Study On The Purification Of Domestic Sewage By Common Wetland Plants In Northern China

Domestic sewage pollution has become one of the major global environmental issues.The root cause of environmental pollution caused by domestic sewage is the increase in nutrients in the water body.The main nutrient is phosphorus,followed by nitrogen,as well as carbon,trace elements,or vitamins,so purification of domestic sewage is the most important thing to purify nitrogen and phosphorus.In the study,four species of aquatic reeds,cattails,calamus,and water-green onions commonly used in cold regions of northern China were selected as test materials to investigate the effect of wetland simulation systems constructed by different plants on the removal of nitrogen and phosphorus from polluted water,and to screen artificial wetland plants.Provide a certain theoretical basis.The main research results of this study are as follows:（1）Purification of TN by soil and plants in wetland systems1)0-10cm soil layer has the largest cumulative amount of TN.In the wetland systems of different plants,under the three concentration gradients of sewage treatment,the TN cumulative proportion of 0-10cm soil layer is between 37.9%and 47.4%,respectively.With the increase of soil depth,the cumulative amount of TN in the soil decreased by layers,indicating that TN accumulated mainly in shallow soil.In the different wetland simulation systems,the cumulated amount of TN in the soil in the order of the order of the typhoid wetland simulation system,the onion wetland simulation system,the Lime wetland simulation system,and the reed wetland simulation system.2)In different wetland simulation systems,the cumulative effect of plants on TN was dominated by the above-ground part of the plant.The total amount of TN accumulated in the aerial parts of reeds,cattails,calamus,and green onions accounted for 69.9%-80.2%,63.2%-79.0%,40.4-65.7%and 61.7%-77.3%,respectively.The order of the accumulated amount of TN in sewage by plants is water onion,reed,cattail and calamus in order.3)During the purification process of TN,the contribution of plants is much larger than that of soil.The average value of soil contribution rate is in the sequence of water onion wetland simulation system,cattail wetland simulation system,reed wetland simulation system,and Lime wetland simulation system.The order of contribution of plants is in the opposite order.（2）Purification of TP by soil and plants in wetland system1)0-10cm soil layer has the largest cumulative amount of TP,and in the wetland systems of different plants,under the three concentration gradients of sewage treatment,the proportion of TP accumulation in the 0-10cm soil layer ranges from 36.7%to 46.5%,respectively.With the increase of soil depth,the cumulative amount of TP in soil decreased by layers,indicating that TP accumulated mainly in shallow soil.In the different wetland simulation systems,the cumulative amount of TP in the soil was in the order of the Xiangmu wetland simulation system,the Lime Wetland Simulation System,the Reed Wetland Simulation System,and the Wetland Wetland Simulation System.2)In different wetland simulation systems,the absorption of TP by plants is mainly root-based,but due to the influence of biomass,the TP content of each plant is still mostly aboveground,exceeding 50%,and reeds,cattails,calamus,and water-onions The accumulative amount of TP on the aerial parts accounted for 52.4%-58.9%,53.4%-62.4%,58.2%-67.5%and50.5%-55.4%respectively.The order of the cumulative amount of TP on plants was cattail,iris,reed,and onion.3)During the purification process of TP,the contribution of plants is much larger than that of soil.The order of the average contribution rate of soil is the Xiangmo Wetland simulation system,Lipu Wetland simulation system,Shuicong Wetland simulation system,and Reed Wetland simulation system.The order of contribution of plants is in the opposite order.（3）Comprehensive evaluation of purification of domestic sewage in wetlandsIn different wetland simulation systems,with the increase of TN and TP concentration,the removal rate of TN and TP in sewage increased accordingly,indicating that high-concentration sewage treatment is beneficial to the removal of TN and TP from sewage.The removal rate of TN in domestic sewage by the four kinds of wetland plants ranged from80.3%to 93.6%,and the removal rate of TP ranged from 75.7%to 97.2%.By adopting the method of water quality comprehensive pollution index evaluation,the evaluation result of the sewage purification result is“basicly qualified”.Under the treatment that the sewage disposal is both TN concentration 8 mg·L^-1 and TP concentration 1 mg·L^-1,the plants are separately treated.The wetland simulation system for reeds,scallions,and calamus shows that the wetland simulation system for planting these three kinds of plants has a good purifying effect on lightly eutrophic wastewater,reaching basic qualification standards,and the water body function has not been significantly damaged.The result of the evaluation of the sewage purification result was“passed”.In the treatment configuration in which the concentrations of TN and TP in the sewage were 8 mg·L^-1 and 1 mg·L^-1,respectively,a simulation system for wetlands of cattail was planted,thus indicating The wetland simulation system for planting cattails has the best purification effect on lightly eutrophic wastewater,and the purified water quality meets the required standards.The nitrogen and phosphorus water quality indicators can basically meet the corresponding functional standards,and the water function can be fully utilized.This paper concludes that in the wetland system,sewage purification is mainly plant-based,and the ability to purify different domestic sewage plants with different degrees of eutrophication is different.Among the four kinds of common wetland plants in the north of China selected,the plant with the best purification of TN and TP in domestic sewage is cattail.