Potable water, residues

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.)... 

Magnitude of the residue in potable water, fish, irrigated crops Magnitude of the residue in food handling estabHshments... 

The mobility of slowly degradable compounds or persistent metabolites present in surface water or bank filtration-enriched ground water is of particular concern in the production of potable water. Certain surfactants, and especially their polar metabolites among others, have the potential to bypass technical purification units used, which may include flocculation, (active charcoal) filtration, ozonation or chlorination. As such, these compounds can reach drinking water destined for human consumption [4-6]. In most cases the origin of surfactant residues and their degradation intermediates in raw water is from wastewater treatment plant (WWTP) effluents (see Chapters 6.1 and 6.2) or direct emissions of wastewater, with the latter still common in many less developed countries. 

Sandhu SS, Warren WJ, Nelson P. 1978. Pesticidal residue in rural potable water. Journal of the American Water Works Association 70 41-45. 

SungW. 1985. Residual aluminum in potable water. Technical completion report. University of New Hampshire, Water Resource Research Center, Durham, NH. Project Number G856-05. NTIS No. PB85-214963. 

Mosinska [106] has described a semi-quantitative thin layer chromatographic method for the determination of trichlorphon in potable water. The sample is extracted with redistilled chloroform. The extract is dried with sodium sulphate, reduced in volume to 5mL in vacuo and then evaporated to dryness in a stream of air. The residue is dissolved in acetone and chromatographed on chloride-free silica gel G plates (activated at 100°C for lh) with benzene-methanol (17 3) as solvent. The spots, revealed with ammoniacal silver nitrate in acetone, are compared with those of standards for semi-quantitative determination. The detection limit is 0.02mg L 1 and the efficiency of extraction is 70%. 

This chapter only discusses the applications of chlorination and chloramination in potable water treatment. In case the two processes are to be used for wastewater treatment, residual chlorine concentration in the plant effluent may become a regulatory issue (30). Selection of an alternative disinfectant becomes more important. New alternative disinfectants have been studied by Wang (19-25). Wang (35,36) also reported that UV is an effective process for dechlorination, dechloramination, or de-ozonation. 

Free chlorine is highly reactive and relatively unstable. Utilities using free chlorine for disinfection have been known to use secondary chlorination stations to maintain residual chlorine concentrations in the potable water distribution system as regulated by the Clean Water Act (CWA). One of the key concerns in using free chlorine for disinfection is that, under certain conditions, free chlorine may react with organic substances in water to form carcinogenic trihalomethanes (THMs) (1,2). 

Chemical oxidizing agents have been used for the control of organic residues in wastewaters and in potable water treatment. Among the organics for which oxidative treatment has been reported are aldehydes, mercaptans, benzidine, and unsaturated acids. For these applications, sodium hypochlorite, calcium hypochlorite, potassium permanganate, and hydrogen peroxide have been reported as effective oxidants. In one application nitrous acid was used. 

For some water reuse applications, activated carbon may be employed to adsorb 90 to 98% of any residual degradation-resistant organics when necessary. The resultant effluent quality is adequate for many industrial coolant or irrigation applications. After minimal further treatment, such as by reaeration and chlorination, it could even be reused for potable purposes in an emergency [55]. However, not enough is known about the potential for accumulation of trace toxins to recommend this procedure for long-term potable water use. 

When used for the production of potable water, ozone kills bacteria as effectively as chlorine. It kills and deactivates viruses far more thoroughly than chlorine. In addition, it oxidizes residual organic contaminants that are difficult to remove by conventional processes. Paris, France has used ozone treatment for many years. It allows them to convert contaminated Seine river water to high quality drinking water. 

Contents indude chlorine manufacture, properties, hazards and uses, hypochlorination. onsite generation, chlorine residuals, potable water and wastewater chlorination, facility design, dechlorination, operation and maintenance, chlorine dioxide, ozone, peroxone andAOxPs, bromine, iodine, and ultraviolet... 

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. 

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