Experimental Research On Wavy Subsurface-flow Constructed Wetland For Heavily Polluted River Treatment

River is not only an important source of urban water resources, but also the main receptor of pollutant emissions. With the intensification of urban development and the contiguous utilization of land, river water quality is badly deteriorated. Constructed Wetlands(CW) is a friendly eco-technology for water environment management and restoration with the advantage of low costs of construction, operation and maintenance, good treatment effect and ecological landscape effects.In this study, it is supported by the National Water Pollution Control and Treatment Science and Technology Major Project, combining with local environmental governance requires, 4 modules including river water pollution source apportionment, CW substrate screening test, wavy subsurface flow constructed wetland(W-SFCW) dynamic experiment-scale test and demonstration project designing of heavily polluted tributary of Gaopu River treatment were carried out. The main conclusions of thesis are shown as follows:(1) Downstream water quality is poor and the main pollutants are considered from Gaopucun tributary when analyzing four water quality indicators of Gaopu River. Principal component analysis method(PCA) is applied to identify the pollution sources with 8 variables of Gaopu River. The results show that, pollution sources are respectively from agricultural non-point source pollution, distributed domestic discharge, point sources of nutrients.(2) Two different composite fillers columnar reactor in lab-scale for the Gaopucun tributary river treatment effect are compared. Although influent CODcr concentration is low and the NH3-N and TN concentrations are high, reactor A and B still have a good removal efficiency for NH3-N and TN: the average removal rates of NH3-N and TN are 88.82% and 85.15% in the reactor A, 91.84% and 85.92% in the reactor B, respectively. A kind of sustained-release solid carbon source(sawdust) is added in the composite fillers package to promote the removal efficiency of TN.(3) An inoculation biofilm way is taken to start W-SFCW. Artificial aeration, buried device and other measures are taken to ensure the smooth progress of the biofilm, reducing the starting time of hanging film to some extent in cold winter. We compared the effect of differences in W-SFCW on nitrogen and phosphorus removal of a single gravel packing W-SFCW(control group) and composite fillers W-SFCW(experimental group). The results show that experimental group still has a good effect of nitrogen in the case of low C/N of influent with TN removal ratio up to 72.33%; due to lack of required carbon source for denitrifying bacteria, denitrification is inhibited in the control group, TN average removal rate is lower with only 40.96%. The removal of TP in experiment group mainly depends on the role of physical and chemical effects, such as adsorption of composite fillings and micro-electrolysis. The removal rate can reach 62.97%. Effluent pH is higher than the influent both in experimental group and control group. The value of pH changes are mainly affected by microbial nitrification and denitrification, buffer of substrate, the iron-carbon micro-electrolysis and microbial metabolism and other factors. Under different hydraulic loading rate, two wetlands have good contaminant removal effect, indicating the system resistance to shock loading. Compared to the control group, experimental group under high hydraulic loading rate conditions have a more substantial increase on the removal of pollutants, indicating stronger resistance to shock loading capability of the experimental group than the control group.Taking into account substrate filling in the practical application of engineering and cost issues, local soil mixed with charcoal, wood and iron as a composite package is recommended when packing wetland substrate. W-SFCW filled with composite packages has good results to the removal of contaminants, especially to nitrogen and phosphorus removal. When applying the results to Gaopucun tributary engineering designs, it is meaningful technical reference for river treatment in our country.