The Influence Of DOM To The Production And Releasing Of DMS In The Constructed Wetland

The subsurface flow constructed wetland is widely used in domestic sewage,industrial wastewater and agricultural wastewater treatment because of its good performance for heat preservation and high removal rate of organic pollutants.Removal of organic matter has been considered as an emphasis of research works.The key factor for controlling the performance of organic matter removal in constructed wetland has important significance on the complete utilization of the constructed wetland.Dimethyl sulfide(DMS),as one of the important volatile organic sulfur compounds,has an important impact on the global sulfur cycle,climate change,odor occurrence processes.In lakes,rivers,wetlands and other freshwater ecosystems,DMS is mainly produced through the process of methylation of sulfide. Although DMS amount generated in subsurface flow constructed wetlands is minor,its effect on environmental is not be ignored due to its very low odor threshold.Currently,major studies concerning the constructed wetlands are concentrated on the effect of design and operation parameters on removal of organic matters.It is rare to study the relationship among various parameters in the constructed wetlands for waste water treatment system,especially the effect of other parameters on COD removal.Due to the complex structure and important significance of the environmental impact,dissolved organic matter(DOM) has become an important subject in many researches.However,there is no report on the effect of DOM on DMS formation in constructed wetland. This master thesis focused on the following two aspects:1.Performance evaluation of constructed wetlands system by statistical analysis of data obtained by long term monitoring of organic matter and other substances in the influent and effluent;2.Study on the effect of DOM on the formation of DMS.The major conclusions are summarized as follows: 1.The removal of organic matters(COD) in a pilot-scale subsurface flow constructed wetland system was studied in the present study.Factors such as influent COD concentration,total suspended solids,BOD, total organic carbon,total carbon affecting COD removal were investigated.The results indicated that the concentrations of influent COD,TSS,BOD,TOC and TC had significant effect on COD removal.A survey of COD profiles along the wetland length revealed that COD removal was mainly occurred in the area located in the middle of the constructed wetland;2.The effect of DOM such as methanol,ethanol,and acetic acid on formation of DMS using sludge from substrate in the subsurface flow constructed wetland under anaerobic conditions was investigated. The experimental results showed that(1) DMS formation is mainly from the bio-methlation of inorganic sulfur,and also from the chem-methlation of inorganic sulfur in the presence of excess inorganic sulfur;(2) Addition of methanol,ethanol,and acetic acid could significantly decrease the formation of DMS.The effect of methanol,ethanol,and acetic acid on DMS formation showed the same trend,probably indicating the same mechanism of their effect on DMS formation;(3) Inorganic sulfur is major sulfur donor for DMS formation,and methanethiol is probably major intermediate for DMS formation.The bio-methylation of sulfur in the presence of microbial is major mechanism of DMS formation.