anaerobic digestion of total raw olive-oil waste water in a two-stage pilot-plant (up-flow and...

8/2/2019 Anaerobic Digestion of Total Raw Olive-oil Waste Water in a Two-stage Pilot-plant (Up-flow and Fixed-bed Bio Rectors)

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ELSEVIER P I I : S 0 9 6 0 - 8 5 2 4 ( 9 6 ) 0 0 0 5 I - X

Bioresource Technology 57 (1996) 237-243Copyright 1996 El~vier Science LimitedPrinted in Great Britain. All rights reserved0960-8524/96 $15.00

A N A E R O B I C D I G E S T I O N O F T O T A l . R A W O L IV E -O I LW A S T E W A T E R IN A T W O - S T A G E P I L O T - P L A N T ( U P -F L O WA N D F I X E D - B E D B I O R E A C T O R S )D . D a l i s , a * K . A n a g n o s t i d i s , a A . L o p e z , a I . L e t s i o u a & L . H a r t m a n n b

aSection of Ecology and Systematics, U niversity of Athens, Panepistimiopolis, At hen s 15 784, GreecebBiotechnology D epartment, University of K arlsruhe, Karlsruhe, Germany(Received 6 A ugust 1995; revised version received 15 March 1996; accepted 3 A pril 1996)

AbstractA s tu d y wa s u n d er ta k en t o e v a l u a t e t h e a n a er o b i cd i g es t i o n o f t o t a l r a w o l i v e - o i l wa s t ewa te r i n a two -s tage p i lo t -p lan t wi th reac tors conne cted in ser ies. Tw od i f feren t types o f anaerob ic d iges ters were used , an up -f l o w t yp e a n d a f i x e d - b e d t y pe . T h e m a i n p u p o s e o f t h es tu d y wa s t o e v a l u a t e t h e p e r fo r m a n ce o f a n u p - f l o w-type reac tor work ing in ser ies wi th a f i xed -bed - typer ea c to r, w h i ch w a s u s ed a s a co m p l em en ta r y t r ea tm en t .Th e p i l o t - p l a n t s y s t em o p er a t ed i n t h e m es o p h i l li cr a n g e ( 3 5 + 1 C) d u r i n g a p p r o x i m a te l y 3 9 0 d a ys, a n dwi th organ ic load ing leve ls tha t ranged be tween 2 .8a n d 1 2 . 7 g CO D / l . d a y . Co n cen t r a t ed a q u eo u sa m m o n i a w a s a d d e d t o t he t o ta l ra w w a s t e w a t e r t oa d ju s t t h e C /N r a t io t o t h e o p t i m u m v a l u e o f 2 0 /1, a n dth i s a ls o a ch i ev ed s t a b i l is a t i on o f t h e p H v a l u es i n t h ed iges ters wi th in a range abou t neu tra l i ty . In a ser ies o fseven conse cu t ive exper imen ts , for the f i r s t s tage (up -f l o w d i g es t er ) o p t i m u m v a l u es o f s p ec if i c b io g a sproduct ion ra te s tab i l i sed a t a va lue o f 2 .1 l i t res / l i t red iges ter .day wi th a very sa t i s fac tory COD reduct ion o f8 3 % ( w i th a v o l u m e t r i c l o a d o f 1 1 g CO D / l . d a y ) . F o rthe secon d s tage ( f i xed -bed d iges ter ), the b iogas p ro -duct ion ra te s tab i l i sed a t a va lue o f 0 .22 l i t res / l i t red i ges te r .d a y w i th a CO D r ed u c t i o n o f 8 % ( w i th a v o l u -m e t r ic l o a d o f 0 . 1 9 g C O D / l . d ) . A c c o r d i n g t o th eresu l ts repor ted in the l i tera ture fo r to ta l raw w as te-wa te r, t h e p e r fo r m a n ce o f t h e a p p l i ed s y s t em i sa m o n g s t t h e b e s t f o r b i o g a s p r o d u c t i o n , C O D r ed u c -t ion a nd load ing ra te repor ted so fa r, especia lly for theup - f low d iges ter. Ph eno ls were grea t ly reduce d d ur ingthe anaerob ic d iges t ion p rocess in bo th d iges ters , wi tha co n cen t r a t i o n r ed u c t i o n wh i ch r ea ch ed 7 5 % i n t h eup - f low d iges ter; w i th the use o f the second s tage( f ix ed - b ed r ea c to r ) a f u r th e r r ed u c t i o n o f 4 5 % wa so b ta i n ed . W i th t h e a b o v e en co u r a g i n g r e s u l t s we m a ys u g g es t t h e em p l o ym en t o f t h e u p - f l o w t yp e d i g es t e r a sa n e co n o m i ca l a n d e f f ec t i v e t r ea tm en t f o r s i g n i fi ca n t lyr ed u c i n g t h e o r g a n i c l o a d o f t o t a l r a w wa s t ewa te r .M o r e s a t i s fa c to r y r es u lt s m i g h t b e e x p ec t ed f r o m th e*Author to whom correspondenceshould be addressed.

use o f a f i xed -bed - typ e d iges ter conne cted in series wi tha p rev ious one , a s a second t rea tm en t s tage. Copy r igh t 1 9 9 6 E l s ev i e r S c i en ce L td .Key wo r d s : Anaerobic d iges t ion, o l ive-oi l mil l was te-water , b iogas product ion, f ixed-bed diges ter , up-f lowdiges ter .INTRODUCTION

Olive-o i l was tewate r , toge ther w i th the was tewate rf rom dis t i l ler ies (v inasse) , is cons idered as one ofthe m os t po l lu t ing ag ro - indus t ri a l r e s idues due to i t sh igh o rgan ic load ( the was tew ate r o f an average p ro -duct ion capaci ty o l ive-oi l mil l : 50 m3/day, BOD5 of40g/ l , i s equivalent to the was tewater of a c i ty with apop ulat io n o f 30 000 inhabi tants ) .Th e t r ea tm e n t and d i sposa l o f such was tewate r s isvery dif f icul t for reasons that are re la ted to i ts phys i-ca l and chem ica l con ten t s ( low pH va lues , h ighpheno ls concen t r a t ion , vo la t i l e f a t ty ac ids , phy to -tox ic p roper t i e s , e t c . ) ; the t echn ica l and econom ica ls t ruc tu re o f the o l ive -o i l m i l l s ( average econom icpote nt ia l m ainly pr ivate , but a lso in agro- indu s tr ia lco rpora t ions o f s easona l opera t ion ) ; and f ina l ly tothe fact that the o l ive-oi l mil ls are geographical lys c a t t e r e d a l o n g t h e M e d i t e r r a n e a n r e g i o n , w h e r ea lm os t a l l the wor ld p roduc t ion o f o l ive -o i l i s con-cen t r a ted .The o l ive -o i l -p roduc ing coun t r i es a r e t ry ing toface the negat ive impacts of the o l ive-oi l was te-w a t e r s i n t h e e n v i r o n m e n t . T h e m o s t i m p o r t a n t o fthese a t t em pts i s the anaerob ic t r ea tm e n t o f o l ive -o ilw a s t e w a t e r f o r t h e p r o d u c t i o n o f m e t h a n e ( D a l i s e ta l . , 1982 ; Da l i s , 1991 ; F ies tas Ro s de Urs inos et a l . ,1982; Aveni , 1983 ; Boa r i et a l . , 1984 , Rozz i et a l . ,1984 ; Aven i & Lam arca , 1986 ; Georgaca k i s & Dal i s,1993) o r fo r the r ecovery o f va luab le m ate r ia l s , suchas co lour ing com pounds and po lysacchar ides ( In io -takis et a l . , 1989) . The was tewate r can a l so be usedas a soi l -qual i ty recoverer and as l iquid fer t i l iser(Bal ice et a l . , 1990).23 7


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23 8 D. Dalis , K . Anagnost idis , A . Lopez , I . Lets iou , L. HartmannT h e m o s t i m p o r t a n t r e a s o n s f o r t h e c h o i c e o fa n a e r o b i c d i g e s t i o n a s a t r e a t m e n t m e t h o d a r e t h e

f e a s ib i l i t y t o t r e a t w a s t e w a te r s w i th a h igh o r ga n icl o a d a n d t h e t e c h n o - e c o n o m i c a l s t r u c tu r e o f t h eo l ive - o i l m i l l s . A c c o r d ing to i n t e r na t iona l e xpe r i e nc e( H a r t m a n n , 1 99 3) , t h e a e r o b i c t r e a t m e n t o f s u c h aw a s t e w a t e r r e q u i r e s b i o l o g i c a l p u r i f i c a t i o n s y s t e m sw i t h h i g h c o n s t r u c t i o n a n d o p e r a t i o n a l c o s t s ( e n e r g yc o n s u m p t i o n ) , b e s i d e s w h i c h s t a b i li s a ti o n o f t h e b i o -log i c a l r e a c t ions i s no t a s su r e d ( a c t iva t e d - s ludgeta nks ) , o r t he w a s t e s c a use c logg ing o f i n s t a l l a t i onssuc h a s a e r ob ic b io log ic a l f i l t e r s a nd b iod i sc s . I n t hec a s e o f s e a s o n a l o p e r a t i o n o f t h e p r o d u c t i o n u n i t s ,t h e d i s a d v a n t a g e o f a s l o w s t a r t - u p a f t e r t h e n o n -f e e d i n g co n d i t io n s m a k e s t h e a e r o b i c t r e a t m e n tu n a c c e p t a b l e f o r t h e t r e a t m e n t o f m i l l w a s t e w a t e r .W i t h b i o r e a c t o r s f o r a n a e r o b i c f e r m e n t a t i o n t h e s ep r o b l e m s a r e n o t p r e s e n t .

T h e s u b je c t o f th e p r e s e n t p a p e r w a s t h e s t u d y o ft h e a n a e r o b i c d i g e s t i o n o f t o t a l r a w o l i v e - o i l w a s t e -w a te r i n a tw o- s t a ge p i lo t - p l a n t ( up - f low a ndf i x e d - b e d d i g e s t e r s c o n n e c t e d i n s e r i e s ) . R e p o r t s o nt o t a l r a w w a s t e w a t e r u s i n g t w o - s t a g e i n s t a l la t io n s a r en o t r e f e r r e d t o i n t h e l i t e r a tu r e .

M E T H O D ST h e o l i v e -o i l w a s t e w a t e r u s e d i n t h e a n a e r o b i c t r e a t -m e n t p i l o t - p l a n t w a s o b t a i n e d f r o m t h e c e n t r i f u g a lo l ive - o i l m i l l i n K a l iv i a ( Ea s t A the ns ) . The un i t ,w h i c h w a s s h e l t e r e d a l o n g s i d e t h e o l i v e - o i l m i l l ,o p e r a t e d i n s e r i e s f r o m D e c e m b e r 1 9 9 3 t o M a r c h1995.T h e a n a e r o b i c d i g e s t i o n s y s t e m c o n s i s t e d o f a 2 0m 3 s t o r a g e t a n k o f r a w w a s t e w a t e r a t t h e s t a rt , a n da n u p - fl o w s l u d g e - b l a n k e t r e a c t o r o f 2 m 3 u s e f u lv o l u m e , a n d a f i x e d - b e d -t y p e r e a c t o r o f 2 m 3 u s e f u lvo lum e , w i th f i l l i ng m a te r i a l c ons i s t i ng o f po ly -e t h y l e n e p l as t ic r i n g s ( P A L L ) , w o r k i n g i n s e r i e s w i tht h e p r e v i o u s o n e . B o t h d i g e s t e r s w e r e m a d e o f o r d i -n a r y s t e e l a n d i n s u l a t e d b y a 6 - c m t h i c k g l a s s w o o ll a y e r, e x t e r n a ll y c o a t e d w i t h a l u m i n i u m s h e e t s f o rp r o t e c t i o n . E a c h o n e o f t h e d i g e s t e r s w a s s u r -r o u n d e d b y a h e a t e x c h a n g e r w h i c h k e p t t h et e m p e r a t u r e i n t h e m e s o p h i l l i c r a n g e ( 3 5 + I C ). T h ed i m e n s i o n s o f e a c h d i g e s t e r w e r e 0 . 7 m i n d i a m e t e r

Olive-oilmill Storage tank

OutflowFixed-bed Up-flowreactor reactor

F i g . 1. Flow diagram o f the pilot treatm ent plant.

a nd 2 . 5 m he igh t . F igu r e 1 show s a s im p l i f i e d d i a -g r a m o f t h e a n a e r o b i c p i l o t - p la n t .T h e s t a r t i n g o f t h e u p - f l o w o p e r a t i o n w a s d o n e b ya d d i t i o n o f 3 50 1 o f a n a e r o b i c b i o m a s s f r o m a s i m i -l a r d o m e s t i c - w a s t e w a t e r i n s t al l at i o n , t o g e t h e r w i t h6 5 0 1 o f r a w o l iv e - o il w a s t e w a t e r . A t t h e b e g i n n i n gt h e s y s t e m o p e r a t e d i n b a t c h c o n d i t i o n s f o r a p p r o x i -m a te ly 2. 5 m o n th s un t i l i t s s t a b i l is a t i on .

T h e o p e r a t i o n o f th e w h o l e s y s te m s t a rt e d i nD e c e m b e r 1 9 9 3 , f i r s t w i t h t h e u p - f l o w d i g e s t e r ,f o l l o w e d b y t h e f i x e d - b ed d i g e s t e r 4 m o n t h s l a t er . B yt h e e n d o f A u g u s t t h e s y s t e m w as s t o p p e d b e c a u s eo f t h e l a c k o f o l i v e - o i l w a s t e w a t e r , a n d i t r e s t a r t e di t s n o r m a l o p e r a t i o n i n D e c e m b e r 1 9 9 4 .T h e b i o g a s p r o d u c e d b y e a c h d i g e s t e r w a s m e a -s u r e d b y d o m e s t i c n a t u r a l - g a s m e t e r s a n d s t o r e d i na n i n v e r t e d g a s h o l d e r . F o r t h e C / N r a t i o a d j u s t m e n tt o 2 0/1 c o n c e n t r a t e d a q u e o u s a m m o n i a w as a d d e dto t he t o t a l r a w w a s t e w a te r , a nd th i s a l so s t a b i l i s e dt h e p H v a l u e s i n th e d i g e s t e rs a t n e a r n e u t r a l it y .

T h e q u a n t i t a t i v e c h a r a c t e r is t i c s o f t h e s e v e n s e r i e so f e x p e r i m e n t s , e x p r e s s e d a s m e a n v a l u e s , a r e l i s t e din Ta b le 1 .C h e m i c a l a n a l y s i sC h e m i c a l o x y g en d e m a n d ( C O D ) , t o t a l o r g a n icn i t ro g e n , p h e n o l s c o n c e n t r a t i o n a n d p H w e r e d e t e r -m i n e d a s d e s c r i b e d i n S t a n d a r d M e t h o d s ( A m e r i c a nP ub l i c H e a l th A ssoc i a t i on , 1985 ) . To ta l o r ga n ic c a r -b o n ( T O C ) c o n t e n t w a s d e t e r m i n e d b yp h o t o c h e m i c a l o x i d a t io n o f t h e o r g a n i c c o m p o u n d s .

Table 1. Quantitative average characteristics of the experimentsExper imenta l pa ram ete r 1 2 3 4 5 6 7Duration , days 188Rete ntion t ime up-flow 14.8(fixed-bed), l/dayFlow rate up-flow 135(fixed-bed), l/dayInflow CO D (TO E), g/l 46.3 (9.2)Vo lum e load up-f low, 3.6 (0.6)g COD /1.day (g TO C/l.day)Vo lume load f ixed-bed,g COD/l.day (g TOC/l.day)

53 24 23 19 6015.3 (10) 10 (10) 10.7 (10) 11.1 (5) 7.5 (5)131 (200) 196 (200) 187 (200) 181 (400) 267 (400)46.6 (13 .8) 56 .8 (14 .5 ) 117.7 (23 .3) 59 .8 (16) 54 (15 .5)2.8 (0.9) 5.6 (1.4) l l (2.2) 5.4 (1.4) 7.2 (2.1)0 .13 (0 .04 ) 0 .15 (0 .04 ) 0 .19 (0 .07) 0 .19 (0 .07 ) 0 .25 (0 .08)

225.635 771.3 (15.2)12.7


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D ig es t io n o f w h o le raw o l i ve w as tew a ter 239A S Y B R O N - E - 3 50 0 - ty p e p h o t o c h e m i c a l a n a l y se r o fo r g a n i c c a r b o n w a s u s e d . F o r m e a s u r e m e n t o f t h eb i o g a s p r o d u c t i o n , t h e O R S A T m e t e r w a se m p l o y e d .T h e s a m p l e s f r o m e a c h r e a c t o r w e r e t a k e n d a i l yand t es ted fo r pH , t em pera tu re , b iogas p roduc t ion ,and chem ica l oxygen dem and . W eek ly ana lys i s o fpheno ls , to ta l o rgan ic n i t rogen , and vo la t i l e f a t tyac ids we re a l so pe r fo rm ed .

R E S U L T S A N D D I S C U S S I O NT h e p e r f o r m a n c e o f t h e b i o l o g i c a l f e r m e n t a t i o ndur ing the s even exper im en ts was t e s ted w i th theuse o f the fo l lowing param ete r s : d eg rada t ion l eve l o fthe o rgan ic load expres sed as r educ t ion o f to ta lo r g a n i c c a r b o n ( T O C ) a n d o f c h e m i c a l o x y g e ndem and (COD) in the up - f low reac to r , a s we l l a s inthe f ixed -bed r eac to r ; f luc tua t ion o f pH va lues andspecif ic b iogas product ion (Rg) , expressed as l i t reso f b iogas p roduced per l i t r e d iges te r pe r day ; t r ans -fo rm at ion o f the d i s so lved o rgan ic ca rbon in to thefo rm o f gaseous ca rbon ; overa l l va lues o f thespecif ic b logas y ield (Yg) in s teady-s tate condi t ionso f the p roces ses ; r educ t ion o f concen t r a t ion o f phe-n o l i c c o m p o u n d s i n t h e w a s t e w a t e r a n d r e d u c t i o neff ic iency of volat i le fa t ty acids .pH valueThe s tab i l i s a t ion o f the pH va lues w i th in a neu t r a lr eg ion (6 . 9 -7 . 4 ) in the up - f low reac to r du r ing theseven consecut ive exper iments is shown in F ig . 2 . I ti s in te res t ing to no te tha t no bu f fe r so lu t ion wasused fo r co r rec t ion o f the unusua l ly low pH va lueso f the in i ti a l subs tr a te (5 . 0 -5 .5 ) . Th i s was because o fthe bu f fe r ac t ion o f the NI - I~ ions wh ich were p ro -duced dur ing the anaerob ic d iges t ion f rom the r awwas tewate r , p rev ious ly m en t ioned as be ing en r ichedwi th aqueous am m onia fo r ad jus t ing the C /N ra t ioto the op t im um va lue o f 20 /1 (F ies tas Ros de Urs i -

nos , 1 983 ; Cabbe lo e t a l . , 198 6; Da lis , 1991). I t iswor th no t ing tha t the C /N ra t io o f the in i t i a l sub -s t r a te f luc tua ted be tween 40 and 45 /1 .Organic load degradat ionI t i s in te res t ing to no te tha t du r ing the fou r thexper im en t the in s tal l a tion opera ted w i th a ve ry h ighvo lum e t r ic load ing r a te (2.2 g TOC / l .day o r11 g CO D/l .day) . In spi te of the g radua l incre ase inthe vo lum et r ic load (Br ) in the up - f low reac to r , a swel l as in the f ixed-bed, dur ing the seven consecut iveexper im en ts (F igs 3 -5 ) , a s a t i s f ac to ry r educ t ion o fthe o rgan ic po l lu t iona l load o f the was tewate r wasob ta ined . Th is r anged be tween 68 and 77% as TOCup- f low reduc t ion (o r 75 -85% as COD up- f lowreduc t ion ) .The use o f the f ixed -bed r eac to r connec ted ins e ri e s g a ve f u r t h e r T O C a n d C O D r e d u c t io n s w h ic hf luc tua ted be tween 15 and 20%.S im i la r h igh degrada t ion va lues o f the o rgan icload w i th co r respond ing h igh vo lum et r ic load ingra tes have no t been m en t ioned in the l i t e r a tu re con-ce rn ing to ta l r aw o l ive -o i l was tewate r . Georgacak i sand Dal i s (1993) r epor ted a COD ou t f low reduc t ionwhich f luc tua ted be tween 94 and 95%, bu t on ly fo rthe superna tan t l iqu id f r ac t ion o f was tewate rob ta ined a f t e r na tu ra l s ed im en ta t ion o f the to ta l r awwas tewa te r and r em ova l o f the s e t t led s ludge . Th is i seas ily deg radab le was tewate r com pared w i th the r awolive-oi l was tewater . Rozzi e t a l . (1984) , Aveni andLamarca (1986) , Carr ier i and Bal l ice (1986) , Car-r ier i and Bal l ice (1988) and Tsonis andGr igoropou los (1988) , am ong o ther s , r epor ted tha tthe ou t f low o rgan ic load r educ t ion f luc tua ted f rom40 to 85% us ing lower vo lum e t r ic load ings.F inal ly , i t i s wor th not ing that the observed s tabi-l isat ion of the b iological process in the four thexper im en t , bes ides the g radua l inc rease in the vo lu -m et r i c load ing , was apparen t ly due to adap ta t ionwi th t im e o f the m ic roorgan i sm popu la t ions in s idethe two diges ters .

8

7

6

5

3210

6 11 ~ 6 21 26 31 36 41 46Week

4

3 ,5

3

2 ,5 ~2 ~1 , 51~

CO0, 5 ~:~

Fig. 2. Specific biogas production rate (Rg) (=) and pH ([]) fluctuation in up-flow digester.


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240 D . D a l i s , K . A n a g n o s t i d i s , A . L o p e z , I . L e t s i o u , L . H a r t m a n n

c-O0"(3E0O~"00k "

1 00

9 0

8 0

7 0

6 0

5 0

4 0

3 0

2 0

10

01 2 3 4 5 6 7

ExperimentFig. 3. Percentage TOC degradation in up-flow (=) and fixed-bed (D) digesters in steady-state conditions.

BiogasDur ing the seven consecut ive exper iments a gradualincrease of the specif ic biogas production (Rg) inthe f irst stage (up-f low reactor) was observed, whichfluctuated from 2.1 to 2 .3 l itre biogas/l itre digesterday (F igs 2 and 6 ) . These va lues are cons idered h igh

according to those previously reported [Dalis e t a l .(1982); Boar i e t a l . (1 9 8 4 ) ; Ro z z i e t a l . (1984); Geor-gacak is & Dal is (1993) ] .

In the f ixed-bed bioreactor the biogas productionstabil ised at 0 .5 l itre biogas/l itre digester .day. Theopt imum values of spec i f ic b iogas y ie ld (Yg) for the

10 0

9 0

8Ot -O~ 7 0I1~ 5O

' ~ 4 Oo J 3 o

20

1 2 3 4 5 6 7

ExperimentFig. 4. Percentage COD degradation in up-flow (m) and fixed-bed ([]) digesters in steady-state conditions.

90

80

7Oe"0

so" O

3 0

2O

10

~ I I ) I I~) I : I~ I ; ; l~F l I~I ; ; ;11 1 I I I I I I ~ I : I~ I I )I : : :6 1 1 1 6 2 1 2 6 3 1 3 6 4 1 4 6

Week

1 00

9 0

8 0

7 0OD

6 0 ~5O ._ =4 o ~3o ~2O100

Fig. 5. Dissolved oganic carbon reduction (o) and its transformation into biogas (,,) in up-flow d igester.


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D i g e s t i o n o f w h o l e r a w o l i ve w a s t e w a t e r 241

2,5

~ 2"I~ 1,5

1

0 ,5

0

/2 3 4 5

Experiment6 7

Fig. 6. Specific biogas production (Rg) in up-flow (t) and fixed-bed ([]) digesters in steady-state conditions.up-f low reac tor (F ig . 7 ) dur ing the second and th irdexper iments ranged be tween 21 and 22 l i t re b iogas /gT O C degraded .Phenols and volat i le fat ty ac ids degradat ionThe percentage reduct ion of phenols in the up-f lowreactor reached 73% in the f ir s t exper iment (F ig . 8 ) .

2,5

Furthermore, in the f ixed-bed reactor there was a35% phenols reduct ion . The phytotoxic i ty t es tshowed that the out f low from the f ixed-bed reac tordid not promote toxicity react ions. It is probablethat th is was due to the cons iderab le reduct ion inphenol ic comp ound s , as w e l l as the concentrat ion ofvolat i le fatty acids (Fig. 9), whose degradation

2oF -

1, 5" o

-I- 1Ot ~>,. 0, 5

4E x p e r i m e n t

5 6 7

Fig. 7. Specific biogas yield (Y g) in up-flow (m) and fixed-bed (D) digesters in steady-state conditions.

7Ot -OO=" 0 soq )

" 0 4 On"6e - a or -

1 3 . 2 0

10

0

m

i

4E x p e r i m e n t

5 6 7

Fig. 8. Percent phenols degradation in up-flow (m) and fixed-bed (D) digesters in steady-state conditions.


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24 2 D. Dalis , K . Anagnost idis , A . Lopez , I . Lets iou , L. Hartmann

I7 0

"1~ 60"5

v ,- "O 40

0 O~ 30-6~o>o~ 20

10

8 0

m - -1 2 3 4 5 6 7

E x p e r i m e n tFig. 9. Perc enta ge volatile acids degrad ation in up-flow (B) and fixed-bed (D) digesters in steady-sta te conditions.

r e a c h e d 7 5 % d u r i n g t h e f i r s t e x p e r i m e n t i n t h e u p -f l o w r eac t o r , w h i l e w i t h t h e u s e o f t h e f i x ed - b edr e a c t o r a f u r t h e r r e d u c t i o n o f 4 5 % w a s p r o d u c e d .

A s i s k n o w n , t h e s t r o n g p h y t o t o x i c i t y w h i ch t h eo l i v e - o il w a s t ew a t e r ex e r t s i s m a i n l y d u e t o t h e h i g hc o n c e n t r a t i o n o f p h e n o l s a n d a c id s .P o s s i b l e u s e f u l a p p l i c a t io n s o f t h e m e t h o dT h e a b o v e s a t i s fa c t o r y r e s u lt s f r o m t h e o p e r a t i o n o ft h e p i l o t - p l an t co n f i r m t h e p o s s i b i l it y o f t h e p r ac t i c a la p p l i c a ti o n o f t h e m e t h o d r e s ul t in g f r o m b o t h t h ec o n s i d e r a b l e r e d u c t i o n o f t h e r e t e n t i o n t i m e ( in t h ef o u r t h ex p e r i m en t t o 1 0 d ay s ) an d t h e s i m p l i f i c a t i o no f th e t o t a l t r e a t m e n t p r o c e s s ( w i t h o u t c a l c i u mh y d r o x i d e a d d it i o n a n d p r e - t r e a t m e n t s y s te m s ) . A sa n o v e r a l l c o n s e q u e n c e , r e d u c t i o n o f t h e c o n s t r u c -t i o n an d o p e r a t i o n co s t s o f t h e i n s t a l l a t io n s h o u l d b eo b t a i n e d .I n p a ra l le l , w i t h a n a p p r o p r i a t e u s e o f t h e c o n -s i d e r ab l e b i o g as p r o d u ced ( 2 .3 2 l i t r e s b i o g as / l i t r ed i g e s t e r . d ay ) i t s h o u l d b e p o s s i b l e t o ach i ev e t h er ep a y m en t o f t h e i n i ti a l c ap i ta l i n v es t m en t i n a s h o r tt i m e .H o w e v e r , i t s h o u l d b e k e p t i n m i n d t h a t t h e s u c -c e s s o f t h e p r o p o s e d m e t h o d o l o g y r e l i e s i n n o tc o n s i d e r in g t h e m e t h o d j u s t a s a w a y t o a c h i e v ee n e r g y r e c o v e r y , b u t a s a m e t h o d t o c o n t r o l t h ee n v i r o n m e n t a l p r o b l e m s c a u s e d b y s u c h p o l lu t e dw a s t e w a t e r s .

R E F E R E N C E SAmerican Public Health Association (1985). S tan dardMethods o f Wastewater Analys is . APHA, Wash ing ton ,D.C.Aveni, A. (1983). Biogas recovery from olive oil produc-t ion waste by anaerobic digest ion, R and Dprogram --recycling of urban and industrial w aste Broni(Pavia). Instituto Ricerche, Breda, Italy, 17-19 May1983.Aveni, A. & Lamarca, A. (1986). Biogas recov ery fromolive-oil mill wastewater by anaerobic digestion. In

Anae robic Digest ion: Result s o f Research and Dem onstra-tion Projects, ed. M. P. Ferranti, G. L. Fe rrero a nd P. L.Hermite. Elsevier Applied Science, London, UK, pp.236-240.Balice, C. et al. (1990). Effect of olive-oil mill wastes onsoil fertility. In Tratamiento de Alpechines , Cordoba, 2May-1 June 1990 .Boari, G., Brunetti, A., Passino, R. & Rozzi, A. (1984).Anaerobic digestion of olive oil mill wastewaters. Agric.Wastes, 16, 161-175.Cabbelo , L . R . et al. (1986) . Determination of polyphenolsand carbohydrates in vegetat ion waters by advancedassay techniques. In In t. S ymp . on O live By-products Val-orisation, Seville, pp. 119-127.Carrieri, C. & Ballice, V. (1986). Anaerobic treatment ofolive mills effluents and sewage sludge in conventionaldigesters. In Int . Symp . on Olive By-produ cts Valorisation,Seville, pp. 195-206.Carrieri, C. & Ballice, V. (1988). Anaerobic treatment ofolive mill effluents and sewage sludge in conventionaldigesters. In 5th In t. Symp . on Anaerobic Diges tion , ed .A. Niche & A. Rozzi, Bologna, Italy, pp. 481-484.Dalis , D. (1991) . Optimisat ion o f the C/N rat io dur ing theanaerobic digestion of olive-oil waste waters. In Proc.13th Na t ional Congress o f the Hellen ic Bio logical SciencesUnion , Heraklion, Crete ( in Greek) .Dalis, D., Hartmann, L. & Anagnostidis, K. (1982). Anae-robic treatment of ol ive oi l waste waters . R&D

program --recycling of urban and industr ial w aste(RUW -056) , Brussels , Belgium.Fiestas Ros de Ursinos, R. J . (1982) . Depuracion anaero-bia del alpechin como, fuente de energia. Grasas yAceites , 5, 265-270.Fiestas R os de U rsinos, J. A. (1983). Purification of vege-tat ion water by anaerobic digest ion as a means ofproducing energy. Valorisation of Olive By-products.Technical Committee Meeting, Mad rid, pp. 132-140.Georgacakis , D. & Dalis , D. (1993) . Control led anaerobicdigestion of settled olive-oil mill wastewater. Biores.Technol., 46, 221-226.Har tmann, L. (1993) . Biologische Abwasserein igung 3.Uberarbeitete. Springer, Berlin.Iniotakis, N~, Mich ailidis, P. & Koum akis, M. (1989).KctOctptal~o~ K~.ztrt])~poo #~ z~o zoxp ovt ~tonot~ ltrt lXp~lqtluov t~2tx~ov. Flpct~cr. ~ll~p. FEf~YEE - - Aprlz~l(.Opctx2eto, pp. 81-88.Rozzi, A., Santori, M. & Spinosa, L. (1984). Anaerobicdigestion in Italy with special reference to treatment of


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Digestion of whole raw olive wastewater 24 3olive-oil mil l wastes . In Anaerabic Digest ion of SewageSludge and Orga nic Agricultural W astes, ed . A . M. Br uce ,A . K outze l l - K a ts i r i & P . J . N ew man. E lsev ie r A ppl iedS c i en c e , L o n d o n , U K , p p . 5 5 - 6 5 .

Tsonis , S . P . & G r igor opoulos , S . ( 1988) . H igh r a te anae-r obic t r ea tm ent of o l ive o i l mi ll w as te w a te r . I n Proc. 5thInternational Symp. in Anaerobic Digestion. P e r g a m o nPr ess , O xf or d , U K , pp . 115- 124 .

anaerobic digestion of total raw olive-oil waste water in a two-stage pilot-plant (up-flow and...

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