Evaluation of different management scenarios for trout farm effluents using dynamic water quality modeling

Trout farm effluents are among the important sources of water pollution by nutrients, organics, and suspended solids. This research study was conducted to investigate and manage the impacts of trout farm effluents on Esen Stream water quality, which is located at the southwest of Turkey. A water quality monitoring program was conducted for a period of 1 year at 21 stations to determine river hydraulics and water quality characteristics. Monthly water quality analyses were conducted for inflow and outflow of a number of selected farms to determine their characteristics and contribution to water pollution. About 1460 t of suspended solids, 230 t of nitrogen, and 46 t of phosphorus were annually discharged into Esen Stream from the farms. A dynamic water quality simulation model developed by the US-Environmental Protection Agency, WASP8, was applied to Esen Stream to predict and manage pollution from trout farms and the tributaries. The calibrated and verified model was used to evaluate the impacts of different management scenarios on stream water quality. Solid removal with a rotating micro-screen, establishment of a partially recirculated system and increasing production capacities of farms were among the simulated scenarios. The best management practice was the combined application of solids removal and reuse of treated farm effluents in a partially recirculated system, which provided significant improvements in the receiving stream water quality. This study showed that dynamic water quality models are powerful tools for basin-scale management of land-based aquaculture for capacity planning, assimilation capacity estimation, sustainable operation, and environmental impact assessment.