application of hybrid systems to the treatment of meat industry wastewater

Presented at the 2nd Membrane Science and Technology Conference of Visegrad Countries (PERMEA),Polanica Zdroj, Poland, 18–22 September 2005.

Desalination 198 (2006) 33–40

Application of hybrid systems to the treatment ofmeat industry wastewater

Jolanta Bohdziewicz*, Ewa SrokaInstitute of Water and Wastewater Engineering, Silesian University of Technology,

ul. Konarskiego 18, 44-100 Gliwice, PolandTel. +48 (32) 237-2981; Fax: +48 (32) 237-1047; email: [email protected]; [email protected]

Received 3 November 2005; Accepted 16 February 2006

Abstract

The study aimed to assess the effectiveness of meat industry wastewater treatment applying two hybrid systemsof activated sludge and ultrafiltration in: (1) an aerobic bioreactor in combination with ultrafiltration and (2) abioreactor equipped with separate denitrification and nitrification tanks in combination with ultrafiltration. It wasfound that it is feasible to treat this wastewater in both systems; however, the aerobic bioreactor necessitated the useof a very low activated sludge loading of 0.017 gCOD/gTS×d. Consequently, the bioreactor equipped with separatedenitrification and nitrification tanks proved to be more favourable. The substrate loading of 0.15 gCOD/gTS×d,aeration intensity of 800 dm3 and constant activated sludge loading of 4 g/dm3 were used in this system. Thewastewater treated under these conditions satisfied the requirements of the Regulation of the Minister of theEnvironment of 8 July 2004 and could be discharged into receiving water.

Keywords: Membrane bioreactor; Activated sludge; Ultrafiltration; Meat industry wastewater

1. Introduction

Owing to its nature and high loading, meatindustry wastewater has to be thoroughly treatedbefore being discharged into receiving water.

*Corresponding author.

Otherwise, it might bring about some unfavour-able processes such as the excessive use of oxy-gen dissolved in water that adversely affects themineralization of organic compounds, the growthof wastewater fungi on the bottom and banks ofa water reservoir, as well as bacteriological con-tamination causing diseases among people and

doi:10.1016/j.desal.2006.09.0060011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved.

J. Bohdziewicz, E. Sroka / Desalination 198 (2006) 33–4034

animals [1,9]. Such a reservoir can be used forneither household nor recreational purposes.

Pressure-driven membrane operations havemany advantages which make them highlyrecommended for wastewater treatment. Mem-branes, notably microfiltration and ultrafiltrationones, can be used in membrane bioreactors toenhance the transport of substances in biochemi-cal reactions. There are two ways to combinepressure-driven membrane operations with bio-logical treatment of wastewater using activatedsludge [2,8]. The first one uses a bioreactor inwhich a membrane module is physically sepa-rated from it, while in the other the membraneconstitutes an integral part of the bioreactor.

In both techniques, the biological treatment ofwastewater is based on the rules used in tradi-tional biological treatment plants in which themembrane functions as a secondary settling tank.The filtration module a complete separation ofbiomass from treated wastewater, and this con-siderably increases the concentration of activatedsludge in the aeration tank. The concentration ofthe retained sludge may be even tenfold com-pared to the amount of biomass used in thetraditional technologies which employ secondarysettling tanks. The membrane also enables theretention of swollen sludge. Thanks to theretention of suspension particles in the system

and long retention time of scarcely biodegradablesubstances, a decrease in contamination indi-cators of the treated wastewater is found. Thedecrease in COD and BOD5 reaches 96% at acomplete removal of suspension [2].

2. Materials

The wastewater was sampled from the Uni-lang meat-processing plant in Wrzosowa whoseactivity covers the slaughter and processing ofpigs. The values of the basic and eutrophicpollution indicators were high and ranged widelyduring the whole production cycle. The waste-water was red and brown in colour, smelled nastyand tended to foam and putrefy. The character-istics of the raw wastewater are presented inTable 1.

3. Methods

The wastewater pre-treated on screens, sieves,grease trap and finally flotation unit was subse-quently treated in two hybrid systems whichcombined: (1) activated sludge technique andultrafiltration (aerobic bioreactor), and (2) acti-vated sludge technique (bioreactor equipped withseparate denitrification and nitrification tanks and

Table 1Contamination characteristics of raw wastewater and their permissible values

Pollution indexes Concentration of pollution in raw wastewater [g/m3] Load [kg/d] Permissiblestandardsa [g/m3]

Range Mean value Mean value

pH 6.0–7.2 6.6 — 6.5–9.5COD 2780–6720 4584 309.2 125BOD5 1200–3000 2100 126.8 25Total nitrogen 49–287 198 13 30Total phosphorus 15–70 32 2.1 3Total suspension 112–1743 396 26.1 30

aRegulation of the Minister of the Environment of 8 July 2004 concerning the requirements of wastewater discharge intoreceiving water and ground (Bills and Acts Bulletin 168, 1763).

J. Bohdziewicz, E. Sroka / Desalination 198 (2006) 33–40 35

ultrafiltration. The studies aimed at comparing theeffectiveness of wastewater treatment in bothsystems.

The tests determined the most favourable sub-strate loading of activated sludge in the range of0.002 gCOD/gTS×d to 0.25 gCOD/gTS×d. Biomassconcentration was 4 g/dm3 in both systems. Themain criterion of wastewater treatment assess-ment was a decrease in BOD5 and COD, and theconcentrations of nitrogen and phosphorus. COD,phosphorus and total nitrogen concentrationswere determined in a Merck SQ 118 photometer[3], while BOD5 was assayed using OxiTOPmeasuring cylinders produced by WTW [4]. Theweight of activated sludge was determined usingthe gravimetric method [5].

The volumetric permeate flux (Jv) duringultrafiltration was assayed measuring the volumeof treated wastewater passing through unit area ofa membrane per unit time [m3/m2×s] [6].

4. Determination of wastewater treatment ef-fectiveness in an aerobic membrane bioreactor4.1. Apparatus

The apparatus consisted of a balancing tankjoined with a membrane bioreactor equipped witha microfiltration capillary module. Raw waste-water, degreased in a mechanical grease removalsystem, was pumped from the balancing tank intothe bioreactor filled with activated sludge. Thevolume of the reaction tank was 25 dm3.

The bottom part of the bioreactor was filledwith air whose bubbles, going upward along thecapillaries, caused them to vibrate making itimpossible for the sludge to be deposited on thesurface. This is important when the moduleoperates at a high activated sludge concentration.This method of tank aeration also enabled tho-rough mixing. The reaction tanks were equippedwith sensors that detected the level of wastewater.It was also necessary to install a balancing tank toensure a constant, assumed loading of the sludge.The schematic of the system is shown in Fig. 1.

Fig. 1. Schematic of aerobic membrane bioreactor. 1 rawwastewater tank, 2 pump, 3 membrane module, 4 aeratedtank with activated sludge, 5 air inlet, 6 treated waste-water outlet.

The polymer capillary membranes used in thetests and manufactured in Canada were purchasedfrom Zenon System (Tychy). They were of highmechanical strength and chemical resistance [7].

Fig. 2 shows the schematic of the capillarymodule and its operation. Thus far, this type ofcapillary module has been used in Zee Weed totreat surface waters of different contaminationlevels [7]. During the tests, the capillary moduleoperated at a low pressure of 2.5×10!4–11×10!4

MPa, created by the pump of the filtrate. Air(800 dm3/h) was pumped into the bottom part ofthe aerobic tank. The wastewater treated biologic-ally flowed inside through the walls of thecapillaries.

4.2. Results and discussion

Fig. 3 shows the correlation between adecrease in COD of treated wastewater andactivated sludge loading. The highest CODremoval of 98.1% which corresponded to a CODconcentration of 73 gO2/m3 (raw wastewater3880 gO2/m3) was observed for the loading of0.063 gCOD/gTS×d. The lowest removal of con-taminants (93.2%) was found for the sludgeloading of 0.004 g COD/gTS×d. The decrease inBOD5 in the treated wastewater was limited, simi-larly to COD, by the value of activated sludgeloading (Fig. 3). Its maximum removal reached99.4% for a sludge loading of 0.063 gCOD/gTS×d


Fig. 2. Schematic of capillary module and itsoperation.

Fig. 3. Correlation between COD and BOD5 removal andsubstrate loading of activated sludge.

(from 1600 gO2/m3 down to 10 gO2/m3). Thelowest removal of organic substances of 97.6%

Fig. 4. Correlation between nitrogen and phosphorusremoval and activated sludge loading.

was observed at the sludge loading of 0.004gCOD/gTS×d (BOD5 of treated wastewater,20 gO2/m3).


A strong impact of sludge loading on theconcentration of total nitrogen in the treatedwastewater was also observed. The highestdecrease in the concentration of that biogene byas much as 82.1% (treated wastewater, 29 gNtot/m3) was found for the sludge loading of0.017 gCOD/gTS×d. The lowest removal oftotal nitrogen amounted to 65.7% for the load-ing of 0.05 gCOD/gTS×d (treated wastewater,55.6 gNtot/m3).

Phosphorus was the next element to be deter-mined (Fig. 4.). The most favourable results wereobtained for the sludge loading of 0.003 gCOD/gTS×d (89.6%: 3.0 g/m3 in treated wastewater).The lowest removal of phosphorus of 67.9% wasobserved for the loading of 0.063 gCOD/gTS×d(treated wastewater, 9.3 gP/m3).

It was found that not all the values of contami-nation indicators determined were the lowest forthe same loading of activated sludge. Since thehighest substrate loading of activated sludgewhich ensured the satisfactory removal of Ntotfrom the wastewater reached 0.017 gCOD/gTS×d,it was chosen as the most favourable to carry outthe process.

Table 2 gives the values of contaminationindicators in the treated wastewater for the opti-mum activated sludge loading of 0.017 gCOD/gTS×d. Under those conditions, it was possible totreat it to the extent which enabled its directdischarge into receiving water.

5. Wastewater treatment in a membrane bio-reactor equipped with separate denitrificationand nitrification tanks

5.1. ApparatusThe apparatus used consisted of a balancing

tank, anaerobic tank and finally aerobic one inwhich an ultrafiltration capillary module wasinstalled. Raw wastewater was pumped from thebalancing tank into the 25 dm3 anaerobic tank andsubsequently to a 25 dm3 aerobic tank. The recir-

Fig. 5. Schematics of a membrane bioreactor equippedwith a capillary immersion module: 1 balancing tank (rawwastewater), 2 pump, 3 mechanical stirrer, 4 anaerobictank, 5 activated sludge recirculation, 6 air inlet, 7 aero-bic tank, 8 membrane, 9 treated wastewater outlet.

culation of the sludge from the aerobic tank intothe anaerobic one was 300%. Denitrification tookplace in the anaerobic tank while nitrification inthe aerobic one. The schematic of the apparatus isshown in Fig. 5. The tests employed the samemembrane capillary module used in the aerobicmembrane bioreactor.

5.2. Results and discussion

It was found that COD and BOD5 for treatedwastewater depended negligibly on the activatedsludge loadings applied (Fig. 6). Their removalwas stable and ranged from 97% to 99%. Theydid not exceed the permissible standards forwastewater discharge into receiving water (15–28 COD/dm3, 8–10 gBOD5/dm3).

The subsequent stage of the research showeda significant correlation between biogenic com-pounds removal from treated wastewater andactivated sludge loading. As far as total nitrogenis concerned, its highest removal of 81.4% wasfound for the activated sludge loading of0.14 gCOD/gTS×d (Fig. 7) (raw wastewater,130 gNtot/m3; treated wastewater, 24.2 gNtot/m3).The lowest removal of total nitrogen of 72.7%(raw wastewater, 154 gNtot/m3; treated wastewater


Table 2Decrease in contamination indicators for treated wastewater at activated sludge loading of 0.017 gCOD/gTS×d

Pollution indices Concentration of pollution in rawwastewater [g/m3]

Retention R[%]

Concentration of pollution in purifiedwastewater [g/m3]

COD 3880 96.9 115BOD5 1600 99.1 14Total nitrogen 162 82.1 29Ammonia nitrogen 48 98.8 0.6Total phosphorus 29 86.5 3.9

Table 3Effectiveness of wastewater treatment in membrane bioreactor using an activated sludge loading of 0.14 gCOD/gTS×d

Pollution indices Concentration of pollution in rawwastewater [g/m3]

Retention R[%]

Concentration of pollution in purifiedwastewater [g/m3]

COD 1480 98.1 22.0BOD5 980 99.0 9.0Total nitrogen 130 98.2 24.2Total phosphorus 7.4 87.3 2.9

Fig. 6. Correlation between COD and BOD5 removal andactivated sludge loading.

42.1 gNtot/m3) was observed for the loading of0.25 gCOD/gTS×d.

Phosphorus removal appeared to be the mostdependent on sludge loading. Its lowest concen-tration in the treated wastewater of 2.9 gP/m3

(60.7% of removal) was found at the activatedsludge loading of 0.14 gCOD/gTS×d. The lowestphosphorus removal was observed for the sludge

Fig. 7. Correlation between biogenic compound removaland activated sludge loading.

loading of 0.26 gCOD/gTS.×d (41.2%), whichcorresponded to the removal of phosphorus fromraw wastewater to the concentration of 4.4 gP/m3

(Fig. 7). This all points to the conclusion that0.14 gCOD/gTS×d was the most favourable sub-strate loading of activated sludge for the processin question (Table 3).


6. Conclusions

The most favourable substrate loading of acti-vated sludge in the aerobic membrane bioreactorwas 0.017 gCOD/gTS×d. Despite being low, thisloading enabled a satisfactory removal of totalnitrogen (and other contaminants as well) fromthe treated wastewater. It was found that the bio-reactor equipped with separate denitrification andnitrification tanks yielded similar results as theaerobic bioreactor when applying a tenfold acti-vated sludge loading. Thus, this solution has beenconsidered as more favourable.

In previous research the purification of waste-water coming from the meat industry was unde-rtaken but in a different hybrid systems: (1) acti-vated sludge (SBR) with reverse osmosis [10,11];(2) activated sludge (SBR) with coagulation [12];(3) ultrafiltration with reverse osmosis [13];(4) coagulation with reverse osmosis [13]; and(5) coagulation with ultrafiltration and reverseosmosis [14]. It was proved that there was thepossibility of effective purification of wastewatercoming from the meat industry in all analysedprocesses. Depending on the method of purifi-cation, the cleaned wastewater could be drainedaway to receiving water or turned back to theproduction cycle.

However, the most profitable system from allthose analyzed during the entire research periodwas the bioreactor equipped with separate denitri-fication and nitrification tanks. The resultsobtained during wastewater treatment in thissystem are discussed in a subsequent article.

The membrane bioreactor has an advantage incomparison to conventional wastewater treatment(e.g., SBR), as it does not only serve as asecondary settling tank but also removes macro-molecular contaminants. The activated sludgecontact period is extended; however, the hydrau-lic retention time of treated wastewater in theaerobic tank is reduced.

As the research shows, it is possible to usehigher concentrations of suspensions in the

activated sludge tank (up to 30 kg/m3, while it isonly 1.5–3.0 kg/m3 in conventional treatmentplants), which enables the sludge to operate atlower substrate loadings.

When the wastewater needs to be recirculatedto the production cycle, an additional treatmentusing reverse osmosis is recommended.

References

[1] B. Koziorowski and J. Kucharski, Ściekiprzemysłowe, WNT, Warszawa, 1980.

[2] P. Cote, H. Buisson and M. Pruderie, Proces oczy-szczania ścieków komunalnych osadem czynnymz filtracją na membranach zanurzeniowych,Materiały z III Międzynarodowego ForumGospodarki Odpadami nt. Techniczne i społeczneaspekty gospodarki odpadami, Poznań, 1999.

[3] User’s manual, Photometer SQ 118, Merck.[4] User’s manual, Determination of BZT using respiro-

metric Method, Oxi Top, WTW.[5] W. Hermanowicz, (Red.), Fizyczno-chemiczne

badanie wody i ścieków, Arkady, Warszawa, 1998.[6] M. Bodzek, J. Bohdziewicz and K. Konieczny,

Techniki membranowe w ochronie środowiska,Wydawnictwo Politechniki Śląskiej, Gliwice, 1997.

[7] A. Potrzebka and J. Wawrzyńczyk, Zastosowanietechnologii mikrofiltracji Zee Weed do uzdatnianiazanieczyszczonych wód powierzchniowych dlaprodukcji wody pitnej, Zeszyty NaukowePolitechniki Śląskiej, Inżynieria Środowiska, 2002,pp. 137–146.

[8] N. Cicek, Membrane bioreactors in the treatment ofwastewater generated from agricultural industriesand activities, Presented, AIC Meeting, Saskatoon,Saskatchewan, 2002, Paper No. 02-404.

[9] P.O. Bickers and A.J. van Oostrom, Availability fordenitrification of organic carbon in meat-processingwastestreams, Biores. Technol., 73 (2000) 53–58.

[10] J. Bohdziewicz and E. Sroka, Integrated system ofactivated sludge–reverse osmosis in the treatment ofthe wastewater from the meat industry, ProcessBiochem., 40(5) (2005) 1517–1523.

[11] E. Sroka, W. Kaminski and J. Bohdziewicz, Bio-logical treatment of meat industry wastewater,Desalination, 162 (2004) 85–91.


[12] J. Bohdziewicz, E. Sroka and E. Lobos, Applicationof the system which combines coagulation, activatedsludge and reverse osmosis to the treatment of thewastewater produced by the meat industry, Desali-nation, 144 (2002) 393–398.

[13] J. Bohdziewicz, E. Sroka and I. Korus, Applicationof ultrafiltration and reverse osmosis to the treatment

of the wastewater produced by the meat industry,Polish J. Environ. Stud., 12(3) (2003) 269–274.

[14] J. Bohdziewicz and E. Sroka, Treatment of waste-water from the meat industry applying integratedmembrane systems, Process Biochem., 40(3–4)(2005) 1339–1346.

application of hybrid systems to the treatment of meat industry wastewater

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