Removal of nutrients from aquaculture wastewater using cattail (Typhaspp.) constructed wetlands

The aquaculture industry is among the fastest growing food production sectors in the world. Land‐based aquaculture systems continue to increase in popularity as they offer the benefits of controlling diseases, managing water quality, and minimizing threats to wild populations of fish. However, these systems discharge wastewater high in N and P. The ability of cattail (Typhaspp.) constructed wetlands (CWs) to remove N and P from aquaculture wastewater (AWW) was examined here. Cattail CWs were established in mesocosms and had a gradient of AWW applied weekly for a total of 5 weeks. Total N and P loadings ranged from 13.7 to 209.2 mg m−2and 3.01 to 45.97 mg m−2over 28 days, respectively. Additions of AWW did not cause elevations in total dissolved N, total ammonia N, or nitrite N in CW water; however, concentrations of nitrate N and P in CW water were related to nutrient loading conditions. Elevations in P persisted for 3–4 weeks among high nutrient loading treatments, providing an opportunity for eutrophic conditions to develop in CW systems. However, after 33 days of treatment, >95% total P concentration reduction was achieved in all mesocosms with final concentrations <0.05 mg L−1, equivalent to reference conditions. High‐loading treatments achieved greater P load reduction (856.8–955.0 mg m−2year−1) than low‐loading and reference treatments (591.7–792.7 mg m−2year−1). This study demonstrates the effectiveness of cattail CWs to remove nutrients during AWW treatment and highlights the potential for end‐of‐season use in northern climates, providing insights regarding the operational timeline of such systems. Land‐based aquaculture systems discharge high‐nutrient effluents that are environmentally concerning.The ability of cattail constructed wetlands (CWs) to treat nutrients in aquaculture wastewater (AWW) was assessed.Higher P load reductions were achieved under high nutrient loading conditions.Cattail CWs can be used to treat nutrients in AWW and perform well during end‐of‐season use.Future considerations include P removal mechanisms and remediation capacity of cattail CW systems.