Basic Study On Application Of The Remediation Of Eutrophic Landscape Water By Ecological Floating Bed Coupled With Iron-Calcium Materials

Ecological floating bed is an important means of purifying eutrophic landscape water,but traditional ecological floating bed has limited purification capacity for nitrogen and phosphorus nutrients,algae and organic matter.Calcium-based and iron-based materials have been widely used in water environmental remediation in recent years due to their green and environmental characteristics.Among them,calcium peroxide（CP）,as a material that releases oxygen and provides calcium ions,can effectively increase the concentration of dissolved oxygen in water and form stable calcium phosphorus complexes with phosphates;Sponge iron（SI）can release iron ions into water,playing a certain role in the conversion of nitrogen and phosphorus in water.This study first explored the effectiveness of traditional floating beds and strengthened floating beds coupled with CP and SI in purifying landscape water in winter;Secondly,the effectiveness of CP and SI in purifying landscape water under two different dosing methods of suspension and coverage was explored;Finally,through on-site experiments,CP and SI were coupled with traditional ecological floating beds in two ways（suspension and coverage）.The purification effects of ecological floating beds on actual landscape water under different coupling methods were explored.The main results and conclusions obtained in this study are as follows:（1）During winter,the nitrogen and phosphorus concentrations in the overlying water of each experimental group continued to decrease.Compared to the control group（CK）,the average removal rates of TN by traditional floating bed（CFB）and strengthened floating bed（SFB）were 7.40%and 12.72%,and the average removal rates of TP were 20.00%and 35.71%,respectively.The results of the sediment static release test showed that the average concentrations of TN in the overlying water of CFB and SFB were 70.13%and 72.37%of CK,and the average concentrations of TP were 72.22%and 44.44%of CK,respectively.The ability of CFB and SFB sediment to release pollutants is lower than that of CK,which can effectively alleviate endogenous release.（2）For CP,coverage is more conducive to the removal of phosphorus in overlying water,with an average removal rate of 83.63%for TP;suspended dosing is more conducive to nitrogen removal in overlying water,with an average removal rate of20.29%for TN.For SI,coverage addition is more conducive to the removal of nitrogen and phosphorus in overlying water,with an average removal rate of 25.76%for TN and 87.46%for TP,respectively.SI suspension addition is more conducive to the removal of organic matter in overlying water,with an average removal rate of 34.74%for COD.（3）Covering CP reduces the richness and diversity of sediment species,while covering SI increases them.The dominant bacterial genera of sediment microorganisms in different CP dosing methods are different.Under the coverage dosing method,the dominant bacterial genera are Denitratisoma and Thiobacillus,while under the suspension dosing method,the dominant bacterial genera are Silanimonas and Desulfatiglans.The dominant microbial genera in sediment with different SI addition methods are the same,which are Denitratisoma,Smitherla and Methyloteera,among which Methyloteera is a denitrification bacteria that oxidize Fe²⁺.（4）The ecological floating bed coupled with CP and SI has a significant purification effect on the landscape water supplied by reclaimed water.Among them,the removal rates of TN,TP,COD and algae density of overlying water by CFB-S（CP and SI coupled with traditional floating bed by suspension dosing）can reach 22.02%,50.00%,35.52%and 39.26%;the removal rates of TP,PO₄^3--P,COD and algal density of overlying water by CFB-C（CP and SI coupled with traditional floating bed by covering）can reach 81.82%,93.75%,48.42%and 62.75%.CFB-C can maintain landscape water at a medium nutrient level,effectively avoiding eutrophication.