Purification performance of a shallow free-water-surface constructed wetland receiving secondary effluent for about 5 years

摘要: Abstract The effluent from combined household wastewater treatment facilities used in unsewered areas of Japan is generally high nitrogen (N) and phosphorus (P). In Japan, environmental quality standards for zinc (Zn) pollution were enacted recently because the toxicity Zn to aquatic ecosystems. 2004 a fallow paddy field at Koibuchi College Agriculture Nutrition central was converted into shallow, 500-m 2 , free-water-surface constructed wetland polish secondary dormitory. planted with Zizania latifolia . efficiencies removal N, P, by evaluated about 5 years. average total N P concentrations influent 20.0 mg/L 1.95 mg/L, respectively; corresponding 10.3 mg/L 0.95 mg/L, respectively. acid-soluble concentration decreased 0.048 0.023 mg/L after passing through wetland. Inorganic PO 4 -P, dissolved principal forms removed system. Very little particulate Zn, very plus organic or removed. mean first-order rate constants ( k ) inorganic-N, 10.3 m/yr, 18.8 m/yr, 16.5 m/yr, effectively not only nutrient salts but also throughout 5-year study period. values inorganic-N -P significantly influenced temperature, although value not. These results mass balance data suggest that mainly denitrification secondarily adsorption soil plant uptake; soil. There sedimentation particulates shallow