Efficiency Analysis Of Submerged Macrophytes Combined With Active Capping Material On Controlling Phosphorus And Nitrogen Release From Sediment

With the rapid development of industrialization and urbanization,eutrophication become an increasingly serious problem.Nitrogen(N)and Phosphorus(P)concentrations are both regarded as the mainly limitations for the eutrophication,and sediment plays an important role in eutrophication because it is regarded as a source or a sink for N and P in water.Therefore,in situ reducing N and P released from sediment will be an effective solution for controlling eutrophication,once the external pollutant has been decreased already.This paper introduce a remediation technique for controlling N and P released from polluted sediment using submerged macrophytes and active capping material through the simulation experiment in laboratory.The feasibility,efficiency and mechanism of the technique was studied at the same time.The study mainly carried out as the follows:(1)The reduction efficiency of N and P in eutrophic waters of Vallisneria natans,Hydrilla verticillata,Ceratophyllum demersum.,Myriophyllum spicatum was studied.The max reduction rate of NH4+-N of the 4 submerged macrophytes above was87.2%,90.9%,90.1% and-11%,respectively;the max reduction rate of PO43--P was76%,83.4%,79.8% and 68.4%,respectively.The results showed that Vallisneria natans,Hydrilla verticillata and Ceratophyllum demersum.had a good effect on N and P reduction in eutrophic waters,while Myriophyllum spicatum was not so obvious.Therefore Vallisneria natans and Hydrilla verticillata were selected as the research subject in follow-up works.(2)Efficiency of Vallisneria natans and Hydrilla verticillata to immobilize N and P release from sediments was researched.The reduction rate of NH4+-N in interstitial water was 0.2% and 21.7%,respectively;the reduction rate of PO43--P in interstitial water was 79.5% and 84.8%,respectively;the reduction rate of TN in sediment was 17.7% and 19.2%,respectively;the reduction rate of TP in sediment was-18% and 5% respectively;the enrichment of N was 29.38mg/g and 34.19mg/g,respectively;the enrichment of P was 7.58mg/g and 9.13 mg/g,respectively.The result showed that submerged macrophytes could absorb the nutrient in the overlyingwater and sediment.Vallisneria natans bagan to decompose at the end of the experiment,so Hydrilla verticillata was selected as the research subject in follow-up works.(3)Efficiency of combination Hydrilla verticillata with Water Treatment Plant sludge(WTP sludge)to immobilize N and P release from sediments was researched.The reduction rate of PO43--P and TP in interstitial water was 66.8% and 59.8%,respectively;the reduction rate of ammonium nitrogen and TN in sediment was 46%and 40.0%,respectively;the reduction rate of TP in sediment was 7.9%;the P enrichment of Hydrilla verticillata and WTP sludge was 7.13mg/g and 0.76 mg/g,respectively;submerged macrophytes transformed phosphorus contents in the sediment from labile Fe/Al-P to stable Ca-P.The result showed that the conbination technique showed a certain effect on the reduction of N and P in overlying water and sediment,as it could control the re-suspension of sediment at the same time.It is feasible that controlling N and P released from polluted sediment using submerged macrophytes and active capping material,which can provides technological support and theoretical basis for eutrophication treatment.