| A large amount of malodorous gas is generated during the normal operation of municipal sewage treatment plants.With the improvement of people’s living standards and the strengthening of environmental protection awareness,the public has higher and higher requirements for the treatment of odor in sewage treatment plants.This paper selects the most typical malodorous gas VSCs in municipal sewage treatment plants as the research object,carries out long-term monitoring of VSCs in three different municipal wastewater treatment plant,explores its concentration distribution characteristics and influencing factors,and evaluates its sensory effects And health risks.And collected the sludge from different sludge treatment units in Plant C,and explored the potential odor influence of the sludge without being affected by actual working conditions and meteorological factors.Through these studies,some theoretical basis and data reference are provided for the prevention and control of odour in municipal sewage treatment plants,and a way of thinking is provided for the comprehensive evaluation of odor in municipal sewage treatment plants.During the monitoring period,the concentration levels of H2S,MT,DMS,and DMDS in Plant A were:N.D.～1400μg/m~3,N.D.～4.7μg/m~3,N.D.～120μg/m~3,N.D.～110μg/m~3.The concentration levels of H2S,MT,DMS,DMDS,CS2and COS in Plant B are:N.D.～260μg/m~3,N.D.～10.25,N.D.～18.9μg/m~3,N.D.～16.91μg/m~3,N.D.～15.25μg/m~3,N.D.～16.75.The concentration levels of H2S,MT,DMS,DMDS,CS2and COS in Plant C are:N.D.～29.35μg/m~3,N.D.～5.99μg/m~3,N.D.～35.86μg/m~3,N.D.～23.93μg/m~3,N.D.～13.52μg/m~3,N.D.～13.52μg/m~3.The highest concentration of H2S in the three plants is concentrated in the pretreatment unit,which may be due to the release of H2S generated in the sewage pipe network and promoted by the anaerobic conditions of influent water under the disturbance of the pretreatment unit.Secondly,MT is the VSCs with the smallest concentration in all processing units,and it has the characteristics of low concentration level and low detection rate.According to the results of three different sensory evaluation,H2S and MT contributed the most to the sensory perception of the three plants,and the pretreatment unit was the place with the most concentrated odor in the three water plants.In addition,according to the health risk assessment results,the HQ of H2S in each treatment unit of Plant C is less than 1,while the HQ of H2S is greater than 1 in both Plant A and B because they are not equipped with corresponding odor treatment facilities,which indicates that H2S in these treatment units may have a non-carcinogenic risk under long-term exposure.the release concentration of H2S will be lower than a certain temperature,and the change tends to be gentle and at a lower level;when the redox potential is low,the concentration of H2S is higher,and the highest concentration of H2S is measured at-256mv;when the ambient temperature is less than 7.5℃,the corresponding H2S concentration fluctuates less and both are at a lower concentration level.During the monitoring period from 5:00 to 23:00,the TVSCs and H2S concentrations at the grille changed greatly,and the highest concentration of H2S often appeared at 11:00,14:00,and 17:00.In general,the release potential of VSCs of dehydrated sludge is the highest,while the release potential of VSCs of sludge stabilized by thermal hydrolyzation-anaerobic digestion is significantly reduced.In addition,the release of VSCs in ambient air is different from that directly released by sludge due to the specific operation characteristics of each treatment unit.Among them,MT is the key odor gas produced by sludge and contributes the most to the senses.However,due to its chemical activity,MT in the final ambient air is at a low concentration level.However,CS2and COS,which account for a large proportion in the ambient air,do not come from the sludge itself. |
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