Characteristic Of Nonpoint Pollution In Industrial Cluster Area And It’s Control By Constructed Wetland

With the rapid development of industry, the non-point source pollution of cities’ industrial cluster areas is increasingly serious, which results in the continuous deterioration of the quality of the receiving water and the gradual loss of the functions of the environment and landscape. At present, there are relatively few researches about the characteristics of non-pointsource pollution in industrial clusters and the mechanism of control technique at home and abroad, especially, the industrial clusters of developing countries formed during rapid urbanization severely impeded the improvements of urban water environment quality and landscape functions. This study chooses Tongsha reservoir catchment of Dongguan in the core area of the Pearl River Delta region as the typical representative of the cities’ industrial clusters, and systematically researches on the non-point source pollution characteristics, constructed wetland control technology and removal mechanism of the catchment area of Tongsha reservoir of Dongguan City.On account of the monitor of runoff water yield and water quality, analyze and study the pollution status of rainfall runoff non-pointsource in different domains of the area, the process of pollutant output in various rainfall scenarios, and the existence of pollutants. Study and evaluate the influence of different rainfall features and parameters of water collecting area on the non-point source pollution of industrial clusters. Conduct a study on the first sourcingeffects of main pollutantsin Tongsha reservoir catchment, evaluate and identify the first sourcingeffects of pollutantsvia combining the M(V) curve and MFFn curve with parameter b qualitatively and quantitatively, and discuss the output characteristics of non-point source pollution in industrialclusters. According to the rules of runoff pollution blowdown of industrial clusters and allocation of burden, we discussed the standard of prime rain water interception, and studied the major rainfall characteristic of prime rain water loadand the effect of characteristic parameter of the land use. Based on the analysis of the non-point source pollution characteristics of the industrial clusters, this study adopts two types of constructed wetlands of IBSSF and HSSF to conduct a simulation purification study on the non-point source pollution of the industrial clusters, analyzes the purification characteristics and influential factors that wetlands of various types have on runoff pollutions, and probes into the variation characteristics of microorganism population during the purification of non-point source pollution in industrial clusters of different wetlands with an attempt to provide feasible references for the application and promotion of constructed wetlands in this field. Provide the effective technical means for study, control, management work of the non-point source pollution of urban rainfall, and provide the theoretical foundation for reduction of the pollution of the receiving water body. The main research findings of this paper are as follows:(1)The research found that the pollutant emission concentration of different functional areas in the industrial cluster has similar time change regulation. At the beginning of rainfall, the concentration of the pollutants quickly rises and reaches the peak fast. The peak of concentration lags behind the peak of the rainfall, but leads the peak of the runoff, which has comparatively apparent time characteristics; The main pollutants of rainfall runoff in water-gather district are TSS, COD, TN and TP. The concentration value of regular pollutants in industrial areas and commercial and residential district areas is close to typical domestic sewage with high pollution load; The main factors that affect the industrial cluster’s EMC are the biggest rain density, the drouthy time before rain, rainfall duration and rainfall.(2) The research compares and analyses the first scouring intensity in the industrial cluster on the basis of dimensionless cumulative M(V) analysis and the MFFn ratio curve method. The verification results of MFFn can effectively eliminate the pattern recognition errors caused by the intuitive minor differences; The quantitative analysis results of the first sourcing intensity of rainfallin this region according to the parameter of b are consistent with the MFFn curve analysis results. The research shows that the bigger the biggest rain density and rainfall capacity, the more obvious the first sourcing effect. In low rainfall incidents, the impervious grounds mainly act as the runoff pollution source; while in high strength rainfall incidents, the pervious grounds act as the runoff pollution source.(3) By analyzing the load distribution characteristic of the initial rainwater pollution, the study adopts FF40 as the standard of the initial rainwater runoff interception of the Tongsha reservoir catchment area, which means that the minimum standard of the economical consideration of the regional pollution control in this study is separating and intercepting 40% of the initial rainwater runoff. By the analysis with methods such as relativity, PCA and multiple linear regression, we find that the length of drought period before raining(ADD), the average rainfall intensity(I) and rainfall(R D) are the main factors controlling the size of the pollution load of the initial rainwater.(4) The study showed that the variation difference of DO and p H of the upper and the lower IBSSF bed body was smaller than that of HSSF, and the characteristics of bed body were more suitable for the growth of aerobic microorganisms. IBSSF was earlier and more stable than HSSF after planting plants, and its range of pollution load was also greater. After running steadily, the two wetland systems have good purification effects on the non-point source pollution in the industrial cluster. IBSSF improves the average treatment efficiency of COD, TN, NH4+-N and phenanthrene more significantly than HSSF by 4.55%, 6.36%, 15.42% and 2.52% respectively, with little improvement of the removal efficiency of TP and heavy metal. The removal of COD, TP and phenanthrene has been basically completed in the front 1/4 segment of the bed body. The removal efficiency of TN in the front 1/2 segment and NH 4+-N of the upper layer of the bed body is both up to 81%. The upper layer of the bed body is the main part of the removal of the pollutants, and IBSSF has a higher removal efficiency in the lower layer compared with HSSF.(5) The research on wetland matrix enzyme’s activity indicates that on different bed bodies of the two wetlands, the seasonal variation trends of the activity of Dehydrogenase(DHA) and Catalase(CAT) are similar. Polyphenol Oxidase(PPO) activity intensifies because of the existence of PAHs and degradation of PAHs, the enzyme activity in the first 1/4 segment of the bed body is higher, but the difference is not obvious after 3/4 segment. Nitrate Reductase(NR) activity,and NO3--N concentration are significantly positive correlation(p<0.01). Compared with HSSF, DHA and CAT in IBSSF in the upper and lowerlayers of the bed body are more uniform, and are much more correlated to removal loading of COD, TN and TP.(6) According to research on the structures of microbial communities in wetlands, IBSSF and HSSF, the two microbial community structures in wetland system, are complicated with obvious space-time dynamic changes including space-time dynamic differences and dynamic changes. The number of dominant microorganism in summer is obviously more than that in winter. The microbe diversity of IBSSF is greater than that of HSSF, the difference between which are 0.01 and 0.04 respectively in the upper layer and lower layer in summer while 0.14 and 0.24 in winter, and they are distributed relatively symmetrical in the bed body. The spatial differences of biodiversity index accords with the space distribution rule of pollutants removal efficiency, and there is a positive correlation between pollutants removal efficiency and biodiversity. Through rubber cutting sequencing, we found that the preponderant stripes were mainly focused on Proteobacteria sp.(32%) and Bacteroidetes sp.(29%), and detected out bacterial strains relevant with the degradation of denitrification and leek in IBSSF and HSSF.