Treating eutrophic water for nutrient reduction using an aquatic macrophyte (Ipomoea aquatica Forsskal) in a deep flow technique system

Wetlands can be used in a cost-effective manner to treat nutrient-rich water for release to freshwater ecosystems. Eutrophic water was treated with the freshwater macrophyte, Ipomoea aquatica Forsskal (swamp cabbage), in a horizontal-flow, Deep Flow Technique (DFT) system. Plants were also exposed to a Hoagland and Arnon [Hoagland, D.R., Arnon, D., l938. The water culture method for growing plants without soil. Calif. Agr. Expt. Sta. Circ., 347] solution using the same exposure system. After a 48-h exposure to the plant, chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total suspended solids (TSS) and chlorophyll a (Chla) in the effluent were reduced by 84.5, 88.5, 91.1, and 68.8%, respectively, and the removal of nutrients (total nitrogen and total phosphorus) varied between 41.5 and 75.5%. Vitamin C and NO3-N concentrations in plants grown in the eutrophic water were significantly different from those grown in a standard nutrient solution. Chlorophyll a, chlorophyll a/b and shoot to root dry weight ratio were not significantly different between the different waters. The concentrations of cadmium, copper, lead and zinc were lower than the permissible levels set by the FAO and WHO for human consumption. The results of this study indicate that cultivating edible, aquatic macrophytes with nutrient-rich, eutrophic water in a DFT system can be an effective, low-cost phytoremediation technology to treat water with undesirable levels of nitrogen and/or phosphorus.