| With the vigorous development of China’s economic undertakings,the operating mileage of high-speed rail is increasing year by year,and the higher number of transport vehicles and passenger flow make the amount of toilet sewage with high ammonia nitrogen,high COD and low carbon nitrogen ratio increase,which increases the difficulty of treatment of sewage discharge in the station section.Therefore,it is necessary to choose an efficient treatment process to remove contaminants,especially nitrogen from the sewage.This study uses pretreatment A/O process and short-range nitrification-anaerobic ammonia oxidation coupling denitrification process to study the pollutant removal efficiency of the toilet sewage at the outlet of the anaerobic pool of the high-speed rail EMU,focusing on the initiation,hanging film and pretreatment of the anaerobic ammonia oxidation coupling process,the degradation effect of the coupling process on the pollutants in the actual toilet sewage,and the microbial analysis is taken at different stages of the experimental operation,the main contents and conclusions are as follows:1.After about 137 days of operation,the reactor was successfully started and achieved good nitrogen removal effect.Under the conditions that the temperature is about 32℃,p H 7.7-8.1,DO concentration at 0.1-0.4 mg/L,FA range of 10-25 mg/L,FNA < 0.2 mg/L,inlet water ammonia nitrogen and total nitrogen concentration of 550mg/L,effluent ammonia nitrogen concentration of 54.95 mg/L,total nitrogen concentration of 90.82 mg/L and a certain amount of nitrite nitrogen and nitrate nitrogen are generated in the system,ammonia nitrogen and total nitrogen removal rate of90.01% and 84.39%,and the removal load reached 0.137kg· N/(m3·d)and0.127kg· N/(m3·d)respectively.Marks the good operation of the coupling process of anaerobic ammonia oxidation.Also,The sponge filler has an overall red color after successful start-up,marking the growth and reproduction of anaerobic ammonia oxidizing bacteria,indicating the success of the system hanging film.2.The A/O pretreatment process provides a preliminary degradation of contaminants in the toilet effluent,and the removal rate of ammonia nitrogen and COD is about 44% and 73%.The anaerobic ammonia oxidation coupling process keeps the parameters of the start process unchanged,and the pre-treated toilet sewage is added in accordance with the principle of phased water inlet,and the content of nitrosin and nitrate nitrogen in the system is significantly reduced under the increase of COD and denitrification.After stabilization,the ammonia nitrogen and total nitrogen removal rates of the system were 90.84% and 86.9%,respectively,and the nitrogen removal load was up to 0.141 kg·N/(m3·d).The removal rate of ammonia nitrogen,COD and total nitrogen from the anaerobic pool outlet toilet wastewater in the whole pretreatment +coupling process reached 94.9%,91.8% and 93.6%,respectively.This paper shows that the system combines nitrogen denitrition under the synergistic effect of short-course nitrification,anaerobic ammonia oxidation and denitrification.3.The community diversity of microorganisms in the fillers in the system during different stages of reactor operation was analyzed and found that the dominant phylums in the coupling process are Chloroflexi,Proteobacteria,Bacteroidota,Planctomycetota and Actinobacteriota.Among them,planctomycetota as a genus of anaerobic ammonia oxidizing bacteria,gradually increased with the enhancement of anaerobic ammonia oxidation,reaching 31.4% at the end of the reaction.Candidatus_Brocadia is the dominant anaerobic ammonium oxidation in the system,and the relative abundance reaches 30.7% after the coupling process treats the toilet and the operation is stable,indicating the good growth of anaerobic ammonia oxidized bacteria in the filler,corresponding to the excellent denitrification performance of the coupling system. |
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