Reuse of treated wastewater in metal-mechanics industry: A technical-economic evaluation

Abstract

Metal-mechanical industries are intensive in the consumption of water and, consequently, in the wastewaters production. Thus, reuse is essential because it preserves the environmental resources, diminishing the water footprint of the obtained products. Despite the advanced techniques, the economic cost limits the wastewater treatment to the most common techniques. This study evaluated the technical potential and costs involved in the reuse of wastewater in a metal-mechanical industry. Mistakes were found in the reagents dosage, what precluded reuse of the treated wastewater. The optimum condition for coagulation/flocculation was evaluated using the bench scale jar test. The parameters of wastewater, such as turbidity, pH, alkalinity, hardness, electrical conductivity, chloride and total solids were evaluated. The ideal condition was tested at the plant and some adjustments were made. The improvements resulted in 50.96% cost reduction of wastewater treatment without new investments. Also, the treatment became faster and more efficient. The wastewater achieved the standards for reuse in toilet flushing and floor washing.