Studies On Oxygen Input By Convection In VF Constructed Wetland And Simulation Model

With the increasing of villas in the suburb, the treatment of the household wastewater produced from which is critical due to it is far from the sewage system in city. With the advantages of low investing, low running costs, energy-saving and simple maintenance, the constructed wetland system is paid more and more attention. Combined the advantages of surface-flow wetland and subsurface-flow wetland, VF constructed wetland has high nitrogen destruction rate and good purifing. In this paper, the principle of oxygen input by convection in the VF constructed wetland and the effect of running modes to the oxygen input by convection in the VF constructed wetland are discussed. The mechanism of VF constructed wetland is analysed by using the theory of system dynamics. Also, a simulation model of system dynamics of VF constructed wetland was established and is validated by using the system of minitype VF constructed wetland practically. Main conclusions were drawn as followings:(1) Oxygen inputing by convection can be found in the VF constructed wetland, which makes the content of the oxygen in the bed is more than that in other wetlands, intensified the nitrification and increase the NH4+-N removal rate. The top-down percolation of the water and process of the convection of air into bed is in correspondence with the Darcy's law with great causality. There is a linear relationship between oxygen inputing and drained volume in the wetland(2) With certain feeding loading, the wastewater should be distributed intermittently. Lowest accumulative time of 3.7hr was obtained when frequence of the the wastewater feeding is two daily, which indicated that better oxygen transmission was found at short air isolated.(3) The VF constructed wetland is analysised as a complete ecosystem by using the principle of system dynamics. Six subsystems and the interrelation between them are also studied. The influence to the treatment efficiency by the mechanical rules, the quality of water supply and the temperature was observed. There is a strong correlation between carbon, nitrogen and dissolved oxygen in the wetland. The growth parameters of the microbe has great influence to pollution destruction in the wetland.