Full-scale remediation of a grey iron foundry waste surface impoundment

Abstract

A large grey iron foundry was facing remediation of a surface impoundment containing approximately 300,000 cubic yards of EP-Toxic sludge. The sludge was generated by the settling of wastewater solids from air emission control systems connected with cupola melting operations. Bench-scale treatability testing was used to evaluate various chemical treatment possibilities for rendering the sludge non-EP-Toxic. Several phosphate sources and different engineering options were evaluated for cost-effectiveness of full-scale remediation. The most economical option was to dredge the solids continuously as a slurry (while the impoundment remained in operation) with injection of phosphoric acid into the slurry pipeline. The treatment process was controlled by monitoring residual phosphate in the treated slurry. The remediation process was tested in a month-long field trial using full-scale equipment, and was followed by successful remediation during a 6-month period. A technical overview and performance data on the remediation process are presented.