Solar-Driven Interfacial Evaporation for Decentralized Direct Potable Reuse of Domestic Wastewater

Abstract

Water scarcity in arid areas requires the exploitation of unconventional water resources like domestic wastewater (DWW). Although direct potable reuse (DPR) of DWW as an alleviation is mature based on membrane and advanced oxidation, it is energy- and carbon-intensive with requirement of well-developed infrastructure. Recently emerging solar-driven interfacial evaporation for sustainable freshwater reclamation has been practiced on seawater desalination but its feasibility of DPR from DWW has not been investigated. Herein, delignified wood (DW) coated by black reduced TiO2 (b-TiO2) as a solar-absorber is presented to conduct DPR from DWW in a solar-thermal system, wherein b-TiO2-DW absorber with anisotropic thermal conductivities enhances sunlight absorption, facilitates thermal concentration at air-water interfaces, and drives DWW evaporation. With the condensation of vapor by ambient temperature, high-quality potable reuse water (PRW) of ~7.65 kg·day-1·m-2-absorber can be produced outdoors under real solar-illumination and satisfy the demand of daily drinking-water for 2-3 persons. The moderate temperature at evaporation interfaces, physical adsorption, and reactive oxygen species by b-TiO2-DW synergistically inhibit conventional and emerging (in)volatile contaminants into PRW and prevent biofouling on absorbers. A life cycle assessment (10-years life-cycle amortization) shows that solar-thermal system has lower cost ($~0.027 kg-1 PRW) and carbon footprint (~0.085kg CO2-eq kg-1 PRW) than current technologies ($0.25-1.14 kg-1 PRW and 0.67-1.17kg CO2-eq kg-1 PRW). Although DPR efficiency of solar-thermal system needs further enhancement, its flexibility indicates a promising scenario for decentralized DPR in undeveloped areas with laggard infrastructures.

Keywords: Direct potable reuse, Potable water, Domestic wastewater, Decentralization, Solar-thermal interface, Water-energy nexus