Attaining water efficiency and reduction in chromium release through wastewater reuse in basic chromium sulfate production industry

Current study was aimed to investigate potential water savings and pollution reduction through effluent reuse at basic chromium sulfate (BCS) plant located in Lahore, Pakistan. Specific water consumption and effluent discharge were calculated as m3/ton product based on an average production in 2016 and 2017. Based on assessment criteria, the environmental performance was evaluated through best available options including improving washings, controlling leakages, enhancing efficiency of SO2 scrubber. Further, reuse applications of chromium rich effluent were tested in process using standard methods at pilot and production scale without advance treatment techniques. As a result, process/non-process water consumption was reduced by 2.96–1.5 m3/ton product reflecting overall 49.6% as well as effluent discharge by 1.63–0.73 m3/ton product reflecting overall 55%, which resulted in 2,142.6 m3/y of water savings led to achieving zero liquid discharge (ZLD). Economic benefits were gained as the production of sodium sulfite after scrubbing which gives $6,000 annually as well as the recovery of chromium resulted in excessive BCS yield which gives an annual saving of $8,420 to the industry. This study proved a sustainable model of increasing water use efficiency and achieved ZLD economically to the industry with reduced environmental impacts through chromium release.