| The thesis was supported by the project of making and revising on national environmental protection standard-effluent standard of pollutants for aquatic products processing industry. In this thesis, the aquatic products processing wastewater was treated by the Anoxic/Aerobic Membrane Bioreactor(A/O-MBR). The operation characteristics of A/O-MBR and the applicability of this process for aquatic products processing wastewater treatment and water reuse had been studied in this thesis.As a new water treatment technology, Membrane bioreactor (MBR) has been widely used in urban sewage and industrial wastewater treatment and water reuse in recent years. Membrane modules are the core part of MBR, hollow fiber membrane modules are mostly used in domestic engineering application research at present, while flat-sheet membrane modules are relatively low in domestic engineering application because of its small loading density, difficult making, etc. But some properties of flat-sheet membranes in MBR engineering application are superior to hollow fiber membranes, especially in the aspect of membrane fouling. Therefore, taking into the need to improve the performance of the system denitrogenation, the system combined with flat-sheet membrane bioreactor and A/O process were studied in this thesis.Firstly, through the orthogonal test, when the HRT is20h, the reflux ratio is400%and the DO concentration range of3mg/L-4mg/L, the A/O-MBR will achieve the best treatment effect. In the best operating conditions, the concentration of CODco NH3-N and TP in the effluent treated by A/O-MBR process could meet the standard of existing and newly-built enterprise’s separately, but the removal effect of TN is not good, the concentration of them could not meet standards of existing enterprises’.It is shown by the experiment of filling suspended carrier in the aerobic tank, if the fill ratio of the aerobic tank is15%, the effluent quality will meet the standards of existing enterprise’s; if the fill ratio of the aerobic tank is25%, the effluent quality will meet the standards of newly-built enterprise’s. Meanwhile, according to experimental results, the effluent quality of A/O-MBR can meet the water reusing standards, this process is feasible in aquatic products processing wastewater treatment and water reuse.Secondly, the stable operation status of flat-sheet membranes and the flux restoration of cleaned flat-sheet membrane modules were observed in this topic. The results showed that the TMP of flat-sheet membrane system went through three stages during the whole operation process, those were almost unchanged stage, slow increase stage and rapidly increase stage. After filling suspended carrier in the aerobic tank, membrane fouling rate has slowed down in a small margin, but the trend for the TMP were not affected. And internal pollution caused by pore blocking was the main factor of flat-sheet membrane fouling, internal resistance accounted for80%of the total resistance. Besides, a cleaning test was made on the contaminated membrane modules, the total rate of membrane flux in the system was recovered to97.8%after water flushing+pickling+caustic washing method, and the caustic washing achieved the best effect with the recovery rate. In addition, this article also analysed the influence of the membrane fouling preliminarily from different aspects including the effluent discharging mode, the filtration mode, the aeration rate, the filtration pressure, the flows through the membrane and the sludge concentration, it was concluded that adjusting the operational conditions of this process in this experiment reasonably was beneficial to slowing down membrane fouling.Finally, the thesis performed the cost estimate and economic analysis of the A/O-MBR process for aquatic products processing wastewater treatment. Considering the investment costs, operating costs, floor space and water quality, A/O-MBR process is economically feasible, and from the long-term development, this process as a wastewater treatment and reuse technology will have prominent advantages. |
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