Evaluation of plant bed filter ditches for the removal of T-N and T-P from eutrophic pond water containing particulate N and P

Cultivation of useful terrestrial and aquatic plant species in plant bed filter ditches enables to treat domestic wastewater in addition to resource recycling and amenity functions. We reported previously that a ditch planted with papyrus removed N and P most effectively from artificial wastewater. We evaluated the effectiveness of plant bed filter ditches in the treatment of eutrophic pond water, which unlike artificial wastewater, contains particulate N and P. Experimental ditches were planted with papyrus, African marigold, peppermint, and impatience. These plant species were effective in removing N and P from artificial wastewater and could be used by rural communities for the production of handicrafts, cut flowers, and ornamental purposes. The control ditch did not contain plants (plant-free ditch). Pond mater was continuously supplied to the ditches at a loading rate of 0.6-0.9 g m(-2) d(-1) for N and 0.2-0.35 g m(-2) d(-1) for P. In the plant-free ditch, particulate N and P in the influent were removed by passage through the bed filter, unlike NO3-N and PO4-P. A larger amount of PO4-P was dissolved from particulate P in the bed filter. The planted ditches effectively removed NO3-N, PO4-P as well as particulate N and P. The planted ditches were able to purify eutrophic pond water, resulting in clear water with a concentration below 0.3 mg L-1 for N and 0.02 mg L-1 for P, concentrations at which water bloom does not occur. The average removal rate of pollutants by the planted ditches during the experiment, except for the first 2 weeks, was 0.67 g m(-2) d(-1) for total N and 0.03 g m(-2) d(-1) for total P. We recommend that plant bed filter ditches containing papyrus and flowers be used for ornamental purposes and removal of N and P from pond water along with the supply of clear water as ornamental streams.