Research On Removal Efficiency Of Pollutants In Surface-flow Constructed Wetland

Constructed Wetland is a new sewage treatment technology. Because of the advantage of surface effluent quality, good resistance to shock-loading, low construction and operation cost and easy to maintain, aesthetic value, good effect in pollutant removal, and the function of nitrogen and pHospHorus removals, it is getting more and more attention. Constructed Wetlands is widely used in the studies of the pollutants removal effect of organic, but it is rarely on dealing with the heavy metal pollutants in wastewater in our country.The research chose two models of the constructed wetlands as the object, one is the wetlands of the mouth of Weihe river connected with Zaohe river and another is the wetlands of the Zaohe river. In the constructed wetlands of the mouth of the Weihe river of connected with Zaohe river, the research uses four systems:the first and the second level surface flow wetland of Cattails (Bland B2), the first and the second level surface flow wetland of PHragmites (B3and B4). In the constructed wetlands of Zaohe river, the research uses two systems:the first and the second level surface flow wetland of both pHragmites and cattails (B5and B6). The research tests the concentrations of the heavy metals (Cu, Pb, Zn, Cr, Cd, Ni) and organic pollutants (COD, NH3-N, TP) in the samples in each sample region, analyses the effect and mechanism of the purification on these heavy metals and organic pollutants. The results prove that:1.The results of the removal of heavy metals in the constructed wetlands systems:1) in level-1surface flow system:(1) The removal rate of Cu、Pb、Zn Ni in the system is5.8%-86.4%、45.8%-86.3%,30.1%-65.8%、37.1%-63.9%. The removal effect of Cu、Pb、Zn、Ni of cattails is better than the one of pHragmites.(2) The removal rate of Cr、Cd in the system is57.9%-90.0%、57.9%-95.3%. The removal effect of Cr in the system of pHragmites+cattails is better than the one of pHragmites and the system of cattails.2) In the second level flow system:(1) The removal rate of Cu、Pb、Zn、Ni in the system is38.4%-95.4%、43.5%-87.9%,38.3%-98.8%、50.4%-79.0%. The removal effect of Cu、Pb、Zn、Ni in the system of cattails is better than the one of pHragmites.(2) The removal rate of Cr、Cd in the system is70.3%-94.2%,71.3%-97.2%. The removal effect of Cr in the system of pHragmites+cattails is better than in the system of pHragmites and the system of cattails.2. the analysis of the heavy metals Cu、Pb、Cd、Cr、Ni、Zn in different level-2surface flows are different.(1) The analysis of the heavy metals in cattails level2surface flow and pHragmites level-2surface flow shows that:the differences in plants in cattails level2surface flow and pHragmites level-2surface flow, with the same running time and inflow, cause the significant differences of Cr、Cu、Zn.(2) The analysis of the heavy metals in cattails level-2surface flow and pHragmites plus cattails level-2surface flow shows that:because of the differences in running time, water conservancy time, inflow and ground substance, the Pb、Cu are different significantly in the two systems.(3) The analysis of the heavy metals in cattails level-2surface flow and pHragmites plus cattails level-2surface flow shows that:the differences are not significant in the two systems.3. The research results of the removal rate of the organic pollutants show that the organic pollutants in waste water can be removed effectively and stably.(1) In level1surface flow the removal effect of COD、NH3-N in pHragmites system is44.5%,53.5%; The removal effect of TP in cattails system is good, which is46.9%.(2) surface flow the removal effect of COD、NH3-N in pHragmites system is52.6%、55.6%; The removal effect of TP in cattails system is good, which is71.3%. The removal rate of the organic pollutants in level-2surface flows all exceed50%and the concentrations of COD、NH3-N、TP in effluent quality are61.96mg/L、9.072mg/L、0.494mg/L, which reach A level.