| Activated sludge process as a technique of wasterwater biological treatment often exhibited substantial drawbacks in sludge activity, sludge sedimentation performance and removal efficiency of COD and NH4-N in the actual run. Activated sludge enhanced technique enhancing microbe in actived sludge through physical, chemical and biological methods so as to promote its treatment efficiency. Zeolite as an inorganic ion exchange material had priority of ion exchange for NH4+ and had favorable adsorption properties because of its polarity on surface. Zeolite was abundant and low cost in addition to higher surface for microbe attaching because of its specific surface area and porosity, so it has properties using zeolite to enhance actived sludge process in wastewater treatment and water quality improvement. Zeolite enhanced activated sludge process, namely, adding zeolite to the conventional activated sludge process changed the biomass and microbial existent form enhancing the microbial function, therefore promoted the system's removal efficiency.The primary influence factors in run of modified zeolite enhanced activated sludge wastewater treatment and their effects on function of activated sludge and wastewater removal efficiency were studied in this paper, so as to determine the optimal operating parameters. Firstly, the effects of modified zeolite on activated sludge sedimentation performance, floc surface properties and removal efficiency of wasterwater were studied to observe the enhanced effect of zeolite. On this base, the effects of hydraulic retention time (HRT), operating temperature, pH value, different carbon sources, carbon/nitrogen/phosphorous (BOD5/TN/TP) ratio and seed sludge volumes on activated sludge sedimentation performance and removal rates of COD, NH4-N were studied. The application of zeolite enhanced activated sludge system was studied after the study of treatment of simulated aquaculture wasterwater. The results were as follow:(1) Zeolite increased sludge concentration and promoted activity of activated sludge, meanwhile, zeolite adhered to each other forming the frame of floc and improved the floc structure. The optimal amount of zeolite added was determined as 6 g/L through the study of effects of different amounts of zeolite added on floc structure, removal rates of NH4-N and COD. The optimal HRT was determined as 18 h through the research of effects of different HRT on removal rates of NH4-N and COD. The activated sludge took on better sedimentation performance when the operating temperature was set at 22℃, while set at 5℃and 40℃, sedimentation performance became worse and even occurred sludge bulking. The activated sludge had worse sedimentation performance when the dissolved oxygen (DO) was set at 0.5 mg/L and 5.0 mg/L, meanwhile, revoval rates of NH4-N and COD reduced at the same time. The optimal DO was determined as 2.5 mg/L. The activated sludge sedimentation performance was better using sodium acetate as carbon source, while using sucrose and glucose it became worse. When carbon/nitrogen/phosphorous (BOD5/TN/TP) ratio of inlet water were 100/5/1 and 100/6/1.2, the activated sludge sedimentation performance was normal. The activated sludge had clear sludge-liquid interface from the observation as the seed sludge volume is moderate. Larger or smaller seed sludge volumes will be against sedimentation performance. The activated sludge sedimentation performance was better when the pH value was from 6 to 8.(2) The GIFT strain of Oreochromis niloticus recycling water culture trial was conducted when the zolite enhanced activated sludge sedimentation performance took on well. The seed sludge volumes, HRT, operating temperature, DO, amounts of zeolite added and pH value in run of the system were set at 25%,18 h,22～25℃,2.5 mg/L,6 g/L and 6.5～7.0, respectively. The water samples of the inlet and outlet were delivered and tested three times every week. The results were as follow:The maximum of NH4-N concentration from the inlet was 0.41 mg/L with relatively large variation, while the outlet water quality was stable. The COD concentration and pH value from outlet water was with relatively small variation as compared to that from inlet water. The DO concentration was above 4.3 mg/L and could meet the demand of Oreochromis niloticus.(3) Zolite enhanced activated sludge system could efficiently remove COD, NH4-N, NO2-N and improve water quality, so the water in culture tank was not changed in the trial. The average weight of Oreochromis niloticus increased from 30.34 g to 120.08 g after the culture trial. The average growth speed, survival rate, and special growth ratio were 0.89 g·d-1,85.60% and 1.37%, respectively.
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