l u e s f o r t h e r e s p e c t i v e d e p t h s were h i g h e r

f o r t h e a r e a under was t ewa te r i r r i g a t i o n t h a n t h e l o c a t i o n s

o u t s i d e t h e i r r i g a t e d a r e a . These % d i f f e r e n c e s were 48.89%,

15.8% and 8.72% h i g h e r f o r t h e d i f f e r e n t c o r r e s p o n d i n g d e p t h s

r e s p e c t i v e l y . T h i s c a n be due t o t h e t e x t u r a l compos i t i on of

t h e s o i l . The r e s u l t s of t h e t e x t u r a l compos i t i on of i n d i v i d u a l

l o c a t i o n s r e v e a l t h a t l o c a t i o n s 4 and 5 which have a b o u t t h e

h i g h e s t compos i t i on o f c l a y p a r t i c l e s and t h e l o w e s t . sand

p a r t i c l e s have abou t t h e h i g h e s t w a t e r h o l d i n g c a p a c i t i e s .

Xowever l o c a t i o n 7 v h i c h had v e r y c l o s e l j h i g h w.at?r h o l d i n ?

c a p a c i t i e s a t t h e t h r e e d e p t h s h a s h i g h e r s a n d and lower

c l a y c o n t e n t s t h a n l o c a t i o n s 4 and 5. T h e r e f o r e a n o t h e r

p o s s i b l e r e a s o n f o r t he above d i f f e r e n c e s may be as a r e s u l t - . - . - -- - - - -

o f t h e m o d i f i c a t i o n o f t h e s o i l s t r u c t u r e caused by t h e

o r g a n i c m a t t e r c o n t e n t o f t h e % a s t e w a t e r . T h i s p o s s i b l e

r e a s o n becomes more t e n a b l e when i t i s n o t i c e d t h a t t h e

d i f f e r e n c e s i n f i e l d c a p a c i t y a r e l a r g e s t a t t h e t o p s o i l

l a y e r (0 - 10cm) w:?ere t h s o r g s c i c m a t t e r c o n t e n t of thk-rase*-

w a t e r is .' i n c o b p e r a t e d more. .- -- -4- -. " . - - - ,

Pro longed use o f was t ewa te r as i r r i g a t i o n w . ~ t a r on t h e

n a t u r a l l y p redominan t ly sandy s o i l o f t h e s t u d y s i t e h a s

a p p a r e n t l y i n c r e a s e d t h e f i e l d c a p a c i t y of t h e s o i l and

c o n s e q u e n t l y con f i rmed S a b e r ' s (1986) f i n d i n g i n C a i r o , Esyg t . . -

- -

P o r o s i t y and Bulk Dens i ty .

The p o r o s i t y which was de te rmined at two d e p t h s ( 0 - l 5 c a

a n d 20 - 35cm, , t a b l e 18) showed t h a t t h e i r r i g a t e d a r e a had

s l i g h t l y h i g h e r p o r o s i t i e s a t bo th d e p t h s t h a n t h e n o n - i r r i g a t e d

a r e a . T h i s d i f f e r e n c e can be a t t r i b u t e d t o t h e textural corn-

p o s i t i o n of t h e s o i l and/or t h e m o d i f i c a t i o n o f s o i l s t r u c t u r e

r e s u l t i n g from was tewa te r i r r i g a t i o n .

The b u l k d e n s i t y of t h e s o i l was r e d u c e d under was te-

w a t e r t r e a t n s n t ss s h o u l d 5e e x p e c t e d because o f t h e i n c r e a s e d

p o r o s i t y . The d i f f e r e n c e s i n b u l k d e n s i t i e s were l a r g e r a t

t h e t o p s o i l l a y e r s t r e n g t h e n i n g t h e s u g g e s t i o n t h a t t h e

e f f e c t of w a s t s w a t e r i r r i g a t i o n on t h e p h y s i c a l p r o p e r t i e s

of t h e s o i l is more pronounced a t t h e t o p s o i l l a y e r .

I n f i l t r a t i o n C a p a c i t y

The c o n s t a n t i n f i l t r a t i o n r a t e t e s t s showed v e r y h i g h

i n f i l t r a t i o n r a t e s e x p e c t e d on p redominan t ly s andy s o i l s , The

i n f i l t r a t i o n tests. had some u n f o r s e e n p r a c t i c a l p roblems t h a t

t h e y c o u l d c o t a l l be s u b j e c t e d t o t h e same t ime d u r a t i o n ,

So t h e i n f l c ~ c c e of t h e was t ewa te r a p p l i c a t i o n on t h e i n f g l -

t r a t i o n o f ,-iatsr i n t o t h e s o i l canno t be f u l l y a s c e r t a i n e d .

However t h e i i g h e r nean i n f i l t r a t i o n r a t e s o b t a i n e d under

was t ewa te r t r e s t ~ e n t ( t a b l e 1 8 ) i s i n keep ing w i t h i t s (was t e -

w a t e r ) a l r e a i y p r e s e n t e d e f f e c t on t h e s o i l p o r o s i t y .

5.2.2. E f f e c t s of ' J a s t e v a t e r I r r i g a t i o n on t h e chemica l

P r o p e r t i e s o f t h e s o i l .

The c h e z i - a l p r o p e r t i e s o f t h e s o i l s amples from t h a

w a s t e w s t e r i r r i g a t e d a r e a showed h i g h e r c o n c e n t r a t i o n s of most

e l e m e n t s t h a n rhose from t h e n o n - i r r i g a t e d a r e a (Tab le 19) .

T a b l e 2 0 sno-:#s t h e mean and s t a n d a r d d e v i a t i o n o f t h e s o i l h

c h e a i c a l p r o p a r t i e s as i n f l u e n c e d by Vas t ewa te r aonl;crL;u~i.

The pli v a l u e o f t h e t r e a t e d ales was abou t 5% lower

t h a n t h a t f o r t h e cnnt-n l 1:=:'2n?s- T h i s a g r e e s w i t h

S a b e r ' s f i n d i n g ( 1 9 8 6 ) , t h a t t h e a p p l i c a t i o ~ o f sewage

e f f l u e n t ( o f human w a s t e s ) on s o i l s t ended t o l ower t h e pH.

A l t k ~ . i z h L e i i e r e t a 1 (1984) r e p o r t e d t h a t i r r i g a t i n g w i t h

w a s t e w a t e r produced s u b s t a n t i a l i n c r e a s e i n pH, t h e was te-

wa te r t h e y a n a l y s e d was a l k a l i n e .

The p e r c e n t a g e d i f f e r e n c e approach used t o compare t h e

c h e m i c a l c o n c e n t r a t i o n s -of t h e s o i l ( t a b l e 20) shows t h a t t h e

e l e c t r i c a l c o n d u c t i v i t y a n d magnessium c o n t e n t s were h i g h e r

i n t h e was t ewa te r i r r i g a t e d a r e a by ove r 200%; n i t r o g e n ,

phosphorus and .calcium .by 92%; po ta s s ium by 45% and sodium

by 6%. ,These d i f f e r e n c e s a r e s u b s t a n t i a l enough t o c o n v e r t

a n i n f e r t i l e s o i l i n t o a f e r t i l e s o i l . T h i s a g r e e s w i t h

3 a b e r t s . ( 1 9 8 6 ) o b s e r v a t i o n t h a t was tewater a p p l i c a t i o n t o s o i l

can r e c y c l e n u t r i e a t s t o t h e s o i l .

P r c l o n g e d x a s t e w a t e r i r r i g a t i o n i n t h e s t u d y a r e a

i n f l u e n c e d t h e c h e n i c a l p r o p e r t i e s by c r e a t i n g ( i n c r e a s e d

d i f f e r e n c e s i n t h e compos i t i on of t h e d i f f e r e n t e l e m e n t s o f

t h e i r r i g a t e d a r e a o v e r t h e n o n - i r r i g a t e d a r e a . These

d i f f e r e n c e s a r e hoxever n o t v e r y uni form a c c r o s s t h e i r r i g a t e d

87.

area as shown i n t a b l e s 19 and 20. Such v a r i a t i o n s c o u l d

be due t o t h e d i f f e r e n t s o u r c e s o f was t ewa te r a p p l i e d t o

e a c h s p e c i f i c l o c a t i o n (Tab le 10). L o c a t i o n 5 which h a s

t h e h i g h e s t c o n c e n t r a t i o n f o r a o s t o f t h e e l e m e n t s h a s two

s o u r c e s (pond 1 and d i r e c t a p p l i c a t i o n o f raw was tewater

s i p h o n e d from s e p t i c t a n k s ) . L o c a t i o n 4 which h a s t h e n e x t

h i g h e s t c o n c e n t r a t i o n s is t h e n e a r e s t l o c a t i o n t o t h e i n f l u e n t

and i r r i g a t e d from pond 1. L o c a t i o n 1 which had t h e l e a s t

c o n c e n t r a t i o n s f o r most of t h e e l e m e n t s is n o t as c o n s t a n t l y

i r r i g a t e d w i t h w a s t e w a t e r ss t h e o t h e r l o c a t i o n s . Hence t h e

q u a n t i t y , q u a l i t y c o n c e n t r a t i o n o f was t ewa te r used and t h e

f r e q u e n c y of a p p l i c a t i o n a r e s i g n i f i c a n t i n t h e o v e r a l l e f f e c t

of was t ewa te r on t h e c h e m i c a l p r o p e r t i e s o f t h e s o i l .

Based on t h e f o r g o i n g , d i s c u s s i o n on t h e q u a l i t y of t h e

U n i v e r s i t y of N i g e r i a , Xsukka wa.s tewater a n d i t s e f f e c t on

t h e s o i l p r o p e r t i e s , t h e i n t e r m e d i a t e and f i n a l e f f l u e n t s

o f t h e U n i v e r s i t y of N i g e r i a , Nsukka t r e a t m e n t works is n o t

o n l y a s u i t a b l e i r r i g a t i o n wa te r s o u r c e b u t i t s a p p l i c a t i o n

* a l s o enhances. t h e f e r t i l i t y and t h e most p o s i t i v e c h a r a c t e r i s t i c s

o f t h e s o i l f o r c r o p p r o d u c t i o n ,

5.3 EFFECT OF ;/ASTE;dbT52 ON SOi4E 03 !HZ WIiiERhL

CONSTITUENTS OF AMARANTHUS SPP. VEGJTXBLL LdBVL3.

T a b l e 21 shows t h a t t h e n i n e samples from t h e i r r i g a t e d

a r e a have m i n e r a l c o n t e n t s o f similar c o n c e n t r a t i o n s . T h e i r

c o n c e n t r a t i o n s were however l o v e r t h a n t h o s e of t h e t h r e e

samples i r r i g a t e d w i t h p o t a b l e t a p wa te r ( a n d t r e a t e d v i t h

farm y a r d manure and/or f e r t i l i z e r ) at l o c a t i o n s o u t s i d e t h e

s t u d y a r e a . T h i s may be due t o e i t h e r a r e l a t i v e l y h i g h

s a l i n i t y o f s o i l s o l u t i o n caused by t h e was t ewa te r and which

c a n d e p r e s s n u t r i e n t up take by t h e p l a n t o r t h e i n h e r e n t l ower

n u t r i e n t c o n t e n t i n t h e w a s t e w a t e r i r r i g a t e d s o i l compared t o

t h e s o i l o u t s i d e t h e s t u d y a r e a . The l a t t e r is l i k e l y t o be

t h e c a s e because e a r l i e r a n a l y s i s h a s i n d i c a t e d t h a t t h e

i r r i g a t e d a r e a canno t be c o n s i d e r e d s a l i n e .

The g rowth per formance o f amaranthus gram i n t h e s t u d y

a r e a w i t h o u t t h e use of w a s t e w a t e r shows t h a t t h e s o i l o f t h e

s t u d y a r e a is n a t u r a l l y d e v o i d o f e s s e n t i a l p l a n t n u t r i e n t s and

canno t s u p p o r t p r o f i t a b l e v e g e t a b l e fa rming . T a b l e 24 which

g i v e s t h e compar ison of t h e s e e s s e n t i a l n u t r i e n t s of t h e

i r r i g a t e d a r e a and the n o n - i r r i g a t e d a r e a c o n f i r m s t h i s .

Table 24. Concentra t ions of t h e E s s e n t i a l Macro-nutrients

of t h e wastewater i r r i g a t e d and non- i r r iga ted - .

areas.

*The b r acke t s -show the ranges f o r the r e p l i c a t e s o i l

samples.

Nu t r i en t ( X i n e r a l )

Ni t rogen

Phosphorus

Potassium

Non-Irrigated Area Nsan values( t a b l e 19)

Neg/lOOg

I r r i g a t e d Area Mean values( t ab le 19)

Heg/1 00%

Dif fe rences between t h e two a r e a s Meg/100g

51.615(*28.97-105,396)

0.1135(0.0323-0.2648)

0.2620(0.1125-0.3446)

23.234(+22.984-23.483

0.0484

0.1783(0.1675-0.189)

28.381

0.0651

0.0837

T h i s t s b l e r e v e a l s t h a t t h e d i f . f e r e n c e s i n t h e

c o n c 3 n t r a t i o n . s of t h e s e e l e m e n t s ( n u t r i e n t ) a re h i g h e r t h a n

t h e i r c o n c e n t r a t i o n s i n t h e n o n - i r r i g a t e d a r e a e x c e p t f o r K

a n d H a . Consequent ly it would a p p e a r t h a t w i t h o u t t h e

a p p l i c a t i o n of was t ewa te r t o t h e s o i l s i n t h e s t u d y a r e a , t h e

s o i l n u t r i e n t s a r e t o o low t o s u g p o r t amaran thus SPP. produc-

t i o n . T h i s o p i n i o n w a s conf i rmed by t h e l o c a l f a r m e r s i n t h e

s t u d y a r e a , who a s s e r t e d t h a t t h e r e canno t be any s u c c e s s f u l

v e g e t a b l e c r o p p i n g i n t h e a r e a v i t h o u t was t ewa te r a p p l i c a t i o n .

Such a n a s s e r t i o n is i n l i n e w i t h t h e e x p e r i e n c e o f Chinese

g a r d e n e r s i n Malaya which i n d i c a t e d t h a t by u s i n g l i q u i d manure

( w a s t e w a t e r ) , good v e g e t a b l e s can be grown on poor s o i l s

( A r t h u r , 1965).

Tab le 23 shows t h a t t h e d i f f e r e n c e s i n t h e m i n e r a l

c o n t e n t of t h e samples from t h e t r e a t m e n t s were n o t c o n s i s t e n t .

The v a r i a t i o n s i n m i n e r a l compos i t i on would a p p e a r t o i n d i c a t e

t h a t t h e l o c a t i o n o f t h e was t ewa te r i n t h e t r e a t m e n t l i c rks

w e l l as t h e r e s i d u a l m i n e r a l c o n c e n t r a t i o n i n t h e s o i l a r e

i m p o r t a n t on t h e e f f e c t o f t h e was t ewa te r on c rop . Consequen t ly ,

t h e z a g u l t o f t h e a n a l y s i s r e v e a l s t h a t w a s t e w a t e r a p p l i e d a s

i r r i g a t - i o n w a t e r c o n t r i b u t e s e s s e n t i a l m i n e r a l s n o t o n l y t o

t h e s o i l b u t a l s o t o t h e crop.

CHAPTER SIX

CONCLUSION AND L ~ ~ C O ~ ~ ~ U ~ ~ ~ . ~ T I O N S

T h i s s t u d y i n v e s t i g a t e d t h e use of wastewater from t h e

- U n i v e r s i t y o f N i g e r i a , Nsu!&a (UN, Nsukka Campus) wastewater

t r e a t m e n t works a s i r r i g a t i o n water source. The p h y s i c a l , .

chemical and b i o l o g i c a l c h a r a c t e r i s t i c s of t h e wastewater

a t t h r e e l o c a t i o n s of t h e t r e a t m e n t works were e v a l u a t e d , The

p h y s i c a l and chemical p r o p e r t i e s of the s o i l of t h e s tudy s i t e

which h a s been under wastewater i r r i g a t i o n f o r some t ime now

a s w e l l as t h e minera l composi t ion of wastewater i r r i g a t e d

amaranthus SPP v e g e t a b l e were a l s o eva lua ted .

The wastewater c h a r a c t e r i s t i c s snowed t h a t t o t a l s o l i d s ,

BOD5, he lmin th e g g s , protozoan c y s t s , e l e c t r i c a l c o n d u c t i v i t y ,

phosphate , s u l p h a t e , c h l o r i d e , ca lc ium, magnessium, potassium .

and sodium/sodium a d s o r p t i o n r a t i o were h i g h e r i n t h e wastBwater

and s t a t i s t i c a l l y d i f f e r e n t from s i m i l a r c o n s t i t u e n t s ( e x c e p t

t h e n i t r a t e and s u l p h a t e ) of t h e domestic water supply ( t a p

wa te r ) of t h e U n i v e r s i t y community. S t a t i s t i c a l a n a l y s i s a l s o

showed s i g n i f i c a n t d i f f e r e n c e s i n t h e means of BOD t o t a l 5 '

s o l i d s , and e l e c t r i c a l c o n d u c t i v i t y between t h e i n f l u e n t and

t h o s e of t h e i n t e r m e d i a t e and f i n a l e f f l u e n t s , i n d i c a t i n g t h e

e f f e c t i v e n e s s of t h e t r e a t m e n t ponds, There were however no

s i g n i f i c a n t d i f f a r e n c e s Setwsen t h e c o n c e n t r a t i o n s of t h e s e

e l e m e n t s i n t h e i n t e r m e d i a t e e f f l u e n t and f i n a l e f f l u e n t

which shows t h a t no f u r t h e r s i g n i f i c a n t t r e a t m e n t on t h e s e

c h a r a c t e r i s t i c s o c c u r s i n pond 2.

The w a s t e r a t e r w a s found t o be c o n s i s t e n t l y s a l i n e a t

t h e t h r e e l o c a t i o n s of t h e t r e a t m e n t works w h i l e t h e SBR, t h e

i n d i c a t o r o f s o d i c i t y , w a s low. The combined e f f e c t o f

s a l i n i t y h a z a r d and s n d i c i t y h a z a r d de t e rmined from t h e

' U S D A c l a s s e s o f s a l i n i t y and sodium h a z a r d f o r I r r i g a t i o n

Water ' is however low, i n d i c a t i n g t h a t t h e was t ewa te r ( raw

and t r e a t e d ) i s good f o r i r r i g a t i o n i n t h i s r e s p e c t . Evalua-

t i o n o f t h e pa thogen ic organisms c o n t e n t showed t h e p r e s e n c e

of h e l m i n t h eggs i n t h e i n f l u e n t i n t h e o r d e r of 20 t o 60

t i m e s h i g h e r t h a n t h e r e q u i r e d maximum c o n c e n t r a t i o n f o r was te-

w a t e r i r r i g a t i o n . The i n f l u e n t and t h e was t ewa te r i n pond 1 '

is t h e r e f o r e t o o p o l l u t e d t o s e r v e as i r r i g a t i o n !water s o u r c e

and s h o u l d t h e r e f n r e n o t be used as i r r i g a t i o n water . The

i n t e r m e d i a t e and f i n a l e f f l u e n t s were however f r e e of he lmin th

e g g s and c o n s e q u e n t l y c a n s e r v e as i r r i g a t i o n water . The

c h e m i c a l compos i t i on o f t h e was tewater r e v e a l t h a t i t (was te-

w a t d r ) i s a ' s to re -house1 o f n u t r i e n t s f o r c r o p p roduc t ion .

d a s t e w s t ? r i r r i g a t i o n i n c r e a s e d t h e w a t e r h o l d i n g

c a p a c i t y o f t h s p redominan t ly sandy s o i l and t h i s i n c r e a s e

was l a r g e r a t t h e t o p l a y e r ( 0 - 10cm) of t h e s o i l . The

c h e m i c a l a ~ n l y s i s of t h e s o i l snowed s u b s t a n t i a l d i f f e r e n c e s %n

between t h e :daatewater i r r i g a t e d a r e a and t h e n o n - i r r i g a t e d

a r e a , w i t h t h e i r r i g a t e d a r e a h a v i n g h i g h e r c o n c e n t r a t i o n s

of c h e m i c a l c o n s t i t u e n t s . These d i f f e r e n c e s were i n t h e

o r d e r o f o v e r 2 0 W f o r e l e c t r i c a l c o n d u c t i v i t y and magnessium;

o v e r 10% f o r N i t r o g e n , phosphorus and ca l c ium; 92% f o r

c a t i o n exchange c a p a c i t y (CEC) ; 45% f o r po ta s s ium a n d 6% f o r

sodium. These h i g h e r c o n c e n t r a t i o n s have n o t c a u s e d s a l i n i t y -

o r s o d i c i t y problem i n t h e s o i l . !{astewater i r r i g a t i o n would

t h e r e f o r e a 2 p e a r t o be a means o f r e p l e n i s h i n g needed n u t r i e n t s

i n t h e s o i l t h e r e b y c o n v e r t i n g a n o t h e r w i s e poor s o i l i n t o a

f e r t i l e one f o r c r o p p r o d u c t i o n . Consequent ly was t ewa te r

i r r i g a t i o n i s recommended as a s o i l improvement p r a c t i c e .

The p o o r per formance o f t h e amaranthus SPP. grown i n

t h e s t u d y a r e a and i r r i g a t e d w i t h domest ic ( p o t a b l e ) w a t e r

s u p p l y ( t a p w a t e r ) shows t h a t t h e s o i l i n t h e s t u d y a r e a is

t o o poor t o s u p p o r t p r o f i t a b l e v e g e t a b l e ( amaran thus SPP)

p r o d u c t i o n . The s u p e r i o r growth performance under w a s t e w a t e r

94.

i r r i g a t i o n i s t h e r e s u l t o f t h e d i r e c t c o n t r i b u t i o n o f

n u t r i e n t s from t h e was t ewa te r a p p l i e d and t h e r e s i d u a l - -

m i n e r a l c o n c e n t r a t i o n i n t h e s o i l from t h e p a s t was t ewa te r

i r r i g a t i o n p r a c t i c e i n t h e a r ea . It would a l s o a p p e a r from

t h e m i n e r a l o g i c a l a n a l y s i s of amaranthus SPP. l e a v e s t h a t

t h e l o c a t i o n of t h e was t ewa te r i n t h e t r e a t m e n t works is a n

i m p o r t a n t f a c t o r on t h e o v e r a l l e f f e c t o f t h e was t ewa te r

on t h e m i n e r a l compos i t i on of t h e i r r i g a t e d c rop .

1 . The u s e of t h e was t ewa te r from pond 1 as i r r i g a t i o n

w a t e r s h o u l d be s topped . T h i s is i m p e r a t i v e i n o r d e r

t o e l i i n i n a t e t h e p o s s i b l e t r a n s m i s s i o n o f h e l m i n t h i a s i s

( t h e h i g h e s t h e a l t h r i s k from was tewater i r r i g a t i o n )

T h i s is a l s o s i g n i f i c a n t because the d i s e a s e s which can

be a s s o c i a t e d w i t h was t ewa te r i r r i g a t i o n a r e endemic i n

Nsukka town.

2. I n view o f t h e b e n e f i t s d e r i v a b l e from was tewa te r

i r r i g a t i o n i n t h e s t u d y a r e a , i t is recommended t h a t

a t h i r d pond be c o n s t r u c t e d e i t h e r i n s e r i e s o r i n

p a r a l l e l w i t h pond 2 t o s t o r e s a f e and unused was tewater

* e f f l u e n t d u r i n g t h e r a i n y s e a s o n f o r u s e i n t h e d r y

season. Since vegetables are the least suitable

crops for wast'ewat er irrigation on health ground,

- there is the desirable need to encourage or enforce the

cultivation of alternative crop(s) under wastewater

irrigation.

3. There is the important need to determine the

E' Coli bacteria content of the wastewater to certify

whether or not the wastewater in pond 2 is really safe

for irrigation (in line with Shuval et a1 (1986)

recommendation).

4. The significant nutrient content of vastewater, as

revealed in this study, suggests that wastewater be

recommended as a source of nutrients to complement (if

not replace) chemical fertilizers for crop production.

'9astewater irrigation certified free of health hazard,

may serve as soil improvement practice on very poor

soils.

5- An epidemiological study of diseases that are

associated with wastewater irrigation (such as typhoid

-fever, diarrhea, dysentry etc) should be carried out in

Nsukka town. Such a study should attempt to correlate

such occurences with the consuaption of wastewater

irrigated crop products by the public.

96.

6. .A l o n g term ( a t l e a s t twelve ca lendar aonths)

c o n t i n u o u s a n a l y s i s and e v a l u a t i o n of t h e was t ewa te r

c h a r a c t e r i s t i c s i n c l u d i n g t h e d e t e r i n i n a t i o n of h2avy

m e t a l s s h o u l d be under taken . Heavy m e t a l s i n was tewater

i n e x c e s s amounts can be t o x i c f o r i r r i g a t i o n pu rposes .

Cont inuous e v a l u a t i o n of t h e s o i l p r o p e r t i e s w i l l

r e v e a l t h e i n f l u e n c e ( i f any) o f t h e s e a s o n s an t h e

e f f e c t of was t ewa te r i r r i g a t i o n on t h e s o i l p r o p e r t i e s .

7 Designed expe r imen t s s h o u l d be c a r r i e d o u t t o

de t e rmine t h e e f f e c t of v a r y i n g amoun t s . of was tewater and

. combina t ions o f was tewater and p o t a b l e w a t e r as i r r i g a t i o n

w a t e r on c r o p y i e l d and q u a l i t y .

Agus iob i , O.D.. (1976) . Sewage Trea tment P l a n t at t h e U n i v e r s i t y of N i g e r i a , Nsukka, 3 8 ~ . Unpublished 3 . 3 . P r o j e c t ~ e ~ o r ' t p r e s e n t e d t o t h e Departf ient of C i v i l E n g i n e e r i n g , U.N.N.

American P u b l i c H e a l t h A s s o c i a t i o n , Gae r i can Waster Yorks A s s o c i a t i o n and Water P o l l u t i o n C o n t r o l F e d e r a t i o n (1971). S t a n d a r d Methods f o r t h e Examinat ion of l a t e r and idas tewater . 7 3 t h ed. BPiIA, XiWA and 'iIPCF, New Y ork.

Arar, A. (1987). I r r i g a t i o n w i t h sevage e f f l u e n t : I ts a p p l i c a t i o n i n t h e Near E a s t ( V e s t e r n ~ s i a ) . ';dater Q u a l i t y B u l l e t i n , 1 2 ( 2 ) PP 51-58.

A r t h u r , T. (1965) . Garden ing i n Hot Count r ies .207P, Faber and Fabe r .

Barngboye, O.A. (1986) . Re-use of sewage e f f l u e n t f o r s u p p l e m e n t a l I r r i g a t i o n o f 2a i ze .Pape r p r e s e n t e d a t t h e N i g e r i a n S o c i e t y o f A g r i c u l t u r a l E n g i n s e r s i N a t i o n a l , 1. Conference a t Obafemi Awolovo U n i v e r s i t y , I l e - I f e s e p t . 3 - 5 , 1986.

-:.

Benneth, Y.F; C. J a y n e s and C. Harvey (1973) . E f f e c t o f sewage e f f l u e n t on c e r t a i n chemica l c h a r a c t e r i s t i c s of s o i l , p r e s e n t e d a t t h e 1973 Annual j o i n t mee t ings of ASX, CSSX and SSSh, Las Vegas, Nevada, Mov. I 1 - 16, 1973.

B o l l , R ; H. Dernbach, and R. Xaywer (1986) . Aspec ts o f Land D i s p o s a l o f 3 a s t e w a t e r as e x p e r i e n c e d i n Germany. X a t e r S c i e n c e a n d Technology Vol. 18 Nos. 7/8 PP. 383-390.

Bond, 2.G; and C.P. S t r a u b (1974) . Handbook o f Envi ronmenta l c o n t r o l Vol. I V : Wastewater: Trea tment and Di sposa l .

.. 905P CBC P r e s s i n c ; Parkway, C leve land .

Bouwer, H ; and E. I d e l o v i t c h (1987). Q u a l i t y r e q u i r e m e n t s f o r I r r i g a t i o n w i t h Sewage Yater . J o u r n a l o f I r r i g a t i o n and Dra inage E n g i n e e r i n g 113(4 ) PP 51.6 - 535.

Cromer, R O N ; D. Tonk ins ; N . J . B a r r and P. Hopmans. (1984) . I r r i g a t i o n of Monterey P i n e w i t h Yas t ewa te r : S f f e c t on s o i l chemistry and groundwater composi t ion . J o u r n a l o f Znvi ronmenta l !Qual i ty 1 3 ( 4 ) PP 539 - 542.

Day, A.D.; J.A. Ncfadyen, T.C. Turkey and C.B. C l u f t (1981) . E f f e c t s o f ; 4 i n i c i p a l was t ewa te r on t h e y i e l d and q u a l i t y o f c o t t o n . J o u r n a l o f Env i ronmen ta l q u a l i t y Vol lO(1 ) PP 47 - 49.

G r e e n s i l l , T.M. (1964) . Gardening i n t h e T r o p i c s . 272P. Evans B r o t h e r L t d ; London.

I s r a e l s e n , O.W. and V.E. Hansen (1962) . I r r i g a t i o n P r i n c i p l e s and P r a c t i c e s , 3 r d ed. 4 4 7 ~ , John ! i i l ey and Sons , Inc . N e w York.

X e t c a l f and Eddy, Inc . (1972) . J a s t e w g t e r E n g i n e e r i n g : C o l l e c t i o n , T r e a t m e n t , D i s p o s a l , 782p, McGrnw-Hill Book Company, New York.

Michae l A-hI - (1978) . I r r i g a t i o n Theory and P r a c t i c e 8 0 1 ~ ~ Vikas P u b l i s h i n g House, New Delh i .

M i n i s t r y o f A g r i c u l t u r e , Food a n d F i s h e r i e s , London (1977). Hanual o f V e t e r i n a r y P a r a s i t o l o g i c a l L a b o r a t o r y Techniques . T e c h n i c a l B u l l e t i n No 18 , London 8:450.

Morten, G.C; Y.E. La r son and C.Z. Clapp (1980) . X f f e c t s o f Mun ic ipa l ! i a s t ewa te r e f f l u e n t o.n per formance and f e e d q u a l i t y o f maize vs . Reed c a n a r y g r a s s . J o u r n a l of Env i ronmen ta l - q u a l i t y . Vol 9 ( l ) PP 137 - 141.

P e r c i v a l , NOS. (1984) . P o t e n t i a l f o r i r r i g a t i n g k r a f t pu lp m i l l e f f l u e n t o n t o f a rmland i n t h e C e n t r a l North I s l a n d , N.Z. l a t e r and S o i l M i s c e l l a n e o u s p u b l i c a t i o n No 70 PP 257 - 266.

P f a f f l i n , J.R. and 3.N. Z i e g l e r (1976). Encyc loped ia o f * ' Env i ronmen ta l S c i e n c e a n d E n g i n e e r i n g , Vol. I , 6 0 0 ~

Gordan and Breach S c i e n c e P u b l i s h e r s , New York.

S a b e r , M.S.N. (1985) . p ro longed e f f e c t o f Land d i s p o s a l of human was t e s on s o i l c o n d i t i o n s i n T r e a t m e n t , D i s p o s a l and Nanagemont of Human Vas tes . 'da te r Sc i ence and Technology Vol. 18 Nos 7/8 PP 371 - 374.

S c h i r a d o , T.11 Verga ra , 3.B. S c h a l s c h a and P. P r a t t (1986). Evidence f o r movement of heavy m e t a l s i n a s o i l i r r i g a t e d w i t h n n t r e a t e d was tewater . J o u r n a l of Env i ronmen ta l Q u a l i t y , 1 5 ( 1 ) PP 9 - 12,

S h a i n b e r g , I. and Z.D. O s t e r (1978) . 4 u a l i t y of I r r i g a t i o n 'da te r . 6 5 ~ , i n t e r n a t i o n a l I r r i g a t i o n I n f o r n a t i o n C e n t r e , Bet Dagan. -

S h a p i r o , L. and W.J. Brannock (q962) . Rapid A n a l y s i s o f S i l i c a t e , c u r b o n a t e and Phosphate 2 o c k s . 5 6 ~ ~ U.S. G e o l o g i c a l Survey B u l l e t i n 1144 - A . U . 3 . Government P r i n t i n g Off i c e J a s h i n g t o n .

Sharma, V.K. and B.D. Kansa l (1984) . E f f e c t o f n i t r o g e n , fa rmyard manure, town r e f u s e and sewage wa te r on t h e y i e l d and n i t r o g e n c o n t e n t of maize f o d d e r and s p i n a c h , I n d i a n J o u r n a l o f Ecology l l ( 1 ) PP 77 - 81.

S h u v a l , H . 1 ; A. Avner, B. F a t t a l , E. Rawitz and P. Y e k u t i e l (1986) . ' da s t ewa te r I r r i g a t i o n i n Developing C o u n t r i e s . 3 2 4 ~ . The ' ; iorld aank , ' J a sh ing ton D. C.

T e s t e r , C.F. and J.I. P a r r (1982) . I n t e n s i v e v e g e t a b l e p r o d u c t i o n u s i n g compost , , P a p e r p r e s e n t e d at t h e 7 4 t h Annual N e e t i n g s , XSA, CS34 and SSSA. Anaheim, C a l i f o r n i a , Nov. 28 - Dec. 3, 1982.

Thorne , D - d . and M.D. Thorne (1979) . S o i l , ' da t e r and Crop Production.353P. A V I P u b l i s h i n g Co. Y e s t ~ o r t , Connec t i en t .

T roeh , F.R; J.A. Hobbs and R.L. Donahue (1980). S o i l and Y a t e r C o n s e r v a t i o n f o r P r o d u c t i v i t y and Znvi ronmenta l P r o t e c t i o n . 7 1 8 ~ . P r e n t i c e - H a l l Inc . New J e r s e y .

Whi te , J O B o (1970). The Design of Sewers and Trea tmen t ',iorks. 3 1 8 ~ , S d r a r d h o l d ( P u b l i s h e r s ) L t d ; London.