Study On Degradation Of Organic Pollutants In Subsurface Flow Constructed Wetland Treating Polluted Surface Water

The mechanism of organic pollutant degradation in the constructed wetland treating polluted surface water was studied in this thesis. The study included: (1) With the influent from the Sanhao Lake, three types of constructed wetlands, which were system 1# with single-macrophyte and single-media, system 2# with multi-macrophytes and single-media, system 3# with single-macrophyte and multi-media were built. The COD removal efficiency influenced by the different retention time was studied. (2) Atrazine degradation and the influence caused by different salinity were studied in constructed wetland. (3) The microbial community and its distributing character in the constructed wetland treating polluted water and atrazine with different salinity were studied.The experimental results showed that: (1) As the retention time increasing from 2d to 8d, the COD removal efficiency of the three constructed wetland treating polluted surface water remained 70%～80%. But the COD removal velocity was linely pomoted by the increasing of COD load rate. More than half of the COD was degraded in the first half of the constructed wetland along the direction of water flow. Considering the COD removal efficiency, multi-macrophytes and single-media system was the best, single-macrophyte and multi-media system was the second, and single-macrophyte and media system was the last. (2) Under static state experimental condition, atrazine degradation half-life in the subsurface constructed wetland was about 16d, and it met the first-order reaction kinetics, C=0.09648exp(-0.03939t) (C-atrazine concentration left in the constructed wetland, t-retention time). The atrzine degradation dynamic equation under the salinity concentration of 1.5, 3.0, 5.0, 10.0, 15.0g/L, they also met the first-order reaction kinetics. The relation between salinity and atrazine degradation efficiency was as following equation showing, lnk=3.22105+0.04629M (k-degrading constant, M-NaCl consentration). It was concluded that atrazine concentration declining was not caused by hydrolyzation or adsorption, the microorganism in the constructed wetland degraded atrazine into first...