| Through integrated effect of plants, substrates and microorganisms, constructed wetland system can purify municipal wastewater. This technology is suitable for China, so it has wide applications and perspectives. The research and application of constructed wetland are still developing in China. So far,there are not many relative design documents and application cases.Based on systematic analyses of research status on constructed wetland in home and abroad, in view of"black box phenomenon"existing in constructed wetland system, taking Sihong intermittent subsurface flow constructed wetland (SSFCW) system as research object, according to system theory concept, using combination methods of field research and lab experiment, this dissertation studied physical-chemical properties of substrates and its adsorption, microorganism communities, removal of pollutants in SSFCW. Also, using uncertainty theory, this dissertation optimized the design method of constructed wetland system. The following conclusions were obtained.(1) The experimental results of physical-chemical properties of substrates showed that the bigger the particle size of substrates, the smaller the porosity, the higher the permeability coefficient. The mineral compositions of basalt were mainly quartz and feldspar, the content of calcium oxide was 0.49%. For zeolite, the content of calcium oxide was 4.68%. For basalt, the big holes grew well; the medium and small holes grew badly. For zeolite, the bigger the particle size, the better the big holes; the smaller the particle size, the better the medium and small holes and the bigger the specific surface area.(2) The static adsorption experiment of substrates on nitrogen and phosphorus showed that the adsorption balance time of zeolite on nitrogen was shorter than basalt; the adsorption balance time on phosphorus of both substrates was nearly equal. The adsorption isotherm of basalt on nitrogen and phosphorus were in accordance with Freundlich and Langmuir types respectively. The adsorption isotherm of zeolite on nitrogen and phosphorus were both in accordance with Freundlich type. The maximum adsorption quantity of zeolite on nitrogen and phosphorus was bigger than basalt. So, the adsorption capacity of zeolite was better than basalt.(3) There was close relationship between physical-chemical properties and adsorption capacity. Also, particle size of substrate was associated with HRT of SSFCW, permeability coefficient and adsorption capacity. Hereby, the best particle size of substrate and conceptual model of adsorption were put forward.(4) Whether in spring, summer or autumn, amounts of microorganisms on substrate surface and reed root in Sihong SSFCW showed that the amount of ammonifier was larger than that of denitrifying bacteria, and the amount of denitrifying bacteria was larger than that of nitrosomonas. For the same microorganism, the amount of bacteria on reed root was higher than that on substrate surface. In summer and autumn, the amount of ammonifier was one to two levels larger than that in spring, along the constructed wetland bed the amount of ammonifier at different points varied from one to two levels. Whether in spring, summer or autumn, the amounts of nitrosomonas and denitrifying bacteria varied little.(5) The results of water quality monitoring in SSFCW showed that the concentration of dissolved oxygen was lower than 0.6 mg/L. The kinetic equation of CODcr removal was conformed to the first order reaction. The removal rate of organic matter in first half of SSFCW accounted for 80 percent of whole constructed wetland bed. In spring, summer and autumn, the removal rates of CODcr were 74.4%, 47.7% and 50.9% respectively。(6) The removal rates of TN and TP varied from different seasons. In spring, the removal rates of TN, NH4-N and TP were 64.6%, 70.7% and 44.1% respectively. In summer, the removal rates of TN and NH4-N were 91.4% and 85.1% respectively. In autumn, the removal rates of TN, NH4-N and TP were 49.3%, 50.5% and 13.3% respectively.(7) Sihong SSFCW operated in intermittent way; this could increase the wastewater treatment efficiency. The monitoring results showed that except autumn the effluent could reach the first order B discharge standard(GB18918-2002).(8) There were many uncertain factors in constructed wetland system. The water quality and volume of influent fluctuated in some range. In view of uncertainties of water quality and volume in the deign process of wastewater treatment plant, using the first order kinetic model of pollutants removal in constructed wetland system, based on uncertainty theory, the optimization model of constructed wetland system was established. This model could increase the adaptability of wastewater treatment plant design, and provide decision-making for design of constructed wetland system. Comparing design parameters of Sihong wastewater treatment plant with the established optimization model, the design of Sihong wastewater treatment plant was scientific and reasonable.
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