Abstract: The technique of complex three-dimensional ecological floating-bed is an effective water pollution control technology.The complex floating-bed is composed of a framework with grids made of bamboo,plants and mollusks,such as snails and mussels,on the grids,an elastic material placed on or under the framework.Colocasia esculenta,Sagittaria sagittifolia,Eleocharis dulcis,Oenantha javanica,Ipomoea aquatica and Ganna generalis were used as subjects in the research on their effect in removing nitrogen and phosphorus from slightly polluted water body in summer and fall.Results show that the N and P removing effects of the six floating-beds different in plant on the bed followed the order of Ipomoea aquatica>Ganna generalis,Eleocharis dulcis,Colocasia esculenta>Sagittaria sagittifolia,Oenantha javanica in summer and Colocasia esculentat>Sagittaria sagittifolia,Ganna generalis,Ipomoea aquatica>Eleocharis dulcis,Oenantha javanica in fall.Obviously Colocasia esculenta showed good N-removing effect in both summer and fall,with maximum removal rate reaching 71% and 62%,respectively,of total N,while Ipomoea aquatica is good in P removing with maximum removal rate reaching 30% and 81%,respectively,of total P.Comparison between the new floating-bed with the traditional flat floating bed in N and P removing effect demonstrates that the former enjoys a bright prospect in application to ecological remediation of slightly polluted water bodies.

Key words: complex three-dimensional ecological floating-bed, nitrogen, phosphorus, removal effect, slightly polluted water body