Wastewater control in welding electrode manufacturing - a case study

Metal finishing plants, although the wastewaters and treatment schemes for this category are well defined, require a case by case evaluation to find appropriate solutions and to solve specific problems. In this paper, a case study conducted on a welding electrode plant is presented. The wastewater sources were surface cleaning, copper plating and soap solutions used for drawing which were frequently included in waters. The plant was subjected to pretreatment standards, which necessitated the control of sulfate and organic matter in addition to standard parameters of metals, oil, suspended solids etc. Following a source-based characterization, treatability studies were conducted to treat high concentration of sulfate, organic matter as well as heavy metals and oil-grease. The proposed treatment scheme involved separate treatment of copper bath for recovery, chemical oxidation for soap solutions, sulfate precipitation for sulfuric acid bath and application of hydroxide precipitation to proper combination of other wastewater sources.