Anaerobic digestion of recalcitrant organics and emerging contaminants in pharmaceutical wastewater for carbon neutrality and bioresource recovery: A critical review.

Pharmaceutical wastewater is characterized by complex composition, high toxicity, and a high proportion of recalcitrant organics. Conventional treatment processes, such as the activated sludge process, often suffer from high energy consumption, substantial carbon emissions, and limited resource recovery. To address the challenges posed by recalcitrant organics and emerging contaminants in pharmaceutical wastewater, this review critically examines advanced anaerobic digestion technologies and their applicability to pharmaceutical wastewater treatment, with an emphasis on energy-efficient and low-carbon strategies. The review summarizes key enhancement approaches, including material intensification, co-digestion, bioaugmentation, intelligent control systems, and hybridization with complementary processes (e.g., physicochemical pretreatment, advanced oxidation processes, and anammox-based technologies for nitrogen removal), which may synergistically improve the removal of recalcitrant organics and emerging contaminants. This review provides insights into the future development of sustainable biotechnologies for carbon-neutral pharmaceutical wastewater treatment and offers a technical reference for pollutant removal, bioenergy recovery, and carbon reduction.