PII:S0273-1223(96)OO139-4

~ Pergamon Wal.Sci. Tech. Vol. 32, No. 12, pp. S9-72. 1995.Copyright @ 1996 IAWQ. Published by Elsevier SCience Lid

Printed in Great Britain. All nghls reserved.0273-1223I9S S9'SO +0'00

CHEESE WHEY AND CHEESE FACTORYWASTEWATER TREATMENT WITH ABIOLOGICAL ANAEROBIC-AEROBICPROCESS

F. Malaspina, L. Stante, C. M. Cellamare and A. THehe

ENEA. DivisioneTecnologie di Depurazione e Trattamento Reflui;ViaMartiridi MonteSole, 4, 40129 Bologna. Italy

ABSTRACT

Researchon the anaerobic treatmentof raw cheese whey started in 1990with the objective of developingatechnologysuitable for medium size cheese factories that have growingdisposalproblemsand cannot affordhigh investmentcosts for whey valorisation technologies (such as whey protein and lactose recovery. spraydrying. ete.), In order to couple process stability and high loads. a new downflow-uptlow hybrid reactor(DUHR) has been designed. The reactor was able to reach B, values around 10 g CODeI-I.d-I, with 98%COD convertedto gas and effluentsolubleCOD valuesclose to 1,000ppm; no externaladditionof alkalinityis required to maintain a stable pH thaI was constantly around 6.5-6.7 in the downtlow pre-acidificationchamber and around 7.5 in the bio-methanation uptlow chamber. The high strength of the cheese wheytreated gives an effluent that still contains high amounts of COD, ammonia nitrogen and phosphorus andthereforea post treatmentis required in order to meet standard limits. Tests of post treatmentwere carriedout during two years with a SequencingBatch Reactor (SBR). The SBR was tested at various FIM valueswith different durations of anoxic-anaerobic-oxic cycles, obtaining. under certain conditions, more than90% removal of COD. nitrogenand phosphorus. Copyright @ 1996 IAWQ. Published by Elsevier ScienceLtd.

KEYWORDS

Anaerobic digestion; cheese whey; downflow-upflow hybrid reactor; two-phase anaerobic digestion;Sequencing Batch Reactor; nutrient removal.

INTRODUCTION

Milk whey is a byproduct that the dairy industry can reprocess or transform into other valuable products.Small and medium size cheese factories, like most of those in Italy which produce high quality typicalcheeses, do not have the economic convenience or the market dimension to afford most of the reusetechnologies available. Traditionally, these cheese factories are strictly connected to pig farms where milkWhey is directly used as the liquid basis for animal feed.

If for any reason (environmental, sanitary, economic) the downstream animal farm is lacking, a solution toWhey disposal must be found. This is the case of most cheese factories of the Sardinian Pecorino cheese;OWing to epidemic disease, pig farming in Sardinia was drastically reduced a few years ago. From the

59

60 F. MALASPINA etal:

analysis of the problem that ENEA was called to do, anaerobic digestion - followed by aerobic post­treatment together with process wastewater - came out theoretically as the most convenient solution. Biogasproduced could be economically reused to substitute most or all fossil fuels used for process thermal energygeneration; moreover, anaerobic digestion should destroy the greatest part of COD, allowing the effluent tobe post-treated together with the process wastewater in the existing treatment plants of the factories withonly little modifications to the plant structure. Anaerobic treatment of whey is not a new process. Theliterature about it is very rich, but most of the authors have worked with very diluted whey, a much simplerwaste to treat. Because of its very high biodegradability (close to 99%) and concentration (-70 geCOD-l-l)and the very low bicarbonate alkalinity (-50 meq-l-l), raw whey is a particularly difficult substrate to treat inhigh loaded anaerobic digesters. Moreover, granulation is not supposed to occur using whey as substrate(Hickey et al.; 1991), making difficult the use of UASB reactors.

In the present paper, part of the results of laboratory experiences started in 1990 are reported. The researchwas first carried out on a hybrid upflow reactor, later on a two-phase system and finally on a downflow­upflow hybrid reactor, a new concept that was specifically developed for raw whey treatment. The mainconcepts behind this design are that phases are separated within the same reactor and that, in order to obtainmore stable process conditions and higher resistance to shock loadings, a downflow completely mixed pre­acidification zone is followed by a plug-flow upflow biomethanation zone. The CSTR zone acts as a shockbuffer. In fact, the influent is introduced at the top of the downflow chamber, where mixing is very high andbacterial activity should be correspondingly high. This design could reduce the risk of pH drop in case ofrecycle pump failure. Moreover, the DSFF design of the pre-acidification chamber should reduce thepassage of acidifying biomass to the upflow part.

The effluent from the anaerobic reactor cannot be discharged into surface waters before a post-treatment forthe removal of residual organic matter and nutrients. Its composition is highly unbalanced, because most ofthe organic matter has been destroyed in the anaerobic step, while nitrogen and phosphorus arequantitatively conserved as soluble inorganic compounds. A post-treatment has been therefore designed andtested. The process is based on a Sequencing Batch Reactor. that from previous experiences hasdemonstrated to be very suited to treat wastes containing high nutrient concentrations. The organic matterneeded for the biological removal of nutrients is provided by the addition of a synthetic stream of cheesefactory process wastewater that presents a very high carbon/nitrogen ratio.

MAlERIALS AND METHODS

All experiments were carried out in mesophilic conditions, utilizing raw whey as substrate, obtained from acheese factory nearby Bologna, derived from the manufacturing of cheese from 90% cow and 10% sheepmilk. Its main characteristics are reported in Table I.

Table I.

ParameterTotal CODSoluble CODTSSVSSTKNNH4+-N

Total PP04-P

Raw cheese whey characteristics

Unit Averagerng- I-I 688 J4

mg-I" 57876g-kg" 1.3g-kg" 0.94mg-l" 1462rng-l" 64mg-I" 379mg-l" 326

St. Dcv.11518112721.140.74263314964

Data from previous experiences (Malaspina et al.; 1994) were used for the design of a downflow-upflowhybrid reactor (DUHR) that is still in operation in our laboratory (Fig. 1); results from the first nine monthsare presented here. The reactor, of the total volume of 51 1 is composed of a downflow pre-acidificationchamber where influent is pumped, filled 2/3 with a channelled polyurethane filter; on the bottom of it, this

Cheesewheyand cheesefactorywastewater treatment 61

chamber is connected with an upflow one - arranged as a hybrid reactor - that contains a similar filterlocated in the top 2/5 of it. The volumetric ratio between the two parts of the reactor is 1:5. A recycle fromthe top of the second chamber (r~.5) is applied to provide alkalinity and dilution to the influent.

An SBR of 5 dm3 of maximum capacity (Fig. 2) operated with anoxic. anaerobic and aerobic phases foreach cycle in order to obtain biological removal of organic substances and nutrients. Several tests werecarried out at different loadings and operating cycles. in order to evaluate the best operational condition forCOD. nitrogen and phosphorus removal.

In order to decrease the very high TKN/COD ratio of the anaerobic effluent, a synthetic stream of cleaningwaters of the cheese factory. rich in organic substances and poor in nutrients. was mixed with the anaerobiceffluent in a ratio similar to the true wastewater/whey volume ratio of the Parmigiano Reggiano cheesemanufacturing process: two parts of cleaning water and one part of digested effluent.

Final Volume

Initial volume

Effluenl

ipHi

Fig. I. The DUHR reactor Fig. 2. The SBR

Analyses of COD. TS. VS. TSS. VSS. NTK. total P and sulphides were performed following the StandardMethods (APHA. 1989). Monovalent anions and cations were analysed using a HPIC (Dionex 4000i). Totalalkalinity (TA) was measured titrometically at pH 3.8. Bicarbonate alkalinity (BA) was calculated fromVFA and TA values. VFA were determined gas chromatographically. using a DANI 8510 GC equipped witha 25 m - 0.53 mm 1.2 mm capillary wide bore column (Alltech SO FA bonded FSOT) and a FID detector;hYdrogen was used as carrier gas and 2. 2. dimethylbutyric acid was employed as internal standard. BiogasWas metered with wet tip gas meters and analysed gas chromatographically with a DANI 3865 GC equippedwith a TC detector; a custom made 6m - 3.18 mm teflon packed column filled with Chrompack Hayesep Callowed good separation of N2. CH4•C02 and H2S,

RESULTS AND DISCUSSION

Results of the test carried out on DUHR are presented in Figs 3 to 15. After 40 days needed for theadaptation of the seed sludge taken from a pig waste digester. By was gradually increased up to the designloading rate of 10 g COD-I-I_d-I.

62

1~ -

III

-:;

"-.:

h

1:::~

~

-d

tu "-II I , I I I I I I I I I I I

F. MALASPINA ~t al.

~ooI)

-150 - I

~.,- I ....; t& 1,- I ~ 7E 100 A

_ • --" I If _A-c .- '~ Yt.:J.. • I'" • It ~"A':-

50 ~- ..t-tr, _. h -

?! I r_"I ~ -

0I I I I I I I , I I I I , I

Fig. .l Bv applied 10 DUHR

day

Fig. 4. VFA in acidogenicta) andmethanogen ic (0) section

day

Fig. 5. pH of acidogenic (A) andrnethanogenic (0) section

After three weeks at high load, some methanogenic biomass washout due to the very high mixing caused bygas production and by the passage of acidogenic biomass from the first into the second chamber resulted ingrowth of VFA concentration and particularly of acetic acid, without causing therefore any unbalance of pHin the upflow chamber. On the other hand, the increase of loading rate resulted sometimes in pH decrease inthe downflow chamber. Phase separation allowed us to maintain stable pH in the methanogenic section alsoafter an accidental recycle breakdown happened during a weekend around day 215; during this accident, pHin the first chamber fell down to 4.9, while in the second chamber it didn't show any significant decrease.The process recovered very rapidly after recycle restore and a very little alkalinity supply (5.25 meq.l"Na2C03 + 2 meq-r! CaC03). Recycle ratios in the range 1:4 to I:2.5 were usually sufficient to providealkalinity and dilution to the influent. No external alkalinity was used for pH control, other than after theaccident described.

COD removal was always well over 90%; within the experimental By range, no dependence of CODremoval on By is shown. During a 36 days period of stable operation at 10 g COD.I- 1od-1, 98.4% CODremoval (Fig. 13) and methane production of 0.33 nl-g CODin-1 (Fig . 14) have been calculated. Peak biogasproductions close to 10 volovol-lod- I were achieved at the maximum loading. Methane content in biogasaveraged 53%, with no significant dependence on By. The high gas flow rates resulted in upflow velocities 2orders of magnitude higher with respect to the liquid upflow velocity (Fig . 15). Due to the little sludge yieldand to the absence of granulation. the correct design of a glVs separation device is critical in order tomaintain the reactor biomass content at high loading rates.

During some steady loading periods at different By, intensive profile sampling allowed us to calculate somebasic process parameters. reported in Table 2. Calculations were done making the assumption, derived fromliterature data on the polyurethane support material used (Van Rompu and Verstraete. 1988), that the filtercontained 15 g vss-i-t. Data are in very good agreement with the ones obtained in previous experienceswith a two-phase CSTR.

During the whole experiment the internal reactor liquor always showed a viscous consistency. Thisphenomenon was particularly relevant during period of overloading, like for instance in the load increaseperiods of the start-up phase, when severe washout can occur because the biomass settling capacity is highlyreduced. This phenomenon is probably due to the over-production of ExoPolySaccharides (EPS) of bacterialorigin; their synthesis uses mono- and di-saccharides, glucosamines and uronic acids as substrates, and isfavoured by high concentrations of sugars and by high CIN ratios (Sutherland, 1985; Guiot et al., 1988).

Cheese whey and cheese factory wastewater trealment 63

.....

180160

140 , '?~ 120

't 0 -:,0 ,

~t 100 , &J 2n ,E 80 J. ' , "'5-c

~~ ..,«' ~u, 60 ,

~> ,40 t .. • o·

;:0 '20 ..

Ih~B0

12 0 4 6 8 10 12

Bv gCOD.L·1.d· 1

.. .H.OO

6.00

4.00

2.00

I I

o~ ~ ~~ 8 ~ ~ :i~~~ :; ~- - - - - ""1 t"~ N N

day

Fig. 6. pH vs. Bv in acidogenicfa )and mcthanogen ic (0 ) sect ion ofDUHR

Fig. 7. VFA V5. Bv in acidogenic(. ) and Fig. 8. Biogas ( +) and methane (0)rnethanogenic (0) section of DUHR product ion of DUHR (normal ised volumes)

= N ~ ~ ~ 8 g ~ S ~ ~ ~ ~ ~day

o --t-,.~......~;W~f!1J80 100 120 140 160 180 200 220 2-10 260

day

1000

6000 ..,-- - - - - - - - - - - - ,...-,SOOO

~ 400000E 3000-c~ 2000

l'I

21XX)

IOOll

() + ...,..l.......--,.....~;,a..

SIXXI -r- - - - - - - - - - - - - ---,7 (J<X)

(JO< XI

:..,; 50m"',E ~IXX)

11. .1000>

Fig. 9. Concen trat ion of main VFA in acidogenic section ofDUHR (acet ic acid (+), propionic acid (e). n-butyric acid(A), n-valeric acid ( +) and n-capronic acid (0 )

Fig. 10. Concentration of main VFA in rnethanogenic sectionof DUHR (acetic acid (+). propionic acid (e). n-hutyric acid(A ), n-vuleric acid ( +) and n-capronic acid (0)

Table 2. DUHR kinetic parameters

Period Bv FIM Uspec. Yo!l s. J.I(d) (gCOD·L,J·d ") (gCOD·gVSS" ·d") (gCODr·gVSS-' ·d") (gVSS·gCODr") ul ')

7 7.5 0.58 0.56 0.079 0.0447 9.5 0.63 0.56 0.032 0.019

9 10 0.66 0.55 0.060 0.033

7 8 0.66 0.51 0.120 0.066

average 0.63 0.55 0.075 0.()4

51. Dev. 0.04 0.03 0.04 0.01

64 F. MALASPINAet al:

1.02 ..,...---- - -----,

1-

~ 0'). -

~ 0 .96 _ .

e (} .() .J­

1l .'1~ -•

• • • •.. ..-. Ii •

• • •• •• •,i, •

uay

I . ll ~

" • • ••::; .... •" 1l.9S~ • • • •-; • •ll.% ••::~ • •O .9~~ • •(5

1l.'12 •U • •ll.'l

II ~ I> II I 12

Il l ' ~COD 1.·' u·1

Fig, I I. COD removal during DUHR rest Fig. 12. COD removal of DUHR asfunction of applied Bv

.1I KWI ..,...- - - - - - - - - ----,.,Slop e = 1l . J .1 ~

RA 2 = 1l1)HH

x x '"" " x;::.. :z ~

x x x X x.. '" .. x xc o ;;, =t :r, ~

~ CODIIl

= x'"

51WI

21KK I~

C 151M I :J~

- )(KWI

Slo",' = O')X~

H I\ ~ =0. ( )t)<)

'" x x s x x Xx x x '" x "-r, :; <0 ,:;.. ::: c. =t

~ COD IIl

I ~ I K K I

121KKI

IllIKK) -

s: SI KKI,..(,IKM I

~ I K K I

~( K k)

0

=

Fig 13. T\bss of COD rcm versus mass orCODin Juring a period of 36 d at B v or 10

gCOD·L-l.tl- 1 in DUHR.

Fig. 14. Volume of methane produced frominlet COD during the same period.

10 ..,...- - - - - - - - - - - - - - - -,

-= 0 . 1-:: 11111

II IWIIoo

= c. -r ::!: x " r; =t z x x r: • =t ~i='o c. c. c'd ; l ~

Figure 15. Liquid flow in acidogenic (.) and methanogenic(.) section of reactor and gas flow in both sections(0) of DUHR during tbe experiment

Effluent characteristics are summarized in Table 3. The high total COD values are to be ascribed to therelevant bacterial washout at high loads - also witnessed by the high TSS and VSS figures - due to theabsence, in the laboratory reactor, of a well designed gNs device. The effluent soluble COD was very lowwith respect to the influent values but not enough to approach effluent standards, which were also exceededby nitrogen and phosphorus. It is therefore necessary to provide a post-treatment before effluent discharge.

Cheesewheyand cheesefactorywastewater treatment

Table 3. DUHR effluent characteristics

65

ParameterTotal CODSoluble CODTSSVSS

NH;-NPOrP

Unitmg·r i

mg-l"g-kg"g-kg"mg-I"

mg-I"

Average583910855.193.02816

35

St. Dev.311712633.301.69122

21

sample n.252518146

3

The addition of process wastewater deriving from dairy machinery washing, which presents high CIN ratios,allows us to compose a wastewater that can be biologically treated. Laboratory experiences carried out usinga Sequencing Batch aerobic reactor have already demonstrated the feasibility of combined carbon, nitrogenand phosphorus biological removal. SBR operated with different cycles in order to test the best operationalconditions for removing both organics and nutrients. The cycles are summarized in Fig. 16 and the averagemain characteristics of influent for SBR treatment, made of one parts of effluent from DUHR and two partsof process wastewater, are reported in Table 4.

Table 4. Main characteristics of SBR influent during the tests

Parameter Unit Average valueTotal COD mg·r l 4048Soluble COD mg-l" 2611TKN mg-I" 435NH/-N mg-l" 165.27TSS g-kg" 1.45VSS g-kg" 1.08Total P rng-I" 82.42P04-P mg-l" 27.76

Tesl2-.....-...­­Wlthelr••

Tesl3­....-...­--- Tesl.

Tesl5

II I I I Ii iii Ii iii "i i i "i i i .6 i I I 12iii '4 iii 18iii dili

Figure 16.SBRcyclesfor the five test periods.

I'd! I i ell! i pal

66 F. MALASPINA el al:

The first test lasted three months with 4 NitrificationlDenitrification (N/DN) cycles/24h at loading conditionas showed in Figs 17 and 18 and an average F/M of 0.215 gCOD.gVSS-I.d-1 (corresponding to HRT of 2.5days and B, conditions of 0.93 gCOD.dm-3.d-I).

The reactor gave very good performance both in COD and nutrient removal as shown in Figs 19 and 20.Overall performances are summarised in Table 5 (concentrations are in mgol-I, Relative Standard Deviation(RSD) and removal rates are in percent).

Table 5. Inlet and outlet average value during test #1

Parameter inlet value RSD outlet value RSD removalTotal COD 3841 19 311 42 90.7Soluble COD 2672 22 137 40 94.1TKN 410 16 16 141 93.2NH/-N 166 42 0.49 172 99.6NO,'-N 0.83 80 33 88Total P 66 46 9,63 23 93.2PO"-P 18.6 66 4 34 78.79

800

700

600 ,,-

500EE:

400 00o

300 ]I'5

200 0

5000 -r----::::-----,-- - .,---..,.----,--r--r-r.1500,

.1000

.r 3500

~ 3000

8 :?500

o 2000 -1"'-H-~-r--i--T---Trb

~ 1500

1000 -1========='i:=;= === ===±=f.500 ~ 100

o 0o 10 20 30 40 50 60 70 80 90 100

Day

Fig. 17. COD cone. in SBR during test #1

~g 0 9 +lr_--~-\

c:

0 85

o 10 20 30 40 50 60 70 80 90

Day

Fig. 19. COD removal in SBR during test #1

04 5-:r-,..---,----,.---..,.---- - ---,

04

~ 0.35

-en 0.3+--#-++-i--''----,-~---_i(/)

~025 ,

8 02 +--+---+--"'..~0. 15

~ 0.1 -'j- -+--+-!--i- - -i--1-'-=---10.05+--,--"-~-+-­

0 +--+-..-r...r-,-""""-f-.-"T"'",,,,--,---1o 10 20 30 40 50 60 70 80 90 100

Day

Fig. 18. F/M applied during test # I

0.95

0 9

iii 085>g 0 8

'"c: 0.75 -:f-<-----,--->- y .- ;-

0.7 -:J----;--~J' --+-~-­

0 65

0 6 +--+--i--i---,-.....,.....--,r--.,---.------io 10 20 30 40 50 60 70 80 90

Day

Fig. 20. Nand P removal during text # 1

Cheese whey and cheese factory wastewater treatment 67

The averaged values show quite high COD and nitrate effluent values, but they are due to some peaks thatdon't represent the normal performance, when values very close to the Italian effluent standards werereached. Very good removal of phosphorus was obtained particularly at the end of the period, when stablebiological P removal was established. The sludge had an excellent settleability.

In order to try to improve reactor performance, a second test was carried out with shorter and more frequentN/DN periods (6 cycles/24h) with the following operating conditions: By of 0.86 gCOD.dm·3.d-l, HRT of3.6 days and FIM of 0.128 gCOD.gVSS-I.d· l . Results were not satisfactory, as summarised in Table 6(concentrations are in mg-ll, RSD and removal in %), and the test was stopped after 48 days.

Table 6. Inlet and outlet average value during test #2

Parameter inlet value RSD outlet value RSD removal

Total COD 3241 42 1259 62 61.1Soluble COD 2015 74 210 54 89.5TKN 385 10 65 141 83.1NH;·N 121 79 17.6 156 85.4

NO;·N 0.72 75 60.7 62Total P 28.8 6.45 76

PO.·P 13.24 79 5.5 43 58.4

Outlet data showed high values of ammonia and nitrate due to low rates of nitrification and denitrification,whereas the very high value of COD was caused by washout of sludge due to the very consistent presence offilamentous bacteria.

The third test was run with 5 N/DN cycles/24h with organic loading as reported in Fig. 22 (averge By of0.94 gCOD.dm-3.d-l, HRT of 4 days and FIM of 0.188 gCOD.gVSS-I.d· I). Under these operating conditionsand cycles (Fig. 16) good nitrogen removal with low concentration of ammonia and nitrate in the effluentwas obtained, while P, TKN and CODt removal were poor due to wash-out of high SVI sludge (Figs 23 and24). A summary of reactor performance of this test is reported in Table 7 (concentrations are in mgel· I, RSDand removal are in %).

o 10 20 30 40 50 60 70Day

0.45 -,-- ,----- ----r- - - ---,0.4+-~f_-:...-_i_-+---,t-_i

-; 035 -'}----'I-_ _ -'--+_ -;-_ /

~ 0.3+-+-----+--j-~-I ·- \-_jC/)

~ 0.25 4-- ;-- - -;--i- - - /

g 02 4-- .--::"--.:- -1--1- -7-/

~ 0.15 + - i-- - \--+-.... -H- - _j

~ 0.1+-i---\r--j--~-

0.05+-i----;--j-~---1

o4-- r--r--r----i- --r- .--i

2000 -:;6a

500 or000 ]?so

o500 8

o70605020 30 40

Day

10o

01 )1 /1I

)\1 V rI!f J'/ i\ I j i V '\

I '\. V'T I \ 1

I t "'I / I - ~I I I I I I 1

1\ II I I\ I II i

I \ II I II II I .: I V

I -e- COOl inret II -- COOl outle t I500 2500

4500

-- 4000:..,63500

8300000.s 2500]? 2000.5o 1500

8 1000

500

o

Fig. 21. COD concentration in SBR in test #3 Fig. 22. F/1\1 applied during test #3

68 F. MALASPINA et al.

Table 7. Inlet and outlet average value during test #3

Parameter inlet value RSD outlet value RSD removal

Total COD 3542 21 800 106 77.4Soluble COD 2271 62 194 113 91.43TKN 434 51 148 55 65.7NH

4+-N 136 68 4.21 186 96.8NO,'-N 0.43 140 5.4 100Total P 141 45 49 70 65P04-P 23.4 84 7 34 70

I10 20 30 40 50 60 70

Day

I I II

Q ~ I I0 - ' -

I 0 -

,7 ~ I I If I "J I I I

~ I :"'1I

I II I I h i I

1:- Tot Nrem

~ 'r-,-

TOC al P rem Ii I ~I

I I , I i I i

1. 1

0.3

o

0.9

_ 0.8~@0.7OJ- 0.6

0.5

0.4

o.

0 8-+--~P'

0.4

03 ~"'9="T"""""F--r~,;-"..-...r--l

o 10 20 30 40 50 60 70Day

'"~ 0 7 -I--i-- HE .8 0 6+-~1---i-Cl--!- \

u0 5

Fig. 23. COD removal in SBR during test #3 Fig. 24. Nand P removal during test #3

The fourth test lasted 210 days with 4 NIDN cycles/24h at the operating conditions reported by Figs 25 and26 (average value of B, 1.36 gCOD.dm-3.d-l . HRT 3.68 days and FIM 0.27 gCOD.gVSS-I.d- I). Reactorperformance is reported in Figs 27 and 28, and summarised in Table 8 (concentrations are in mg-I- I, removaland RSD are in %).

Table 8. Inlet and outlet average value during test #4

Parameter inlet value RSD outlet value RSD removalTotal COD 4480 44 1082 99 77.8Soluble COD 3031 67 201 105 93.3TKN 484 12 153 III 68.3NH/-N 267 46 II 239 95.8NO,'-N 1.19 1.56Total P 109 85 44.4 113 59.3PO.-P 59 103 7.49 90 87.3

Also in this test some bulking problems (Fig. 29) caused wash-out and high values of total COD, TKN andtotal Phosphorus in the effluent (low removal as shown in picture); despite the high load, good performancewas obtained for nitrification and denitrification (see graph of Fig. 28).

Cheese whey and cheese factory wastewater treatment 69

10000

8000.:-~

00U0>

S 4000

~o

1.2.,.--:--:-- - ----:--:-----,----,

_ 1 + + + --:--l-+ -,-__''9~ 08en>b 0 6o

Day Day

Fig . 25. COD concentration in test #4 Fig. 26. F/M ap plied during text #4

o 0 0 0 0oq to a:) 0 N

N N

0 0 0co 0 N

o 0 0 aN .. ID

1.2 ...,----r-- - -,....- -.,...-.,--.,-- - ---,

1.1+-+---,--;--i.~_t__:_--

1

~ 0.9 ..:1:.-:f-,-!-.:-,~-+~~,t_--__i

g08+'\"1-~7-r+:' ;I-~~----i.,a: 0 .7

~ 0 .6

'"z 0.5

04 4-- -""Il-"- ,' -'-i0.3 l-l-,=;= c=;;=-= ==-="-0.2++-r~-r-r-r-+_r_.___r---j

g 8 ~N N

o 0.. ID

0.3 + I" ---rl

0.2+:-;-'++H+~r::+~

0.9

08..~ 07

~ 0.6o8 0.5 tt-trt±±±±:±:±:ji l1

0 4

Day Day

Fig. 27. COD removal in SBR dur ing test #4 Fig. 28 . N and P remova l durin g lest #4

-~ 5+-++-+~_t_~_:__+_t·t __j

til~ 4 +-- -l-+-+-+-+-- -l---:'--iH~

§ 3 +t_+,--l-+~~--.---:-- I-ju>-~ 2;;:S1o

8 ~

Day

Fig. 29. Outlet suspended solids du ring lesl #4

In order to remove filamentous bacteri a, a fifth test was carried out with unmixed fill at high load (B; of1.28 gCOD.dm-3.d-l , HRT of 3.66 days and F/M of 0.266 gCOD.gYSS ·I .d· l ) and 3 NIDN cycles/24h (seeFig. 16) according to "K, strategy" in bulking control (Chudoba, 1985).

NST l /· 12·0

70 F. MALASPINA et al:

The test lasted 76 days and gave very good results in filamentous bacteria control: after 60 days only fewfilaments were found in the sludge that, on the other hand, was very rich in big sarcinas similar to G­Bacteria. Good performance on COD and nitrogen removal was obtained (Fig. 32), while phosphorusremoval was poor (Table 9), probably due to conditions that promoted the growth of G-bacteria instead ofpolyphosphatic ones (Cech and Hartman, 1993).

Table 9. Inlet and outlet average value during test #5

Parameter inlet value RSD outlet value RSD removal

Total COD 4737 30 1960 61 58.6Soluble COD 3064 41 375 T2 87.7TKN 463 6 157 61 66.1NH/-N 136 54 6.13 122 95NO'-N 1.56 57 0.78 80

~

Total P 65.65 36 43 96 34.8P04-P 24.42 87 8.41 liS 65.5

80oo -:r-.- r== = = = = " ,

7000 -,1. --+---1

-c; 6000 i--t~i1-"";--r---,---rf--rH

g 5000 4.--hH--+--t-----j:---~O-+-H

g. 4000

:: 3000 + -t-JIU--+- +--:::P-'l82000 + --l;{- + ""'i-- +---+--t-\--+--i

, 000 +---+- +--+- +--+---+- '''P'\,-j

__ 0.25

'"~ 02 -t-~-t-" +--+---+--;-- +--1en>g o,5 -t---+-~-+--"<-i--+---+-+--j

o~ 0 1 -+---+- -'--l-- i-'>"::;u: 005 + -+__;--+_.l---+'\.~I/_~

o-+.-...-r+.,.,.,..,,..;...-....-+"TTTi-rr--+rrrri~r+r-.,..,..j

o 10 20 30 40 50 60 70 80Day

o-+---+""""'+-"-+-""""""'-+"-""""r--""....--rlo ' 0 20 30 40 50 60 70 80

Day

Fig. 30. COD in SBR during test #5 Fig. 31. F/M applied during test #5

806040Day

I ;1-I.......J /_I I;,)

I I / \ CI i 1- l!JI I I~ II~--

I

I

20

II

G." I"';--s.I

'i -B- fla COOI

...j -.- Ela COOs

0.9

08

_ 07 4- - - -;-- - i-- -+- r,-~ 06~ 0 5 +-- -"-,:i-- - :---_t-I-- _ig 0 4 +---.;-.:;~~!__-_t l--_i

U 0 3ir=="'===~"'-o..;;::::_:t--_j0.2

0.1o+::::;:::;:::;:::::;=;:::::::=;'..,..-,...__~..,...,...j

o

Fig. 32. COD removal in SBR during test #5

In summary. the SBR demonstrated to have a very good potential in nutrient and organic removal. In orderto obtain good nutrient removal together with high sludge settleability (low SVI), an equilibrium betweennumber of NIDN cycles, their duration and feeding modalities has to be found. As a general remark, shortand frequent NIDN cycles theoretically allow lower nutrient concentrations to be reached, but too shortcycles can negatively affect nitrification and denitrification. Short cycles probably favour filamentous

Cheesewheyand cheese factorywastewater treatment 71

bulking; fast and unmixed feeding and longer oxic/anoxic-anaerobic time ratios can be promising strategiesof bulking control.

Phosphorus removal was checked during tests by fractionation of cellular P in samples taken at the end ofanaerobic and aerobic phases. During the aerobic phases the content of polyphosphates in sludge (15-20mglgVSS) was about four fold respect to the samples taken during anaerobic phases (3-5 mglgVSS) andtherefore it is possible to state that biological phosphorus removal is involved in the process. Nevertheless ahigh fraction ofP was removed by precipitation as insoluble "metal-bound" compounds (20-50 mglgTSS).

Organic matter removal was very good but it was reduced by wash-out due to filamentous bulking and by abackground of unbiodegradable COD. Moreover the tests show that also in presence of very clearsupernatant, a relatively high amount of COD was found in effluent This condition is caused by abackground of unbiodegradable very fine suspended-colloidal COD coming from anaerobic digestion. Forthis reason the effluent from SBR needed a tertiary treatment to remove the unbiodegradable COD. ThisConditionoccurs only when the cheese factory uses very low amount of water (and therefore discharges lowamount of cleaning-waters) like in our simulation; in many cases however, the volume ratio betweencleaning water and cheese whey is from 4 to 6, with a dilution effect that has a positive effect on effluentquality.

Most of residual colloidal and soluble organic substances, that are not biologically degraded, can thereforebe easily removed by chemical flocculation and physical separation (flotation or settling) .

Coagulation and flocculation tests were carried out dosing FeCl3 (200-400 mg Fe.g CODin'l) and anionicpolyelectrolyte (7-20 mg polyelectrolyte.g CODin·l) with very good results: 80% COD removal and 90%total P removal.

In conclusion the biological anoxic/anaerobic/oxic process is able to treat successfully effluent fromanaerobic digestion of cheese whey when this is mixed with factory cleaning-waters. Physical-chemicaltreatments can be required in order to reach standard values when low amounts of cleaning waters aredischarged from the cheese factory.

CONCLUSIONS

Despite its very high biodegradability, raw cheese whey is a quite problematic substrate to treatanaerobically, because of the lack of alkalinity. the high COD concentration, the tendency to acidify veryrapidly, the difficulty to obtain granulation and the tendency to produce excess of viscous exopolymericmaterials of probable bacterial origin that severely reduces sludge settleability and can be a cause of biomasswashout

The DUHR design demonstrated COD removal rates of 98% at considerably high B, (10 g COD-I-I_d,l)without any need of external alkalinity supply. The particular design allows us to obtain phase separation inthe same reactor, therefore reducing investment costs with respect to separated reactors.

The SBR is a very flexible reactor for both organic matter and nutrient removal from wastewater and isParticularly suitable for post-treatment of digested whey.

The residual unbiodegradable colloidal and soluble organic substances, that are not degraded biologically,can be easily remove-d by chemical flocculation and physical separation (flotation or settling).

ACKNOWLEDGEMENTS

Authors wish to acknowledge Emanuele Sbaffi and Chiara Parmigiani for their precious collaboration .

n

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