Study On Removal Of Heavy Metals In Water By Aquatic Plants

Heavy metal pollutants flow from multiple sources to the water body,causing the natural water bodies to be polluted in varying degrees.When the concentration of heavy metals exceeds a certain range,it will have a toxic effect on the entire water environment,biological physiology,development stagnation,and even death,further through the food chain directly or indirectly to the human health,governance of heavy metal pollution of water no delay.With the advancement of science and technology,phytoremediation has become a research hotspot in recent years.People use aquatic plants to remediate water bodies contaminated by heavy metals,which are low in cost,easy to operate,minimizes the risk to the environment,and thus achieves green governance.Through the preliminary investigation of the heavy metals released by local companies and combined with the pollution of heavy metals in local rivers,five heavy metals such as Pb,Cd,Cr,Cu,and Zn in the water were used as the treatment targets.Through reviewing the literature and referring to the effect of aquatic plants on the removal of heavy metals under domestic and international conditions combined with the conditions for the growth of suitable local plants,four species of aquatic plants,Water hibiscus,Sunshade grass,Yellow iris,and Water celery,were studied.Study the removal of heavy metals in water.Removal of single heavy metals in water by aquatic plants: The study was conducted within the concentration range of Class V Standard of the "Standard for Surface Water Environment Quality Standard"(GB 3838-2002)and "Class A Standard for Wastewater Discharged into Urban Sewers"(GB/T 31962-2015),The removal effects of aquatic plants,Water hibiscus,Sunshade grass,Yellow iris,and water celery,on five single heavy metals such as Pb,Cd,Cr,Cu,and Zn in water.Samples were taken every 72 hours,and the concentration and removal rate was analyzed,and the concentration with high removal rate was screened.Through experiments,it was found that the removal rate increased with the increase of the concentration within a suitable range of plant growth.Under the conditions of pH=5,pH=7 and pH=9,the effect of four aquatic plants on the removal of five single heavy metals in water was studied.Samples were taken every 72 hours,and the effect of different pH on the removal of heavy metals from aquatic plants was analyzed.The results showed that the removal rate of heavy metals by aquatic plants was higher under the conditions of Pb at pH=5 and Zn at pH=9.The removal efficiency of heavy metals by aquatic plants was higher under the condition of pH=7 for other three heavy metals.Experiment on removal of composite metal in water by aquatic plants: The effects of four aquatic plants on the removal of five kinds of heavy metals were investigated.Samples were taken every 72 hours to determine the concentrations of five heavy metals in the water,and aquatic plants with high removal rates of heavy metals were screened.The test showed that the removal of Pb,Cd,Cr,Cu and Zn was better in Sunshade grass and Yellow iris.Therefore,Sunshade grass and Yellow iris were selected as the dynamic test plants.Dynamic test of the removal of composite metals in water by aquatic plants: Combined with the above experimental results,under the dynamic conditions,the removal effect of heavy metals in compound polluted water was studied.Samples were measured every 24 hours.Through experiments,it was found that the removal rate of Pb by Sunshade grass and Yellow iris has reached 39.60%,which has not reached the standard of surface water in category V;the removal rates of Cd and Cr have reached 65.6% and 73.2%,respectively,close to surface water V Standards;The removal rates of Cu and Zn reached 66.70% and 70.12%,respectively,and all met the Class V standard for surface water.The accumulation coefficients of 5 kinds of heavy metals are much higher than that of the ground part,and the transfer coefficient is less than 1.The enrichment coefficient of Pb,Cd and Cr in the root of the Sunshade grass was higher,while the root of Yellow iris was higher in Cu and Zn.The effects of water plants on the removal of heavy metals in water were studied,and the scientific basis for the later restoration of heavy metal contaminated water was provided.