USE OF HIGHER-PLANTS AND BED FILTER MATERIALS FOR DOMESTIC WASTE-WATER TREATMENT IN RELATION TO RESOURCE RECYCLING

A bench scale experiment was conducted to compare the effectiveness of three kinds of bed filters (zeolite, zeolite + shell fossils, charcoa l chips) and five plant species (Chinese water spinach (Ipomea aquatic a Forskal), rice (Oryza sativa L. cv. Takanari), zinnia (Zinnia elegan ce L.), watercress (Nasturtium officinale R. Br.), stock (Matthiona in cana R. Br.)) for use as plant-bed filter systems in order to develop low cost and energy-saving devices for wastewater treatment combined w ith resource recycling and amenity functions. Pots (0.05 m2) filled wi th bed filter materials were prepared as experimental systems. The add ition of higher plants to the bed filters enhanced the nitrogen and ph osphorus removal from wastewater as plant species considerably affecte d the P and N removal efficiency. In the summer-autumn season (June-De cember), Chinese water spinach and rice were more effective than zinni a. In the winter-spring season (January-May), watercress was more effe ctive than stock. Although the effectiveness of the addition of plants to the system on removal of total organic carbon was not conclusive, the use of zeolite and zeolite + shell fossil bed filters was superior to that of charcoal chips for P and N removal. The system consisting of zeolite + shell fossil bed filter planted with Chinese water spinac h in June-December and watercress in January-May showed the highest P and N removal efficiency, i.e. more than 80% during the experimental p eriod. This system removed 91% of P and 90% of N in the inflow and the average removal rate of P and N was 0.11 and 0.42 g per m2 per d, res pectively.