Dow has introduced a series of water treatment polymers, aiming to prevent scaling or fouling on reverse osmosis (RO) membrane surfaces and hard water scale in industrial, commercial, institutional and public water systems.
The figure demonstrates the compatibility of inhibitor to brine containing high levels of calcium. The x-axis indicates concentration of Ca2+ in ppm while the y-axis indicates transmittance generated when an inhibitor precipitates to create a turbid solution. Somil Mehta, technical service and development manager at Dow Energy and Water Solutions, explained, “As filtered water is separated, the impurities from source water gets concentrated in remaining brine, leading to scaling or fouling of RO membranes. Such scaling reduces the performance of operation, increase operating costs and eventually lead to plant shutdowns for cleaning.” Inorganic salt precipitation is called scaling, whereas organic and inorganic or biological deposition is called fouling, which result on membrane surface during its operation. “Thus increased demand for RO with varied source conditions is creating an increased demand for controlling scaling or fouling, the answer to which is Antiscalants and Dispersants,” Mehta stressed. Antiscalants are chemical agents that act by delaying the inorganic salt precipitation from supersaturated brine, whereas dispersants keep particulates dispersed to avoid fouling. Mehta further described that there is a trend of moving away from environmentally harmful phosphorous (P)-based reagents, which cause eutrophication in water bodies upon discharge resulting into harmful effects on aquatic bodies. He said that Dow’s low molecular weight polymers are based on acrylic chemistry backbone and free of phosphorous (P) containing species. These are branded as ACUMER™ Antiscalants, which focus on increasing the recovery rate and decreasing feed water use for given volume of pure water production, avoiding channelling for better utilisation of RO membranes, offering considerable savings in water and energy requirements and reducing the levels of chemicals needed for pre-treatment. Dow’s ACUMER 4450 is a calcium scale inhibitor that is tolerant to high calcium levels observed under high stress conditions. It’s general purpose ACUMER 4035 aims to take care of conventional scaling systems. Mehta added that the company is developing Antiscalant targeted in particular high stress conditions, aiming to help end users achieve higher recovery in RO operations by pushing the limit for amount of silica present in water.