Proceedings of the 13th International Conference on Environmental Science and Technology Athens, Greece, 5-7 September 2013

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TREATMENT OF FISHERY WASTEWATER BY SEQUENCING BATCH

MOVING BED BIOFILM REACTOR (SBMBBR)

HANH VAN NGUYEN and PHONG TAN NGUYEN1 1Faculty of Environment, Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet

Street, District 10, Ho Chi Minh city, Vietnam. e-mail: tanphong69@yahoo.com

EXTENDED ABSTRACT A sequencing batch moving bed biofilm reactor (SBMBBR) system on 5 steps using K3 media with surface area is 175 m2/m3 increases effectiveness compared to traditional sequencing batch reactor (SBR) system on fishery wastewater treatment. The total bio-sludge mass, MLSS value and SRT value of the SBMBBR is higher than the SBR. The total bio-sludge mass is about 32 – 36% higher than the SBR. The F/M value and SVI value is lower than the SBR. The COD removal, TKN removal and TP removal efficiencies of the SBMBBR is about 1 – 2, 4 – 8 and 12 – 14% higher than that of the SBR. The COD removal with HRT 20h (fill 0.25h, anoxic 3h, aeration 15h, settle 1.5h and discharge 0.25h) with the removal efficiency of the SBMBBR was higher than 97% (COD), 74% (TKN), 70% (TP) even when the system was operated under optimum organic loading of 1250 ± 34.5 g COD/m3.day. The effluent COD, TKN and TP were 24.2 ± 1.7, 33.1 ± 2.5 and 4.7 ± 1.2 mg/l. Microbiological analysis results of the nitrification bacteria, denitrification bacteria, poly-P bacteria and ortho-phosphate bacteria on SBMBBR has shown positive results than that the SBR. The biomass/K3 media ratio on the same unit was 0.17 – 0.34 g/g. Keywords: Fishery wastewater, K3, sequencing batch moving bed biofilm reactor (SBMBBR), COD removal, Nitrogen removal, Phosphorus removal. 1. INTRODUCTION Fishery wastewater (FWW), produced from the fishery factories contain mainly organic matter (COD or BOD5), nitrogen compounds (proteins and amino acids), phosphorus compounds, oil and grease. The biological treatment systems commonly used for treatment of such wastewater are aerobic processes (activated sludge systems, aerated lagoons, aeration, trickling filters, rotating biological contractors), anaerobic processes [1]. However, the biological treatment systems do not used the anoxic phase to meet difficulty for nitrogen treatment. In addition, the selection of wastewater treatment process is based on type of treatment system, investment and operating costs. Sequencing batch reactor (SBR) is a fill-and-draw activated sludge treatment system that could be applied for treating organic wastewater [2, 3, 4]. The unit processes involved in the SBR and conventional activated sludge systems are identical. Anoxic, aeration and sedimentation are carried out in both systems. However, there is one important difference. In conventional activated sludge plants, the processes are carried out simultaneously in separate tanks, whereas in SBR operation, the processes are carried out sequentially in the same tank. The SBR system could also be used to treat high nitrogen containing wastewater because such systems facilitate nitrogen removal by nitrification–denitrification [5, 6]. But the system has to operate with a high amount of mixed liquor suspended solids (MLSS) to prevent high excess bio-sludge production and improve the sludge quality [7, 8, 9]. However, the operation with aerobic-SBR still has some problems such as the low settleability of bio-sludge, high excess sludge production

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under high organic loading or hydraulic loading and less increase in the removal efficiency due to the limitation of the increasing of bio-sludge [5]. To solve the above problems, the sequencing batch moving bed biofilm reactor (SBMBBR) might be applied in the traditional SBR to increase the amount and quality of bio-sludge of the system resulting in improvement of the effluent quality and system efficiency. In this study, a new type of SBMBBR was applied into the traditional SBR. The efficiency and bio-sludge quality of the system was determined under various organic loading operation to compare with traditional SBR. 2. MATERIALS AND METHODS 2.1. Fishery wastewater Fishery wastewater (FWW) was prepared based on the characteristics of the mini fishery processing manufacturer. Six organic loading rates (OLRs) are 0.5, 0.75, 1, 1.25, 1.5, 2 kg COD/m3.d with hydraulic retention times (HRTs) of 20 hours were examined. The FWW has pH value from 6.90 – 7.38, BOD5 value from 1284 – 1989 mg/l, COD value from 1716 – 2456 mg/l, TKN value from 164 – 265 mg/l, NH4

+ value from 91 – 238 mg/l, NO3

- value from 0 – 0.36 mg/l and TP value from 15 – 34 mg/l. The organic nitrogen/TKN ratio from 0.42 – 0.82. The BOD5/COD ratio in range of 0.72 to 0.87. 2.2. Moving biofilm The moving biofilm (MB) is made from K3 Kaldness Moving BedTM processes, which has been scientifically tried and tested in fish farming and wastewater treatment for over 10 years. The media is engineered in a wheel shape and is slightly positively buoyant with surface area is 175 m2/m3, diameter is approximately 2.5 cm and thickness is approximately 1 cm. This allows a small amount of water flow to circulate the media throughout the vessel. 2.3. Sequencing batch moving bed biofilm reactor The 30-L reactors, made from acrylic plastic (5 mm thick) as shown in Fig. 1, were used in the experiments. The length of reactor was 30 cm and 30 cm width, the working volume being 25l. Low speed gear motor was used for driving the impeller. The speed of impeller was adjusted to 60 rpm for complete mixing. One of air pump systems was used for supplying air for the reactors (the system had enough oxygen as evidenced by the dissolved oxygen in the system of about 2 – 4 mg/l). One of automatic valve was used for automatic discharge wastewater after treatment. 2.4. Bio-sludge The bio-sludge was used from CAFATEX fishery wastewater treatment plant in Hau Giang province, Viet Nam. The bio-sludge with 5000 – 6000 mg/l MLSS. The MLVSS/MLSS ratio was 0.65 – 0.81. The bio-sludge was mix with FWW containing 400 mg/l BOD5 in the reactor and acclimatized for 1 month. The data were frequent monitoring during this process until the model was stable and significant. 2.5. Operation of SBR and SBMBBR The volume in first (fill), second (anoxic), third (aeration) and fourth (settle) step is 100% of total volume. The volume in fifth (discharge, idle and discharge sludge) step is 25% of total volume after discharge 10% of sludge (depends on sludge age) when the last volume was 35%. The excess sludge was drawn during the draw and idles periods to control the suspended MLSS of SBR system at 3500 mg/l and SBMBBR system at 1500 mg/l.

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2.6. Chemical analysis The chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total kjeldahl nitrogen (TKN), total phosphorus (TP), mixed liquor suspended solids (MLSS), pH, and sludge volume index (SVI) of the influent and effluent were determined by using standard methods for the examination of water and wastewater [10]. SRT (solid retention time/sludge age) was deter-mined as the ratio of total MLSS of the system to the amount of excess sludge waste a day. 3. RESULTS 3.1. Effective of traditional SBR As shown in Fig. 3 and Table 1. The effluent of COD, COD removal, TKN, TKN removal, TP, TP removal with organic loading rates were 0.5 kg COD/m3.d (OLR-1), 0.75 kg COD/m3.d (OLR-2), 1 kg COD/m3.d (OLR-3), 1.25 kg COD/m3.d (OLR-4), 1.5 kg COD/m3.d (OLR-5), 2 kg COD/m3.d (OLR-6) of the traditional SBR. The principles of treatment process based on the principle of conventional SBR with the COD removal, nitrification, denitrification, and phosphorus metabolism on biomass accumulation, sedimentation process and discharge of excess sludge depends on sludge age. The different elements of the two systems are described in details below. The COD, TKN and TP removal efficiency under the last organic loading of 2000 ± 40.4 g COD/m3.d were 94.6 ± 0.2%, 53.4 ± 3.9%, 50.0 ± 3.2% and 89.8 ± 2.5 mg/l, 92.7 ± 0.9 mg/l, 12.5 ± 0.5 mg/l. The results showed that the effectiveness of SBR is not really high because this is the traditional activated sludge wastewater system and it could not be increase the MLSS/MLVSS values or decrease the F/M value in the processes.

Figure 1. Schematic of SBR and SBMBBR reactors

Figure 2. The actual image of SBR and SBMBBR reactors

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Figure 3. The effluent of COD, COD removal, TKN, TKN removal, TP, TP removal with six organic loading rates in the traditional SBR

3.2. Effective of SBMBBR As shown in Table 1 and Fig 7. The effluent of COD, COD removal, TKN, TKN removal, TP, TP removal with organic loading was 0.5 kg COD/m3.d (OLR-1), 0.75 kg COD/m3.d (OLR-2), 1 kg COD/m3.d (OLR-3), 1.25 kg COD/m3.d (OLR-4), 1.5 kg COD/m3.d (OLR-5), 2 kg COD/m3.d (OLR-6) of MBSBBR. To addition of moving bed K3 could increase the efficiency of the system. The effluent quality of SBMBBR was more stable than SBR at the same operating conditions. The COD, TKN and TP removal efficiencies of SBMBBR were slightly increase about 1 – 2, 4 – 8 and 12 – 14% higher at the same operating conditions. The COD, TKN and TP removal efficiency under the last organic loading of 2000 ± 43.7 g COD/m3.d were 96.1 ± 0.1%, 61.6 ± 2.7%, 64.0 ± 6.5% and 65.0 ± 2.1 mg/l, 76.8 ± 1.8 mg/l, 8.7 ± 1.1 mg/l. The TKN removal of SBMBBR was higher than SBR because of the following reasons: the total bio-sludge mass was increased the quantity in the attached bio-sludge in the surface of media, this attached microbial growth provided increased rates of waste degradation and removal, and thought to be particularly well suited for increasing rates of ammonia conversion to nitrate (nitrification). The TKN effluent under very high organic loading 2 kg COD/m3.d (OLR-6) of SBMBBR and SBR were 76.8 ± 1.8 and 92.7 ± 0.9 mg/l showed that the effectiveness of SBMBBR better than SBR. As for the TP removal process depends on the concentration of bacteria in the anaerobic process and the concentration of nitrate in treatment process. Both of these factors were satisfied in SBMBBR because after each discharge cycle, followed by the settle and fill cycle, both the process to facilitate phosphorus removal bacteria developed and continue stirring in the mixing process in the second stage, the phosphorus oxidation stage can be implemented during and after filling stage of the SBMBBR cycle. The anoxic phase was used after the fully aerated process for nitrification and nitrate products. So the readily biodegradable COD uptake and accumulation by phosphorus accumulating bacteria can replace for readily biodegradable COD consumption by denitrification bacteria. The COD, TKN and TP removal efficiencies comparison was shown in the Fig 3, Fig 4 and Fig 5 showed that the in the same operating conditions, the effectiveness of the SBMBBR is always higher than that of the traditional SBR especially for TKN and TP treatment processes. The TKN and TP removal efficiency of the SBMBBR and SBR under OLR-6 were 61.6 ± 2.7, 64.0 ± 6.5% and 53.4 ± 3.9, 50.0 ± 3.2%.

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Table 1. Comparison of the traditional SBR and SBMBBR efficiencies for the treatment of FWW with six organic loading rates under HRT 20h

Type Organic

loading (g COD/m3.day)

COD TKN TP

Effluent (mg/l)

% Removal

Effluent (mg/l)

% Removal

Effluent (mg/l)

% Removal

SBR

500 ± 10.9 4.9 ± 2.0 98.8 ± 0.5 12.7 ± 1.1 74.9 ± 2.3 2.3 ± 0.2 60.4 ± 14.5

750 ± 21.4 8.6 ± 1.9 98.6 ± 0.3 21.7 ± 1.0 71.1 ± 1.9 3.7 ± 0.2 59.0 ± 9.8

1000 ± 27.6 18.6 ± 1.9 97.8 ± 0.2 30.8 ± 1.0 69.4 ± 1.5 4.9 ± 0.4 57.7 ± 8.7

1250 ± 27.3 32.7 ± 1.8 96.9 ± 0.2 39.2 ± 1.5 68.7 ± 1.8 6.8 ± 0.2 57.0 ± 3.3

1500 ± 32.7 44.0 ± 1.7 96.5 ± 0.2 57.3 ± 1.2 61.8 ± 2.6 8.5 ± 0.3 53.3 ± 4.2

2000 ± 40.4 89.8 ± 2.5 94.6 ± 0.2 92.7 ± 0.9 53.4 ± 3.9 12.5 ± 0.5 50.0 ± 3.2

SBMBBR

500 ± 15.9 4.0 ± 1.6 99.0 ± 0.4 10.7 ± 1.4 78.1 ± 4.1 1.5 ± 0.3 75.0 ± 5.5

750 ± 25.1 6.8 ± 1.1 98.9 ± 0.2 18.7 ± 1.4 75.0 ± 2.5 2.5 ± 0.4 73.0 ± 3.9

1000 ± 15.3 15.8 ± 0.9 98.1 ± 0.1 26.7 ± 3.2 73.3 ± 2.7 3.4 ± 0.5 72.5 ± 3.7

1250 ± 34.5 24.2 ± 1.7 97.7 ± 0.2 33.1 ± 2.5 73.5 ± 2.2 4.7 ± 1.2 70.1 ± 7.6

1500 ± 42.3 34.2 ± 2.4 97.3 ± 0.2 48.2 ± 2.0 67.7 ± 2.2 5.9 ± 1.0 68.2 ± 6.1

2000 ± 43.7 65.0 ± 2.1 96.1 ± 0.1 76.8 ± 1.8 61.6 ± 2.7 8.7 ± 1.1 64.0 ± 6.5

Figure 4. Comparison of the COD removal efficiency of SBMBBR and SBR

Figure 5. Comparison of the TKN removal efficiency of SBMBBR and SBR

Figure 6. Comparison of the TP removal efficiency of SBMBBR and SBR

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Figure 7. The effluent of COD, COD removal, TKN, TKN removal, TP, TP removal with six organic loading rates in the SBMBBR

3.3. Effective of moving bed biofilm K3 media on quality of bio-sludge of SBMBBR As shown in Table. 2. The MLSS of SBR was controlled 3500 mg/l and MBMBBR was controlled at 1500 mg/l. The bio-film mass of the SBMBBR reactor was about 1186 – 3353 mg. The total bio-sludge mass of SBMBBR was higher than that of the aerobic-SBR under the same organic loading conditions. The F/M of SBMBBR was also about 16.5 – 22.1% lower than that of the SBR under same organic loading as shown in Table 2. The bio-sludge age (solids retention time: SRT) of the MBSBBR was longer than that of the aerobic-SBR under the same organic loading conditions as shown in Table 2. The SRT of the SBR at an HRT of organic loading of 1250 g COD/m3.d was lower than that of the SBMBBR. The SVI of the SBMBBR was about 11% lower than that of the SBR under the same organic loading operation as shown in Table 2. The increasing of bacteria was expressed through the value of F/M reduction and increase the metabolic rate on the surface of each media surfaces was major factor increasing the efficiency of the reduction of TKN, TP, COD compared with the conventional methods. The increase in processing rate between processes are created on the surfaces of media by bacteria, including anoxic/aerobic faster and more efficient compared with conventional SBR process using activated sludge suspended process. The MLSS value not including in media was keep at a stable to fix the processing efficiency, renewable bacteria layers in media and discharge of excess sludge from the system. Table 2. Comparison of the traditional SBR and SBMBBR performance for the treatment

of FWW with six organic loading rates under HRT 20h

Type Organic loading (g COD/m3.day)

MLSS (mg/l) Biomass/Media

(mg/l) SVI (ml/g) SRT (day)

F/M (g BOD5/g MLSS.day)

SBMBBR

500 ± 15.9 1500 ± 45 2208 ± 880 83 ± 2.1 9.6 ± 4.2 0.10 ± 0.02 750 ± 25.1 1500 ± 36 2309 ± 464 80 ± 2.5 8.2 ± 4.5 0.14 ± 0.03

1000 ± 15.3 1500 ± 64 2470 ± 504 73 ± 3.2 7.5 ± 5.2 0.18 ± 0.03 1250 ± 34.5 1500 ± 78 2299 ± 651 68 ± 3.7 7.1 ± 5.3 0.23 ± 0.04 1500 ± 42.3 1500 ± 59 2478 ± 555 62 ± 4.3 6.2 ± 4.9 0.27 ± 0.04 2000 ± 43.7 1500 ± 93 2496 ± 478 57 ± 5.2 5.7 ± 4.3 0.37 ± 0.05

SBR

500 ± 10.9 3500 ± 127 - 94 ± 2.4 9.1 ± 4.9 0.12 ± 0.02 750 ± 21.4 3500 ± 58 - 86 ± 2.5 7.8 ± 5.1 0.17 ± 0.02

1000 ± 27.6 3500 ± 96 - 81 ± 2.8 7.5 ± 5.4 0.23 ± 00.3 1250 ± 27.3 3500 ± 112 - 78 ± 3.2 6.3 ± 4.7 0.29 ± 0.03 1500 ± 32.7 3500 ± 75 - 73 ± 3.8 6.0 ± 4.3 0.35 ± 0.04 2000 ± 40.4 3500 ± 67 - 66 ± 4.5 5.1 ± 4.1 0.46 ± 0.04

Remark: The MLSS in SBR and SBMBBR was controlled at 3500 mg/l and 1500 mg/l by wasting the excess

sludge daily.

4. CONCLUSIONS The SBMBBR is an effective process for the treatment of fishery wastewater with the anoxic, aerobic, settle and discharge processes in one reaction tank with the COD, TKN

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and TP removal efficiencies were about 1 – 2, 4 – 8, 12 – 14 higher than the traditional SBR, respectively. The total bio-sludge mass is about 32 – 36% higher than the SBR resulting in decrease the F/M of the system. The F/M of SBMBBR was about 16.5 – 22.1% lower than the SBR. The system was operated under lower F/M producing less excess bio-sludge and the quality of bio-sludge was improved resulting in SVI value was reduced. The SBMBBR efficiency was decreased with the increase of organic loading. The COD, TKN and TP removal efficiency were increased 96 – 99%, 62 – 78%, 64 – 75% when the organic loading was decreased from 2000 ± 43.7 to 500 ± 15.9 g COD/m3.day. However, the removal efficiency of the SBMBBR was higher than 97% (COD), 74% (TKN), 70% (TP) even when the system was operated under optimum organic loading of 1250 ± 34.5 g COD/m3.day. The effluent COD, TKN and TP were 24.2 ± 1.7, 33.1 ± 2.5, 4.7 ± 1.2 mg/l, respectively. The biomass/K3 media ratio on the same unit was 0.17 – 0.34 g/g. For the determination of the quality of MLSS, the SVI was less than 100 ml/g (68 ± 3.7 ml/g), but the SRT was only 7.1 ± 5.3 days. Microbiological analysis results of the nitrification bacteria, denitrification bacteria, poly-P bacteria and ortho-phosphate bacteria on SBMBBR has shown positive results than that the SBR. Acknowledgement. The authors gratefully acknowledge the financial support from Japan International Cooperation Agency (JICA). In addition, the authors would like to thank CAFATEX Corp for allowing the collection of bio-sludge.

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