Pilot scale recovery, and removal of chromium from tannery wastewater by chemical precipitation: Life cycle assessment and cost analysis.

This study investigated the sustainable approach to removing and recovering chromium by chemical precipitation using sodium hydroxide (NaOH) and sulfuric acid (H₂SO₄). The raw tannery wastewater was studied under varying pH and agitation speed to assess and optimize the process variables using an atomic absorption spectrometer, exhibiting promising removal and recovery rates. The highest chromium removal efficiency of 96.9 % was obtained at a pH of 10.0 with an agitation speed of 500 rpm, while the maximum recovery efficiency of 83.4 % was achieved at pH 2.8 under similar conditions. The life cycle environmental impacts were also assessed for 10 different indicator categories, including particulate matter (PMFP), stratospheric ozone depletion (ODP), human damage ozone formation (HOFP), ecosystem damage ozone formation (EOFP), terrestrial acidification potential (AP), marine eutrophication (ME), global warming potential (GWP), mineral resource scarcity (MRS), water consumption (WC), and fossil resource scarcity (FRS). The scope of the LCA study is to estimate the energy consumption and environmental burden of recovery of chromium from tannery wastewater and evaluate whether the proposed method is environmentally justifiable. Environmental impacts associated with 1 Kg of recovered chromium were utilized as the functional unit for this study to correlate the inputs and outputs of the process using GREET.net v2022 software. Furthermore, the cost analysis showed that chromium recovery could generate an estimated net profit of 588,248 USD/year, confirming the economic viability of the process. This research offers significant insights into improving chromium recovery efficiency while reducing environmental and economic costs, presenting a scalable solution for industrial wastewater treatment.