| With the rapid advance of urbanization and industrialization, impervious areas increasedsharply in cities and towns, time of runoff yield and concentration shortened, and flush abilityof runoff enhanced, rainfall runoff, carrying a large number of pollutants, has become one ofthe main sources of water pollution in receiving waters. In order to minimize the risk of waterquality deteriorated by rainfall runoff and protect the health of water environment, besides aseries of manegement system, a certain amount of engineering measures are essential. As therepresentative of the plant purification system, constructed wetland technology, because of itslow cost and simple operation and maintenance, holds an important place in controllingrainfall runoff pollution. In this research, a horizontal subsurface flow constructedwetland(HSSFCW) was adoped to treat simulated rainfall runoff, hoping to provide feasiblebasis for the application and generalization of constructed wetland in this area.Simulated rainfall runoff was purified using a constructed wetland and results showedthat COD, NH4+-N and TN were significantly positive related to DO (p<0.05, p<0.05, p<0.01,respectively), and NH4+-N was also significantly positive correlated with pH(p<0.01). Theremoval of COD, TP and PAHs-phenanthrene(Polycyclic Aromatic Hydrocarbons, PAHs)occured mainly in the front quarter of the wetland system, and in the front half of the system,the purification efficiencies of NH4+-N(upper layer) and TN accounted for81%of the totalremoval rates. In the vertical, the removal rates of COD, TP, TN, NH4+-N and phenanthrenewere1.17-1.36,2.04-2.11,1.40-1.92,1.37-2.30,1.07-1.36times higher than the bottom,respectively. The vertical variation of purification efficiency was more significant than thelongitudinal variation.Enzyme activities were monitored and results showed that, in longitudinal and verticaldirection the variations of enzyme activity of DHA(Dehydrogenase) and CAT(Catalase) infour seasons were both similar. PPO(Polyphenol Oxidase) activity was promoted because ofthe existence of phenanthrene, and the activity varied little in the back third fourth of thewetland bed. NR(Nitrate Reductase) activity had a significant positive correlation with theconcentration of NO3--N (p<0.01). Compared with DHA, the correlation between CATactivity and the removal loads of COD and TP was more significant, thus, CAT activity couldbe a preferable index for evaluating the removal efficiency of COD and TP in the wetlandsystem.Tempral and spacial distribution of microbial community structure and species diversitywere analysed and results suggested that, microbial community structure change dynamically in time and space, dominant bacteria groups of spring and summer surpassed those of autumnand winter season, what’s more, within the same quarter, microbial population structurevaried in space, and the difference was particularly significant in summer and winter. Spatialheterogeneity of microbial diversity index was in conformity with the space distributioncharacteristics of the pollutants removal efficiency, furthermore, the microbial diversitypositively correlated to the pollutants removal efficiency. The results of DNA sequencingindicated that,30bands were similar to the uncultured bacteria in the database, similarity wasmore than97%, some even reached100%, only a small part was around91%-92%. Dominantbands concentrated mainly in Proteobacteria sp.(35%) and Bacteroidetes sp.(21%),meanwhile,3bands which may be associated with the degradation of the phenanthrene werediscovered. |
