SHRIMP POND EFFLUENT - POLLUTION PROBLEMS AND TREATMENT BY CONSTRUCTED WETLANDS

An intensive shrimp culture in Thailand has rapidly expanded especiall y along the coast during the last decade. Excessive feed basically giv en during the culture causes water and sediment in the pond to contain organic matter and nutrients in high concentration. After harvesting, discharging sediment is prohibited; however, pond water is mostly dis charged directly to natural water resources without any effective trea tment. The nutrient load discharged from shrimp ponds can form signifi cant source of nutrients causing pollution and eutrophication in litto ral areas of Thailand. The possibility of a subsurface-flow constructe d wetlands application for treating shrimp pond effluent containing hi gh salinity was studied. An experimental-scaled model planted with Acr ostchum aureum (mangrove fern) in gravel was studied by comparison wit h one containing only gravel. The results showed that models can reduc e suspended solids, biochemica oxygen demands, total organic carbon, t otel nitrogen (T-N) and total phosphorous (T-P) up to 84%, 91%, 46%, 4 8% and 31%, respectively. Higher removal efficiencies for TOC, T-N and T-P of the planted model compared with the gravel model were clearly found. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.