Membrane-based hybrid systems incorporating nanomaterials for wastewater treatment

Membrane separation is emerging as a key technology in wastewater treatment solutions particularly where high quality of treated water is targeted. Wastewaters from industrial processes are complex and based on the constituents, a combination of physico-chemical-biological steps are used to comply with discharge standards. Domestic wastewaters are also increasingly contaminated with recalcitrant (difficult to biodegrade) components such as pharmaceutically active compounds and personal care products. To improve industrial water security and meet zero liquid discharge norms (where applicable), there is growing interest in options that lead to (1) treated wastewater of suitable quality that can be reused/recycled on-site and/or (2) recovery of resources (chemicals, etc.) that can be reused in the production process. Resource recovery and removal of emerging contaminants in domestic wastewaters is also becoming a priority. Consequently, hybrid processes comprising membrane technologies integrated with other treatment steps have been developed. Biological treatment is combined with microfiltration/ultrafiltration/nanofiltration/forward osmosis in membrane bioreactors for wastewater reclamation. To enhance removal of recalcitrant compounds, adsorption and catalysis have been employed. Other membrane processes such as reverse osmosis membrane distillation, and electrodialysis have been coupled with MBRs for tertiary treatment. Nanomaterials-based membrane systems have evolved aiming to enhance overall performance, e.g., higher flux (flow rate per unit membrane area), higher removal of targeted contaminants, and lower membrane fouling. This chapter provides an overview of state of the art and challenges in nanomaterial-based membranes and corresponding hybrid treatment systems.