The Plants Selection And Demonstration Of Ecological-floating-island Restoration Of Eutrophic Riverways In Hangzhou

The water eutrophication is one of the major problems of water environment that the whole world has to face. There are numerous and developed rivers in Hangzhou city, but the eutrophication influences rivers' normal function on water ecological. As a new, economical, low energy consumption, easily managed and ecological sound technology, artificial-floating-island eco-restoring project has the other eutrophication treatment technology incomparable merits. It is adapt to act as forceful supplement rivers government engineering.This paper aims at practical artificial-floating-island technology. Based on the investigation of common emerging plants in Hangzhou area, the uptaking ability of nitrogen and phosphorus of different plants was evaluated. The plants used in the artificial-floating-island were selected by nutrient absorption kinetics. Further, we applied the artificial floating island technology in Caijia River and monitored water quality at regular intervals in order to test its ability to restore water.The results were summered as follows:(1) Alternanthera paronychioides and Cyperus alternifolius are the most suitable species to lower N concentration in high levels of N nutrient environment; while Acorus calamus and Colocasia tonoimo Nakai are suited to maintain water quality in N deficient environment.(2) Alternanthera paronychioides,Sagittaria sagittifolia,Cyperus papyrus and Colocasia tonoimo Nakai are the optimum species in high levels of P nutrient environment; while Colocasia antiquorum,Canna indica,Acorus calamus and Caldesia parnassifolias can grow better in low levels of P nutrient environment. Lythrum salicaria Lin. and Typha orientalis Presl can be used in various concentrations water bodies.(3) The demo project demonstrated that:after three months, the concentrations of BOD and TP could be lowered by the artificial floating island technology. The applied artificial floating island of 300-square-metre could remove the amount of 61.19g of TN and 164g of TP. If the planting density is 50 plant/m2, TP concentration could be dropped to 0.2mg/L so that the standard of water quality raised by one grade.(4) Though vegetables absorb nutrient from eutrophic water, its content of pesticides and metal haven't exceeded the eating standard.Therefore the artificial floating could be applied as effective and economic technology in the eutrophic rivers treatment projects.