Polymers in Potable Water

Figure 2 Synthetic scheme for a water-insoluble Whalamine polymer disinfectant for use in potable water sanitization.

Water [83] Detection of different stages of differentiation of Streptomyces in potable water 14 conducting polymers... 

There is a demand for non-toxic flocculants for use in potable water treatment and similar applications. The toxic component of polymers is the residual acrylamide monomer content. To enable a formal classification of low toxicity, the acrylamide content must be 0.025% or less for use in most European countries (0.05% in the USA). Some standard polymers meet this requirement, but extra work, and thus extra cost, is required to provide the certification and enforce the quality control. 

Conducting polymers have been demonstrated to be an important material for electronic nose apphcation. Demonstration of their properties has been provide in the assessment of seafood freshness, the detection of streptomyces in potable water, and the quality of ohve oils. ... 

Anionic and nonionic polyacrylamides effectively remove suspended soHds such as silt and clay from potable water. SuppHers provide special grades which meet EPA/FDA regulations for residual acrylamides. A recent pubHcation (102) states that hydrolyzed polyacrylamides with narrow interchain charge distributions provide better performance in flocculation of clay. These polymers were prepared by alkaline hydrolysis. (See Flocculating agents.)... 

Most of water-soluble acrylamide polymers find practical applications as highly efficient flocculents for clarification and treatment of potable water and municipal and industrial effluents and in the mining, papermak-... 

NOTE The same polymer chemistries employed in the BW deposit control treatment market sector are also made available to other markets such as waste water, cooling water, potable water production from brackish or saline supplies, metal finishing, paint and coatings, electronics, pulp and paper, and more. 

Until 1990 the EPA maintained a list of chemicals suitable for potable water treatment in the United States. Since then the entire question of certification and standards has been turned over to a group of organizations headed by the National Sanilalion Foundation, which has issued voluntary standards. As of January 1992. standards had been issued for most of the principal inorganic products, hut only for three polymers, polytDADMAC). Epi-DMA (epichlorohydrindimethylamine) polymers and polyacrylamide. Certifications for commercial products meeting specified standards are issued by Ihe National Sanitation Foundation. Underwriter Laboratories, and Sab Water Addilives Institute (SWAI),... 

A variety of reverse osmosis membrane systems based on cellulose acetate, aromatic polyamides, and other polymers have been tested for their potential applications. Reverse osmosis membrane equipment is available for large-scale operation since the process is widely used for the production of potable water from sea or brackish waters and upstream of ion exchange in the preparation of ultrapure water for steam-generating boilers. In these applications, the feed concentrations may vary from 500 to 40,000 mg/L of dissolved solids. The RO technique can be used at pH values between 3 and 12 and up to 45°C. 

Membrane research and development started in Du Pont in 1962 and culminated in the introduction of the first B-9 Permasep permeator for desalination of brackish water by reverse osmosis (RO) in 1969. The membrane in this B-9 Permasep module consisted of aramid hollow fibers. In 1969, proponents of RO technology had ambitious dreams and hopes. Today, RO is a major desalination process used worldwide to provide potable water from brackish and seawater feeds. Du Font s membrane modules for RO are sold under the trademark Permasep permeators. The RO business is a virtually autonomous profit center that resides in the Polymer Products Department. The growth and success of the Permasep products business is a direct result of Du Font s sustained research and development commitment to polyamides, a commitment that dates back to the 1930 s and the classic polymer researches of Wallace H. Carothers. Since 1969, improved and new Permasep permeators have been introduced six times, as shown in Table I. 

Peter Teasdale, Ph.D., is a senior lecturer in environmental chemistry at Australian Rivers Institute, Griffith University Gold Coast Campus. His current research interests include in situ sensors for metals and nutrients, natural, recycled and potable water quality, microbial toxicology, and sediment biogeochemistry. Peter is the current chair of the Royal Australian Chemical Institute Environment Division. He has published over 40 refereed publications. Coauthoring this book reflects his interest in the field of conducting electroactive polymers, the area in which he completed his Ph.D. in 1993 at the University of Wollongong. 

Poly(diallyldimethylammonium chloride) was the first quaternary ammonium polymer approved for potable water clarification by the United States Public Health Service, and has historically been the most widely produced cationic polyelectrolyte. There have been several studies on the kinetics (26-37) and uses of diallyldimethylammonium chloride (DADMAC) (38-45) however, there have been no investigations in inverse microsuspension, the most common industrial method of polymerization. Furthermore, there is considerable disagreement between published reactivity ratios, probably because no satisfactory analytical methods have been described in the literature for residual monomer concentration or copolymer composition. For other commercially important quaternary ammonium polymers, such as dimethylaminoethyl methacrylate and dimethylaminoethyl acrylate, few kinetic data are available (46-51) only Tanaka (37) measured the reactivity ratios. 

Polymers of many chemical compositions are used to make materials and composites for use in appliances, electrical equipment, telecommunications equipment and fiber optics, computers, aircraft, aerospace, automobiles, food and beverage packaging, potable water delivery systems, and medical devices, to name a few applications. Adequate knowledge of the polymer structure and its relationship to the performance of these polymeric materials is crucial to their successful use. NMR is extremely useful in polymer characterization. and are the elements most commonly examined, followed by Si, and N. NMR can be used to determine the monomer sequence, branching,... 

Certain anionic polyacrylamides are approved by the U.S. Environmental Protection Agency for clarification of potable water. Polymer treatment also allows filters to operate at higher hydraulic rates. The function of clarification is not explained by a simple mechanism. The long-chain linear polymer apparently functions to encompass a number of individual fine particles of the dispersed material in water, attaching itself to the particles at various sites by chemical bonds, electrostatic attraction, or other attractive forces. Relatively stable aggregates are thus produced, which be removed by filtration, settling, or other convenient means. 

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