THESIS
2007
xv, 130 leaves : ill. ; 30 cm
Abstract
A novel saline sewage treatment process, namely a sulfate reduction, autotrophic denitrification and nitrification integrated process (SANI process), has been developed at HKUST. The process consists of an up-flow anaerobic sludge bed (UASB), an anoxic filter and an aerobic filter. The goal of this novel process is to achieve a significant reduction in excess sludge production as well as in treatment cost and space. The objective of this study is therefore to investigate the performance of each unit reactor of the SANI process and its overall performance in removal of organic matter and nitrogen. The research emphases were placed on the impact of recirculation flow ratios between both filters on the autotrophic denitrification in the anoxic filter....[
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A novel saline sewage treatment process, namely a sulfate reduction, autotrophic denitrification and nitrification integrated process (SANI process), has been developed at HKUST. The process consists of an up-flow anaerobic sludge bed (UASB), an anoxic filter and an aerobic filter. The goal of this novel process is to achieve a significant reduction in excess sludge production as well as in treatment cost and space. The objective of this study is therefore to investigate the performance of each unit reactor of the SANI process and its overall performance in removal of organic matter and nitrogen. The research emphases were placed on the impact of recirculation flow ratios between both filters on the autotrophic denitrification in the anoxic filter.
A lab-scale of the SANI system was operated continuously with synthetic saline sewage. The performance was mainly assessed by monitoring TOC removal rate, nitrogen removal rate, sulfur balance, and sludge yield. The proposed system has been successfully operated for more than 360 days with an organic loading rate at 0.14 kg TOC/m
3/d. The TOC removal efficiency was 80-85%.
The nitrogen removal efficiency was found to be sensitive to the recirculation flow rate of the aerobic filter effluent to the anoxic filter. When this rate was controlled at 3Q (Q is the system influent flow rate), the system achieved more than 70% of total nitrogen (TN) removal. However, a further increase in this rate resulted in poor performance of the system in terms of TOC and TN removal.
Batch kinetic experiment results revealed that autotrophic denitrifying bacteria (ADB) and heterotrophic denitrifying bacteria (HDB) coexisted and shared the utilization of nitrate for denitrification in the anoxic filter. ADB were proven to be more actively participating in the denitrification than HDB. Key parameters of V
max_ADB, K
NOx_ADB, and K
H2S in the proposed bio-kinetics for ADB were estimated to be 22.8 mg/hr, 15.1 mg N/L, and 15.8 mg S/L, respectively.
Further studies on the autotrophic denitrification process in the anoxic filter showed that the anoxic filter was sensitive to the concentration of DO in its influent. If the influent contained 50 mg N/L nitrate, the denitrification efficiency would decrease from 92.5 to 81% when the influent DO level increased from 0-1 to 2-3mg/L.
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