In Situ Covering Control Nitrogen And Phosphorus Release From Sediment Of Baihua Lake

In recent years, the phenomenon of lakes’ eutrophication often happened,and tends to be worse. In order to control the phenomenon of eutrophication, active measures have been taken to control the external pollution. In the case of exogenous pollution is controlled effectively, some areas which sediment pollution(especially nitrogen and phosphorus) serious because of the endogenous pollution causes eutrophication continued to erupt. So the inhibition of endogenous pollution has become an important measures of controlling the lakes’ eutrophication. This study choose Guizhou Baihua lake endogenous pollution to research cover’s inhibition effect to the release of N, P, providing technical support for the engineering of controlling lakes’ endogenous pollution in our country.First,this study compared zeolite, clay, biochar, limonite and kaolin five cover material’s inhibition effect of releasing nitrogen and phosphorus in sediments, the results showed that the kaolin’s inhibition effect of TP release in the sediment is significantly better than any other four kinds materials; Based on the study,research the influence of kaolin cover thickness and material particle size to the effects of situ covering,The optimum thickness of kaolin used in situ covering is 3 cm to 5 cm, the best size is 60 yard to 100 yard;Then use high temperature and Ca Cl2 to modified kaolin, verify kaolin’s inhibition effect of releasing nitrogen and phosphorus in sediments which is modified by the high temperature and Ca Cl2.Then combining passivation technology and in situ covering technology, validate it’s inhibition effect of nitrogen and phosphorus in sediments. Finally based on the results of above simulation experiment design the pilot experiment of 12017m2, validate kaolin’s inhibition effect to the release of pollutants in Baihua lake sediments under the condition of natural. The results are listed as follow:1)After 45 days covered, the lowest concentration of ammonia nitrogen in overlying water is biochar, the inhibition effect of ammonia nitrogen release rate was 73%. At the end of experiment,the concentration of ammonia nitrogen is zeolite > limonite > clay > kaolin > biochar. Achieved the best effect is char and kaolin, ammonia nitrogen concentration are 0.41 mg/L, 0.42 mg/L respectively.After 45 days covered, the lowest concentration of TN in overlying water is clay, the inhibition effect of TN release rate was 95%. At the end of experiment,the concentration of TN is zeolite > limonite > kaolin > clay > biochar. Achieved the best effect is biochar, TN concentration is 0.74 mg/L,the overlying water TN concentration of the other four kinds of material are basically the same.For TP,the excessive pollutants of Baihua lake, except the biochar other cover material has achieved very good effect, TP concentration in overlying water was clay > limonite >zeolite > kaolin. Achieved the best effect is kaolin, TP concentration was 0.027 mg/L, the inhibition effect of TN release rate was 94%.2)The best size of kaolin used in Baihua lake in situ covering is 60 yard to 100 yard, and the best thickness is 3-5 cm, under the condition of the optimal size and thickness the maximum ammonia nitrogen concentration of overlying water is 1.35 mg/L, Inhibition rate is 27%;The maximum TN concentration of overlying water is 3.56 mg/L, Inhibition rate is 52%; The maximum TP concentration of overlying water is 0.026 mg/L, The inhibition rate is 97%.3)800℃ high temperature modification weaken the inhibition effect of cover layer, But enhances the microorganism growth ability in covering surface. The maximum TP concentration of overlying water in Ca Cl2 modified kaolin is 0.016 mg/L, Compared to kaolin decreased by 41%, TP inhibition strengthened; The concentrations of ammonia nitrogen and TN in overlying water of three experimental group compared with little difference.4)Combined passivation technology with situ covering technology can obviously enhance the inhibition effect of pollutants release, TP concentration in overlying water of Al2(SO4)3 passivation and kaolin covering combination group is 0.012 mg/L, Compared to kaolin is reduced by 56%; Combination group of Ca Cl2 passivation and kaolin cover is 0.016 mg/L, compared to kaolin is decreased by 41%,Theconcentrations of ammonia nitrogen and TN in overlying water of three experimental group compared with little difference.5)Through pilot experiment, TN concentration of experimental area is 0.071 mg/L-1.01 mg/L, TN concentration is 0.007 mg/L-0.014 mg/L, meet the class III and class I standard of surface water,achieved obvious effect compared with the control area; Environmental ecological monitoring found that kaolin dosing will not affect the activity of fish, and can obviously control in the occurrence of eutrophication.