Recycled RO Membrane Performance Evaluation on Tap Water, ICW, and MBR Permeates; an Approach Towards the Circular Economy in Desalination

Abstract

The unprecedented spike in the RO spiral wound membranes generation reached 93.5 % for the desalination purpose in the world in 2020. Due to this exponential growth, annually 14,000 tons of RO membranes are discarded and ended up in landfills. The current study aims to convert the end-of-life RO membrane using chemicals, followed by its performance evaluation on water from 3 different sources i.e., tap water (TW), integrated constructed wetland permeate (ICW-P), and membrane bio-rector permeate (MBR-P) respectively. For this, 06 years spent Filmtech (LC-LE-4040) BWRO membrane was selected, then alkaline cleaning was done, followed by acidic cleaning both for 2 h and the final step of conversion with 6 % sodium hypochlorite (NaOCl) with 300,000 ppm/h exposure by the active system (AS) using the clean in place (CIP) pump at 2 bars for 10 h duration. The recycled RO demonstrated a water recovery of 67 % for TW, 68 % for ICW-P, and 74% for MBR-P respectively and consistent saltwater rejection of <1 % was observed. While R-RO exhibited an effective COD removal % of 65.79 %, 62.96 %, and 67.72 % in TW, ICW-P, and MBR-P respectively, and the highest turbidity removal of 96% in the ICW-P was observed. The MPN (most probable number) showed >23 CFU/100 ml in the feed of all 3 sources and complete removal of total coliforms after passing through R-RO was observed. These features made R-RO an excellent choice for drinking water treatment and domestic wastewater post-treatment. This solution can help to develop nations, be efficient in resource recovery, and contributes in the circular economy.