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Microcosm Wetlands for Wastewater Treatment with Different Hydraulic Loading Rates and Macrophytes
- Jing, Shuh-Ren, Lin, Ying-Feng, Wang, Tze-Wen, Lee, Der-Yuan
- Journal of environmental quality 2002 v.31 no.2 pp. 690-696
- Commelina communis, Ipomoea aquatica, Ludwigia, Phragmites australis, Pistia stratiotes, chemical oxygen demand, constructed wetlands, emergent plants, municipal wastewater, wastewater treatment, Taiwan
- Constructed wetlands (CW) usually require large land areas for treating wastewater. This study evaluated the feasibility of applying CW with less land requirement by operating a group of microcosm wetlands at a hydraulic retention time (HRT) of less than 4 d in southern Taiwan. An artificial wastewater, simulating municipal wastewater containing 200 mg L−1 of chemical oxygen demand (COD), 20 mg L−1 of NH+ 4–N (AN), and 20 mg L−1 of PO3− 4–P (OP), was the inflow source. Three emergent plants [reed, Phragmites australis (Cav.) Trin. ex Steud.; water primrose, Ludwigia octovalvis (Jacq.) P.H. Raven; and dayflower, Commelina communis L.] and two floating plants [water spinach, Ipomoea aquatica Forssk.; and water lettuce, Pistia stratiotes L.] plants were tested. The planted systems showed more nutrient removal than unplanted systems; however, the type of macrophytes in CW did not make a major difference in treatment. At the HRTs of 2 to 4 d, the planted system maintained greater than 72, 80, and 46% removal for COD, AN, and OP, respectively. For AN and OP removal, the highest efficiencies occurred at the HRT of 3 d, whereas maximum removal rates for AN and OP occurred at the HRT of 2 d. Both removal rates and efficiencies were reduced drastically at the HRT of 1 d. Removals of COD, OP, and AN followed first-order reactions within the HRTs of 1 to 4 d. The efficient removals of these constituents obtained with HRT between 2 and 4 d indicated the possibility of using a CW system for waste-water treatment with less land requirement.