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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 treatment of milk industry wastewater Suntud Sirianuntapiboona,*, Narumon Jeeyachokb, Rarintorn Larplaia aDivision of Environmental Technology, School of Energy and Materials, King Mongkut’s University of Technology Thonburi (KMUTT), Thungkru, Bangmod, Bangkok 10140, Thailand bDivision of Biochemical Technology, School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, Thungkru, Bangmod, Bangkok 10140, Thailand Received 22 October 2003; revised 27 November 2004; accepted 19 January 2005 Available online 21 April 2005 Abstract A sequencing batch reactor biofilm (MSBR) system was modified from the conventional sequencing batch reactor (SBR) system by installing 2.7 m2 surface area of plastic media on the bottom of the reactor to increase the system efficiency and bio-sludge quality by increasing the bio-sludge in the system. The COD, BOD5, total kjeldahl nitrogen (TKN) and oil & grease removal efficiencies of the MSBR system, 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 they were only 87.0G0.2, 79.9G0.3, 48.7G1.7 and 79.3G10%, respectively, in the conventional SBR system. The amount of excess bio-sludge in the MSBR system was about 3 times lower than that in the conventional SBR system. The sludge volume index (SVI) of the MSBR system was lower than 100 ml/g under an organic loading of up to 1340 g BOD5/m3 d. However, the MSBR under an organic loading of 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 and 94.8G0.5%, respectively, without any excess bio-sludge waste. The SVI of suspended bio-sludge in the MSBR system was only 44G3.4 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-sludge 1. Introduction The annually increasing milk consumption in Thailand has demanded an increase in milk production resulting in an increasing amount of industrial wastewater (Department of Industrial Works, 2001, Information center). Milk industry wastewater contains high concentrations of COD, BOD5 and TKN of up to 11,000, 5900 and 720 mg/l, respectively (Viraraghavan, 1994; Department of Industrial Works, 2001). Several biological treatment systems have been used such as the activated sludge system, anaerobic pond, oxidation pond, trickling filter, and the combined trickling filter and activated sludge system (Department of Industrial Works, 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 effluent quality fluctuated (Metcalf & Eddy, 1991; Department of Industrial Works, 2001). The anaerobic pond produced a bad smell caused by H2S and NH3 (Ince, 1998; Metcalf & Eddy, 1991). The activated sludge system was also selected to treat milk industry wastewater due to its high removal efficiency (Garrido et al., 2001; Zayed and Winter, 1998), but it consumed a high amount of energy and the biosludge was often raised and bulked in the clarifier (Sirianuntapiboon and Tondee, 2000; Cecen and Orak, 1996; Metcalf & Eddy, 1991). The SBR system might be suitable to treat milk industry wastewater because of its ability to reduce nitrogen compounds by nitrification and denitrification (Sirianuntapiboon, 2000; Metcalf & Eddy, 1991; Keller et al., 1997), but the SBR system still has some disadvantages such as the high excess sludge produced and the high sludge volume index (Barnett et al., 1994; Bernet et al., 2000; Kagi and Uygur, 2002; Wilen and Balmer, 1998). Journal of Environmental Management 76 (2005) 177–183 www.elsevier.com/locate/jenvman 0301-4797/$ - 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 2 4279062/4708660. E-mail address: suntud.sir@kmutt.ac.th (S. Sirianuntapiboon). In this study, an attached growth system was applied in the conventional SBR reactor by installing plastic media on the bottom of the SBR reactor to increase the system efficiency, bio-sludge quality and to reduce the excess bio-sludge. The experiments were carried out in both SBR and MSBR systems to observe the phenomena of the systems and the removal efficiencies and quality of the bio-sludge. 2. Materials and methods 2.1. Laboratory wastewater treatment units Two types of sequencing batch reactor (SBR) systems were used in this study, the conventional SBR system and the 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 the MSBR and the SBR reactors (each of 25 l capacity) were made from acrylic plastic (5 mm thick). The dimensions of each reactor were 0.29 m (diameter) by 0.35 m (height), the working volume being 20 l. A low speed gear motor, model P 630A-387, 100 V, 50/60 Hz, 1.7/1.3 A (Japan Servo Co. Ltd, Japan), was used for driving the paddle-shaped impeller. The speed of the impeller was adjusted to 60 rpm. One set of air pumps, model EK-8000, 6.0 W (President Co. Ltd, Thailand), was used for supplying air for two sets of reactors. 2.2. Milk industrial wastewater (MIWW) MIWW collected from a milk factory in Bang-pa-in industrial estate, Ayuthaya province, Thailand was used in this study. The factory produced mainly pasteurized milk and UHT milk products. The wastewater samples were Fig. 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) 177–183 collected from the sump tank of the wastewater treatment plant once/day for 1 week to determine the chemical properties. The chemical properties of the wastewater are shown in Table 2. 2.3. Acclimatization of bio-sludge for MSBR and SBR systems Bio-sludge from the bio-sludge storage tank of the central sewage treatment plant of Bangkok city (Sriphaya plant) was used as the inoculum for both the SBR and MSBR systems after being acclimatized with milk industrial wastewater for 1 week. 2.4. Operation of SBR system The operation program of the SBR system consisted of 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 in each reactor of both the SBR and MSBR systems, and MIWW was added (final volume of 20 l) within 2 h (fill step). During the feeding of MIWW, the system had to be fully aerated. The aeration was then continued for another 19 h. (react step: aeration). Aeration was then shut down for 3 h (settle step: sedimentation/clarification). After the bio-sludge was fully settled, the supernatant had to be removed (the removed volume of the supernatant was based on the operation program as mentioned in Table 3) within 0.5 hr (draw step: decant) and the system had to be kept under anoxic conditions (idle step) for 0.5 h. After that, fresh MIWW was filled into the reactor to the final volume of 20 l and the above operation program was repeated. For the removal of excess bio-sludge to control the stable bio-sludge concentration of the reactor, the excess biosludge was wasted from the bottom of the reactor (Fig. 1) during the idle step. In each operation condition as shown in Table 3, the reactor was operated for 30 d. 2.5. Chemical analysis The biochemical oxygen demand (BOD5), chemical oxygen demand (COD), suspended solids (SS) total kjeldahl nitrogen (TKN), oil & grease, total phosphorus (TP) and pH of influents and effluents, mixed-liquor suspended solids (MLSS), excess sludge, and sludge volume index (SVI) were determined by using standard methods for the examination of water and wastewater (APHA, AWWA and WPCF, 1995). The bio-film on the media was removed by washing with an acetate buffer (pH 7.0). The washed bio-film in the solution was then determined as the bio-film mass (APHA, AWWA and WPCF, 1995). Solid retention time (SRT), or sludge age, was determined by measuring the average residence time of the suspended microorganisms (suspended bio-sludge) in the system. F/M was presented as a ratio of BOD5 loading and the total bio-sludge of the system. Table 1 Properties of the media Properties Value Size of each media, cylindrical shape 5 cm in diameter and 1.25 cm in high Volume of each media 2.50 cm3 Surface area of each media 0.03 m2 Weight of each media 2.40 g Density of each media 0.96 g/cm3 Number of media in each MSBR reactor 90 pieces Total surface area of media in each MSBR reactor 2.7 m2 Total volume of media in each MSBR reactor 225 cm3 Total weight of media in each MSBR reactor 220.5 g Table 2 Chemical compositions of milk industrial wastewater Chemical compositions Range AverageGSD COD (mg/l) 5000–10,000 7500G324 BOD5 (mg/l) 3000–5000 4000G59 TS (mg/l) 3000–7000 5000G46 Oil & grease (mg/l) 70–500 200G7.3 TKN (mg/l) 50–150 120G2.8 TP (mg/l) 50–70 60G0.41 pH 4.0–7.0 6.0G0.62 Temperature (8C) 34–35 34.5G0.47 Table 3 Operation parameters of SBR and MSBR systems Parameters HRT (d) 3 4 6 8 Working volume of reactor (l) 20 20 20 20 Flow rate (l/d) 6.7 5.0 3.4 2.5 Replacement volume (l/d) 6.7G0.3 5.0G0.3 3.4G0.2 2.5G0.1 Operating cycle (times/d) 1 1 1 1 Operating step (h) 24 24 24 24 Fill up (h) 2.0 2.0 2.0 2.0 Aeration (h) 19.0 19.0 19.0 19.0 Settling (h) 1.5 1.5 1.5 1.5 Draw & Idle (h) 1.5 1.5 1.5 1.5 Hydraulic loading (m3/m3 d) 0.34 0.25 0.17 0.13 Hydraulic loading (m3/m2 d)a 0.0025 0.0019 0.0012 0.0009 Volumetric organic loading (g BOD5/m3 d) 1340 1000 680 500 Surface area-organic loading (g BOD5/m2 d)a 993 741 504 370 a They were used for the MSBR system. S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 179 2.6. Statistical analyze method Each experiment was repeated at least 3 times. All the data were subjected to two-way analysis of variance (ANOVA) using SAS Windows Version 6.12 (SAS Institute, 1996). Statistical significance was tested using least significant difference (LSD) at the p!0.05 level and the results shown are the meanGstandard deviation. 3. Results 3.1. Effects of organic loading on the SBR system The SBR system was operated with milk industrial wastewater (Table 2) under HRTs of 3, 4, 6 and 8 d as shown in Table 3. The results are shown in Fig. 3, Tables 4 and 5. The system under the organic loading of up to 1000 g BOD5/m3 d reached steady state within 9–10 d of acclimatization while it was delayed to about 12 d under the organic loading of 1340 g BOD5/m3 d as shown in Fig. 3. Also, the effluent qualities of the system were almost stable when the organic loading was decreased. The standard deviation of effluent BOD5 under the organic loading of 1340 g BOD5/m3 d was 12 while it was only 5 under the organic loading of 500 g BOD5/m3 d as shown in Table 4. The removal efficiencies of the system increased with decreased organic loading or increased HRT, as shown in Table 4. The BOD5 removal efficiency of the system under the lowest organic loading of 500 g BOD5/m3 d was 10% higher than that under the highest organic loading of 1340 g BOD5/m3 d as shown in Table 4. The amount of excess bio-sludge was also increased with the increase in organic loading as shown in Table 5. An amount of 13.5G 1.72 g/d of bio-sludge was wasted in the system with organic loading of 1340 g BOD5/m3 d while it was only 3.4G0.47 g/d at an organic loading of 500 g BOD5/m3 d. The SRT of the system under the lowest organic loading of 500 g BOD5/m3 d was 15 d longer than under the highest organic loading of 1340 g BOD5/m3 d. Also, the SVI increased with increased organic loading, as shown in Table 5. The SVI of the system under the highest organic loading of 1340 g BOD5/m3 d was 3 times higher than under the lowest organic loading of 500 g BOD5/m3 d. 3.2. Effects of organic loading on MSBR system The MSBR system was operated with milk industrial wastewater under various HRT similar to the experiment with the SBR system above (Table 3). The results are shown in Fig. 4, Tables 6 and 7. The system under the organic loading of up to 1000 g BOD5/m3 d reached steady state Fig. 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) 177–183 within 5–6 d of acclimatization and maintained an almost stable removal efficiency as shown in Table 6. The standard deviation of the BOD5 removal efficiency was only 0.1. But it was delayed to about 7–8 d under the highest organic loading of 1340 g BOD5/m3 d as shown in Fig. 4. The excess bio-sludge of the system under the organic loading of 1340 g BOD5/m3 d was about 6.7G0.93 g/d while there was almost no excess sludge under the organic loading of up to 680 g BOD5/m3 d. The bio-film mass on the media also increased with increased organic loading, as shown in Table 7. The total bio-film mass under the highest organic loading of 1340 g BOD5/m3 d was 52.3G0.47 g while it was only 35.5G0.21 g under the lowest organic loading of 500 g BOD5/m3 d. The total bio-sludge mass values Table 5 Properties of bio-sludge of SBR system under various HRTs of 3, 4, 6, 8 days HRT (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 142G13.1 4 1000 3500G193 0.29G0.02 10.3G1.14 6.8G0.57 97G8.9 6 680 3500G107 0.19G0.02 5.6G0.96 12.5G0.92 70G6.6 8 500 3500G96 0.14G0.01 3.4G0.47 20.6G1.77 55G4.8 Table 4 Effluent qualities and removal efficiencies of SBR system under various HRTs of 3, 4, 6, 8 days HRT (d) Organic loading (g BOD/m3 d) COD BOD TKN Oil & grease Effluent SS (mg/l) Effluent (mg/l) % Removal Effluent (mg/l) % Removal Effluent (mg/l) % Removal Effluent (mg/l) % Removal 3 1340 912G16 87.0G0.2 805G12 79.9G0.3 51G2 48.7G1.7 41G3 79.3G1 100G12 4 1000 456G11 93.5G0.2 423G10 89.4G0.3 44G1 56.4G0.8 26G1 87.1G0.6 80G10 6 680 190G8 97.3G0.1 176G8 95.6G0.2 38G1 62.3G1.0 16G1 92.1G0.6 25G6 8 500 122G4 98.3G0.1 106G6 97.4G0.2 21G1 79.4G1.1 11G1 94.6G0.5 15G5 Fig. 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) 177–183 181 of the system under organic loadings of 1340 and 500 g BOD5/m3d were 112.3G13.1 and 91.5G8.6 g, respectively. Then, the F/M ratios of the system under the above organic loadings were 0.22G0.02 and 0.11G 0.01 dK1, respectively. The removal efficiencies of the system increased with increased HRT or decreased organic loading, as shown in Table 6. The BOD5 removal efficiency of the system under organic loading of 1340 g BOD5/m3 d was about 15% lower than under organic loading of 500 g BOD5/m3 d. The SVI of the bio-sludge was less than 100 ml/g, even when the system was operated under the highest organic loading of 1340 g BOD5/m3 d, as shown in Table 7. However, the system under an organic loading of up 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, with good settling of bio-sludge (SVI of 44G3.4 ml/g) and without wasting any bio-sludge. 3.3. Comparison of the efficiencies of SBR and MSBR systems The results are shown in Tables 4–7 and Figs. 3 and 4. The MSBR system was 2–3 d faster than the SBR system in reaching steady state and maintained almost stable removal efficiencies due to the low standard derivation values as shown in Tables 4 and 6. The COD, BOD5, TKN and oil & grease removal efficiencies of the SBR and MSBR systems under the highest organic loading of 1340 g BOD5/m3 d were 87.0G0.2, 79.9G0.3, 48.7G1.7 and 79.3G1%, and 89.3G0.1, 83.0G0.2, 59.4G0.8, and 82.4G0.4%, respectively, as shown in Tables 4 and 6. The total bio-sludge of the MSBR system was higher than the total bio-sludge of the SBR system in all cases of operation. The F/M of the MSBR system was lower than that of the SBR system under the same organic loading, as shown in Tables 5 and 7. The F/M of the MSBR and SBR systems under organic loading of 680 g BOD5/m3 d were 0.13G0.01 and 0.19G 0.02 dK1, respectively. Also, the amount of excess biosludge of the MSBR system was lower than that of the SBR system under the same organic loading as shown in Tables 5 and 7. The excess bio-sludge of the MSBR and SBR systems under the highest organic loading of 1340 g BOD5/m3 d were 6.7G0.93 and 13.5G1.72 g/d, respectively, and the amount of excess bio-sludge waste of the MSBR system under an organic loading of up to 680 became zero. The quality of bio-sludge of the MSBR system was better than that of the SBR system due to the SVI value. The SVI of the MSBR system under organic loading of 1340 g BOD5/m3 d, or HRT of 3 d was only 97G8.3 ml/g while it was 142G 13.1 ml/g in the SBR system as shown in Tables 5 and 7. 4. Discussion and conclusions It can be suggested that the application of an attached growth system, by installing plastic media (2.7 m2 surface area) on the bottom of the SBR system to obtain a MSBR system, could increase the removal efficiencies, improve sludge quality, reduce the amount of excess bio-sludge, and also reduce the acclimatization period of the system. The acclimatization time of the MSBR system was 2–3 d shorter than that of the SBR system. The COD and BOD5 removal efficiencies of the MSBR system were about 5–7% higher than those of the SBR system under the same organic loading condition. This can be explained by the fact that the total bio-sludge mass of the MSBR system was higher than that of the SBR system due to the increased amount of biofilm mass on the media of the MSBR system (Wanner et al., 1998; Watanabe et al., 1994), and as a result the MSBR showed a higher removal efficiency than the SBR system (Gebara, 1999). Another advantage of the MSBR Table 6 Effluent qualities and removal efficiencies of MSBR system under various HRTs of 3, 4, 6, 8 days HRT (d) Organic loading (g BOD/m3 d) COD BOD TKN Oil & grease Effluent SS (mg/l) Effluent (mg/l) % Removal Effluent (mg/l) % Removal Effluent (mg/l) % Removal Effluent (mg/l) % Removal 3 1340 750G7 89.3G0.1 681G10 83.0G0.2 41G1 59.4G0.8 35G1 82.4G0.4 75G11 4 1000 403G6 94.2G0.1 323G6 91.9G0.1 31G1 69.4G1.0 22G3 89.1G1.7 62G8 6 680 150G3 97.9G0.0 120G3 97.0G0.1 21G1 79.3G1.0 11G1 94.8G0.5 15G6 8 500 102G2 98.6G0.0 91G4 97.7G0.1 13G1 87.0G1.3 6G1 97.1G0.5 10G7 Table 7 Properties of bio-sludge of MSBR system under various HRTs of 3, 4, 6, 8 days HRT (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 the reactor (mg/l) Excess biosludge (g/d) 3 1340 97G8.3 3500G174 6.7G0.93 10.5G1.02 52.3G0.47 122.3G13.1 0.22G0.02 4 1000 50G5.2 3500G113 3.9G0.61 18.2G1.68 45.2G0.34 115.2G15.2 0.17G0.02 6 680 44G3.4 3250G84 – – 38.4G0.36 103.4G9.4 0.13G0.01 8 500 44G2.8 2800G56 – – 35.5G0.21 91.5G8.6 0.11G0.01 182 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 system was the low excess sludge generation due to the high total bio-sludge mass in the reactor (Metcalf & Eddy, 1991; Gebara, 1999). The in