Performance evaluation of a commercial land-based integrated multi-trophic aquaculture system using constructed wetlands and geotextile bags for solids treatment

• A marine integrated aquaculture system was operated with zero waste discharged during the study.
• Presence of constructed wetlands resulted in a net loss of nitrate.
• Sale of macrophytes and fish result in a net return of $45,700 after one year.
• Only the combination of plants sales and Florida pompano made the integrated system profitable.

The water chemistry and economics of a commercial-scale inland marine integrated multi-trophic aquaculture (IMTA) system was investigated. The system used a combination of a constructed wetland, sand filter followed by a constructed wetland, and geotextile bags to treat solids waste. This study is a demonstration of a zero-discharge system where commercial nursery production of wetland plants was combined with a marine RAS to treat saline solid waste. Total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations were measured. Plant and soil samples were analyzed for TN and TP. A significant (p < 0.05) difference in the effluent concentrations was not found. The variability inherent in a commercial-scale system made it difficult to isolate the individual efficiencies of the three treatment systems. Production of wetland plants was critical for aiding nutrient removal by facilitating aggregation of solids and providing conditions for denitrification. On average the nitrate concentration decreased over time due to the denitrification occurring in the plant beds. Water samples were analyzed for dissolved metals: Mn, Ni, Se, Sr, Cd, Li, Hg, Mo, Fe, B, Cu, Pb, Zn, La, Ca, K, and Mg; Mn and Fe showed a gradual increase in concentration over time. This IMTA system successfully produced Florida pompano, and the fish waste and uneaten feed provided enough nutrients to produce multiple cohorts of wetland plants over a two-year period. An economic analysis indicated that after one year of production the system would produce a profit, but the production of Florida pompano alone would not result in a positive net return. The sales of wetland plants were necessary for the system to break-even and ultimately produce a profit for the production facility in Sarasota, FL.