Study On Remediation Of Black And Odorous Water And Sediment By In-Situ Chemical Method

Black and odorous water bodies in rivers,lakes and reservoirs have occurred frequently in recent years at home and abroad.The treatment of black and odorous water bodies has become one of the key tasks in the comprehensive treatment of water environment in China,there are two kinds of pollutants that cause the water body to be black and smelly:The external pollution and the internal pollution.On the premise of controlling the external pollution,the treatment of the internal pollution becomes the key to the treatment of the black and smelly water body.Based on the premise investigation,this paper determined that Lezhi Tongjia river black and odorous bottom mud as the experimental object,the Xi Lake water sample as the overlying water in the Xi Pu campus of Southwest Jiaotong University.The degradation and inhibition of release of endogenous pollutants by chemical agents were simulated under the control of exogenous pollutants.During the experiment,the effects of the dosage of chemical agent,the depth of chemical agent,the mode of chemical agent application and the water temperature in different seasons on the remediation of sediment were set up,at the same time,the p H,DO,CODcr,NH₃-N,TP,TN and organic matter,TN and TP of the overlying water were monitored for 35 days,to determine the effects of chemicals on the degradation of pollutants in the sediment and the quality of the overlying water in the remediation process of black and odorous water,the changes of microorganisms in the sediment before and after chemical treatment were analyzed.The main conclusions are as follows:1.In the system of repairing black and odorous bottom mud by CaO₂,（1）when the dosage of CaO₂ is studied,it is found that the dosage of CaO₂ is 20g,the experiment result is better,the CODcr,NH₃-N,organic matter of bottom mud and TN of overlying water all show a downward trend,the concentration of DO in the overlying water increased by 3.67%,while p H showed the opposite relationship.In the 20g experiment,the Ph in the overlying water was the highest and higher than that in the control group.（2）in the study of the effect of the depth of CaO₂ addition,it was found that the depth of CaO₂ addition was 20cm and the effect of CODcr,NH₃-N,TN,TP and TN in the overlying water decreased by 32.86%,54.69%,44.40%,70.75%and 43.66%,respectively,at the same time,the concentration of DO in the overlying water increased by 2.45%,and the p H in the two groups showed an increasing trend due to the addition of CaO₂ of 10g,but there was no significant difference between the two groups.（3）in the study of the effect of CaO₂ adding mode,it was found that the concentration of NH₃-N,TN and the contents of organic matter,TN and TP in the bottom mud decreased by 53.78%,36.87%,45.36%,36.55%and 44.80%,respectively The concentration of CODcr and TP decreased by 40.0%and 67.69%,and the concentration of DO increased by 2.45%.（4）when simulating the influence of water temperature in different seasons,it was found that the simulated water temperature in summer was beneficial to decrease the contents of NH₃-N,organic matter,TN and TP in overlying water by 46.45%,45.79%,33.36%and 33.26%,respectively The simulated winter water temperature was beneficial to decrease the concentration of CODcr,TN and TP in the overlying water,which decreased by 50.0%,38.12%and 70.58%respectively,while the concentration of DO in the overlying water increased by 13.64%.2.In the system of repairing black and odorous bottom mud with Ca（NO₃）₂,（1）in the study of the effect of Ca（NO₃）₂ dosage,in the experiment of 20g dosage,the overlying water TP,organic matter of bottom mud and bottom mud TN showed a good downward trend,the removal rate of NH₃-N from overlying water and TP from bottom mud decreased by 62.71%,52.76%and 11.69%respectively,while the removal rate of NH₃-N from overlying water and TP from bottom mud decreased by 75.16%and 28.92%respectively,in each experimental group,the increase of TN in overlying water was the lowest,129.85%.（2）When Ca（NO₃）₂was added to the surface layer（10cm）of the bottom mud,the repair effect was better.CODcr,ammonia nitrogen,organic matter and TP of the bottom mud decreased by 38.11%,72.5%,44.57%and 24.29%respectively,while TN of the bottom mud increased by 0.72%The bottom layer（30cm）had a significant decrease of 66.10%to the TP of overlying water.（3）in the study of the effect of Ca（NO₃）₂ feeding mode,it was found that the batch feeding was beneficial to the removal of CODcr,TP,organic matter and TP in the overlying water,which decreased by 45.76%,54.88%,51.10%and 27.76%,respectively However,the removal effect of ammonia nitrogen by one-time addition was obvious,which decreased by 72.55%.（4）when simulating the influence of water temperature in different seasons,it was found that the simulated summer water temperature was beneficial to decrease the concentration of NH₃-N and TP in the overlying water,by 70.98%and 52.45%respectively,and to restrain the increase of TN concentration The simulated water temperature in winter was beneficial to decrease CODcr,organic matter and TP of overlying water,which decreased by 44.30%,44.40%and 23.85%respectively.3.According to the results of sobs dilution curve,most of the microorganisms in the sediment of different experimental groups were included in this diversity sequencing,the main reason is that Ca（NO₃）₂ and CaO₂ produced by the reaction of Ca（OH）₂ and water are nitrate,which destroy the physiological structure of microorganism and lead to low community structure.At the same time,Proteobacteria,Firmicutes and Chloflexi were relatively abundant in different experimental groups,and Bacteroidota could degrade macromolecular organic matter into small molecular organic matter,it is beneficial to the stabilization of sediment and the denitrification process.