Low-cost recycled end-of-life reverse osmosis membranes for water treatment at the point-of-use

Abstract

Decentralized systems applied at the point-of-use (POU) could be an alternative for a safe drinking water supply in isolated regions and developing countries. Based on that, it was investigated the recycling of end-of-life reverse osmosis (EoL-RO) household modules as an alternative for groundwater treatment at the POU. The membranes were recycled through chemical oxidation using NaOCl (440,000 ppm h) and were validated in a long-term operation. The systems operated in a dead-end configuration mode without external energy requirements for permeation, only the hydraulic force provided by the water grid. The increase in permeability from 4.5 to 50.4 L/m2h.bar and decrease in salinity rejection from 99.4 to 11.6% suggests that the EoL-RO was effectively converted to ultrafiltration (UF). The recycled membrane still presented a lower resistance to filtration due to its porous characteristics (average pore size 0.04 ± 0.01 μm). In the perspective of POU application, the lower energy requirement for the recycled membranes compared to EoL-RO would represent advantages if compared to reverse osmosis household modules, more energy-demanding filters. Effective water treatment and a low fouling propensity were observed for long-term operation at the POU. The monitoring data demonstrates a steady permeate flux (21.2 ± 0.46 L/m2h) and filtration resistance (6.37 ± 0.16 × 1014 1/m), producing a total permeate volume (3,000 L) comparable with commercial filtration systems and in compliance with the 109 potability standards analyzed. From a broader perspective, the advantages of using recycled membranes could be extended to environmental aspects, preventing the production of waste from spent membranes and focusing on cleaner production of technical processes.