Study On Anoxic/Aerobic/Aerobic Hybrid Membrane Bioreactor For Aquatic Products Processing Wastewater Treatment

With the rapid development of industrial enterprises, water shortage and pollution has become a prominent issue on restricting China's development. The more increasing the state environmental protection requirements, the more stringent corresponding emission standards. Currently, the industrial pollutants emission standards develop progressively to every industry. In 2006, the former State Environmental Protection Administration called for emission standards for aquatic products industry in the revision plan of the national environmental protection standards, which indicates that the wastewater discharge standards of aquatic products industry will be more stringent.Based on the need of environmental management under such circumstances, through collecting the related information of aquatic products processing industry, and surveying some aquatic products processing enterprises, the development overview of this industry, the characteristics, treatment status and process of aquatic products processing wastewater were understood. Pilot study on a modular wastewater treatment and reuse technology—anoxic/aerobic/aerobic(A/O²) hybrid membrane bioreactor for aquatic products processing wastewater treatment was tested. The study includes:①Removal efficiency of effluent water index of A/O² hybrid membrane bioreactor was investigated, and comparison with reuse water standards was conducted.②Removal efficiency of micro-bubble aeration on organic in the carbon oxidation aerobic zone, and effects of large-bubble aeration on membrane fouling in the nitrification aerobic zone were all studied.③Microbial populations and composition were observed by electron microscopy. Microbiological characteristics on A/O² hybrid membrane bioreactor for aquatic products processing wastewater was analyzed.④Specific oxygen uptake rate (SOUR) was determined, and sludge metabolic activity and nitrification activity in the carbon oxidation aerobic zone and nitrification aerobic zone were analyzed and compared.The results show that: A/O² hybrid membrane bioreactor system had a good purification capacity. The effluent SS was almost zero, the average turbidity was 2.4NTU, and the average concentration of pollutants were BOD₅=4.24mg/L, COD=15mg/L, NH₃-N=3.99mg/L, TN=22.7mg/L(the corresponding average removal rate was 99.4%, 98.9%, 92%, 82% respectively). Compared with the standard of Urban wastewater reuse-Urban miscellaneous water quality (GB/T18920-2002), the water quality indicators all met the requirements. The aerobic zone is divided into two parts of carbon oxidation aerobic zone and nitrification aerobic zone, and two different ways of aeration were used respectively. Micro-bubble aeration was used in the carbon oxidation aerobic zone, which increased the utilization of oxygen and accelerated the removal of organic matter. Experimental analysis showed: Organic pollutants removal was still high when the aeration capacity was 300L/h. In this case, comparing other devices of the same treatment size, aeration energy consumption was lower. Large-bubble aeration was used in the nitrification aerobic zone, and the scouring action of large-bubble slowed down the rate of membrane fouling. Experimental analysis showed: When the aeration capacity was 700L/h, the rate of pressure rise was lowest. It indicated that development of membrane fouling was lowest. The measured results of specific oxygen uptake rate were obtained: The SOUR of the carbon oxidation aerobic zone was 0.5167mgO₂/(gMLSS·min). It was higher than the normal value(0.3333mgO₂/(gMLSS·min)), which illustrated that the water quality was poor and still contained large amounts of organic pollutants. The SOUR of the nitrification aerobic zone was 0.3071mgO₂/(gMLSS·min), which illustrated that the water quality was better. Then after membrane filtration, effluent can meet the standard requirements fully. In addition, nitrification activity of nitrification aerobic zone was about 2.5 times of that of carbon oxidation aerobic zone, which was consistent with the originally tentative plan of process design.