Gravity-driven ultrafiltration and nanofiltration recycled membranes for tertiary treatment of urban wastewater

Abstract

Water scarcity push towards increased number of desalination plants which suppose an exponential increase of end-of-life (EOL) reverse osmosis (RO) membranes. This research is focused on converting EOL RO membranes into ultrafiltration- (UF-like) and nanofiltration-like (NF-like) membranes to be used as tertiary treatment for water reuse. Converted UF- and NF-like membranes were installed in a gravity driven membrane (GDM) setup. The system was fed with secondary effluent of an urban wastewater treatment plant (WWTP) in Girona (Spain), operated during 6 weeks with a driving force of 0,184 bar, applying daily membrane flushing and, chemical cleaning after 2-3 weeks of operation. UF-like membrane achieved permeabilities of 12,2 and 8,8 L·m−2·h−1·bar−1 pre- and post-chemical cleaning respectively. NF-like membranes demonstrated also to be of interest for GDM systems, achieving permeabilities of 2,2 and 3,4 L·m−2·h−1·bar−1 pre- and post-chemical cleaning respectively. High permeate quality was obtained with turbidity rejection above 87,2 % and Escherichia coli (E. coli) Logarithmic removal value (LRV) of 4 and 5 for UF-like and NF-like membrane respectively. UF-like and NF-like membranes installed in a GDM system allowed to produce recycled water in accordance with Real Decreto 1620/2007 positioning it as a low-cost, and compliant solution for water reuse applications