Research On The Treatment Of Domestic Wastewater In A/O Constructed Wetland

Constructed wetland is an integrated eco-system, which applies speciessymbiosis, material recycling principle, the coordination principle of structure andfunction, under the premise of promoting wastewater pollutants virtuous circle, itgives full play to the potential resource production, to prevent environmental furtherpollution, and obtains the best efficiency of sewage treatment and resource. Theconstructed wetland has high treatment capacity, strong adaptability to loadfluctuation, simple proeess and instruments, convenient maintenance, low investment,and ecological benefits. A great appliance prospcet can be predicted in thecountryside and rural area where the municipal sewage network cannot reach.Thetechnology has been widely used in China’s agricultural point-source and area-sourcepollution control, sewage treatment and management of eutrophic water bodies.In this paper, the traditional single constructed wetland on the basis ofimprovements in the analysis of previous studies, a series of wetlands, based on thetwo vertical flow constructed wetland in series, put A/O process and artificialwetlands together, namely, it consisted of upstream anaerobic anoxic aerobicwetlands and wetlands downstream, two wetlands were connected with two outlets.Wetlands in the bottom of the upstream and the surface of downstream water wereused to UPVC pipe uniform water distribution, water eventually flowed downstreamfrom the bottom of the water aerobic wetland to water tanks. Flow direction was fromupstream to downstream. To Increase the refluence device in the anaerobic wetlandand to increase the aeration tube in the aerobic wetland bottom of the pool, aerationtubes were wrapped in gauze to prevent blockage, and the aeration gas was control byflowmeter.This study investigated the effect of composite wetland treatment in theoxygenation conditions, in different reflux ratio and under different hydraulic loadingparameters, and under different aeration’s effect on pollutant removal, and the verticalflow constructed wetlands with conventional state operating conditions are compared. The test results can be shown that:In the normal condition, the effect of pollutants removal in the vertical-flowconstructed wetlands was not very good, mainly due to the lack of dissolved oxygenwithin the wetland; when increasing aeration device, the system significantlyenhanced removal of pollutants, COD、BOD₅、NH₃-N removal efficiency can reach90%, to meet the “Discharge standard of pollutants for municipal wastewatertreatment plant”（GB18918-2002） basic control program standards for maximumallowable emission concentration A-level standard in the standard. As the reflux ratioincreases, TN removal efficiency was significantly enhanced.Vertical-flow constructed wetlands in0.2,0.4,0.6m³/（m²·d） three kinds ofhydraulic load, COD, BOD₅, NH₃-N and TP removal has little effect by the refluxratio changes, but the system in the hydraulic loading of0.4m³/（m²·d）, theappropriate removal of COD, BOD₅, NH₃-N, then the system was running morestable. In the reflux ratio of2:1, TN removal efficiency was the best.In the hydraulic loading of0.4m³/（m²·d）, reflux ratio2:1, COD, NH₃-N removalefficiency were significantly increased with the amount of aeration increased. The TNand TP removal would be showing the first increase and then decreased. To sum up,when the dissolved oxygen in the aerobic wetlands reached the3mg/L, the removal ofvarious pollutants would reach the best condition.