Experimental Study On The Bio-slow Sand Filtration Of Small-scale Water Supply Plant In Rural Area Of Yunyang Country

Bio-slow sand filtration method has many advantages,such as less investment,good treatment effect,miniaturization,and simple operation,which is suitable for processing rural drinking water sources.According to drinking water quality in Yunyang Town of Chongqing City,this thesis is aimed to optimize the structure and operation parameters and study the microbial diversity of bio-slow sand filtration technology through the pilot scale test,which has guiding function for practical construction engineering.By the study of optimizing the structure of bio-slow sand filtration,main conclusions are drawn as follows:?1?Smaller filter particle size leads to less biofilm maturation time and better treatment effect,but when the range of particle size is 0.1⁰.5 mm,the running period will be shorter,which is not a good choice;?2?Compared with quartz sand,riversand as filter of bio-slow sand filtration has advantage in removing COD_Mn,ammonia nitrogen and turbidity;?3?when the height of filter in the bed is 10cm,it is more efficient in the removal of pollutant.When the height of filter is 70cm,most pollutants will be removed,and the water will meet the quality and hygiene standards of the State for drinking water in urban and rural areas.By the study of optimizing the operation parameters of bio-slow sand filtration,main conclusions are listed as follows:?1?when the filtration rate ranges from 0.1m/s to 0.3m/s,variation of filtration rate has little less effect on removing COD_Mn,ammonia nitrogen and turbidity,when the filtration rate is more than 0.3m/s,it will have a bad influence on removal rate;?2?when the depth of water is 20cm,the removal rates o are 61.9%,65.8%and 93%respectively,which is the highest.In this state,dissolved oxygen content in the water can been guaranteed and the microbial film can be protected;?3?The bio-slow sand filtration at low temperature formed film completely in about 45 days,which is 15 days later than the one in proper temperature and the removal rate is also lower.Through the high throughput analysis about microbial communities of bio-slow sand filtration,main conclusions are drawn as follows:?1?The Simpson index of 1^#is highest,so the microbial diversity of 1^#is highest.According to the results that the removal rates of COD_Mn,ammonia nitrogen and turbidity of 1^#is highest,it suggests that rare microbial community has some connection with the decomposition of some organic contaminants;?2?The first dominant bacteria of bio-slow sand filtration is proteobacteria,Nitrospirae belongs to proteobacteria.Alphaproteobacteria accounts for about 54.1%of total,besides,Betaproteobacteria is about 15.4%,they are almost compatible bacteria.Organic substance are used as carbon,they are the main degradation participant of COD_Mnn in bio-slow sand filtration.Deltaproteobacteria also has degradation ability for COD_Mn.Bacteroidetes is a kind of chemoheterotrophic bacteria which can break down carbohydrates,all the strains make up a stable microbial ecosystem through the complicated food chain,this way,biofilm structure is stable enough to impact resistance;?3?Through the principal component analysis?PCA?,we get the conclusion that quartz sand and riversand as the filter of bio-slow sand filtration has less impact on microbial community of biofilm,but the particle size of filter media has big effect on microbial community.