Soluble Organic Matters Recovery from Municipal Wastewater: Activated Carbon Adsorption and Volatile Fatty Acids Generation via In Situ Alkaline Anaerobic Fermentation

Abstract

Conventional carbon redirection strategies poorly utilize soluble organic matter (SOM). This study proposes an innovative integrated method featuring activated carbon (AC) adsorption, followed by desorption and in situ alkaline anaerobic fermentation, for SOM valorization into volatile fatty acids (VFAs). Among the evaluated materials, 7# AC exhibited the most promising performance due to its unique pore size distribution and balance between adsorption and subsequent processing. In synthetic wastewater trials, alkaline conditions (pH 10.0–12.0) enhanced desorption (15.9–58.1% recovery). Crucially, integrating desorption with in situ fermentation at pH 11.0 propelled the recovery rate to 89.8% (127.3 mg VFA/g chemical oxygen demand [COD]). In real municipal wastewater treatment using 7# AC, a 3 h adsorption period was sufficient to reach equilibrium, achieving a cumulative capacity of 299 mg COD/g over multiple cycles. Subsequent desorption and in situ alkaline fermentation at pH 12 yielded 113.0 mg VFA/g COD. This integrated approach was robustly verified using synthetic and real wastewater, demonstrating stable performance in SOM recovery and VFA generation, which provides a concrete experimental basis for sustainable organic resource recovery from municipal wastewater.