Heavy metals removal from influents to prevent mortality in salmon fry

•For salmon culture, Cu and Zn limit value are 0.04 and 0.3 mg/L, respectively, in water with hardness equal to 100 mgCaCO3/L.•Al, Fe and Mn removal from fresh water in RAS is possible by precipitation, filtration and ionic exchange.•Cu and Zn removal from fresh water in RAS is possible by ionic interchange until concentration compatible with salmon life.

The concentration of heavy metals in water, above certain values, threaten industrial salmon production and have occurred in two of the most important salmon producers, Norway and Chile. Aluminum and iron are two of the main heavy metals found in fresh water of the salmon industry, although manganese, zinc and copper have also been detected. In Chile, an experimental study found a solution to remove aluminum, iron and manganese. The present works studies copper and zinc removal by ionic exchange using AMBERLITE IRC747. The resin's removal capacity is 0.025 meq/g and does not depend on the solution's pH. An ionic exchange column was designed and continuously operated to remove copper and zinc from concentrations equal to 1000 μg/L of each metal. Then, the column was modularly operated with an aluminum, iron and manganese abatement system removing them by precipitation, oxidation (for iron and manganese) and granular filtration. When operating the modular system, the final aluminum, copper, iron, manganese, and zinc concentrations were 0.1, 0.4, 0.6, 0.8 and 0.3 μg/L, respectively. As a result, the system implemented obtained values below the maximum limits allowed for aluminum, iron, manganese, copper and zinc.