| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系 === 101 === ABSTRACT
In recent years, wastewater treatment technologies are developed to provide effective nitrogen and carbon removal before discharge into water system. Membrane bioreactor (MBR) has lately been the process of interest for carbonaceous compound and nutrient removal due to various advantages. Nowadays, biological nitrogen removal has been achieved by various configurations of MBR systems and pre-denitrification has always been the preferred configuration.
In this study, the effect of chemical oxygen demand to total nitrogen (COD/TN) ratio, recirculation rate and solid retention time (SRT) were investigated in the performance of a laboratory scale biocarrier-aerobic MBR (A/O) system on COD and nitrogen removals from synthetic domestic wastewater. The system was conducted for around 300 days with four experimental stages under different COD/TN ratio, recirculation rate and SRT. To evaluate the effect of carbon source addition, the COD/TN ratio was adjusted from 3 to 7 by adding extra carbon source. For recirculation ratio adjustment, internal recycle flow rate was changed from 2Q to 2.5Q. SRT was varied from 20 days to 10 days to study the effect of retention time on bacteria growth.
The results illustrated that the highest removal efficiencies of COD, NH4+-N and TN of 99.9%, 100% and 93%, respectively, were achieved when the A/O MBR system was operated under optimal condition of 2.5Q recirculation rate, COD/TN ratio of 7, and SRT of 20 days. Influent COD/TN ratio, recirculation rate and SRT influenced the COD and nitrogen removal performance significantly. Under optimal condition, the system reached complete nitrification and high denitrification. Addition of carbon source, recirculation rate and SRT correlated with biomass concentration and the removal capacity. Biomass in anoxic tank and MBR increased under optimum condition. It indicated that the system could provide good condition for biomass growth resulting in high removal efficiency. The results of this study also showed that TN existed in the permeate by the form of nitrate only wherein the lowest level was 3 mg/L. It indicated that this biocarrier anoxic-oxic system can replace an anaerobic-oxic system for high nitrogen and COD removals from wastewater.
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