Waterhyacinths for Water Quality Improvement and Biomass Production

Abstract

AbstractThis paper discussed the potential use of waterhyacinth [Eichhornia crassipes (Mart.) Solms] for biomass production and for nutrient removal from wastewaters. Warm climates in tropical and subtropical areas are conducive for establishing wastewater treatment systems and biomass production farms with waterhyacinth. Sources of nutrients available to culture waterhyacinths include sewage effluent, agricultural drainage water, runoff from animal waste operations, methane digestor effluent, and water from eutrophic lakes and rivers.Growth rates of waterhyacinths were found to be influenced by the nutrient composition of the water, plant density, solar radiation, and temperature. Annual yields of waterhyacinth biomass were found to range from 47 to 106 Mg dry wt ha−1 y−1, with approximately 50% of the biomass produced during May through August. About 35 to 50% of the total biomass was roots when plants were cultured in nutrient‐poor waters (eutrophic lake water and drainage effluents), while 14 to 25% of the total biomass was roots for the plants grown in nutrient‐rich waters (sewage effluent). Waterhyacinth systems were found to be more efficient in N removal (70–80% reduction) than in P removal (40–50% reduction).A pond with a surface area of 2.65 ha and 1.0 m in depth containing 15 to 30 kg wet wt of waterhyacinth per square meter (750–1500 g dry wt m−2) and a detention period of 7 d is adequate to treat 3785 m3 d−1 [million gallons per day (mdg)] of sewage effluent. This hypothetical system would achieve 70 to 80% N removal, 40 to 50% P removal, and would produce a biomass yield of 690 to 1060 kg dry wt d−1 (13–20 g dry wt m−2 d−1). The biomass upon anaerobic digestion would yield 180 to 280 m3 of methane/d. This is equivalent to 549 to 843 GJ ha−1 of energy from waterhyacinth produced at a rate of 48 to 73 Mg dry wt ha−1 y−1.