Study On The Nitrogen Removal Performance And Microorganism Distribution Of Biological Aerated Filter

At present, China’s nitrogen water pollution problems have been very serious. With theincrease of annual emissions of water, lots of nitride discharged into rivers and lakes, causingsevere nitrogen pollution, destruction of the ecological balance of the water, the water qualitydeterioration, the impact of fisheries development and human health. According to the studyshowed that, in addition to molecular nitrogen, all of the nitrogen cycle intermediatesaccumulation will have adverse effects on humans and the environment, which NH3-N,NO3--N, NO2--N is the most serious hazards. On the basis of traditional theory, biologicaldenitrification processes must be separated from the nitrification process and denitrificationprogress, resulting in excessively complex process, high operation cost, and lowdenitrification efficiency. BAF is a new advanced treatment process, because of its technicalcharacteristics, which is simplifying the denitrification process, saving investment andovercome the shortcomings of traditional biological nitrogen removal process. Therefore, howto achieve good denitrification process in the BAF, and through the biofilm characteristics toanalyze the structure of the microbial community BAF removal mechanism has importantsignificance.To deal with the simulated wastewater by BAF pilot system, and using sluge dischargemethod to startup the system. After30days of continuous operation, the removal of CODCr,NH3-N and TN is stable. There are dark brown biofilm around the ceramic, and microscopicexamination shows sessile ciliates and other protozoa. The microbes and treatment effectshow that biofilm reactor startup success.Then there is a study about the influence of hydraulic retention time (HRT), TCODCr/TN, gas-water ratio, pH on the BAF denitrification and optimize performance. Get the bestoperating conditions: HRT is4h, TCODCr/TN is2:1, gas-water ratio is5:1, pH is7.0~8.0.Under optimum operating conditions, the removal rates of CODCr, NH3-N and TN are85.71%,86.54%and57.58%and effluent concentrations are23mg/L,7mg/L and28mg/L.Under the Optimum operating conditions, there is a study about the changes ofdenitrification performance, microbial biomass and bacterial community structure along thedepth of BAF. The result shows that organic pollutants are mainly removed in the front of thefilter layer and denitrification mainly happenes in the rear of the filter layer. BAF biomass isgradually decreasing along the flow direction and there is a larger difference between inletend and outlet, but the change of bacterial populations is little and the reactor has richmicrobial. The concentration of NO3--N decrease after the first increase, and has a certain Synchronization reduce with the TN concentration in the depths of160~240cm of the filterlayer. NO2--N has not found cumulative phenomenon. Denitrification is the main way toremove nitrogen, and did not found the short-nitrification and denitrification. Simultaneousnitrification and denitrification is the major way to remove nitrogen in BAF.