Effects Of Dissolved Oxygen On Microbial Community At Multi-phase Interface Of Drinking Water Reservoir

Dissolved oxygen is the main factor affecting the microbial community change at the water-sediment-microbial multiphase interface of drinking water reservoir.Based on water reservoirs?Shibianyu reservoir and Zhoucun reservoir?as the main research object,method of laboratory simulation was adopted.Firstly,in the process of natural oxygen consumption in simulated reactor,the effects of DO degradation on sediment microbial communities?bacteria,methanogens and denitrifying bacteria?were studied by using PCR-DGGE and clone sequencing techniques.Secondly,under different dissolved oxygen conditions,Miseq high-throughput sequencing technique was used to study the structural changes of bacterial communities at the water-sediment-microbial multiphase interface and the role of bacterial communities in driving the cycling of nitrogen,sulfur,iron,manganese and hydrogen.The crucial results and conclusions are as follows:?1?Effects of dissolved oxygen on functional microorganism and gas production in sediments of drinking water reservoir:The results showed that sediment released significant amount of orthophosphates and ammonia.The maximum concentration of NH₄-N reached 10.26 mg·L^-1;orthophosphates maximum release rate was 3.4 mg/m²/d.The diversity indices of methanogens in the surface sediment increased 0.54 to 0.87,meanwhile produced a large amount of methane gas(DO decreases from 2mg·L-1 to 1mg·L^-1).The diversity indices of denitrifying bacteria in sediments increased obviously(DO<1 mg·L^-1).RDA showed that NO₃-N affect sediment bacteria communities most significantly,as NH4-N to denitrifying bacteria and methanogens communities in sediments;SOM affect bacteria and denitrifying bacteria communities in sediments,as STP to methanogens communities in sediments.?2?Effects of dissolved oxygen on bacterial community in overlying water at multi-phase interface:Proteobacteria,Actinobacteria,Bacteroidetes and Firmicutes in the overlying water all accounted for more than 85%of the total bacterial sequence.Under the condition of dissolved oxygen of 3-5 mg·L^-1,the proportion of bacterial communities participating in sulfur oxidation cycle,nitrogen cycle,iron and manganese cycle and hydrogen cycle in overlying water is higher than that under other conditions of dissolved oxygen;Under the condition of dissolved oxygen?DO?of 3-5 mg·L^-1,the proportion of bacterial communities participating in sulfur oxidation cycle,nitrogen cycle,iron and manganese cycle and hydrogen cycle in overlying water was higher than that under other DO conditions;under DO of 0-2 mg·L-1,the proportion of bacterial communities participating in sulfur reduction cycle in overlying water was higher than that under other DO conditions.The proportion of bacterial community participating in methane oxidation cycle in overlying water was higher than that in other dissolved oxygen conditions when the oxygen dissolution was 7-9 mg·L-1.?3?Effects of dissolved oxygen on bacterial community in surface sediments at multi-phase interface:Proteobacteria,Actinobacteria,Bacteroidetes,Firmicutes,Cyanobacteria,Nitrospirae,Chloroflexi,Chlorobi and Acidobacteria in surface sediment all accounted for more than 80%of the total bacterial sequence.The proportion of bacterial communities participating in sulfur oxidation cycle,nitrogen cycle,methane cycle and hydrogen cycle in surface sediments was higher than that in other dissolved oxygen conditions when DO was 3-5 mg·L^-1.The proportion of bacterial communities participating in sulfur reduction and iron and manganese cycle in surface sediments was higher than that in other dissolved oxygen conditions when DO was 0-2 mg·L^-1.