序批式反應(yīng)器處理工業(yè)廢水的牛奶生物膜系統(tǒng)Sequencing batch reactor biofilm system for treatmentof milk industry wastewaterSuntud Sirianuntapiboona,*, Narumon Jeeyachokb, Rarintorn LarplaiaaDivision of Environmental Technology, School of Energy and Materials, King Mongkuts University of Technology Thonburi (KMUTT),Thungkru, Bangmod, Bangkok 10140, ThailandbDivision of Biochemical Technology, School of Bioresources and Technology, King Mongkuts University of Technology Thonburi,Thungkru, Bangmod, Bangkok 10140, ThailandReceived 22 October 2003; revised 27 November 2004; accepted 19 January 2005Available online 21 April 2005AbstractA sequencing batch reactor biofilm (MSBR) system was modified from the conventional sequencing batch reactor (SBR) system byinstalling 2.7 m2 surface area of plastic media on the bottom of the reactor to increase the system efficiency and bio-sludge quality byincreasing the bio-sludge in the system. The COD, BOD5, total kjeldahl nitrogen (TKN) and oil & grease removal efficiencies of the MSBRsystem, under a high organic loading of 1340 g BOD5/m3 d, were 89.3G0.1, 83.0G0.2, 59.4G0.8, and 82.4G0.4%, respectively, while theywere only 87.0G0.2, 79.9G0.3, 48.7G1.7 and 79.3G10%, respectively, in the conventional SBR system. The amount of excess bio-sludgein the MSBR system was about 3 times lower than that in the conventional SBR system. The sludge volume index (SVI) of the MSBR systemwas lower than 100 ml/g under an organic loading of up to 1340 g BOD5/m3 d. However, the MSBR under an organic loadingof 680 g BOD5/m3 d gave the highest COD, BOD5, TKN and oil & grease removal efficiencies of 97.9G0.0, 97.9G0.1, 79.3G1.0 and94.8G0.5%, respectively, without any excess bio-sludge waste. The SVI of suspended bio-sludge in the MSBR system was only44G3.4 ml/g under an organic loading of 680 g BOD5/m3 d.q 2005 Elsevier Ltd. All rights reserved.Keywords: Sequencing batch reactor (SBR); Bio-film; Milk industry wastewater; Excess bio-sludge1. IntroductionThe annually increasing milk consumption in Thailandhas demanded an increase in milk production resulting in anincreasing amount of industrial wastewater (Department ofIndustrial Works, 2001, Information center). Milk industrywastewater contains high concentrations of COD, BOD5and TKN of up to 11,000, 5900 and 720 mg/l, respectively(Viraraghavan, 1994; Department of Industrial Works,2001). Several biological treatment systems have beenused such as the activated sludge system, anaerobic pond,oxidation pond, trickling filter, and the combined tricklingfilter and activated sludge system (Department of IndustrialWorks, 2001; Garrido et al., 2001; Irvine and Busch, 1979;Perle et al., 1995). However, each system had disadvantages(Ince, 1998; Metcalf & Eddy, 1991; Rusten et al., 1993).The aerated lagoon required a greater area and the effluentquality fluctuated (Metcalf & Eddy, 1991; Department ofIndustrial Works, 2001). The anaerobic pond produced abad smell caused by H2S and NH3 (Ince, 1998; Metcalf &Eddy, 1991). The activated sludge system was also selectedto treat milk industry wastewater due to its high removalefficiency (Garrido et al., 2001; Zayed and Winter, 1998),but it consumed a high amount of energy and the biosludgewas often raised and bulked in the clarifier(Sirianuntapiboon and Tondee, 2000; Cecen and Orak,1996; Metcalf & Eddy, 1991). The SBR system might besuitable to treat milk industry wastewater because of itsability to reduce nitrogen compounds by nitrification anddenitrification (Sirianuntapiboon, 2000; Metcalf & Eddy,1991; Keller et al., 1997), but the SBR system still has somedisadvantages such as the high excess sludge produced andthe high sludge volume index (Barnett et al., 1994; Bernet etal., 2000; Kagi and Uygur, 2002; Wilen and Balmer, 1998).Journal of Environmental Management 76 (2005) 177183www.elsevier.com/locate/jenvman0301-4797/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.jenvman.2005.01.018* Corresponding author. Tel.: C66 2 4708602; fax: C66 24279062/4708660.E-mail address: suntud.sirkmutt.ac.th (S. Sirianuntapiboon).In this study, an attached growth system was applied inthe conventional SBR reactor by installing plastic media onthe bottom of the SBR reactor to increase the systemefficiency, bio-sludge quality and to reduce the excessbio-sludge. The experiments were carried out in both SBRand MSBR systems to observe the phenomena ofthe systems and the removal efficiencies and quality of thebio-sludge.2. Materials and methods2.1. Laboratory wastewater treatment unitsTwo types of sequencing batch reactor (SBR) systemswere used in this study, the conventional SBR system andthe MSBR system as shown in Fig. 1. For the MSBR system,plastic media with a total surface area of 2.7 m2 (Fig. 2,Table 1) was installed on the bottom of the reactor. Both theMSBR and the SBR reactors (each of 25 l capacity) weremade from acrylic plastic (5 mm thick). The dimensions ofeach reactor were 0.29 m (diameter) by 0.35 m (height), theworking volume being 20 l. A low speed gear motor, modelP 630A-387, 100 V, 50/60 Hz, 1.7/1.3 A (Japan Servo Co.Ltd, Japan), was used for driving the paddle-shapedimpeller. The speed of the impeller was adjusted to60 rpm. One set of air pumps, model EK-8000, 6.0 W(President Co. Ltd, Thailand), was used for supplying air fortwo sets of reactors.2.2. Milk industrial wastewater (MIWW)MIWW collected from a milk factory in Bang-pa-inindustrial estate, Ayuthaya province, Thailand was used inthis study. The factory produced mainly pasteurized milkand UHT milk products. The wastewater samples wereFig. 1. MSRB and SBR systems.Fig. 2. Shape of plastic media in MSBR reactor.178 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177183collected from the sump tank of the wastewater treatmentplant once/day for 1 week to determine the chemicalproperties. The chemical properties of the wastewater areshown in Table 2.2.3. Acclimatization of bio-sludge for MSBRand SBR systemsBio-sludge from the bio-sludge storage tank of thecentral sewage treatment plant of Bangkok city (Sriphayaplant) was used as the inoculum for both the SBR andMSBR systems after being acclimatized with milk industrialwastewater for 1 week.2.4. Operation of SBR systemThe operation program of the SBR system consistedof five steps: fill, react (aeration), settle (sedimentation/clarification),draw (decant) and idle (Metcalf & Eddy, 1991)3.5 l of 10 g/l acclimatized bio-sludge was inoculated ineach reactor of both the SBR and MSBR systems, andMIWW was added (final volume of 20 l) within 2 h(fill step). During the feeding of MIWW, the system hadto be fully aerated. The aeration was then continued foranother 19 h. (react step: aeration). Aeration was then shutdown for 3 h (settle step: sedimentation/clarification). Afterthe bio-sludge was fully settled, the supernatant had to beremoved (the removed volume of the supernatant was basedon the operation program as mentioned in Table 3) within0.5 hr (draw step: decant) and the system had to be keptunder anoxic conditions (idle step) for 0.5 h. After that,fresh MIWW was filled into the reactor to the final volumeof 20 l and the above operation program was repeated. Forthe removal of excess bio-sludge to control the stablebio-sludge concentration of the reactor, the excess biosludgewas wasted from the bottom of the reactor (Fig. 1)during the idle step. In each operation condition as shown inTable 3, the reactor was operated for 30 d.2.5. Chemical analysisThe biochemical oxygen demand (BOD5), chemicaloxygen demand (COD), suspended solids (SS) total kjeldahlnitrogen (TKN), oil & grease, total phosphorus (TP) and pHof influents and effluents, mixed-liquor suspended solids(MLSS), excess sludge, and sludge volume index (SVI)were determined by using standard methods for theexamination of water and wastewater (APHA, AWWAand WPCF, 1995). The bio-film on the media was removedby washing with an acetate buffer (pH 7.0). The washedbio-film in the solution was then determined as the bio-filmmass (APHA, AWWA and WPCF, 1995). Solid retentiontime (SRT), or sludge age, was determined by measuring theaverage residence time of the suspended microorganisms(suspended bio-sludge) in the system. F/M was presented asa ratio of BOD5 loading and the total bio-sludge of thesystem.Table 1Properties of the mediaProperties ValueSize of each media, cylindrical shape 5 cm in diameter and1.25 cm in highVolume of each media 2.50 cm3Surface area of each media 0.03 m2Weight of each media 2.40 gDensity of each media 0.96 g/cm3Number of media in each MSBR reactor 90 piecesTotal surface area of media in each MSBRreactor2.7 m2Total volume of media in each MSBR reactor 225 cm3Total weight of media in each MSBR reactor 220.5 gTable 2Chemical compositions of milk industrial wastewaterChemicalcompositionsRange AverageGSDCOD (mg/l) 500010,000 7500G324BOD5 (mg/l) 30005000 4000G59TS (mg/l) 30007000 5000G46Oil & grease (mg/l) 70500 200G7.3TKN (mg/l) 50150 120G2.8TP (mg/l) 5070 60G0.41pH 4.07.0 6.0G0.62Temperature (8C) 3435 34.5G0.47Table 3Operation parameters of SBR and MSBR systemsParameters HRT (d)3 4 6 8Working volume ofreactor (l)20 20 20 20Flow rate (l/d) 6.7 5.0 3.4 2.5Replacementvolume (l/d)6.7G0.3 5.0G0.3 3.4G0.2 2.5G0.1Operating cycle(times/d)1 1 1 1Operating step (h) 24 24 24 24Fill up (h) 2.0 2.0 2.0 2.0Aeration (h) 19.0 19.0 19.0 19.0Settling (h) 1.5 1.5 1.5 1.5Draw & Idle (h) 1.5 1.5 1.5 1.5Hydraulic loading(m3/m3 d)0.34 0.25 0.17 0.13Hydraulic loading(m3/m2 d)a0.0025 0.0019 0.0012 0.0009Volumetric organicloading(g BOD5/m3 d)1340 1000 680 500Surface area-organicloading(g BOD5/m2 d)a993 741 504 370a They were used for the MSBR system.S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177183 1792.6. Statistical analyze methodEach experiment was repeated at least 3 times. All thedata were subjected to two-way analysis of variance(ANOVA) using SAS Windows Version 6.12 (SASInstitute, 1996). Statistical significance was tested usingleast significant difference (LSD) at the p!0.05 level andthe results shown are the meanGstandard deviation.3. Results3.1. Effects of organic loading on the SBR systemThe SBR system was operated with milk industrialwastewater (Table 2) under HRTs of 3, 4, 6 and 8 d asshown in Table 3. The results are shown in Fig. 3, Tables 4and 5. The system under the organic loading of up to1000 g BOD5/m3 d reached steady state within 910 d ofacclimatization while it was delayed to about 12 d under theorganic loading of 1340 g BOD5/m3 d as shown in Fig. 3.Also, the effluent qualities of the system were almost stablewhen the organic loading was decreased. The standarddeviation of effluent BOD5 under the organic loading of1340 g BOD5/m3 d was 12 while it was only 5 under theorganic loading of 500 g BOD5/m3 d as shown in Table 4.The removal efficiencies of the system increased withdecreased organic loading or increased HRT, as shown inTable 4. The BOD5 removal efficiency of the system underthe lowest organic loading of 500 g BOD5/m3 d was 10%higher than that under the highest organic loading of1340 g BOD5/m3 d as shown in Table 4. The amount ofexcess bio-sludge was also increased with the increase inorganic loading as shown in Table 5. An amount of 13.5G1.72 g/d of bio-sludge was wasted in the system withorganic loading of 1340 g BOD5/m3 d while it was only3.4G0.47 g/d at an organic loading of 500 g BOD5/m3 d.The SRT of the system under the lowest organic loading of500 g BOD5/m3 d was 15 d longer than under the highestorganic loading of 1340 g BOD5/m3 d. Also, the SVIincreased with increased organic loading, as shown inTable 5. The SVI of the system under the highest organicloading of 1340 g BOD5/m3 d was 3 times higher than underthe lowest organic loading of 500 g BOD5/m3 d.3.2. Effects of organic loading on MSBR systemThe MSBR system was operated with milk industrialwastewater under various HRT similar to the experimentwith the SBR system above (Table 3). The results are shownin Fig. 4, Tables 6 and 7. The system under the organicloading of up to 1000 g BOD5/m3 d reached steady stateFig. 3. Effluent BOD5, COD, TKN, and oil & grease profiles of SBR system %, 1340 g BOD/m3 d; &, 1000 g BOD/m3 d; :, 680 g BOD/m3 d; !,500 g BOD/m3 d.180 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177183within 56 d of acclimatization and maintained an almoststable removal efficiency as shown in Table 6. The standarddeviation of the BOD5 removal efficiency was only 0.1. Butit was delayed to about 78 d under the highest organicloading of 1340 g BOD5/m3 d as shown in Fig. 4. Theexcess bio-sludge of the system under the organic loading of1340 g BOD5/m3 d was about 6.7G0.93 g/d while therewas almost no excess sludge under the organic loading of upto 680 g BOD5/m3 d. The bio-film mass on the media alsoincreased with increased organic loading, as shown inTable 7. The total bio-film mass under the highest organicloading of 1340 g BOD5/m3 d was 52.3G0.47 g while itwas only 35.5G0.21 g under the lowest organic loadingof 500 g BOD5/m3 d. The total bio-sludge mass valuesTable 5Properties of bio-sludge of SBR system under various HRTs of 3, 4, 6, 8 daysHRT (d) Organic loading(g BOD/m3 d)Suspended bio-sludge:MLSS (mg/l)F/M (dK1) Excess sludge(g/d)Sludge age(SRT) (d)SVI (ml/g)3 1340 3500G320 0.38G0.03 13.5G1.72 5.2G0.41 142G13.14 1000 3500G193 0.29G0.02 10.3G1.14 6.8G0.57 97G8.96 680 3500G107 0.19G0.02 5.6G0.96 12.5G0.92 70G6.68 500 3500G96 0.14G0.01 3.4G0.47 20.6G1.77 55G4.8Table 4Effluent qualities and removal efficiencies of SBR system under various HRTs of 3, 4, 6, 8 daysHRT (d) Organic loading(g BOD/m3 d)COD BOD TKN Oil & grease EffluentSS (mg/l)Effluent(mg/l)% Removal Effluent(mg/l)% Removal Effluent(mg/l)% Removal Effluent(mg/l)% Removal3 1340 912G16 87.0G0.2 805G12 79.9G0.3 51G2 48.7G1.7 41G3 79.3G1 100G124 1000 456G11 93.5G0.2 423G10 89.4G0.3 44G1 56.4G0.8 26G1 87.1G0.6 80G106 680 190G8 97.3G0.1 176G8 95.6G0.2 38G1 62.3G1.0 16G1 92.1G0.6 25G68 500 122G4 98.3G0.1 106G6 97.4G0.2 21G1 79.4G1.1 11G1 94.6G0.5 15G5Fig. 4. Effluent BOD5, COD, TKN, and oil & grease profiles of MSBR system %, 1340 g BOD/m3 d; &, 1000 g BOD/m3 d; :, 680 g BOD/m3 d; !,500 g BOD/m3 d.S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177183 181of the system under organic loadings of 1340 and500 g BOD5/m3d were 112.3G13.1 and 91.5G8.6 g,respectively. Then, the F/M ratios of the system underthe above organic loadings were 0.22G0.02 and 0.11G0.01 dK1, respectively. The removal efficiencies of thesystem increased with increased HRT or decreased organicloading, as shown in Table 6. The BOD5 removal efficiencyof the system under organic loading of 1340 g BOD5/m3 dwas about 15% lower than under organic loading of500 g BOD5/m3 d. The SVI of the bio-sludge was lessthan 100 ml/g, even when the system was operated underthe highest organic loading of 1340 g BOD5/m3 d, as shownin Table 7. However, the system under an organic loading ofup to 680 g BOD5/m3 d showed the optimal COD, BOD5,TKN and oil & grease removal efficiencies of 97.9G0.0,97.9G0.1, 79.3G1.0 and 94.8G0.5%, respectively, withgood settling of bio-sludge (SVI of 44G3.4 ml/g) andwithout wasting any bio-sludge.3.3. Comparison of the efficiencies of SBRand MSBR systemsThe results are shown in Tables 47 and Figs. 3 and 4.The MSBR system was 23 d faster than the SBR system inreaching steady state and maintained almost stable removalefficiencies due to the low standard derivation values asshown in Tables 4 and 6. The COD, BOD5, TKN and oil &grease removal efficiencies of the SBR and MSBR systemsunder the highest organic loading of 1340 g BOD5/m3 dwere 87.0G0.2, 79.9G0.3, 48.7G1.7 and 79.3G1%, and89.3G0.1, 83.0G0.2, 59.4G0.8, and 82.4G0.4%, respectively,as shown in Tables 4 and 6. The total bio-sludge of theMSBR system was higher than the total bio-sludge ofthe SBR system in all cases of operation. The F/M of theMSBR system was lower than that of the SBR systemunder the same organic loading, as shown in Tables 5 and 7.The F/M of the MSBR and SBR systems under organicloading of 680 g BOD5/m3 d were 0.13G0.01 and 0.19G0.02 dK1, respectively. Also, the amount of excess biosludgeof the MSBR system was lower than that of the SBRsystem under the same organic loading as shown in Tables 5and 7. The excess bio-sludge of the MSBR and SBR systemsunder the highest organic loading of 1340 g BOD5/m3 dwere 6.7G0.93 and 13.5G1.72 g/d, respectively, and theamount of excess bio-sludge waste of the MSBR systemunder an organic loading of up to 680 became zero. Thequality of bio-sludge of the MSBR system was better thanthat of the SBR system due to the SVI value. The SVI of theMSBR system under organic loading of 1340 g BOD5/m3 d,or HRT of 3 d was only 97G8.3 ml/g while it was 142G13.1 ml/g in the SBR system as shown in Tables 5 and 7.4. Discussion and conclusionsIt can be suggested that the application of an attachedgrowth system, by installing plastic media (2.7 m2 surfacearea) on the bottom of the SBR system to obtain a MSBRsystem, could increase the removal efficiencies, improvesludge quality, reduce the amount of excess bio-sludge, andalso reduce the acclimatization period of the system. Theacclimatization time of the MSBR system was 23 d shorterthan that of the SBR system. The COD and BOD5 removalefficiencies of the MSBR system were about 57% higherthan those of the SBR system under the same organicloading condition. This can be explained by the fact that thetotal bio-sludge mass of the MSBR system was higher thanthat of the SBR system due to the increased amount ofbiofilm mass on the media of the MSBR system (Wanneret al., 1998; Watanabe et al., 1994), and as a resultthe MSBR showed a higher removal efficiency than the SBRsystem (Gebara, 1999). Another advantage of the MSBRTable 6Effluent qualities and removal efficiencies of MSBR system under various HRTs of 3, 4, 6, 8 daysHRT (d) Organic loading(g BOD/m3 d)COD BOD TKN Oil & grease EffluentSS (mg/l)Effluent(mg/l)% Removal Effluent(mg/l)% Removal Effluent(mg/l)% Removal Effluent(mg/l)% Removal3 1340 750G7 89.3G0.1 681G10 83.0G0.2 41G1 59.4G0.8 35G1 82.4G0.4 75G114 1000 403G6 94.2G0.1 323G6 91.9G0.1 31G1 69.4G1.0 22G3 89.1G1.7 62G86 680 150G3 97.9G0.0 120G3 97.0G0.1 21G1 79.3G1.0 11G1 94.8G0.5 15G68 500 102G2 98.6G0.0 91G4 97.7G0.1 13G1 87.0G1.3 6G1 97.1G0.5 10G7Table 7Properties of bio-sludge of MSBR system under various HRTs of 3, 4, 6, 8 daysHRT (d) Organic loading(g BOD/m3 d)SVI (ml/g) Suspended bio-sludge (MLSS) Sludge age(SRT) (d)Bio-film mass(g)Total biosludge(g)F/M (dK1)MLSS in thereactor (mg/l)Excess biosludge(g/d)3 1340 97G8.3 3500G174 6.7G0.93 10.5G1.02 52.3G0.47 122.3G13.1 0.22G0.024 1000 50G5.2 3500G113 3.9G0.61 18.2G1.68 45.2G0.34 115.2G15.2 0.17G0.026 680 44G3.4 3250G84 38.4G0.36 103.4G9.4 0.13G0.018 500 44G2.8 2800G56 35.5G0.21 91.5G8.6 0.11G0.01182 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177183system was the low excess sludge generation due to the hightotal bio-sludge mass in the reactor (Metcalf & Eddy, 1991;Gebara, 1999). The in