Decentralized Encapsulated Anaerobic Biological Treatment System for Resource Recovery from High-Strength Wastewater: A Pilot Study

Transitioning water-intensive food and beverage industries toward energy-positive yet profitable wastewater management requires enhanced anaerobic treatment for resource recovery. We developed an encapsulated anaerobic biological treatment system and tested it at pilot scale, with the goals of recovering methane (CH4) in a low-maintenance, small-footprint system. A single-stage and a two-stage system, each with biomass encapsulated in polyethylene glycol beads, were compared with respect to soluble chemical oxygen demand (sCOD) removal and gas production during continuous operation at hydraulic retention times (HRT) of 3, 7, and 13 days at ambient temperature. Over the 289-day experiment, sCOD removal averaged 84 ± 18% and 86 ± 14% for the single-stage and two-stage systems, respectively. Gas production varied with HRT and temperature, with an average CH4 percent of 74 ± 8% for the single-stage system and 76 ± 8% for the two-stage system. An active gas extraction module was briefly implemented on the first-stage reactor of the two-stage system, with no clear auxiliary benefits to overall system performance. The excellent performance of both systems can be attributed to the high concentration of biomass that was retained in the reactors. Future research to advance additional pilot-scale tests and full-scale deployment is recommended.