The growth in the size and complexity of municipal and potable water treatment facilities demands innovative, durable cost-saving water purification solutions. Whether the need is for a large seawater desalination facility or for a municipality that needs to tap lower quality surface water sources to meet expanding needs, Dow Water & Proccess Solutions can assist your efforts with our selection of RO, NF, UF, ion exchange and specialty media suitable for drinking water applications.
The successful sourcing of high-quality drinking water is becoming more challenging as localized demands for higher volumes of clean water stress both the sourcing sites and infrastructures needed for delivery. As new water sources are tapped strategies to deal with a variety of potential contaminants ranging from various biological pathogens, to organic chemicals like pesticides and herbicides, and a variety of inorganic due to the geology of a region or man's activities.
Most municipal sites are required to meet a minimum regulated standard of quality and composition for the water that is supplied to the public. Such Regulatory Standards or "rules" may be based upon an international standard such as the World Health Organization-Drinking Water Standards (WHO), against a national standard like the U.S. Environmental Protection Agency-Code of Federal Regulations (EPA) or state/regional standards such as the U.S. State of California Department of Public Health-Division of Drinking Water and Environmental Management (CDPH).
Although regulations are set at the international or national level they are enforced at the regional or local level. To assist with your targeted application needs defining the water quality of your source waters as compared to the needs of water to be supplied to the end-user is essential to understanding what specific challenges you face. Dow Water & Process Solutions Water Solutions can address a variety of needs with a wide range portfolio of products backed with application know-how.
Potable Water Applications
ARSENICADSORBSIA™ titanium-based media from Dow Water & Process Solutions is available in North America to help municipalities comply with the U.S. Environmental Protection Agency regulations. ADSORBSIA™ As600 is an easy to use granular titanium oxide with strong affinity for arsenic, lead and other heavy metals. This distinct media is designed for non-regenerative applications. The inherently high adsorptive capacity of Dow Water & Process Solutions’ titanium oxide based technology has been formulated into a mechanically stable granulation suitable for use in a broad range of potable water applications. When exhausted, it is removed from the vessel and replaced with new media. |
ASBESTOS FIBERSThe decay of asbestos cement in aging water mains and the erosion of natural deposits in some regions have resulted in needs to remove asbestos fibers that are greater than 7micrometers. One option is by applying the DOW™ UF SFD 2880 module to filter out the undesired asbestos fibers. |
BORONNaturally occurring, Boron appears in an oxidized form as boric acid and its salts. Boric acid is a very weak acid and acts much like silicate so it is difficult to remove from water. It has a very low selectivity for an anion exchange resin, so resin capacity will be limited by the presence of other anions. Borate is a very "weakly held" anion so non-selective methods must remove all other anions before they will remove the borate. The more economical option is to selectively remove borate with DOWEX™ BSR-1/AMBERLITE™ PWA-10. The selective removal of boron (B) is accomplished by a reversible chelating mechanism that allows the removal of B to very low levels. |
CHROMIUMChrome contamination of drinking water usually takes the form of Cr (III) or Cr (VI) (also known as hexchrome). Cr (VI) is an anion so it can be selectively removed from drinking water with AMBERLITE™ PWA-7 for high selectivity and loading capacity on non-regenerated bases. Because of very strong binding of Chrome, it can be difficult to regenerate thus for regenerated systems an acrylic weak base like AMBERLITE™ PWA-8 or a Type II strong base anion exchange resin like DOWEX SAR are simpler to regenerate. |
MICROORGANISMSProtection from water-borne pathogens like Cryptosporidium, Giardia and other microbes that can make individuals sick in the short term is a key requirement for drinking water providers. As more water is sourced from surface water or groundwater that is under the influence of surface water, while at the same time some locations are looking to reduce the levels of disinfection chemicals other routes for pathogen control are being met via filtration. The physical removal of microorganisms by Ultrafiltration (UF), particularly those like cryptosporidium which is somewhat resistant to primary disinfection practices such as chlorination and chloramination. |
NATURAL ORGANIC MATTERNatural Organic Matter (NOM) in surface water usually refers to humic and fulvic acids that are decayed by-products of plants such as those found in surface waters shallow well aquifers. AMBERLITE™ PWA-9 and the innovative very wide pore resin designated DOWEX™ TAN-1 should be consider for your NOM removal needs. These resins can help reduce color, trihalomethanes (THM’s) and other similar disinfection by-products (DBP’s) that can be formed during chlorination processes. |
NITRATE/NITRITENitrate and nitrite are the most common nitrogen contaminants of drinking water. Since anion exchange resins are generally more selective for sulfate over nitrate, the capacity of a resin for nitrate removal will be limited by the concentration of sulfate. If the ratio of sulfate to nitrate is low, a high capacity resin like DOWEX™ 1 is recommended. If the ratio of sulfate to nitrate is high, a nitrate selective resin should be considered like DOWEX™ NSR-1/AMBERLITE™ PWA-5 resin. These resins can be regenerated using NaCl. In regions where brine waste handling is of issue, the Advanced AMBERPACK™ Municipal can help reduce NaCl waste levels. |
PERCHLORATE REMOVALPerchlorates (ClO4-) are man-made chemicals used in munitions and rocket propellants. They are highly soluble in water so they can be widely found in groundwater due to their high mobility. Once dispersed ClO4- can remain in the environment for decades as it does not readily degrade. The use of the DOWEX™ PSR-2 to bind and remove ClO4- at the ppb levels as a non-regenerated media is proving to be an effective remediation strategy. |
PESTICIDE/ORGANIC REMOVALDOW™ FILMTEC™ nanofiltration (NF) membranes have a pore size in the order of nanometers (10 angstroms). Dow offers a portfolio of nanofiltration membranes that can remove organics with molecular weights greater than 200 (e.g., Total Organic Carbon (TOC) and disinfection by-products) while allowing varying amounts of salt and hardness passage. These NF elements can remove organics like atrazine while still allowing for a minimum level of hardness passage for organolepic properties and the preservation of distribution networks. |
RADIONUCLIDES/RADIUMRadium exists as a divalent cation in groundwater, so processes that remove water hardness components like calcium and magnesium are effective. Radium can be non-selectively removed from groundwater via standard cation exchange resins such as DOWEX™ MARATHON™ C (Na) strong acid cation exchange resin. Dow Water & Process Solutions manufactures a distinct ion exchange product designated as DOWEX RSC resin that is extremely effective at removing radium and barium from drinking water. DOWEX™ RSC does not remove other water hardness ions. The RSC resin is not regenerable and it concentrates the radium into a small volume for economical disposal. |
SELENIUMSelenium can be selectively removed with ADSORBSIA™ As600 arsenic removal media due to the chemical similarities of selenium and arsenic. ADSORBSIA has an excellent capacity for Se (IV) (selenite) while Se (VI) (selenate) is not removed. |
SOFTENINGWater softening can be approached via a standard ion exchange process using NaCl regeneration and a number of available resins. Waste volumes can be minimized using Dow Water & Process Solutions’ Advanced AMBERPACK™ Municipal system. Or membrane softening can be considered as Dow Water & Process Solutions offers DOW™ FILMTEC™ nanofiltration elements for use as an alternative to lime softening of public drinking water supplies. Membrane softening reduces hardness and removes organics, color and other impurities from raw water. The durable NF 270-400 element is a good starting point membrane softening applications. |
SULFATESulfur oxides as sulfuric acid, sulfate and sulfite are anions and readily removed with anion exchange resins. For potable water at neutral pH, a high capacity strong base anion exchange resin like DOWEX™ 1 is recommended. |
URANIUMUranium in the uranyl (UO2) can be removed from drinking water with a type I strong base DOWEX™ 1 type resin or with the AMBERLITE™ PWA-8 weak base resin. |
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