The water purification process being demonstrated at the City of San Diego’s Advanced Water Purification Facility uses the multi-barrier approach of consecutive treatment steps — Membrane Filtration, Reverse Osmosis & Ultraviolet Disinfection/Advanced Oxidation –which work together to remove or destroy unwanted materials. Each barrier includes frequent and continuous water quality monitoring. Safeguards are built into the process to ensure that an error at any given treatment step would not compromise public health.