Anaerobic digestion of Purified Terephthalic Acid (PTA) production wastewater: process overview and metal handling

Purified terephthalic acid production wastewater (PTA-WW) represents a significant industrial challenge, containing both recalcitrant aromatic organics (5-20 kg m -3 of chemical oxygen demand - COD) and high trace metal (TM) concentrations (up to 30 mg L -1 ), particularly cobalt (Co) and manganese (Mn). While anaerobic digestion (AD) is an established treatment technology for such wastewaters, dual challenges of organic compound degradation and micronutrient management have hindered a stable, long-term operation. This comprehensive review synthesizes the current understanding of TM dynamics in AD systems treating PTA-WW or similar matrices, with an emphasis on Co and Mn behavior, speciation, bioavailability, and recovery opportunities aligned with circular economy principles. A systematic literature review has been conducted of peer-reviewed publications from ScienceDirect, Scopus, Web of Science, and Google Scholar, with no temporal restrictions, to identify the maximum relevant literature on PTA-WW treatment, management, and resource recovery. Key findings include bioavailable metal concentrations that influence methanogenic activity (11 mg L -1 Co). The sequential extraction procedure (SEP) indicates that bioavailable pools range from 5-35% of the total accumulated metal, with the remainder being associated and sulfide-bound fractions. Metal recovery technologies demonstrate complementary strengths: alkaline precipitation achieves 90-100 % removal; zeolite adsorption achieves 90-95 % Co/Mn removal while preserving WW COD for downstream AD; magnetic adsorbents enable easy separation but require validation on real PTA-WW. Research gaps include limited direct validation of metal recovery technologies on actual PTA-WW; long-term metal speciation dynamics; the reusability of adsorbents and their valorization pathways in PTA-WW applications; and the lack of techno-economic analyses of integrated recovery-AD systems. Therefore, this review aims to determine whether integrated metal recovery-AD systems for treating PTA-WW offer technically feasible pathways to achieve simultaneous environmental compliance and critical material recovery, thereby supporting both industrial sustainability and global supply chain resilience. • Bioavailable metal comprises 5-35% of total accumulated metals in AD sludge • Cobalt bioavailability occurs 11 mg/L • Zeolite NaA removes 90-100% of Co and Mn while preserving WW COD for AD • Integration of upstream metal recovery with AD may support circular economy