| Intensive aquaculture is one of the widely used methods in the aquaculture industry. It improves the aquaculture production, requires less land use and brings better economic benefits. However, it has higher requirements on the end equipment and the quality of circulating water. At present, the physical and chemical method and the biological method are the two commonly used methods in the initial formation of the aquaculture water treatment technology. But both methods encounter fundamental problems such as low level of system integration and water quality fluctuation. Membrane bioreactor (MBR), as a new sewage treatment technology, shows great advantage in various aspects including high quality effluent, lower space requirement, and high decomposition rate. Therefore, this technique is widely applied in the treatment of various kinds of domestic sewage and industrial wastewater. In this study, the integrated membrane bioreactor was applied to the treatment of aquaculture wastewater in order to optimize the operational condition of the removal of water pollutant and the reduction of membrane pollution. The reliability was verified and the integrated membrane characteristics in the process of operation was analyzed with the long-term stable operation.In view of the disadvantage of high energy consumption and poor denitrification effects of the traditional membrane bioreactor, an independently designed integrated membrane was used in this experiment. The operation parameters of hydraulic retention time (HRT), aeration quantity and mixed liquid suspended solid (MLSS) were designed in combination to shed light on the effects on COD, NH4+-N, NO2--N, NO3-N, TN, TP and membrane fouling. The results showed that the influence degree of the parameters to the water quality indicators was MLSS>HRT> aeration quantity under this experimental conditions, while the influence degree of the parameters to the membrane fouling was aeration quantity>HRT> MLSS. The optimal operation parameters to the water quality indicators of the reactor were as follows:HRT3.25h, aeration quantity375L·h-1, MLSS2.2g·L-1’. At the same time, for aeration quantity of437.5L·h-1, HRT of4.25h, and sludge concentration of2.2g·L-1were the optimal parameters for the membrane fouling. The study focused on the removal of water pollution as the primary objective, therefore, the condition with HRT of3.25h, aeration quantity of375L·h-1, MLSS of2.2g·L-1was chosen as the final operating parameters in the long-term stable operation.Under this experimental condition, microbial removal and membrane intercept had different impact on different water quality indicators with the long-term stable operation. The effluent COD, NH4+-N, NO2--N, NO3--N and TN concentrations reached the reuse water standard ranging from5.3-7.5mg·L-1,0.13-0.16mg·L-1,0.07～0.08mg·L-1,0.33-0.37mg·L-1and0.78-0.83mg·L-1. Simultaneous nitrification and denitrification were found in the reactor through the analysis on the balance of N elements.Under this experimental condition, the membrane pressure, while maintained within an acceptable range, grew faster than that under the optimal condition. The TMP presented three stages of fast, steady and rapid increase. The analysis of the distribution of the membrane resistance indicated that the absorption film pollution caused by extracelluar polymeric substances (EPS) and soluble microbial products (SMP) was the main reason for membrane foulingPackage weighing analysis showed carbon fiber material had a good bio-film. The intuitive analysis of the membrane surface showed that the membrane interception ensured the stability of the effluent.The goal of the study is to expand the application of the MBR in aquaculture industry by conducting research on integrated membrane bioreactor applied to the aquaculture wastewater treatment and to provide a reference for its large-scale application in the area. |
