Researches On Hydraulic Load Of Plant Roots In Constructed Wetlands

This paper is based on the requirement of vertical flow constructed wetlands system, building the constructed wetlands that with the sand(for lmm-2mm in diameter) as substrate,with the phyllostachys as wetlands plant, decorating glass funnel in the bottom of plant roots, remove the treated effluent by the plant roots from the U-tube that connected with glass funnel, research the capacity of treat domestic wastewater on different hydraulic load of plant roots of constructed wetlands,and find out the optimal hydraulic load and variation of plant roots remove the contaminant.Research the change of the effluent concentration and removal efficiency of pollutants in the start-up period of system by complete the test of the start-up period. In stable period, by changing the influent hydraulic load, explore the removal efficiency of all kinds of pollutants and the changes under the different hydraulic load and different hydraulic retention time of the pH、DO of water.In the initial period of system, concentration of pollutants in outlet is unstable, so the removal efficiency is low, with the domestication of constructed wetlands, in the later period, the change trends of all kinds of pollutant’s concentration in outlet is roughly consistently effluent achieve stability.In the stable period of system, using the way of continuous flow, investigated the changes of concentration of pollutants、pH and DO in outlet under seven hydraulic load conditions of16mm/d、21mm/d、26mm/d、32mm/d、64mm/d、96mm/d、128mm/d respectively (the corresponding hydraulic retention time is8d、6.1d、5d、4d、2d、1.3d、1d respectively).Through the study find that the removal efficiency of pollutants is best under the conditions of the hydraulic load is26mm/d and the corresponding hydraulic retention time is5d, the removal rate of COD、NH3-N and TP is95.04%、84.58%and93.04%respectively; the pH and DO has no obvious change rule under the different of hydraulic load.This study sets a model based on the first order kinetic equation of constructed wetlands, the correlation coefficients of the model are above0.9, so we can use the model to simulate degradation law of the plant roots to the COD, NH3-N,and TP in the vertical flow constructed wetlands system, and it also have the certain reference value, moreover, the concentration of COD, NH3-N and TP in outlet can meet the "A-level,1st grade" standard of "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant"(GB18918-2002).