Removal Of Heavy Metals In Farmland Irrigation Water In Agriculture And Mining Polluted Area By Constructed Wetland

In order to solve the environmental problem of increasingly heavy metal pollution in farmland irrigation water,a surface-flow constructed wetland(SFCW)in the form of a grit chamber+plant pond combination was used to repair heavy metal pollution in farmland irrigation water sourced from pollution of aquaculture wastewater and pollution of mine wastewater.H.Verticillata,E.Crassipes,and Water Lotus were used as aquatic plants in the constructed wetlands,the concentrations of Cd,Pb,Zn,and Cu in the inflow and outflow of the constructed wetlands and in each unit were monitored,and the removal rate of heavy metals in constructed wetlands was measured.The contribution rate of each SFCW cell was calculated,and the performance of the constructed wetland for heavy metal removal was evaluated by the data.The distribution and enrichment of heavy metals in aquatic plants were monitored.The enrichment of Cd,Pb,Zn,and Cu in the three plants were found through the data,and a comparison was made among the plants to find out the advantage plant for HM removal.The main results obtained are the following:(1)The Ansha wetland has a certain effect on the removal of organic matter.The concentration of COD at the inflow of the constructed wetland is 103 mg/L,the outflow concentration is 31 mg/L,and the removal rate reaches 69.9%.The concentration of BOD was reduced from 16.3 mg/L at the inflow to 9.6 mg/L,with a removal rate of 41.1%.It also had a good removal efficiency for ammonia nitrogen,and the ammonia concentration at the inflow was 0.842 mg/L,which was repaired by the constructed wetland.After treatment,it was 0.447 mg/L,with a removal rate of 46.9%.At the same time,it also had a certain removal effect in terms of total phosphorus total nitrogen.The removal rates were 26.9% and 56.1%,respectively,and were slightly weaker than other organic removal effects..The removal efficiency percentage of Cd,Pb,Zn,and Cu in the Ansha Constructed Wetland was 77.8%,70.71%,62.56%,and 61.94%,respectively,and the removal efficiency of the constructed wetlands for different heavy metals reached more than 60%.Through the analysis of the contribution rate,the removal of Cd from 1st pool,2nd pond and 3rd pond was 18.69%,24.09%,and 28.39%,respectively,indicating that plant ponds(2nd and 3rd ponds)can remove Cd.Play a catalytic role.Contrary to the removal of Cu,the contribution rate of 1st pond was 28.19%,that of 2nd pond was 20.21%,and that of 3rd pond was 13.57%,indicating that the aquatic plants in the Ansha constructed wetland(H.Verticillata,E.Crassipes)failed The removal of Cu promotes,and the Cu content in the water decreases significantly with the increase of the distance of the water flow,resulting in a decrease in the removal efficiency.For the removal of Pb and Zn,except for the removal of Zn,the 2nd pool was only 13.73%,and the contribution rate of each unit of the constructed wetland did not differ much.(2)The removal of organic contaminants from the Huanggu Constructed Wetland was monitored.The COD content was reduced from 76 mg/L to 17 mg/L with a removal rate of 77.6%;the BOD content was reduced from 13.5 mg/L to 6.6.Mg/L,the removal efficiency is 51.1%.The removal rate of ammonia nitrogen,total phosphorus,and total nitrogen reached 46.9%,44.5%,and 58.3%,respectively,for the constructed wetlands.For the removal of heavy metals in water bodies,the removal efficiencies of Cd,Pb,Zn,and Cu in the Huanggu Constructed Wetland were 60.63%,77.78%,63.85%,and 66.86%,respectively.The removal of Pb was the best,and the removal rate of Cd was the lowest.The removal rate of heavy metals remained above 60%.Through the analysis of the contribution rate of each wetland unit,when the removal of Pb and Zn in the water body,the contribution rate of plant ponds(2nd pond and 3rd pond)is obviously higher than that of 1st pond,for Cd and Cu Plant ponds failed to promote repair.(3)The aquatic plants in the constructed wetland have different removal effects on different heavy metals,among which the removal effect of Pb is the most obvious,and the removal of Pb in the plant pond is the largest in the wetland unit.By sorting the BCF values of various heavy metals enriched by plants in wetlands,it can be concluded that in the course of the restoration of Cd,Pb,and Cu,the order of BCF of each aquatic plant is water E.Crassipes> H.Verticillata> Water Lotus,water E.Crassipes> H.Verticillata> Water Lotus,water E.Crassipes> H.Verticillata> Water Lotus,in which the enrichment of Zn by aquatic plants can not sort their enrichment ability due to incomparable incommensurability.According to the data,the four heavy metals are sorted into Zn>Pb>Cu>Cd according to the amount of enrichment in plants.Except for Zn,other heavy metals follow the rule of enriching the root>stem>leaf in the plant,while Zn is in the plant.Each site exhibits the same high concentration of enrichment.By comparing the plants in the constructed wetlands,it was concluded that water E.Crassipes are advantage plants in the enrichment of Cd,Pb,and Cu,especially in the enrichment of Pb and Cu,which has a very high bio-concentration factor.H.Verticillata is a advantage plant for Zn enriching.