XiongZhong Tan Yong Tan GuangHua Liu WenJun Zhang Zhongmeng Environmental Construction Co., Ltd., Guangzhou, China Guangdong AIB Polytech College, Guangzhou 510507, China School of Life Sciences, Sun Yat-sen University, Guangzhou, China Proceedings of the International Academy of Ecology and Environmental Sciences ISSN 2220-8860 http://www.iaees.org/publications/journals/piaees/online-version.asp 2026 16 4 145 161 International Academy of Ecology and Environmental Sciences Hong Kong 12 April 2026 3 May 2026 1 December 2026 tannery wastewater chromium removal advanced oxidation processes membrane bioreactor sequencing batch reactor zero liquid discharge resource recovery circular economy The tannery industry is a significant contributor to global economic development but also generates highly complex and hazardous wastewater that poses serious threats to aquatic ecosystems and human health. Tannery wastewater is characterized by extremely high concentrations of organic matter, chromium compounds, sulfides, chlorides, sulfates, nitrogenous species, and total dissolved solids. This review provides a comprehensive and critical analysis of treatment technologies for tannery wastewater reported in peer-reviewed literature. Conventional treatment schemes comprising physicochemical pretreatment, biological secondary treatment, and tertiary polishing are examined in detail. Individual unit processes including chemical coagulation-flocculation, various biological systems (activated sludge, sequencing batch reactors, anaerobic digestion, constructed wetlands), membrane technologies (microfiltration, ultrafiltration, nanofiltration, reverse osmosis, membrane bioreactors), advanced oxidation processes (Fenton, photo-Fenton, sono-Fenton, ozonation, photocatalysis), and adsorption techniques are critically evaluated in terms of their removal efficiencies, operational conditions, and limitations. The review highlights that no single technology can achieve complete remediation, and integrated treatment trains combining complementary processes are essential for meeting stringent discharge standards. Particular attention is given to emerging trends toward zero liquid discharge, resource recovery (chromium recycling, water reuse, energy generation), and circular economy principles. Persistent challenges including membrane fouling, sludge management, high salinity, and economic feasibility are discussed. Future research directions emphasizing hybrid systems, novel materials, process intensification, and life-cycle assessment are proposed to guide sustainable tannery wastewater management. http://www.iaees.org/publications/journals/piaees/articles/2026-16(4)/tannery-wastewater-treatment-technologies.pdf