Building Artificial Floating-island for Treating Bailianjing River in Shanghai

An artificial floating-island composed of fish,shellfish and aquatic plants was designed for bioremediation in Bailianjing River,Shanghai.From September 2007 to March 2008,water samples were collected respectively twice a month and DO,SS,TN,NH3-N,NO3-N,NO2-N,TP and PO4--P were analyzed to test system efficiency.Results showed that artificial floating-island can not only increase DO obviously,reduce SS,enhance transmittance of water body,but also remove nutritious substance in water body dramatically.In early stage of artificial floating-island constructed from September to October 2007,efflux of the system was not steady,and results showed that DO in general was lower than 5mg/L,while SS,TN,NH3-N,TP and PO4--P exceeded 40mg/L,2.0mg/L,1.0mg/L,0.15mg/L and 0.05mg/L respectively.In the middle period of research from Nov.2007 to Feb.2008,whole ecosystem composed of Acorus calamus Linn,Hypophthalmichthys molitrex,Aristichthys nobilis and Hyriopsis cumingii was steady,and all kinds of organisms in floating island were in good condition,resulting in the improvement of water quality.Results showed that DO inside the floating island increased to 8.0mg/L or above,SS was reduced to 10mg/L,TN and NH3-N was 2.0mg/L and 3.0mg/L lower than the outside,while TP was generally reduced to 0.06mg/L and PO4--P decreased to 0.03mg/L.During the latter stage of the study in March,2008,because of lacking of necessary maintenance and management,growth of hydrophytes was restrained,the treatment effect of artificial floating island was significantly reduced,and resulting in secondary pollution and deteriorate water quality.