Effect of effluent recycling and chloride salts on a simulated anaerobic swine lagoon

Abstract

The effect of salts accumulation—a result of effluent recycling and chloride salts addition—in a simulated anaerobic swine lagoon has been studied. Three laboratory scale reactors were used to simulate actual lagoon conditions. The cations Na, K, Ca and Mg were added as chloride salts, and via the sun dried lagoon effluent, to two of the reactors at the concentrations and ratios found in the sun dried effluent. The results indicated that salts accumulations caused similar effects on biological activity, according to a general toxicity model suggested in earlier work. Salts accumulation was expressed as electrical conductivity (EC). Optimum biological activity was obtained at EC values from 5 to 8 mS for the chloride salts and from 25 to 35 mS for the recycled effluent. Effluent recycling thus caused similar effects on biological activity at much higher salts concentrations than the chloride salts, possibly due to cation antagonisms. A direct conclusion is that effluent recycling is feasible in anaerobic swine lagoons and to a much higher degree than was previously thought. From the practical point of view, effluent recycling will minimize lagoon effluent disposal problems and the treatment cost of the wastes produced in swine farms.