In Situ Remediation Of Pulluted River Using Combination Of Calcium Nitrate And Biofilm Carrier

In this thesis,the technical feasibility of in situ remediation of black odorous river by calcium nitrate-assisted biofilm method was studied.The changes of nitrogen and phosphorus in the overlying water and the changes of organic matter,acid volatile sulfide sulfide,oxidation reduction potential in the sediment were evaluated by experiments.The removal rate of estrogen in the sediment-overlying water system and the microbial changes in the repair process were also studied.A series of lab experiments were used to verify the feasibility of the combined repair and determine the optimum combination of parameters to maximize the repair effect.The surface sediment of the heavily polluted river channel was selected as the experimental sample.In the experiment,five metering levels of Ca?NO₃?₂ were added to the sediment sample including 0.8g/kg,1.6g/kg,2.4g/kg,3.2g/kg,4.0g/kg?calculated as dry matter sediment quality?,exploring the optimal dosage of calcium nitrate.Based on this,the influence of sediment-water ratio,aeration volume,pH and temperature were studied.The results show that the best sediment-water ratio is 1:3,the aeration amount is10ml/?min·L?and the temperature is 20?.Moreover,calcium phosphate precipitation at slightly alkaline pH values water.Finally,the optimum biofilm density was determined.The experiment suggest that the optimum density was771kg/m³ when combined with calcium nitrate.The low density can't accumulate biomass.However if the density is too dense,it will affect the dissolved oxygen content of the overlying water.The AVS removal rate in sediment of the combined repair reached 92.71%,but the process may bring the ecological risk of heavy metal dissolution.The combined remediation of calcium nitrate with biofilm can alleviate the problem of increased total nitrogen concentration in the overlying water due to the addition of calcium nitrate.Moreover,it can effectively reduce the content of organic substances in the overlying water.The combined method can repair V water to?or?water.The experiment further explored the effects of combined remediation technology on the natural and synthetic estrogens in the overlying water level of the river.A set of methods for determining estrogen and sediment estrogen in water was established.Setting three groups experimentes including natural degradation,degradation with calcium nitrate,and degradation with calcium nitrate-assisted biofilm to evaluate the remedation.The results show that the addition of calcium nitrate contributes to the degradation of estrogen.The analysis of microorganisms showed that calcium nitrate can promote the growth of denitrifying bacteria such as Parcubacteria?Thiobacillus?Denitratisoma.Moreover,main functional bacteria include Chlorobi,Bacteroidetes,Sphingobacteriaceae,Aeromonas,Nitrospira were presented in experiments.