Maximizing Biochemical and Energy Recovery from Wastewater Using Vapor-Gap Membranes

Carbon, nutrients, and heat are available in vast quantities in wastewater. However, technologies that can effectively extract chemicals and energy are needed to realize wastewater as a sustainable resource. Recent advances in wetting-resistant porous membranes, termed vapor-gap membranes (VGMs), have demonstrated that they are well-suited to the facile, selective, and cost-effective recovery of volatile resources and energy from wastewater. In this review, we examine the promise and limitations of VGM-based processes with a particular focus on two types of resources from wastewater: dissolved volatile compounds and low-grade heat. We begin by discussing the driving forces and selective mechanisms required for the extraction of different resources through VGMs. Then, the current status and challenges for the recovery of volatile compounds using VGMs are presented. We also analyze the resource potential of thermal energy in wastewater and its recovery using VGMs. Based on the membrane capabilities, process requirements, and resource availability, we assess the feasibility of wastewater valorization using VGMs and identify the research needs to achieve high recovery efficiency, long-term reliability, and scalability.