Comparison of useful terrestrial and aquatic plant species for removal of nitrogen and phosphorus from domestic wastewater

To develop a low cost and energy-saving wastewater treatment technique in combination with resource recycling and amenity functions, we constructed a plant bed filter ditch in which useful terrestrial and aquatic plants can be utilized for nitrogen and phosphorus removal from wastewater. Screening studies were conducted to evaluate and compare the effectiveness of 20 kinds of plant species which are economically important or exhibit on aesthetic value, including 13 terrestrial species, for domestic wastewater treatment. Artificial wastewater containing 20 mg L-1 of N and 3.3 mg L-1 of P, was supplied to the ditch at the rate of about 1.41-2.08 g m(-2) d(-1) for N and 0.20-0.33 g m(-2) d(-1) for P. The experiments were performed in a glass house with windows opened from April to November, The ditches showing high N and P removal rates were planted with plants which exhibited high biomass production rates. In the case of the papyrus ditch, N and P removal rates exceeded 0.8 g m(-2) d(-1) for N and 0.15 g m(-2) d(-1) for P from late spring to autumn, in the case of the kenaf ditch and sorghum ditch, from summer to autumn and in the case of the Italian ryegrass ditch and barley ditch, in early spring. These findings indicated that efficient wastewater treatment can be performed consistently except in the winter season, by cultivating these plants in an appropriate combination in the ditches.