Research On Sediments Pollution And Control Of Urban Rivers

The pollution of urban rivers is a worldwide environmental problem. Most urban rivers in China were polluted during the urbanization process. Massive pollutants were entered into aquatic environment. As both the sink and source of pollutants, sediments play vital roles in the aquatic environment. Therefore, Knowing sediments pollution conditions, researching sediments release and control have important meanings. Urban rivers in Changzhou were selected as the objects of study. By analysis of sediments ingredients and water quality, the main pollutants were ascertained. Based on the analysis, the research of sediments release and control was carried out. The results were obtained as follows:1. Organic pollution of sediments in Changzhou rivers was not serious, N and P pollution was serious relatively, and benthic biocoenosis was suffered certain harm. Heavy metals pollution of sediments was not serious either. Most of heavy metals below moderate pollution except Cu. Five kinds of heavy metals pollution level was: Cu>Zn>Pb>Cr>Hg. Sediments pollution of Beishihe river was similar with Changzhou rivers.2. Water quality of Beishihe river was inferior to V level for a long time. Pollution level was TN>NH3-N>TP>COD. NH3-N was the head species in TN, which accounted for 65%. The average concentration of DO was 1.30mg/L.3. On the different DO conditions, sediments had a little release of COD, the release was relatively larger on the anaerobic condition. The release of NH3-N was both obvious on the different DO conditions and it was larger on the anaerobic condition. On the aerobic condition, there was not release of TP, but on the anaerobic conditions, the release of TP was obvious.4. The performance of commercial products which control sediments release was not good. Zeolite powder, polyferric sulphate(PFS), CaO2, and flyash were chose as materials to research complex preparation. According to the experimental analysis, the complex preparation was composed of zeolite powder and PFS. The mass ratio was 95:5. 5. Addition of the complex preparation to the sediments-river waters system effectively controlled the release of NH3-N and TP, and slowed down the consume of DO in a certain extent. It also reduced turbidity quickly, and removed COD to some degrees. Complex preparation had little effect on pH, and did not any harm to aquatic environment.6. As a key component of complex preparation, zeolite powder was modified for enhancing removal capability of NH3-N. When the concentration of NaCl was 1mol/L, the modification condition was optimal. Compared with natural zeolite powder, the removal capability of NH3-N by modified zeolite powder enhancd 32%. Ion exchange was the major action for adsorption of NH3-N by zeolite powder. On the condition that low-concentration NH3-N, the major ion exchange with NF4+ was Na+ for zeolite powder, so modification could effectively enhanced adsorptivity for low-concentration NH3-N.