Sustainable management of tannery wastewater: Integrating advanced treatment technologies with environmental assessments

The leather tanning industry is one of the most polluting sectors in terms of water, originating chromium-loaded effluent which contains high salinity, sulfides, suspended solids, and organic loads, leading to aquatic ecosystems, soil quality, and even human health at risk. Despite a number of studies reporting the removal of individual pollutants, there remains an industrial challenge of integrating treatment technologies into efficient, scalable, and sustainable processes to fulfil increasingly demanding discharge and water reuse targets. Thus, this review goes beyond the focus of single-process evaluation and critically evaluates integrated treatment strategies for tannery wastewater with particular emphasis on hybrid systems targeting simultaneous removal of chromium and co-existing pollutants. Biological, chemical, and physical processes were compared with emphasis on membrane-based, as well as advanced oxidation processes, with respect to several key considerations, e.g., removal performance, operational feasibility or ease of implementation, sludge generation, and thus reuse potential. This article provides a sustainability and application-oriented analysis of treatment technologies for the management of real-world tannery effluent, where cost and management are key barriers. This study also identifies the efficiency of treatment in relation to circular water management and implementation challenges, providing a more explicit direction for researchers, industry, and policymakers looking for better solutions for tannery wastewater treatment with a sustainability perspective.