Modeling of hollow fiber membrane contactors (HFMCs) for the recovery of dissolved methane from anaerobic effluents

Abstract

Anaerobic treatment of wastewater from various sources is becoming increasingly popular as it can convert 73% of the chemical oxygen demand present in the wastewater to biogas. Methane in the biogas is the major contributor to produce energy in subsequent downstream processes. However, a significant amount of methane usually escapes to the environment through the treated effluent. This study proposes a model that can predict the recovery of dissolved methane and other performance parameters from the effluent of an anaerobic reactor using porous and dense hollow fiber membrane contactors (HFMCs) for the pilot- or large-scale application. The model introduced a distribution factor, m, to the liquid mass transfer coefficient to fit the experimental removal of dissolved methane and the methane desorption flux, JCH4, through the HFMCs. The factor m was found to have a linear relationship with the average JCH4. Further, it was found that a net energy gain of 0.34 MJ·m-3 (0.024 MJ·kg-1CH4 for 16 mg·L-1 dissolved methane in the feed) is achieved for an effluent flow rate of 11 m3·d-1, with a methane content of 35% recovered from the HFMC. A break-even payback period will be attained when multiple modules of HFMC are used. The model provides simplified investigation of the potential and effectiveness of the HFMCs for dissolved methane recovery from anaerobic effluent, with further verification using data from pilot- and large-scale systems.