Effect Of Hydraulic Conditions On Degradation Of Pollutants By The Stable Surface Flow Wetland

Stable surface flow wetland can make use of deserted river, swamp, ravine,abandoned reservoir area construction, and stable surface flow wetland pools can alsobe designed into irregular shape, rectangular, circular or square. In order to further studythe different shape and different structure of the stable surface flow wetland underdifferent water conditions affect the degradation of various pollutants in domesticsewage. This topic designed a group of stable surface flow wetland pond, designed tooptimize the running condition of the wetlands, to improve the wetland effluent waterquality. The specific research contents and results were as follows:（1） Designed the test system composed by four wetland pools were rectangularpush flow stable surface flow wetland（RPSSFW）, rectangular baffle flow stable surfaceflow wetland（RBSSFW）, circular push flow stable surface flow wetland（CPSSFW）,circular baffle flow stable surface flow wetland（CBSSFW）.（2） In the condition of the water velocity were2.31ml·s^-1,4.63ml·s^-1,6.94ml·s^-1,this paper comparative studied the CODcr, TP, TN and NH₃-N removal efficiency of therectangular push flow stable surface flow wetland, rectangular baffle flow stable surfaceflow wetland, circular push flow stable surface flow wetland and circular baffle flowstable surface flow wetland to domestic sewage. The result showed that water velocityaffects the degree of mixing of various substances and the hydraulic retention time ofsewage in the wetland, control various substances transfer rate within the wetland, andalso influence the size of the dead water region. There exist significant differences onthe removal rate of CODcr, TP, TN and NH₃-N in the wetland. Different shape andstructure of wetlands on pollutants removal efficiency was different when the wetlandhad the same water velocity.（3） Different way of influent run stage, in the condition of the quantity of waterintake was0.4m₃·d^-1for the rectangular push flow stable surface flow wetland andrectangular baffle flow stable surface flow wetland, this paper comparative studied alittle water（pond front-end influent） and two points influent water（pond front-end andthe middle at the same time into the water）. The result showed that the influent pointhole were increased made more uniform water distribution within the wetland when thetwo points influent,and also complemented the carbon source in the back half of thewetland. But the sewage flow through the path in the wetland and the hydraulicretention time were shortened, it was not conducive to wetland on nitrogen andphosphorus removal.（4） In the condition of the water velocity was4.63ml·s^-1and the hydraulic loadingwas0.53m₃·m^-2·d^-1, this paper comparative studied no return and100%return to theinlet side of the circular push flow stable surface flow wetland. The result showed thatbackflow of wetland water to inlet zone could dilute the sewages consistence in the wetland inlet zone and reaction area, made the stillness of the water flowing, improvedthe mass transfer rate of various substances in wetland and combination of varioussubstances, reduced the formative area of dead water region in the wetland, improvedthe wetlands effective utilization, optimized the water flow regime and it was good forthe wetlands on pollutants removal, especially for nitrides.（5）In the condition of the quantity of water intake was0.2m3and the water velocitywas2.31ml·s^-1, the test researched stable surface flow wetland system with differenthydraulic retention time, analyzed the effect on the degradation of pollutants in sewageon different hydraulic retention time. Studies have shown that:①T heremovalefficiency of CODcrwere increased with the extension of hydraulic retention time for allkinds of stable surface flow wetlands, but the change was not much. When the hydraulicretention time was1d in summer, the average concentration of CODcreffluent was38.11mg·L^-1,48.83mg·L^-1,41.25mg·L^-1,35.89mg·L^-1which derived from RPSSFW,RBSSFW, CPSSFW and CBSSFW, respectively. And all of these data achieved the levelof A standard of urban sewage treatment plant pollutant discharge standard（GB18918-2002）. In order to achieve a better CODcrremoval efficiency, could extendthe hydraulic retention time in winter.②The hydraulic retention time had larger impacton the removal rate of TP in the folds stable surface flow wetland compared with thepushing surface flow wetland. When the hydraulic retention time increased from oneday to four days, the average removal rate of TP increased by28.9%and22.5%,respectively, in RBSSFW and CBSSFW, but only increased by12.62%and8.05%,respectively, in RPSSFW and CPSSFW. The removed rate of TP in the pushing surfaceflow wetland had an obvious positive relationship with the concentration of TP.③Thehydraulic retention time had greatly influenced on nitrogen removal in wetlands, toachieve production needs in practical applications could by extending the hydraulicretention time.