End-of-Pipe Horticultural Reuse of Recirculating Aquaculture System Effluent: Comparing the Hydro-Economics of Two Horticulture Systems

To assist waste management decision-making, there is a need to assess the economics of commercial-scale reuse of recirculating aquaculture system (RAS) effluent in horticulture. This study compared the feasibility/viability of using two representative horticulture systems, considering their distinct hydrological characteristics, in horticultural reuse schemes for RAS effluent. These representative systems included a soil-based system in field conditions (SOIL-FIELD) and a hydroponic system in greenhouse conditions (HYDRO-GH). A novel two-step hydro-economic modelling approach was used to quantify and compare the effluent storage volume, total land area, capital expenditure and crop price required for feasible/viable end-of-pipe reuse in the two systems. The modelling assessed several water management scenarios across four Australian climates. Results showed HYDRO-GH, reusing 100% of the annual effluent load and targeting an internal rate of return of 11.0%, required approximately 3 times more land, 14 times more capital expenditure and 5 times the crop price of SOIL-FIELD, targeting a 3.6% internal rate of return. As well as comparing two horticulture systems, this study presents a method to assess feasibility/viability of horticultural reuse schemes for other industrial wastewaters, using a water balance design approach.