Experimental Study On Nitrogen And Phosphorus Release And Modified Adsorption Of Sediment From Landscape Lake

Urban landscape lake belongs to shallow water lake,which has the characteristics of fuzzy boundary layer boundary,obvious wind-generated flow characteristics and intense material and energy exchange in the vertical space,which further intensifies the influence of sediment on the quality of overlying water.At present,most of the landscape lakes are man-made lakes,and the overflow water is directly connected to the municipal drainage network.There is a lack of long-term and stable water replenishment,and the lake water cannot maintain good liquidity,resulting in the continuous accumulation of nutrients such as N and P.When the nutrient inputs of foreign N and P are reduced,only the release of internal primary pollutants can still make the water body in an eutrophication state.Therefore,it is necessary to control the release of pollutants such as N and P in sediments to the overlying water for the prevention and control of environmental pollution of surface water.Release is necessary to prevent and control environmental pollution of surface water.According to the above problem,this study analyzes the landscape lake sediment releasing mechanism of N,P,based on the physical and chemical properties of sediment samples?including pH,WC,the LOI,nitrogen and phosphorus content?,proposed by calcining modified to regulate and improve the sediment adsorption performance,and with the sludge flocculation pool,bentonite,zeolite powder composition,preparation of modified sediment composite materials;Furthermore,the adsorption properties of the composites were systematically evaluated by various characterization methods?SEM,EDS,XRD,specific surface area and pore structure?,and the effects of in-situ coating of the composites on controlling the release of sediment N and P were discussed.The specific research contents are as follows:?1?evaluation of sediment physical and chemical properties and eutrophication status of landscape lake:sediment pollution in landscape lake is serious.The average contents of TN,NH₄⁺-N and TP are 6.703 mg/g,0.094 mg/g and 0.327 mg/g respectively,belonging to the heavy pollution level.The comprehensive nutrient status index of the water body fluctuated between 57.02 and 61.40 from September to November in a normal year,presenting a general state of mild eutrophication.?2?Environmental factors affect the release of nitrogen and phosphorus from sediment:ph,temperature,DO and disturbance have great influence on the release of N and P from sediment.Increasing temperature and low DO concentration can accelerate the release of N and P in sediment,acidic condition is conducive to the release of TN and NH₄⁺-N,alkaline condition is conducive to the release of TP,disturbance can accelerate the release of nitrogen in sediment,and the disturbance rate is proportional to the release amount,but has little effect on the release of total phosphorus.?3?Study on the modification method and optimization ratio of landscape lake bottom mud:by studying the adsorption effect of NH₄⁺-N and TP on sediment and flocculation tank sludge of water purification plant at different calcination temperatures,the optimum calcination modification conditions are determined as follows:the optimum calcination temperature of sediment is 550?,the adsorption capacity of NH₄⁺-N and TP is 0.37 mg/kg and 0.12 mg/g respectively.The optimum calcination temperature of sludge from flocculation tank of water purification plant is 400?,at this time,the adsorption capacity of NH₄⁺-N is 0.48 mg/g,and the adsorption capacity of TP is 0.604 mg/g.At the same time,the adsorption efficiency of Reed biochar,zeolite,diatomite,kaolin,bentonite and alumina was optimized by single factor adsorption test,and the combination ratio of materials was carried out.Through the design of orthogonal test,the optimal scheme is preliminarily determined as modified sediment:modified water purification plant flocculation tank sludge:zeolite powder:bentonite=1:2:3:1.?4?Study on the characterization of sediment modified composite material and the adsorption efficiency of nitrogen and phosphorus by covering sediment:various characterization methods were used to analyze the covering materials before and after compound.the results showed that the materials had good crystallinity and rich micropore and mesoporous pore structures.at the same time,the specific surface area and micropore volume of the composites were 37.332 m²/g and 0.0036 cm³/g respectively,which were much higher than those of the modified sediment?12.016 m²/g and 0.0024 cm³/g?,and the adsorption properties were good.Through the study on the effect of covering to control the release of N and P from the sediment,compared with the blank group,when the thickness of the cover is 3 cm,the reduction rate is61.58,79.59 and 82.20%,which has a significant effect on controlling the release of N and P from the sediment and the reduction of nutrients in the overlying water body.?5?Through simulation test study on the sediment of modified composite material under different temperature override control the effect of sediment nitrogen and phosphorus release,the results show that temperature increase leads to sediment of N,P release a quantity to increase,the sediment of modified composite material has good adsorption on N,P,in controlling sediment nitrogen and phosphorus release can overcome the negative effects of rising temperatures.