Effect Of Flow Pattern Change On Pollutant Distribution And Biochemical Transformation In Confluence Area Of Sewage Network

As our economy and society continue to develop,urban sewage effluents transport pollutants in particle form,which will gradually deposit at the bottom of the pipeline under the action of gravity during the transmission process of the sewage network to form a sedimentary layer,bringing serious pipeline siltation problem.At the same time,the pollution in the sediment layer lays a good environmental foundation for the reproduction of microorganisms,and it produces a large number of toxic and dangerous gases,which seriously threatens the safe operation of the gas pipeline network.To demonstrate the convergence of the variation in speed of the urban sewage network to the sediment polluting sewage and the influence of the succession of biological bacteria,this study by controlling the confluence sewage main pipe and branch pipe flow,Simulating a different bus mode under urban sewerage network conditions investigates the different flow under changing wastewater quality conditions over time,sediment of the nature of the spread of carbon,nitrogen and sulfur spokesman,and the distribution of microorganisms,and therefore,for the city’s drainage network network provides a theoretical basis for solid operations.The distribution of carbon,nitrogen and sulfur pollutants and their effects on biochemical transformation in pipelines under different confluence conditions were pointed out through the detection and research of sewage and sediment layer under different confluence conditions.The results showed that the changes of COD,NO₃-N,sulfide and sulfate are the most obvious in the low flow rate confluence state of the main and branch pipes,while the changes of TN and NH₃-N contents are the most significant in the high flow rate state.In addition,increasing the flow rate of the pipeline is also conducive to the transfer of carbon,nitrogen and sulfur pollutants in the sediment layer.Combination of bus network system internal DO and ORP change analysis,proved the convergence of three transformation of pollutants in the water and sediment under the conditions of the similarities and differences,and show that in bus network system in sewage of sediment flushing strength condition of different is the convergence of three kinds of pollutants transfer into the main influence factors.Through the comparative analysis of effluent biodegradability and C/N ratio under three confluence conditions,the results show that increasing the flow rate of the main pipe can effectively increase the C/N ratio to 0.26 in the duration of 7.5h,making the effluent from the pipe network more conducive to the denitrification of the sewage treatment plant.Further combined with the monitoring results of microbial population distribution in the sediment layer,the microbial population distribution in the sediment layer under three confluence conditions was compared and analyzed.The results show that with the increase of the flow velocity of the confluence pipeline,Proteobacteria and Bacteroidetes have obvious superiority,and there are abundant hydrolytic fermentation population.The abundant and high-quality carbon sources released by metabolism provide a good material basis for other biochemical metabolic reactions in the pipeline.However,the dominance of Euryarchaeota decreased significantly,and its methane-producing capacity weakened.Methanosaeta,a horizontal microorganism,was the most dominant microorganism population in the confluence state of low flow velocity of main and branch pipes,and the abundance along the depth of the sedimentary layer increased from 0.79%to 19.72%,showing a stronger ability to release methane gas in this area.By using FAPROTAX method,the distribution law of functional microorganisms under three confluence flow rates was further discussed.Studies have shown that under different flow velocity,the significant difference of pollutants and environmental factors affecting the methanogens（MA）,sulfate reducing bacteria（SRB）,sulfur oxidizing bacteria（SOB）hydrolysis and fermentation bacteria（FB）population distribution,by changing the flow pipe flow,control functional microorganism distribution in different flow velocity of pipes,the research results can provide theoretical support for the pollutant deposition and transformation of sewage network and its safe and stable operation.