Performance Of Two Unit Multi-point Influent Biological Aerated Fiflet On Municipal Wastewater Treatment

Water pollution is one of the most serious environmental problems in ChinaWith the development of economy and the improvement of people’s living standard,the contradiction between the polluted source water and people’s demand for livinghas become increasingly obvious. Biological aerated filter (BAF), which includesbiofilm and activated sludge, is a reactor with double functions. Therefore, BAF hasgreat application potential in the secondary treatment of municipal wastewater.After a long time of application,there are some problems exposed inbiological aerated filters.For the problems of existing biological aeratedfilters,experiment test was conducted to analyse the degradation of pollutants alongthe flow direction in biological aerated filters, and the conclusion was drawn thatwithin a reactor,the conventional biological aerated filter has a differentdegradability on different substances and the degradation of pollutants is difficult toachieve unification of time and space. The idea of biological filter with two stage ofproportional influent was put forward through experimental analysis. The techniqueseperated the removal of carbon and nitrogen in two stage by two series of reactors,and with the method of step-inflow and reflux,it makes the first section has thedenitrifying effect and can remove the total nitrogen.Firstly this research choosed the suitable biological aerated filters with twostage of proportional influent. Through comparing the physical and chemicalcharacteristic parameters of five kinds of ceramsite, combining the removalefficiency of pollutant with the reactor filled with packing column ceramsite, T2and T4were regarded as the most optimum ceramsite in two stage of aerationfiltration tank.Then experimental reactor as biological aerated filters with two stage ofproportional influent was established.Using the raw water from Taiping wastewatertreatment plant, through regulating the operation parameters of two stage ofaeration biological reactor and exploring the removal efficiency of reactorsinfluenced by different hydraulic retention time、reflux ratio and the gas waterratio,it comes to the conclusion that under the condition of hydraulic retention timeat4h, gas water ratio at6:1,the reactor has the highest pollutant removal efficiency.Finally the treatment efficiency of biological aerated filters with two stage wasinvestigated.The biological aerated filters with two stage was working continuously and stablely for3months, and the effluent value can reach: COD <60mg/L,ammonia nitrogen <10mg/L, total nitrogen <20mg/L, total phosphorus <1mg/L.Efflunet quality can reach the level B emission standard of urban wastewatertreatment plants. It is hardly influenced by the impact of load and backwash.At the end of the dissertation, the diversity and activity of microbialcommunity in biological aerated filters was analyzed,so as the biologicalcommunity structure at different height. Combining the removal of contaminants atdifferent height, where different types of microorganisms locates in system wasdiscussed. All the above provide a basis of microorganisms for the design andoperation of biological aerated filters.This process can reach the requirments of level B emission standard of urbanwastewater treatment plants.It is a kind of biological aerated filter improvementprocess with a wide application prospect.