~ Pergamon

PH: S0273-1223(99)00401-1

War &i Tech Vol. 40, No. I, pp. 323-329,1999<C> 1999IAWQ

Published by ElsevierSCIence LtdPrintedin GreatBritain. Allnghts reserved

0273-1223/99 520.00 + 0.00

BIOLOGICAL TREATABILITY OFPOULTRY PROCESSING PLANTEFFLUENT - A CASE STUDY

G. Eremektar, E. Ubay Cokgor, S. OYeZ,F. Germirli Babuna and D. Orhon

Environmental Engineering Department. Istanbul Technical University. I. T. U. IrqaatFakultesi, 80626 Maslak; Istanbul. Turkey

ABSTRACT

Poultry processing generates strong wastewaters with characteristics that may be tailored by appropriateadjustment of the operation. The organic content has a residual fraction in the order of 200-400 mgl",depending on the strength of the wastewater. The values of kinetic and stoichiometric constants related tobiological treatability are observed to be quite comparable with domestic sewage. The hydrolysis of slowlybiodegradable organics is best described by dual-hydrolysis kinetics with appreciably different rate constantsfor soluble and particulate components. The experimental results of the study may be used to evaluate theachievable compliance with existing effiuent limitations and to defme the optimum in-plant operation andwastewater treatment and disposal strategy. @ 1999 IAWQ Published by Elsevier Science. All rightsreserved.

KEYWORDS

Activated sludge; conventional characterization; COD fractionation; endogenous decay model; processkinetics; poultry processing wastewaters.

INTRODUCTION

The concept of biological treatability can be evaluated and utilized by means of two different approaches.The first approach relies on information derived from practical and empirical experience, often with aquestionable value for industrial wastewaters. The second and more rationale approach is the application offundamental microbial process kinetics through mathematical modelling. The models are used in designingthe activated sludge systems appropriate for the treatment of specified wastewaters to target levels that intum result in obtaining the requested effiuent quality, as well as in evaluating the behaviour of the systemsunder different operational conditions. Expressing the activated sludge treatment kinetics in terms of twocomponent (biomass and substrate) mathematical models is proved to be incorrect, because, in these models,firstly parameters used for substrate measurements do not correspond to the theoretical concepts, secondly,the effiuent quality is independent of the influent substrate concentration, and lastly, the influent and effiuentsubstrate characteristics are taken to be identical. Since recent studies show that these assumptions are notvalid. new multi-component models have been developed (Henze et al., 1987; Orhon and Artan, 1994).However, the application of multi-component models requires reliable experimental information on CODfractionation and kinetic and stoichiometric constants. Unfortunately, while experimental studies necessaryfor the use of such models have been conducted on domestic wastewaters, they have not been applied to

323

324 G. EREMEKTAR et a/.

industrial wastewaters apart from a few pioneering studies (Orhon et al., 1993; Gorgiin et al., 1995; GermirliBabuna et al., 1998).

In this context, the main objective of the study was to generate a new link to the available chain ofinformation on the experimental basis for biological treatability, by examining wastewaters originating froma poultry processing plant. The experimental studies involved COD fractionation with specific emphasis onthe assessment of the readily biodegradable COD component and inert COD fractions of influent origin aswell as generated as microbial products. Respective values of the yield coefficient and the maximumspecific growth rate were obtained with respirometric measurements. Values of other rate coefficients wereobtained by model simulation and calibration against observed OUR profiles. The experimental results ofthe study were used to evaluate the achievable compliance within existing effluent limitations and to definethe optimum in-plant operation and wastewater treatment and disposal strategy.

DESCRIPTION OF THE INDUSTRY

As shown in Figure 1, in the poultry processing industry live chickens are shocked with electricity and thenslaughtered. Blood is separately disposed of as solid waste. The chickens are then conveyed through a 55°Cwater bath which helps the feather plucking operation. After the feather plucking machine, feathers left onthe chickens are cleaned manually. Then the chickens are cut as demanded.

Blood

oduct

•hickens Electrical Slaughtering Washing Tank-. Shock --+ --+ 55°C

1 IPKb~mg IFeather Plucking Manual Feather Cutting f+L ~PrMachine ~ Cleaning ..

c

Figure I. Schematic process flowchart.

The wastewater sources of this process, are the intermittent disposal of the washing tank and the plantcleaning operations. The washing tank is discharged once a day and the cleaning operations are performed atthe end of the whole process. It must be noted that, no matter how many chickens are slaughtered daily, thewashing tank in every run investigated in this study has a volume of 1.5 m3 and 0.5 m3 of water is used toclean the plant.

CONCEPTUAL APPROACH

It is a well known fact that the usage of multi-component mathematical models eases the evaluation ofactivated sludge systems to a great extent. However, sound results can only be obtained by the application ofsuch models when all the necessary experimental information on wastewater characterization and kineticand stoichiometric coefficients are available. In this context, wastewater characterization covering a detailedCOD fractionation that separately identifies readily biodegradable COD, Ss; slowly biodegradable soluble(filterable) COD, SH; slowly biodegradable particulate COD, Xs; initially inert soluble COD, SI; initiallyinert particulate COD, XI; particulate inert organic products, Xp; soluble inert organic products, Sp, is anessential part of the experimental information. As can be seen from Table 1, the multi-componentendogenous decay model based on growth, decay and hydrolysis processes used in this study identifies allthe COD fractions together with the active heterotrophic biomass, XH and dissolved oxygen, So. The

Biologicaltreatmentof poultryprocessingplanteffluent 325

stoichiometric coefficients for influent soluble and particulate inert COD fractions are not included in thematrix, since S. and XI do not go through biochemical processes.

Table 1. Process kinetic and stoichiometry for carbon removal involving endogenous decay

Component..... 1 2 3 4 5 6 7 ProcessRate

Prccess-l s, SH Xs XH X, S, So ML.Jrl

I _ (I-YH) _ Ss-- I1H---XHGrowth YH I YH (Ks +Ss)

RapidHydrolysis 1 -1SH/XH

khS xH(Kxs +SH I XH)

SlowHydrolysis 1 -1 Xs/XHkh XH(Kx+Xs/X H)

Decay -1 fEX fES -(1-fEl{""fES) bHXH

Parameter, ML-' COD COD COD Cell COD COD COD ~

In the multi-component endogenous decay model, the generation of inert endogenous mass or particulateinert organic products, Xp, and the decay of active biomass are interlinked according to the viability concept.In order to evaluate the activated sludge treatment for carbon removal with the mentioned endogenous decaymodel, reliable information on kinetic and stoichiometric constants ([EX, fES, YH, ilH, Ks, bH, kh, khS, Kxsand Kx) specifically related to each industrial wastewater is also required. fEXis generally accepted as 0.2 gCOD/g cell COD in all similar activated sludge models (Henze et al., 1987). YH, bH and ilH can bedetermined from respirometric measurements by following the experimental procedures given below. fES iscalculated as a function of YHand Ysp from mass balance. For the determination of other coefficients (Ks,kh' khS, Kxs and Kx) curve fitting through model simulation is applied on the experimentally determinedOUR profiles.

EXPE~ENTALAPPROACH

All analyses related to conventional parameters were performed as defined in Standard Methods (1995). Thefiltrates of the samples subjected to vacuum filtration by means of Whatman GF/C glass fiber filter paperswere defined as "soluble" fractions. Whatman GF/C glass fiber filters were also used in the determination ofVSS and SS. Wastewaters subjected to experiments were obtained as composite samples.

The inert COD components XII and SII were determined according to a recently proposed experimentalprocedure (Germirli et al., 1993). The inert COD test involved two aerated batch reactors, of 3 litervolumetric capacity each, one fed with the unfiltered wastewater, diluted to have an appropriate initial CODconcentration, CTI,in the range of 1500 - 2000 mg r', and the other with the filtered wastewater, STI, havingthe same dilution. The seed was obtained from a lab-scale fill and draw aerobic reactor operated understeady state with the same wastewater. The microbial seed was added to secure an initial biomassconcentration of 40 mg r' VSS in both reactors. Aliquots removed periodically from the mixed liquor wereanalyzed for total and soluble (filtered) COD. Experiments were continued until the observation of a stableCOD plateau coupled with no appreciable biomass activity.

The respirometric procedure for the assessment of major kinetic and stoichiometric constants such as thereadily biodegradable COD, Ss, the maximum heterotrophic growth rate, ilH' and the heterotrophic yieldcoefficient, VH, involved using 1 I batch reactors. In the OUR test, nitrification inhibitor (Formula 2533™,Hach Company) was added to prevent any possible interference induced. The reactor was initially fed withthe wastewater sample, seeded with appropriate biomass to start with a suitable initial F/M (CTlIXTI) ratioand constantly aerated to maintain a dissolved oxygen concentration of 6-8 mg r'. The biomass waspreviously acclimatised to the same sample in a fill and draw reactor operated at a sludge age of around 10days. The readily biodegradable COD was determined in accordance with the method suggested by Ekamaet al., (1986). For the assessment of the maximum heterotrophic growth rate, the OUR reactors were run at a

326 G. EREMEKTAR et al.

FIM ratio of 4-5 g COD/g VSS as recommended by Kappeler and Gujer (1992). The heterotrophic yield wasevaluated by comparing the OUR and COD profiles obtained on the same sample in accordance with themethod proposed by Ubay Cokgor, (1997). The determination of the endogenous decay coefficient, bHinvolved removing an activated sludge sample and aerobically digesting it over a period of several days(Ekama et al., 1986). OUR measurements were conducted with a WTW OXI DIGI oxygen meter andrecorder. In the experiments the samples were adjusted to a pH of 7-8, a range suitable for biologicalactivity.

EXPERIMENTAL RESULTS AND EVALUATION

Wastewater characterization and pollution profiles

The conventional wastewater characterization originating from a poultry processing flant given in Table 2shows that, the total COD concentration is varying in the range of 1500 to 3500 mg r . The wastewaters areassociated with high nitrogen and phosphorus contents.

Table 2. Conventional wastewater characteristics

Parameters Run 1 Run 2 Run 3 Run 4Total COD (mg r l

) 3300 3420 1500 2550Soluble COD(mg r' 1495 2920 790 160080D5 (mg r l

) 2100 1050 1400 1830Oil and Grease (mg r l

) 70 79 ND NDT-P (mg r I

) 48 16 18 40TKN (mg l") 392 414 150 414NH3-N (m~ r l

) 180 235 ND NDTSS(mgr) 320 255 500 600N03(mgr1) 0.05 0.07 ND NDN02(mgrl) 0.005 0.005 ND NDPH 7.04 7.19 7.15 7.25ND: not detected

The pollution profiles obtained for different runs are shown in Table 3. As mentioned earlier, theintermittent wastewater flowrate for each run is the same, while a different number of slaughtered chickensare involved in each run. The reflections of this fact together with the varying degree of blood recovery canbe seen on the levels of unit COD loads. As a result, the unit COD loads vary between 2.7 and 3.4kgCOD.IO·3.chicken·'.

Table 3. Pollution profiles

Run NoI234

Wastewater volume (mJ)

2.02.02.02.0

Number of chickens Unit COD load (kgCOD.IO,J.chicken· l )

2400 2.72000 3.41000 3.02000 2.6

COD fractionation

Experimental results related to COD fractionation given in Table 4 indicate that the investigated wastewaterhas a biodegradable nature with a biodegradable COD to total COD ratio of 89 %. This finding is inaccordance with the COD fractionation of meat processing effluents given in literature (Gorgun et al., 1995).

Biological treatment ofpoultry processing plant effluent 327

Table 4. COD fractionation

Run No CTI Sr, S., SII SHI x., XII S.,/~, SII/CTI SH'/~' X.,/CTI XII/CTI(mg 1") (mgr') (mg 1") (mgr') (mgr') (mg 1"> (mg 1">

Thi. StudyRun 2 3420 2920 S60 330 2030 4SS 4S 0.16 0.10 0.S9 0.13 0.01Run 3 ISOO 790 84 14S S60 690 20 0.06 0.10 0.37 0.46 0.01Run 4 2SS0 1600 280 24S 107S 910 40 0.11 0.11 0.42 0.36 0.02

Meatprocessing' 2600 1140 380 30 730 IISS 30S O.IS 0.01 0.28 0.44 0.12• (Gorgunet al.,1995)subscript I defines influent characteristics

Kinetic and stoichiometric constants

The kinetic and stoichiometric coefficients of the poultry processing plant effluent are tabulated in Table 5.Endogenous decay rate bH is assumed to be 0.2 dati for all runs. The maximum specific growth rate forheterotr0phs, iiH is observed to vary between 3.5 - 4.4 dati whereas a mean half saturation constant, Ks of14 mg r is obtained. Table 5 also includes kinetic and stoichiometricdata characterizingdomestic sewage.Comparison of values for constants listed in the Table, shows that poultry processing wastewater exhibits abiodegradability pattern quite similar to that of domestic sewage, aside from the fact that it is significantlystronger,with a higher residualCOD in the effluent.

Table 5. Kinetic and stoichiometric coefficients

Run T YH iiH Ks lei,s Kxs lei, KxNo °C gcell COOl d') mgl" d·1 GCODI dO) gCODI

gCOD gcellCOD gcellCOD

2 18 0.68 3.5 28 3.5 0.12 2.1 0.73

3 19 0.68 4.4 5 3.5 0.05 2.8 0.87

4 22 0.68 3.7 10 3.0 0.05 1.9 0.25

Mean 0.68 3.9 14 3.3 0.07 1.3 0.6

DomesticSewage" 20 0.68 4.8 5 3.1 0.2 1.2 0.5

·(Sozen et al., 1998; Orhon et al., 1998)

As shown in Figure 2, two-stage hydrolysis mechanism considering readily hydrolyzable (soluble) COD, SHand slowly hydrolyzable (particulate) COD, Xs fractions separately provides the best model fit with theexperimentally determined OUR profiles.

250 ......-----------,

200 .

~~150

!.ril005

50

--Modelo Experiment

250 ......-----------....,-Model

200 Ql2II~..-O"l!:=-~.... 0 Experiment

~~150

.s~100o

50

0.10.02 0.04 0.08 0.08

TI-'''"'Y)

(b)

0-1---+--+---+--+----1o

0-1--_+_--+---+--_--1o 0.05 0.1 0.15 0.2 0.25

Tlme.(dly)

(a)

Figure 2. Model Simulation ofthe OUR Profiles for Run No 2. (a)Total wastewater. (b) Soluble wastewater.

328

CONCLUSIONS

G. EREMEKTARetal.

Poultry processing generates a strong wastewater with a COD of 1500-3500 mg 1'1, BOD, 1000-2100 mg 1'1,total nitrogen 150-400 mg 1'1 and total phosphorus 16-50 mg r'. As wastewater is basically the contents ofthe washing tank after arbitrary use, its composition much depends on the extent the tank is used forwashing and on the efficiency of blood recovery. This is a unique feature of poultry processing as comparedto other meat processing plants where the quantity and quality of the wastewater may be tailored by selectedappropriate operation.The total COD of the waste is around 89 % biodegradable, with a practicallynegligible particulate inert and significant soluble inert portion; the latter, together with soluble residualmetabolic products generation, is likely to impart a residual effluent COD concentration not less than 200 ­400 mg r', depending on the strength of the wastewater.

The wastewater exhibits characteristics quite compatible with domestic sewage, as far as coefficients (YH,iiH' K.) related to microbial growth. However, the rate ofhydrolysis of the slowly biodegradable organics isappreciably lower when assessed on the raw wastewater, evidenced by mean values of2.3 d'i for kh and 0.6g COD.g cell COD-I for K". When the same rate is measured on the soluble portion, it assumes almost thesame values as domestic sewage (kh=3.0 d·1 and K" =0.1 g COD.g cell COD'I) indicating that soluble andparticulate organics undergo hydrolysis with significantly different rates, an observation which justifies theconcept of dual hydrolysis in the modelling of activated sludge for industrial wastewaters (Orhon et al.,1998)

From a practical standpoint, the study underlines an issue of prime importance in the control of smallindustrial discharges. When effluent regulations are implemented on the basis of pollution loads, thedischarges of poultry processing may appear quite insignificant; when however, a concentration-basedeffluent control is adopted as in many countries, the discharge is inevitably categorized as a strongwastewater with a high residual COD content where compliance of stringent limitations is not feasible if notimpossible . The issue of inert COD is quite controversial as far as conceptual understanding and practicalapplications are concerned. This fraction is composed of non-biodegradable organic components eitherinitially present in the wastewater or generated as metabolic by-products. The latter is not likely to be toxic,but the initial inert COD may exert inhibitory andlor toxic effects. Therefore, a rational effluent limitationstrategy should involve experimental assessment of inhibitory or toxic effects induced by these compoundstogether with the relative significance of these effects in the receiving medium. If these effects are notsignificant, then a plant operation strategy towards generating a more diluted wash water effluent, withfewer poultry per batch, may be advisable.

NOMENCLATURE

bHCnfEX

fESkh,~s

KsKx, KxsOURSHS,SoSpSsSTXHXIXpXsYH

endogenous decay ratetotal influent CODparticulate inert fractionsoluble residual fractionmaximum specific hydrolysis rateshalf-saturation constanthalf-saturation constants for hydrolysisoxygen uptake raterapidly hydrolyzable CODsoluble inert CODoxygen concentrationsoluble residual COD generated as metabolic productsreadily biodegradable CODinfluent soluble CODactive heterotrophic biomassparticulate inert CODparticulate inert metabolic productsslowly hydrolyzable CODyield coefficient

YSP

iiH

Biological treatment ofpoultry processing plant effluent

soluble residual product ratiomaximum specific growth rate

ACKNOWLEDGEMENTS

329

This study was conducted as part of the sponsored research activities of the Environmental BiotechnologyCenter of the Scientific and Technical Research Council ofTurkey.

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