Effect of Composite Enhanced Water-Purifying Ecological Floating Bed Removing Nitrogen and Phosphorus in Polluted Water

A study was conducted to compare composite enhanced water-purifying ecological floating-beds (CEPEF, Iris pseudacorus + composite packing + Hyriopsis cumingii ) with traditional ecological floating-bed (only I. pseudacorus) in effect of removing N and P in wastewater. Results show that antagonism existed between H. cumingii and microbes attached to the packing on one side and floating-bed plants on the other, which limitinged the growth of the plants on the floating-bed. After 30 days of treatment with the CEPEF, the concentrations of total nitrogen (TN) and total phosphorus (TP) was were reduced from 9.23 and 2.16 mg•L^-1 to 0.59-1.32 and 0.83-1.20 mg•L^-1 ,respectively, with their respective removal rate reaching 85.70%-93.61% and 44.44%-61.57%, which wasere obviously averagely 19.86 and 17.90 percentage point higher than that with the traditional one (with the highest being 24.05 and 24.53 percentage point) respectively. And the effect was quite stable with the time passing on. Meanwhile, it was also found that the CEPEF peaked in its reoxygenation and N, P removal effects when the density of H. cumingii was controlled between 15 and 28 ind per cubic metre.