Evaluation of the performance of an integrated lateritic nickel mine water treatment system for the reduction of total suspended solids and hexavalent chromium

Abstract

Introduction. Laterite nickel mining activities produce water runoff containing high concentrations of total suspended solids and hexavalent chromium (Cr6+). The condition of mining water has the potential to pollute water bodies around the mining area and threaten aquatic ecosystems. Therefore, every mining activity must treat water until it meets environmental quality standards before being released into the surrounding area. Purpose of Research. This study aimed to evaluate the effectiveness of the mining water treatment system operated by PT Vale Indonesia, which is an integrated system for reducing total suspended solids and Cr6+ concentrations on an industrial scale. The treatment system being evaluated integrates three main stages: FeSO₄·7H₂O coagulant injection, sedimentation pond, and lamella gravity separator. Methods. The study was conducted through systematic water sampling at the inlet and outlet points of the treatment system every two hours for one month. Water quality parameters were analyzed using spectrophotometry to determine total suspended solids and inductively coupled plasma optical emission spectrometry (ICP-OES) for the quantification of Cr⁶⁺. Results. Performance evaluation of the treatment system showed that the sedimentation pond was able to reduce total suspended solids with an average efficiency of 81.56% and Cr6⁺ by 99.42%. The addition of a lamella gravity sedimentation unit improved the system's performance, with total suspended solids and Cr⁶⁺ reduction efficiencies reaching 88.62% and 99.31%, respectively. The water quality at the effluent point produced by both treatment systems consistently met the national wastewater quality standards set by the government. Conclusion. The combination of sedimentation ponds and lamella gravity separators has proven to be an effective, stable, and reliable technological approach for the industrial-scale management of water from lateritic nickel mining. This integrated system is recommended as a sustainable solution for water treatment in the nickel mining industry.

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