Advanced neutralization technique for the treatment of highly acidic wastewater from steel rolling mills of western Rajasthan.

In this study, we developed an economical treatment process for highly acidic effluents from steel rolling mills containing toxic heavy metals. Our method involves a pH-dependent approach using mining waste and hydrated lime. The treatment occurs in two steps: First, metal oxides precipitate at pH 3-3.5 using mining waste, followed by lime precipitation at pH 9-9.5. The process, completed in less than 6 h without heavy machinery, reduces sludge formation by extracting high-purity gypsum, a valuable industrial product. Water quality posttreatment matches local groundwater standards. Compared to conventional methods like common effluent treatment plant (CETP) in Jodhpur, India, our approach reduces operational costs by over 58%. In this study, we also characterized the by-product formed, that is, gypsum using various characterization tools and performed a detailed cost analysis. PRACTITIONER POINTS: A quick, efficient, and economical treatment process for extremely acidic (pH ~ 1) wastewater from steel industries. Stepwise treatment strategy without involving heavy machinery or high manpower. Processed water quality closely resembles groundwater with all the major heavy metals been removed. Sludge quantity reduced by regeneration of pure gypsum (96% purity). Reduced the overall operation cost of effluent treatment by 58%.