Research On The Efficiency Of Carbon Emission Reduction In Sewage Pipelines Under The Condition Of Creating A Illuminated Environment

The greenhouse effect has become one of the greatest environmental threats facing mankind.In the process of transporting wastewater through sewage pipelines,the degradation and transformation of various pollutants will be accompanied by a large amount of greenhouse gas emissions,becoming one of the main sources of carbon emissions in the water industry.In order to solve the problem of greenhouse gas emissions in gravity flow sewage pipelines,a new method of creating a lighting environment in sewage pipelines to generate microalgae to control greenhouse gas emissions is proposed in this paper.The feasibility of creating a lighting environment in sewage pipelines to control carbon emissions was comprehensively analyzed through a series of fully mixed reactors built in the laboratory to simulate gravity flow sewage pipelines,using dark and no light conditions as a comparison,from aspects such as carbon emission accounting,greenhouse gas control,changes in EPS in bacteria algae symbiotic biofilms,changes in sewage quality,and changes in microbial community composition.Firstly,through a 90-day continuous test,the actual monitoring and accounting of carbon emissions in pipeline reactors are explored to explore the effectiveness of carbon source material reduction and carbon emission reduction in sewage pipelines after creating a lighting environment.Firstly,continuously monitor the amount of carbon emissions in each reactor,and then calculate the simulated sewage pipeline under different experimental conditions by detecting the concentration change of carbon source substances in each reactor.Finally,compare and verify the calculated value of carbon emissions with the measured value.The test results showed that compared to the control group,the actual monitoring values of CO₂and CH₄in the reactors R1 and R2 in the experimental group decreased by 18.76%,8.62%,and24.51%,17.69%,while the total carbon emissions in the pipeline decreased by 24.08%.Through accounting,under the conditions of pipe diameters DN300,DN500,and DN1000,compared to the control group,the calculated values of CO₂emissions from the experimental group reactors decreased by 22.33%,22.60%,and 22.21%,respectively,while the calculated values of CH₄emissions decreased by 21.86%,20.01%,and 16.15%,respectively,and the calculated values of total carbon emissions decreased by 25.56%,21.16%,and 20.76%,respectively.Compared with the actual monitored greenhouse gas emissions of the reactor,the error between the calculated and actual monitoring values of greenhouse gas emissions in the pipeline under normal operating conditions is only 10.50%.The error between the calculated value of greenhouse gas emissions in the pipeline and the actual monitoring value under the influence of lighting environment is only 8.66%.The accounting results further verify that creating a lighting environment in sewage pipelines can effectively inhibit greenhouse gas emissions in sewage pipelines.Secondly,by analyzing chlorophyll a and chlorophyll b in wastewater suspensions,bacterial community composition,biofilm EPS,and functional groups,the effects of lighting conditions on the morphology and structure of biofilms in wastewater pipelines were studied.The experimental results showed that the maximum values of chlorophyll a and chlorophyll b in the upstream reactor under the illumination environment reached 123.25ug/L and65.23ug/L respectively at 60 days.At the same time,creating a lighting environment will increase the microbial diversity of the biofilm on the pipe wall,promote the growth of Firmicutes and Proteobacteria in the upstream sewage pipes,and facilitate the degradation and transformation of organic pollutants in the sewage pipes.In addition,the lighting environment inhibits the growth of Methanothyrovorans and Methanobrevibates.It is beneficial to inhibit the emission of CH4 gas in sewage pipes.The maximum fluorescence peak of biofilm EPS reached 151.84mg/L at 60d,while the excitation/emission wavelength was at 270 nm/330～360 nm.Fourier transform infrared spectroscopy results showed that the peaks of the biofilm EPS in the upstream reactor under illumination at 1700-1600 cm-1 were C=C and C=O stretching in proteins,and the peaks at 1100-1000 cm-1 were C-O stretching in polysaccharides.The zeta potential value of the biofilm EPS in the upstream reactor under illumination increased by 7.74 m V.This indicates that creating a lighting environment in the sewage pipeline and forming a stable symbiosis of microalgae and bacteria through EPS glue play a positive role in controlling carbon emissions from the sewage pipeline.Finally,the impact of the changes in wastewater quality after creating a lighting environment on the operational efficiency of subsequent wastewater treatment plants was explored.The experimental results show that compared with sewage pipes in a dark environment,the concentration of SCOD in upstream sewage pipes that create a light environment decreases by 28.86%.The concentrations of NH₄⁺-N,NO₃^--N,and TN decreased by 28.67%,42.81%,and 23.51%,respectively;TP concentration decreased by 38.42%.The concentrations of S^2-and SO₄^2-decreased by 38.23%and 42.94%,respectively,while increasing the C/N and C/P of influent water from the sewage treatment plant.In addition,the ORP value of sewage in the upstream sewage pipeline increased by 107 m V after applying light to the environment.This indicates that under the conditions of creating a lighting environment,there is a significant removal effect on organic,nitrogen,phosphorus,and sulfur pollutants in the pipeline.At the same time,fixing carbon in microalgae cells will improve the C/N and C/P of influent water from the sewage treatment plant,alleviate the problem of insufficient carbon source in influent water from the sewage treatment plant,reduce the operational load of nitrogen and phosphorus removal in the sewage plant,and reduce carbon emissions due to normal operation of the sewage plant.