Water Quality And Hydraulic Characteristics Of Typical Large-scale Surface Flow Constructed Wetland

Constructed wetlands(CWs) as a reliable wastewater treatment technology are commonly used for nearly half a century. They features in low cost, simple technology and improving the peripheral ecological environment, increase biodiversity. Transformation and removal of suspended solids; organic matter, nitrogen, phosphorus, pathogens and metals from wastewater go through numerous interrelated physical, chemical and biological processes. The decontamination capability is influenced by many factors such as geography, climate, temperature, hydrologic conditions. The engineering design parameters for CWs are ususlly determined according to experience. There are many problems caused by inappropriate design such as the discharged wastewater can not reached the standards, or higher investment.The typical large-scale surface flow constructed wetland WuHe constructed wetland in ShanDong province was studied. We evaluated the pollutants removal efficiency and the process of pollutants degradation along the wetland through to a-year long monitoring water quality on9monitoring sections. Based on continuous monitoring of water quality index, using the water quality model WASP to simulate the COD removal efficiency in wetland. Through to the model parameter calibration, COD degradation of water quality model is established, which could be useful for the design and construction in constructed wetland. Because of different hydraulic retention time in wetland, there would be different degrees of enrichment for heavy isotopes2H and180caused by evaporation. By measuring the water samples abundances of hydrogen and the oxygen isotopes in different locations, combined with the velocity of each monitoring point, evaluation water flow state in the studied area, bond with the pollutant concentration analysis the relationship between the pollutant degradation and the hydraulic conditions in wetland.Through the long-term monitoring, we realized WuHe CW can effectively removal conventional pollutants such as COD, ammonia nitrogen, total nitrogen, total phosphorus, and the effluent quality met Grade-IV of national surface water standards in China. The load-shedding of COD every year is about3950.85kg/(ha a.), and the NH4-N load-shedding is about748.06kg/(ha. a). the construction of WuHe CW effectively improved the local water environment, and ensure the water quality safety of the Huai river basin. Due to the different removal and transformation mechanism for different pollutants, the main remove position would be different in wetland, this standpoint would be proved in this paper.Based on long-term monitoring data in WuHe CWs, established WASP water quality analysis model, simulation of the wetland on the COD removal efficiency, maximum likelihood method is used to model parameters calibration, found that when the COD degradation coefficient under the condition of20℃is about0.4d-1, and the temperature coefficient is adout1.08, the simulation results with the measured result is most close to. Its average relative error is9.98%, with a maximum of24.21%, the minimum value is4.45%, the relative error less than15%accounted for83.33%of the total. Declared WASP is a kind of practical and effective water quality model, and can be used in water quality simulation of CWs, which could be useful for the design and construction in constructed wetland.Based on the abundances of hydrogen and the oxygen isotopes difference, respectively draw the stable isotope abundance contour in the studied area. Combine with the flow velocity at each monitoring point and the flow field distribution, you can see there are three velocity slower area and a priority flow passway in the wetland.Through the study in this paper, strengthen the recognizes and understanding of the pollutants removal performance in large-scale surface flow constructed wetland. Provides practical experience and theory support for optimization design of CWs. Promote the development of the mathematical model of CWs. Invented a new monitoring method of hydraulic conditions in wetland, namely stable isotope monitoring method. The completion of this paper, provides a new idea and method for further study on the CWs.