Chlorine tolerant reverse osmosis membranes

Sulfonated polysulfone reverse osmosis membranes are unique in the market that is wholly dominated by the polyamide thin film composite membranes that have been in the market since the 1980's. Chlorine bleach or sodium hypochlorite is ubiquitous in the water industry as it is a highly effective and inexpensive oxidizing biocide. Today's polyamide membranes are known to be damaged by even low levels of chlorine bleach. This is a problem for reverse osmosis systems because they suffer from biofouling that can drive an average of 25% of operating costs. Mitigation of biofouling often involves higher capex also, in the form of additional pre-filtration, cleaning, and redundant operations. NALA's new offering is the most chlorine stable, durable, and low fouling membrane available and it is being applied first in high intensity industrial wastewater. These ionic membranes reject salts and organics with particularly excellent rejection of divalent ions such as calcium and sulfate salts. Rapid cleaning of fouled membranes can be accomplished with concentrated hypochlorite (examples using 2% or more have been demonstrated), acids, and bases. Industrial wastewater from textile, brewery, agriculture processing, and machining operations have been treated effectively using NALA membranes. In one example, a concentrated stream from a zero liquid discharge process at a textile facility that previously was sent to a thermal evaporator is filtered using NALA membranes to reduce the volume going to the thermal evaporator by 70%. Opportunities in oil and gas, power, mining, and electronics industries are being pursued to demonstrate the opportunity to save operating costs and the potential for capital cost savings.