| Compared to the natural clinopilolite, the silicon-based zeolite media made by natural clinopilolite and adhesive has improved in porosity, and the surface area, so as breakage rate and wear rate. Parameters of silicon-based zeolite media are line with the national media standard (GB/T17431-1998), and the silicon-based zeolite media is a good use as media in biological filters.The research on the adsorption and desorption performance of silicon-based zeolite media finds that they are improved a lot and its static adsorption capacity of ammonia can be up to 149.9048mg/g, while that of natural clinoptilolite is only 34.8272mg/g. The high static ammonia adsorption capacity of silicon-based zeolite media is physical adsorption and chemical adsorption the result of joint action.The experiment about desorption performance of silicon-based zeolite finds that its desorption capacity of ammonia can be up to 22.1236mg/L,which indicates it is not only superior in performance but also strong in regeneration ability and impact resistance.The whole system start-up lasts 43 days, and the aerobic biofilm is easier and faster in the cultivation and breeding of microorganism, which is provided by that start-up of aerobic biofilter only takes 27 days while that of anoxic biofilter will not be successful until 43 days. At the end of start-up, the effluent nitrate nitrogen concentration of aerobic biological filter can be up to about 8mg/L while that of anoxic biofilter is only 2mg/L or so, and in two biofilers both the surface and interior of media are completely covered with a thick transparent layer of biofilm rich in species, which plays an important role in the degradation of pollutants.Conditions of the operation are studied using three-factor (gas-water ratio, hydraulic retention time and aerobic biofilter return system reflux ratio) and there-level orthogonal design method as guided by removal rate. The optimized conditions are established as follows: gas-water ratio 2:1, hydraulic retention time (HRT) 1.5h, aerobic biofilter return system reflux ratio 3:1. Under these conditions, The effluent quality of A/O biofilters process is relative stable and excellent, and total nitrogen concentration, ammonia concentration and COD concentration are 16.95mg/L, 2.34mg/L and 12.30mg/L, respectively, while the removal efficiencies of total nitrogen, ammonia and COD are up to 75.78%, 91.28% and 93.90%. The result shows that the effluent quality meets I-class criteria specified in the Discharge standard of pollutants for municipal wastewater treatment plant (GB 18918-2002).This paper investigates the removal effect of nitrogen of A/O biofilters process at different gas-water ratios, HRT, and aerobic biofilter return system reflux ratios. The results show that for the municipal wastewater, the ability of ammonia removal changes with gas-water ratio and hydraulic retention time (HRT) while return system reflux ratio has no effect on ammonia removal; and the ability of ammonia removal is affected mainly by gas-water ratio and hydraulic retention time (HRT). All these three factors have great influence on total nitrogen removal. With the increase of return system reflux ratio and HRT, total nitrogen removal rate rises steadily, while it presents the trend of first increase then decrease with the increase of gas-water ratio.The paper analyzes principle of ammonia removal in different biofilters of A/O biofilters with silicon-based zeolite media based on the results under the optimized conditions. All the researches and analyses reveal that high nitrogen removal of A/O biofilters process is the consequence of the interaction between biodegradation of many kinds of microorganisms and ion exchange property and adsorption of silicon-based zeolite media.The results show that both traditional denitrification and anaerobic ammonium oxidation (ANAMMOX) occur in anoxic biofilter, and nitrobacteria plays an important role in the traditional autotrophic nitrification for ammonia removal in aerobic biofilter.
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