| Abstract: | In order to improve the efficiency of nitrogen and phosphorus removal in a multistage pond system which receives polluted natural inflow and outflows to a landscape lake, ecological floating beds (EFBs) were installed along the flow-path of each pond and fixed beds (FBs) were embedded in between each pair of ponds. Such a simple modification of the MPS effectively enhanced the total nitrogen (TN) removal rate from 59.2% to 71.4% and the total phosphorus (TP) removal rate from 37.1% to 51.0%. It was identified that the EFBs mainly contributed to enhanced TN removal by the biomass growth in the stereo-elastic packing and attachment on the surface of ceramsite particles packed in the floating mat, while the FB filled with zeolites contributed to both TP adsorption and biological TN removal to certain extent, as indicated by the denitrification rate and adsorption function experimentally obtained for each part of the bed settings. The superposition effect of the installation of EFBs and FBs was estimated using a tank-in-series model. With a Nash-Sutcliffe efficiency higher than 0.75, calculation results of the model well fitted field measurements and showed that the EFBs (including plant uptake) contributed to the increase of TN and TP removal by 23.3% and 8.12%, respectively, and that contributed by FBs were 19.6% and 10.7%, respectively. |
