Exploration And Research On Controlling Harmful Gases Of The Sewage Pipe By The Intermittent Ventilation

The safe operation of urban sewer network will be seriously affected by the harmful gases such as hydrogen sulfide,methane and carbon monoxide in the pipeline and fine ventilation condition is one of the important measures to enhance the gas environment in sewer network.The measure that entrained fresh air of the construction drainage pipe is introduced into the municipal sewage pipe by the direct connection between the building drainage pipe and the municipal sewage pipe is proposed in this paper to achieve the purpose of natural intermittent ventilation.The influence of different ventilation conditions on the formation and release of harmful gases in different sewer environments is explored on this basis by means of the simulation test.Through the research of the main conclusions are:(1)The flow velocity of the sewage is the greater,the content of harmful gases in the sewer environment with the closed gas flow is the more when the thickness of the sediment is the same.But the methane content will be reduced when the flow velocity reaches 1.0m/s.The average content of sulfates and sulfides at 1.0m/s can be nearly twice as high as the average of sulfates and sulfides at 0.2m/s and 0.6m/s.The oxygen content in the gas phase space of the sewer can be increased,the anaerobic environment of the water phase can be destroyed to a certain extent and the harmful gases in the sewer can be controlled by intermittent ventilation.30%,50% and 75% of ventilation volume have inhibitory effects on hydrogen sulfide and carbon monoxide and they are almost impervious to flow velocity.The inhibition effect on methane is related to the volume of ventilation and the flow velocity.And the influence on sulfates and sulfides also varies with the flow velocity.When the flow velocity increases from 0.2m/s to 1.0m/s,the change of COD of each experimental group will gradually approach and the change rule is basically consistent.(2)When the sediment thickness is different,the maximum content of the hydrogen sulfide,methane and carbon monoxide will increase gradually and the initial content of sulfates and sulfides will increase with the increase of the bottom sediment thickness in the sewer environment with the closed gas flow.The maximum content or initial content of the 3cm sediment thickness and 6cm sediment thickness can be 1~2 times of the 1cm sediment thickness.Anaerobic environment in the liquid phase can be destroyed by intermittent ventilation.Compared with poor ventilation,30%,50% and 75% of ventilation volume have a good inhibitory effect on hydrogen sulfide in sewer and the inhibitory effect is not affected by sediment thickness.The inhibition effect on methane and carbon monoxide is related to the volume of ventilation and the flow velocity.The sulfate content and sulfide content can be restrained by intermittent ventilation with different sediment thickness.The inhibition effect is enhanced with the increase of intermittent ventilation volume and a downward trend of the COD of all the experimental groups is showed.(3)Compared with the poor ventilation,the oxygen content of the gas phase space is increased and the sewer environment is obviously improved by the intermittent ventilation in the environment of clean sewer without sediment.And the harmful gases are obviously restrained because of the increase of intermittent ventilation volume.Hydrogen sulfide decreased by 19% to 53%,methane decreased by 9% to 85% and carbon monoxide decreased by 23% to 49%.And the reduced percentage of sulfate is weakened from 80% to less 56%.The production of sulfide in water is decreased at the same time.