Aquatic Toxicity Reduction and Water Reuse at a Metal Finishing Plant

In 2003, the Bon L Manufacturing Company took the final steps to meet the aquatic toxicity requirements of its NPDES permit. Prior to the final steps, Bon L had implemented water and waste minimization measures within the manufacturing plant to reduce water usage and waste generation. These measures showed a significant reduction in wastewater flow and a decrease in contaminant loading. However the effluent toxicity persisted due to the high levels of total dissolved salts, metals and surfactants.Analyses of treatment alternatives were performed and a treatment system utilizing reverse osmosis was selected. The selected treatment process consisted of metals precipitation, carbon adsorption, ion exchange and reverse osmosis. The effluent from the treatment system is reused by the manufacturing operations. The sludge generated by metals precipitation is dewatered with a filter press. The brine generated from the reverse osmosis process is evaporated to achieve an 80% volume reduction. The plant has been operating successfully since the winter of 2004.