Research On Treatment Of Nitritive Material In Micro Polluted River Water By Hybrid Sub-surface Flow Constructed Wetlands

With the development of economy, many pollutants discharged into the river in China,and most of rivers were heavily polluted in the past several years. The pollutantsconcentrations, the rate of flow and water temperatures of rivers in north Chinachange a lot in different seasons, which make great difficulty for river water treatment.Constructed wetlands(CW) are defined as wetlands specially constructed for thepurpose of pollution control and waste management. Constructed wetlands sewagetreatment technology has the advantage of dealing with high efficiency operation andlow maintenance costs, and applies a wide range, and broad application prospects. Asa new kind of applied wastewater treatment technology, there is a lack of researcheson the complex hydraulics in wetlands and the problems of padding saturation. At thesame time, currently most used wetlands were focused on domestic sewage, and theresearches on the polluted river water treatment are relatively absent. Therefore,hybrid constructed wetland combined by subsurface flow constructed wetland(HFCW) and vertical subsurface constructed wetland (VFCW) are used to treat thepolluted river water.The main contents of this research were as follows:(1) adsorption capacity fornitrogen and phosphorus of two easily got and economically feasible padding(slagsand zeolite);(2) the treatment efficiency in different influence concentration anddifferent fillers;(3) qualitative analysis of the hydraulic characteristics in wetlands;(4)the degradation kinetics of pollutants in wetlands.The results are showed that:(1) Freundlich equation and Langmuir equation can be used to describe the staticadsorption of ammonia nitrogen and phosphorus. Slag has a better adsorption capacityon phosphorus than zeolite, while zeolite has a better adsorption capacity on nitrogen.At30℃, the saturation adsorption capacity of slag and zeolite for phosphorus wererespectively76.92mg/L and3.14mg/L, and the saturation adsorption capacity of slagand zeolite for ammonia nitrogen were respectively232.56mg/L and15.15mg/L. When increasing the temperature, the saturation adsorption capacity of fillersincreases, but it has no influence on the time that fillers reach the saturationadsorption.(2) The remove efficiencies of COD、ammonia nitrogen、nitrate nitrogen and totalphosphorus in HF-VF systems using zeolite and slag substrates are obviouslydifferent. The remove efficiencies of nitrate nitrogen and total phosphorus in slagwetlands are better than zeolite system, and the average removal efficiency canrespectively reach79.79%and91.92%. While the zeolite system has a betterammonia nitrogen removal efficiency which can reached76.63%.(3) The slag hybrid wetland has best removal efficiency for ammonia nitrogen whenthe ammonia nitrogen inflow concentration was6mg/L when changing from3.2mg/Lto12mg/L. And it has best removal efficiency for total phosphorus when the totalphosphorus inflow concentration was1.5mg/L when changing from1.5mg/L to9mg/L. Although the removal efficiency decrease with the inflow concentrationincreasing, the second stage wetland will play an important role in ammonia nitrogenand total phosphorus removal. On the other sides, the nitrate nitrogen removalefficiency decrease when increasing the ammonia nitrogen concentration.(4) The result of study on the degradation kinetics of pollutants indicates that theCOD, ammonia nitrogen and nitrate nitrogen removal are followed first order kinetics,and the kinetics equation are respectively C=Co exp（-0.029X），C=Co exp（-0.012X）and C=Co exp（-0.032X）.(5) There are some blockings located in the side close to inlet and a “short flow” inthe side close to outlet in zeolite horizontal flow constructed wetland and zeolitevertical flow constructed wetland.