Study On A~2/O Biofilm Process For Seafood Wastewater Treatment

With the development of social economy, more and more seawater is widely used, including seafood processing industry. A number of seawater is used for seafood washing and secondary processing, such not only can save a lot of fresh water, but also fresh seafood. Seafood processing industry wastewater increased year by year. Generally, the wastewater treatment has high operating costs, while the treated wastewater can seldom reach the emission standards, which having a great impact on water quality, aquaculture and environment of the coastal waters of the gulf. Therefore, the study of seafood processing wastewater treatment has essential economic, environmental and social benefits. In this thesis, using volcanic rock as biofilm carrier, the A2/O biofilm-process was adopted to treat seafood processing wastewater. By changing HRT, sludge concentration (MLSS), dissolved oxygen (DO) and the mixture reflux ratio, the system’s optimum operation was achieved. This study mainly carried out and achieved the following works and results.(1) By comprehensive analysis of influent water quality, the bench scale A2/O bioreactors was designed.(2) Volcanic rock carrier has high porosity, well biofilm attachment, high mechanical strength and easy to back wash. While the backwash strength was increased and the back wash time was prolonged in this study.(3) Due to the good biodegradability raw of the wastewater and the high temperature (about 20℃ in summer during the experimental duation, the natural biofilm attachment method was used in this study.(4) Optimal operational parameters was obtained by tests. Through the regulation of HTR, the results shows that when the whole HRT was 17.8 h, the NH4+-N and TN maximum removal efficiencies were 68% and 69.8%; when the whole HRT was 18.4 h, the maximum TP removal efficiency was 67.9%. Comprehensive comparison of pollutant removal efficiencies in each tank shows that when the whole pollutants removals were up to the maximum efficiencies, the aerobic, anoxic, anaerobic tank MLSS were 2.3 g/L,2.4 g/L and 3 g/L (except the amount of biofilm), so the average MLSS should be maintained at 2.3-2.7 g/L. For treating with high salinity, the DO levels in the aerobic tank should be higher than the fresh wastewater. Experimental results shows that the TN and NH4+-N removal efficiencies reached the maximum of 60% and 70%, when the DO level was 5 mg/L in the aerobic tank. By regulating the reflux ratio, the TN removal efficiency reached the maximum of about 80% and the maximum anoxic CODCr removal efficiency was about 22% at the reflux ratio of 200%.