Investigating the Potential of Constructed Wetlands for Bioremediating Aquaculture Pond Effluents in Benue State

The discharge of nutrient-rich effluents from aquaculture ponds into receiving water bodies in Benue State, North Central Nigeria, threatens freshwater ecosystem health, and cost-effective treatment technologies adapted to smallholder farm scale are urgently needed. This study investigates the potential of pilot-scale constructed wetlands planted with Phragmites australis and Typha domingensis to bioremediate aquaculture pond effluents from commercial catfish ponds in Makurdi, Benue State. Three parallel surface flow wetland cells and one unplanted control cell were operated at hydraulic retention times of 3, 5, and 7 days over a six-month period. Effluent samples were collected at inlet and outlet points biweekly and analysed for total ammonia nitrogen, nitrite, nitrate, total phosphorus, biochemical oxygen demand, total suspended solids, and coliform bacteria. Results demonstrated that the 7-day hydraulic retention time achieved the highest removal efficiencies: total ammonia nitrogen (91.3%), total phosphorus (78.6%), biochemical oxygen demand (87.4%), and total suspended solids (93.2%). Phragmites australis-planted cells outperformed Typha domingensis cells by 8 to 14% for ammonia and phosphorus removal. Planted cells significantly outperformed the unplanted control across all parameters. The treated effluent at 7-day retention met NESREA discharge standards for all parameters assessed. The study demonstrates the feasibility of constructed wetland treatment for aquaculture effluents at the smallholder farm scale in Benue State and recommends their integration into an incentivised effluent management scheme for commercial fish farmers.

Keywords: constructed wetland, aquaculture effluent, bioremediation, Phragmites australis, Benue State