Study On Performance Of Activated Sludge-MBBR Coupled Process For High Ammonia Nitrogen Wastewater Treatment

Ammonia nitrogen is one of the important reasons leading to eutrophication.High ammonia nitrogen effluent is not only toxic to aquatic organisms,but also has great harm to human health.Therefore,the biological methods that treat nitrogen effluent are the hotspots in the field of effluent treatment at home and abroad.Based on the principle of nitrification-denitrification,the common activated sludge process is mature,stable in denitrification,and low in operating cost,and is widely used in the treatment of nitrogenous effluent.However,the use of activated sludge alone to treat high concentration of nitrogenous effluent is not effective.The MBBR process can strengthen the degradation of COD,nitrogen and phosphorus,and the process occupies a small area and no other structures are needed.Combining the MBBR process with the common activated sludge process is expected to achieve effective treatment of high concentration nitrogenous effluent.However,there are few studies on this effluent by the activated sludge-MBBR coupled process.In order to treat high concentration nitrogenous effluent effectively,this project proposes to add fillers in the traditional activated sludge process(A/O/O+A/O/O)to construct an activated sludge-MBBR coupled process.This project explored HRT,sewage reflux ratio and aerobic tank filling ratio on the removal rates of COD,NH4+-N,TN and TP,thus the optimum process parameters of the entire system were determined.The species on the activated sludge samples and surface of the fillers were determined,and the reason why the activated sludge-MBBR coupled process was superior to the conventional activated sludge process was analyzed from the perspective of microorganisms.On this basis,the surface modification of common fillers by activated carbon method was carried out to study the effect of modified fillers on the removal performance of pollutants.The physical and chemical properties of the surface morphology,hydrophilicity and surface functional groups of the modified fillers were characterized.Through the test,the pollutant removal mechanisms of the modified filler were analyzed.High concentration nitrogenous effluent included COD,NH4+-N,TN and TP concentrations of 1500mg/L,1400mg/L,1500mg/L and 38mg/L in this project.The experimental result showed that the average COD removal rate of the common activated sludge method(A/O/O+A/0/0)process was 84%,and the removal rates of NH4+-N,TN and TP were 45±0.5%,40±0.3%and 32.6±0.05%,respectively.The optimal HRT of the activated sludge-MBBR coupled process was 6h,the optimum sewage reflux ratio was 3:1,and the optimal filling ratio of the aerobic tank was 35%.Under the optimal operating parameters,the removal rates of COD,NH4+-N,TN and TP were 93.9%,64.1%,53%and 52.7%,respectively.The removal effects of the four pollutants were better than the common activated sludge process,which increased by 9.9%,19.1%,13%and 20.1%,respectively.Proteobacteria was dominant phylum in biofilm on filler surface and activated sludge samples.Rhodobacter was dominant genus in the sludge sample that could inhibit the removal of ammonia nitrogen,and its relative abundance was 40.63%.After adding modified fillers,the removal rates of NH4+-N,TN and TP in activated sludge-MBBR coupled process were 86%,77%and 70%,respectively.These were 41%,37%and 37.4%higher than the ordinary activated sludge process,respectively,which were 21.9%,24%and 17.3%higher than the activated sludge-MBBR coupled process with ordinary fillers.