The Study On Treatment Of Polluted River Water By Hybrid Sub-surface Flow Constructed Wetlands

This research was sponsored by the project of "Major Science and Technology Program for Water Pollution Control and Treatment", and the pilot test was performed. After the high nutrient concentrations were determined as the main contamination characters of the polluted river water, vertical-flow (VF)and horizontal-flow (HF) wetland systems were in series to be one hybrid sub-surface constructed wetland.The research is mainly on:①the influence of different pollutants concentration and water level in the slag VF-HF system;②The differences of pollutants removal efficiencies in different kinds of hybrid constructed wetland systems;③The mechanism of the contaminants degradation;④hydraulic characteristics of VFCW and HFCW system using slag as substrate.The main conclusions are as follows:(1) The result of study on the effect of hybrid constructed wetlands’treatment indicated that the remove efficiencies of COD, NH4+-N, NO-3-N and TP were good in VF-HF system using slag as substrate. When the influent COD, NH4+-N, NO3-N and TP concentrations were100mg·L-1,8mg·L-1,16mg·L-1and1.5mg·L-1, respectively, the average removal of these pollutants were98%,72%,54%and85%, respectively. When the water level in this system was changed, the effluent COD and TP concentrations were not obviously fluctuant. Before the VF system was drained, the remove efficiency of NH4+-N was about60%. After the VF system was drained, the remove efficiency of NH4+-N was90%.(2) The remove efficiencies of COD, NH4+-N, NO3-N and TP in HF-VF systems using zeolite and slag substrates were obviously different. The remove of NHJ-N in zeolite HF1-VF1system was87%, and in slag HF2-VF2system was61%. The remove of COD, NO3-N and TP in slag HF-VF system were87%、80%and64%, respectively; The remove of COD, NO3--N and TP in zeolite HF1-VF1system were82%,72%and35%, respectively. The remove efficiencies of COD, NO3-N and TP in slag HF2-VF2system were better than zeolite system. The temperature and DO were equal in both HF-VF systems.(3) The remove efficiencies of pollutants in different hybrid constructed wetlands were different. The remove efficiencies of COD in the both VF-HF systems using zeolite and slag substrates were above95%; In the both HF-VF systems, COD remove were85%. In the VF1-HF1system, the remove of NH4+-N was77%. However, in the HF1-VF1system, the remove of NH4+-N was87%. In the VF2-HF2system, the remove of NH4+-N was58%. In the HF2-VF2system, the remove of NH4+-N was61%. The remove of NH4+-N in the HF-VF hybrid wetland systems was higher than VF-HF systems. In different hybrid wetland systems the remove of NO3-N were in the range of75%-80%. In the VF1-HF1system, the remove of TP was20%. In the HF1-VF1system, the remove of TP was61%. In the VF2-HF2system, the remove of TP was76%. However, in the HF2-VF2system, the remove of TP was66%.(4) The result of study on the actual hydraulic retention time determined by the tracer experiment indicated that the actual hydraulic retention time of water level75cm,60cm,45cm slag VF and75cm slag HF systems were5.5h,27.5h,12h and87.7h, respectively. However, theoretical hydraulic retention times (HRT) in the VF and HF systems were45h and55.8h, respectively.(5) The result of study on the degradation kinetics of pollutants indicated that in the VF1-HF1, HF1-VF1and HF2-VF2systems COD removal were followed first order kinetics, degradation coefficient K were-0.3028,-0.4566and-0.4449, respectively. In the HF1-VF1system NHI-N removal was followed first order kinetics, degradation coefficient K was-0.4982. In the VF1-HF1system NO3--N removal was followed first order kinetics, degradation coefficient K was-0.4114.