The Application Study On Pollutants Removal From Low Pollution Water By Combined Constructed Wetland

In order to solve the problem of low pollution water treatment,a combined constructed wetland pilot system was built in this study.The low pollution water was taken from xipiehonggou in Chaohu City.The combined constructed wetland pilot system on site used combination 1（Artificial floating island+Vertical Flow+Horizontal Subsurface Flow）and combination 2（Vertical Flow+Vertical Flow+Horizontal Subsurface Flow）two low pollution water treatment processes.Compare and analyze the treatment effects of single-stage constructed wetlands and two combined constructed wetlands on pollution factors.Based on high-throughput sequencing technology,the diversity of Canna root microorganisms in different types of wetland units was further studied.The conclusion is as follows:（1）The treatment efficiency of constructed wetlands to pollution factors is susceptible to seasonal and temperature effects.The temperature in Chaohu area in summer is obviously higher than that in spring,generally above 24℃,and the temperature in spring is relatively low,between 12℃²1℃.The quality of incoming and outgoing water in summer is better than that in spring.At the same time,it was also found that the concentration of COD and total nitrogen in the xipiehonggou is relatively high,which is the main pollution factor in low pollution water.（2）Analysis of single-stage constructed wetland treatment effect on low-polluted water.The average treatment efficiency of floating treatment wetland on the low-polluted water was 25.77%（COD）,20.67%（TP）,19.51%（TN）,and 27.22%（NH₄⁺-N）.The floating treatment wetland has the highest treatment efficiency for NH₄⁺-N and the lowest treatment efficiency for TN.The average treatment efficiencies of vertical flow wetland on low-pollution water are 35%（COD）,32.42%（TP）,48.01%（TN）,and 39.06%（NH₄⁺-N）.vertical flow wetland have the highest treatment efficiency for TN and the lowest treatment efficiency for TP.The study found that the vertical flow wetland can greatly extend the residence time of wastewater,has strong oxygen transfer efficiency,can enhance the nitrification and denitrification rates of the CW system,and has a better treatment effect on TN and NH₄⁺-N.The residence time of wastewater in floating treatment wetland is relatively short,resulting in low treatment efficiency of various pollution factors.To sum up,the vertical flow wetland is slightly better than the floating treatment wetland.（3）Analysis of treatment effect of combined constructed wetland on low pollution water.When HRT=12h,inlet waterρ（COD）is 16³6mg/L,ρ（TP）is 0.1⁰.4mg/L,ρ（TN）is1.1¹1.4mg/L andρ（NH₄⁺-N）is 0.2¹.6mg/L,the removal rates of Combination 1 were37.50%⁶3.89%,18.57%⁷0.73%,11.79%⁸6.25%and 36.03%⁹7.44%,respectively,and the removal rates of Combination 2 were 47.06%⁶9.44%,37.15%⁶8.05%,33.90%⁹0.66%and 48.04%⁹5.26%.Combination 1 and combination 2 had significant removal effects on TN and NH₄⁺-N,and average removal effects on COD and TP.In combination 1 and 2,the TN removal rate increased the most,and the COD removal rate increased the least.As far as the treatment effect is concerned,the treatment effect of combination 2 on low-polluted water is better than that of combination 1,and the treatment effect of combination constructed wetland is obviously higher than that of single-stage constructed wetland.（4）To analyze the microbial flora of canna roots in different types of wetland units by high-throughput sequencing technology.The types and numbers of microbial flora in different wetland units are slightly different and change at all times,but still maintain a high similarity and stability.In different wetland units,the richness and evenness of the flora of Canna root were higher,but there was no significant difference.In the two groups of combined constructed wetland system,the community diversity of Canna plant roots gradually decreased along the direction of water flow.The community structure of the same type of wetland units is very similar,and the community structure of different types of wetland units is quite different.It was also found that the community richness and diversity of combination 2 were slightly higher than that of combination 1.Cyanophyta is the main dominant phylum of CW system,and all kinds of bacteria in CW system play their own unique role in maintaining the stability of wetland system.It was also found that the metabolic functions of amino acids,carbohydrates and energy were at the core of the bacterial metabolism,accounting for the largest proportion.In the 6 groups of samples,the metabolism function of microorganisms on the roots of Canna changed with the water quality and wetland environment,but maintained a high degree of similarity,indicating that the microbial community can adapt to different environmental conditions,and can maintain the integrity and stability of its metabolism function at the same time.Figure[49]table[16]reference[83]...