Improving Energy Efficiency and Increasing Water Yield During Membrane Treatment

Drinking water and wastewater reclamation treatment uses low-pressure membrane filtration, such as microfiltration and ultrafiltration, because it provides superior and consistent water quality compared with traditional filtration. However, membrane treatment processes are energy intensive. This intensity is largely because of the fouling of the membrane over time that impedes water flow, increases energy usage to pump water through the membrane, increases chemical costs to remove foulants, and reduces membrane life. The novel membrane evaluated in this pilot study incorporated amphiphilic, anti-adhesive polymers — which are composed of hydrophilic ("water-loving") and hydrophobic ("water-hating") parts — to slow deposits organic and mineral foulants. These materials theoretically allow for higher water flow through the membranes, increased water yield, and improved energy efficiency. The purpose of this study was to determine the technical and economic potential of the proposed technology and generate recommendations to address any identified issues.
The pilot demonstration performed at California Water Services Bakersfield Treatment Plant indicated that using the amphiphilic membrane could minimize membrane fouling and promote energy efficiency, but that differences in water source or quality affect the extent of performance improvements. The project demonstrated reductions in transmembrane pressures by up to 20 percent, cleaning frequencies by as much as 74 percent, and cleaning effectiveness by as much as 94 percent. The technology reduced overall energy use under all pilot testing conditions by around 6 percent, equivalent to a potential statewide energy reduction of 3.5 gigawatt-hours per year. Unfortunately, chemical degradation of the membrane surface that occurred during testing indicated that further manufacturer work is needed to evaluate special chemical resistance specifications and cleaning protocols that may differ from their other membrane offerings. Pilot testing results suggest that the ultrafiltration membrane module used in this project has potential benefit but is not yet market-ready.