Optimization of makeup water in a recirculating aquaculture system
University of New Brunswick
The main objective of this project was to develop a mathematical model that can be used to lower the freshwater consumption in salmon-smelt hatcheries while maintaining the water quality required for the well-being of the farmed species. Excessive use of makeup water increases effluent treatment, heating, and makeup chemical costs. Models for fine particle, ammonia, nitrate, carbon dioxide, phosphate, and salts concentrations as well as water temperature were developed and validated with experimental measurements collected at a salmon-smelt hatchery. Makeup water requirements were calculated based on recommended stress limits and equipment efficiencies. As expected, the models predict that the optimum makeup water usage per unit weight of feed decreases as the efficiency of the water treatment equipment increases. The limiting water quality parameter was found to be a function of feed rate, pH, and time of the year. Recommendations are made for improving system efficiencies and lowering freshwater consumption.