The Experimental Investigation On The Treatment Of Rural Domestic Sewage By Integrated Vertical-flow Constructed Wetland

As the development of social economy and urbanization process, the National Rural Water pollution has become more and more serious, how to properly resolve the problem of rural sewage lakeside areas and protect the Poyang Lake water have become a serious problem in the construction process of Poyang Lake Ecological Economic Zone in Jiangxi region. Vertical Flow constructed wetland has unparalleled advantages relative to the traditional Secondary process of technology in nitrogen and phosphorus removal and investment, operational management in rural areas, but the research about that impact factors in using VFW for removal of various pollutants especially nitrogen and phosphorus in rural domestic sewage and the changes of hydraulic loading which can impact the nitrogen and phosphorus removal are rare. In addition, the dynamic model of reference and the key design parameters are rare, too.This paper has researched the benefit and discipline of nitrogen and phosphorous removal of IVCW in the Jiangxi rural region. First we has determined the main factors and their significant by the L9(34) orthogonal test which concluded that COD_cr, NH₃-N, TN and TP removal effect. Further we has studied the purification effect of IVCW in hydraulic loading of multi-level, discussed the main pollutant removal mechanism of VFW, established removal kinetic model of COD_cr, NH₃-N, TN, TP and determined the kinetic equation parameters.Analyses of the conclusions of the study are as follows:(1) the results of orthogonal test shows that: The C/N, hydraulic loading, pH and the process have significant effect on the removal of pollutants in two IVCWs. four factors which affect the role of COD_cr are listed: hydraulic loading> process> pH> C/N; the role of NH₃-N are listed: process> hydraulic loading> pH> C/N; the role of TN are listed:hydraulic loading> C/N > process> pH; the role of 1#( the system of Vetiveria zizanioiaes and Miscanthus sacchariflorus Anderess) TP is listed:hydraulic loading> process> C/N > pH, the role of 2#( the system of Juncus effuses and Vetiveria zizanioiaes) TP is listed: Process> hydraulic loading> C/N > pH. Thus, hydraulic loading is the most significant factor, C/N and process are followed, pH is the last in the four factors.(2) The results of hydraulic loading test shows that: the hydraulic loading and the IVCW has closely relationship to deal with the pollutantions, the purifying effects of two systems were decreased with the increasing of hydraulic loading,water quality deteriorated. The removal efficiency of 1# wetland system on the COD_cr, NH₃-N, TN, TP are better when the hydraulic loading is 67, 100, 100, 200mm/d respectively, the effluent concentrations are 46.55, 7.21, 12.76, 0.46mg/L that can reach the Grade A standards of "Urban Sewage Treatment Plant Emission Standards (GB18918-2002)", and the removal rates were 88.15%, 71.38%, 67.01%, 89.07%. The removal efficiency of 2# wetland system on the COD_cr, NH₃-N, TN, TP were better when the hydraulic loading is 40, 67, 100, 100mm/d, respectively, the effluent concentrations are 47.75, 7.14, 13.09, 0.31mg/L that can reach the Grade A standards, and the removal rates were 87.52%, 70.09%, 66.15%, 92.33%. Thus, the effluent concentration of pollutants can reach the Grade A standards in hydraulic loading of 40mm/d.(3) The test of winter and summer results show that: the removal effect in summer is better than in winter. When the hydraulic loading is 51mm/d of 1# wetland systems and 40mm/d of 2# wetland systems in winter or the hydraulic loading is 51mm/d in summer, the effluent concentrations of COD_cr all can reach the Grade A standards; When the hydraulic loading is 100mm/d of 1# wetland systems and 51mm/d of 2# wetland systems in winter or the hydraulic loading is 51mm/d in summer, the effluent concentrations of NH₃-N all can reach the Grade A standards; When the hydraulic loading is 100mm/d of 1# and 2# wetland systems in winter or the hydraulic loading is 200mm/d in summer, the effluent concentrations of TN all can reach the Grade A standards; When the hydraulic loading is 200mm/d of 1# and 100mm/d of 2# wetland systems in winter or the hydraulic loading is 200mm/d in summer, the effluent concentrations of TP all can reach the Grade A standards. Thus, the effluent can reach the Grade A standards on hydraulic loading of 51mm/d in summer, while on hydraulic loading of 41mm/d in winter.(4) Kinetic model studies suggest that: the removal laws of IVCW removing COD_cr, NH₃-N, TN, TP in rural sewage in Jiangxi region consistents with a dynamic relationship, The kinetic model correlation coefficient R2 are higher than 0.9. the dynamic model of 1# system for COD_cr, NH₃-N, TN, TP are ln(Ce/Co)=-0.0127t-1.177, ln(Ce/Co)=-0.0124t-0.5133, ln(Ce/Co)=-0.0123t-0.5453, ln(Ce/Co)=-0.0260t-1.5101; the dynamic model of 2# system for COD_cr, NH₃-N, TN, TP are ln(Ce/C0)=-0.0107t-1.1416, ln(Ce/C0)=-0.0107t-0.4525, ln(Ce/C0)=-0.0117t-0.5362, ln(Ce/C0)=-0.0259t-1.4269.The above results shows that: the IVCW can be used to deal with the rural sewage of JiangXi, and the effluent can reach the Grade A standards. The significance of these factors, the law of the hydraulic loading acting on the removal effect and the dynamic equations all can be used in the IVCW system to deal with the rural sewage treatment in JiangXi province in the future.