Effect of a strengthened ecological floating bed on the purification of urban landscape water supplied with reclaimed water.

A floating bed (FB) system vegetated with calamus, iris, lythrum, and Hydrocotyle vulgaris, and a strengthened FB (SFB) system with zeolite and sponge iron as fillers were simultaneously applied to purify urban landscape water in different zones. The urban landscape water, an artificial lake of approximately 326m2, was supplied with reclaimed water during a six-month experiment. Results indicated that the concentrations of nitrogen (N) and phosphorus (P) in the SFB zone (SFBZ) were significantly lower than those in the control zone (CZ) and the FB zone (FBZ) after six months of operation. The average removal efficiencies (AREs) in the SFBZ, FBZ and CZ were 89.98%, 77.39% and 56.37%, respectively, for ammonia nitrogen (NH4+-N); 92.49%, 79.55% and 47.85%, respectively, for phosphate (PO43--P). Meanwhile, the average concentration of Chlorophyll a and the algae density in SFBZ during the experiment were 12.54μg/L and 1.31×104cells/mL, which were lower, obviously, than those in the FBZ and CZ. Moreover, the contribution rates analysis of nutrient removal exhibited that the plant absorption in the removal of N and P occupied 27.85% and 26.36%, whereas the filler adsorption occupied 7.93% and 11.93%, respectively, in the SFB. Thus, the water quality of the artificial lake was improved greatly by the SFB which hybridized fillers and FB together. Finally, it was found that the AREs of NH4+-N and PO43--P in the SFBZ could reach 73.93% and 84.56%, approximately 1.39 and 1.41 times that of the FBZ during the winter. Therefore, the application of an SFB can keep a stable water quality in urban landscape water and avoid the lower removal rate of an FB at low-temperature. In summary, the SFB could effectively improve the water quality of urban landscape water supplied with reclaimed water even in winter.