Experiment And Research On Controlling Harmful Gas In Sewage Pipe Through Creating Environment

Preventing pipeline corrosion and safety accidents is an important direction for improving the quality and efficiency of drainage systems.Poor ventilation of pipelines and harmful gases such as hydrogen sulfide（H₂S）and carbon monoxide（CO）generated in dark environments are the main causes of accidents.As a water delivery method,the open channel can fully contact the outside air and sunlight in a semi-open environment,so as to avoid the anaerobic environment in the pipeline.In order to solve the serious impact of hydrogen sulfide gas in gravity flow sewage pipelines on social public health and pipeline maintenance and management,a new method for controlling harmful gas generation by creating a near-open channel transportation environment in the sewage pipeline was proposed.This research was built through a laboratory Sequencing batch reactor and a series complete mixing reactor that simulates gravity flow sewage pipelines comprehensively analyzes the influencing parameter,harmful gas control,sewage water quality changes and microbial community composition changes in the sewage pipeline to create an environment to control harmful gases feasibility.First of all,through periodic tests,explore the influencing parameter of creating a light environment to control harmful gases.In the experiment,five groups of reactors were set up.The dark environment was used as the control group,and the fixed carrier,light intensity and aeration were used as variable factors to detect the gas phase and liquid phase indexes of each group of reactors.The analysis found that,compared with the reactor under dark conditions,the addition of fixed carrier,higher light intensity and aeration can reduce the concentration of H₂S（g）,sulfide,COD,TN and TP in the reactor.This shows that the fixed carrier,light intensity and aeration will affect the effect of the light environment in the sewage pipeline.Secondly,through a 70-day continuity test,the effect of the fixed carrier on the effect of creating a light environment and improving the gas-liquid environment of sewage pipelines is explored.In the experiment,three sets of series-connected complete mixing reactors were set up.The dark environment was used as the control group,and the fixed carrier was used as the variable to detect the gas phase and liquid phase indicators of each reactor.The test results show that compared with the sewage pipeline in the dark environment,the concentration of H₂S（g）in the upstream sewage pipeline with fixed carrier and without fixed carrier is reduced by 47.2%and 30.6%,and the concentration of dissolved sulfide is reduced by 36.7%,respectively.And 33.3%,the CO concentration was reduced by 59.8%and 52.3%,the COD concentration was reduced by 12.0%,and the NH₄-N concentration was reduced by 9.2%and 5.8%,respectively.This shows that creating a light environment in the pipeline can promote the control of harmful gases and the conversion of pollutants,and the fixed carrier can promote its effect.Through a 90-day continuity test,explore the effect of light intensity on the effectiveness of creating a light environment and improving the gas-liquid environment of sewage pipelines.In the experiment,three sets of series-connected complete mixing reactors were set up.The dark environment was used as the control group,and the light intensity was used as a variable to detect the gas phase and liquid phase indicators of each reactor.The test results show that,compared with the sewage pipeline in the dark environment,the concentration of H₂S（g）in the upstream sewage pipeline with the light intensity of 2300 Lux and 1000 Lux is reduced by 50.0%and 28.1%,respectively,and the concentration of dissolved sulfide is reduced by 23.4%and 23.4%,respectively.14.1%,CO concentration decreased by 51.0%and 32.3%,COD concentration decreased by 14.0%,NH₄-N concentration decreased by 14.2%and 8.0%,ORP increased by 118 m V and 116 m V,respectively.This shows that creating a light environment in the pipeline can promote the control of harmful gases and the conversion of pollutants,and higher light intensity can promote its effect.Finally,the mechanism of creating an environment to change the gas-liquid environment of sewage pipelines is studied.High-throughput sequencing is used to detect microbial diversity of biofilms in upstream and downstream pipe sections at different depths and under different light intensities.The results show that creating a light environment in the sewage pipeline will increase the microbial diversity of the pipe wall biofilm,promote the growth of Gammaproteobacteria（γ-Proteobacteria）and Cloacimonadia,thereby promoting the carbon and nitrogen and phosphorus pollutants in the sewage pipeline.Conversion;the light environment inhibits the growth and reproduction of sulfate-reducing bacteria（SRB）mainly Desulfovibrio（Desulfovibrio）,which indicates that the algae cells grown in the light environment produce oxygen through photosynthesis,which will cause the anaerobic environment in the pipeline A certain degree of buffering reduces the generation of H₂S in sewage pipelines from the source.In addition,the light environment changes the structure of the biofilm,forming some deep internal holes on the surface of the biofilm,which promotes the transfer of metabolites and oxygen in and out of the particles,which is more conducive to the removal of harmful gases.