Water Quality and Waste Production within Intensively Operated Recirculating Aquaculture Systems: The Potential for Use of Nutrient-Rich Effluents in Aquaponics and Agronomics.

The Conservation Fund’s Freshwater Institute (TCFFI) is focused on the development of environmentally sustainable and cost effective technologies to culture food-fish. Through engineering and applied research, TCFFI has helped to develop recirculating aquaculture systems (RAS) that minimize water use, enhance biosecurity, and minimize environmental impacts, while growing fish in a controlled and optimized culture environment. These technologies provide tremendous opportunity for value-added use of waste flows in a variety of applications, such as aquaponics and agronomics. The relatively small and concentrated waste streams produced by RAS offer the potential for enhanced nutrient recovery in the biosolids (after treatment with dewatering technologies) and from larger volume over-topping effluents that are rich in dissolved nutrients.

Several research projects will be overviewed that describe the water quality produced within six replicated RAS (1/10^th of commercial scale) and within the effluents from these systems. Key studies to be discussed include: 1) Comparing the effects of alternative protein diets without fish meal and traditional fish meal-based diets on fish performance, water quality, and waste production; and 2) Comparing waste and nutrient accumulation within RAS operated at high and low water exchange rates. Concentrations of the following water quality parameters will be reported for each study: nitrogen, phosphorous, suspended solids, dissolved metals and nutrients, pH, and alkalinity. The results indicate: 1) Inclusion of alternative protein ingredients in aquaculture diets can alter the nitrogen, phosphorous, and nutrient concentrations within RAS effluents, and 2) RAS effluent water quality can vary substantially depending on the water flushing rate of the system.

The goal of the presentation is to provide specific water quality data from relevant scale aquaculture systems operated under various conditions in order to demonstrate the potential for the integration of aquaculture with other agricultural sectors that could benefit from the use of nutrient rich waste streams.