Full Description

Natural organic matter (NOM) is important in drinking water treatment because of its potential to react with chlorine to form disinfection byproducts (DBPs), which may have adverse health effects. Enhanced softening might be able to remove natural organic matter (NOM) and decrease DBP formation; however, it has received inadequate research attention. The objective of this research was to evaluate the impact of different conditions of softening on NOM removal and subsequent DBP formation. Jar tests were performed on five source waters (Austin, TX; St. Louis, MO; Ft. Lauderdale, FL; Sioux Falls, SD; and Omaha, NB), using covered jars to prevent CO2 transfer. Sioux Falls water was collected twice, in December and again in May during the spring snow melt when the dissolved organic carbon (DOC) is high. These waters represent a broad spectrum of hardness and NOM conditions among waters that are softened. A variety of operating scenarios were tested, including lime softening alone, lime softening with various chemical additions, and lime softening with sludge recycle. Softening, NOM, and DBP parameters were measured. Softening parameters included pH, Ca+2, Mg+2, and alkalinity. NOM parameters included DOC, ultraviolet absorbance at 254 nm (UV254), and SUVA (UV254 normalized by the DOC concentration). Samples were chlorinated using softening uniform formation conditions (SUFC), a standardized chlorination procedure identical to UFC5 but at pH 9 instead of pH 8, as appropriate for softening plant effluents. DBP parameters included dissolved organic halides (DOX) and 21 specific DBPs: four trihalomethanes (THMs), nine haloacetic acids (HAAs), four haloacetonitriles (HANs), two haloketones (HKs), chloropicrin (CP), and chloral hydrate (CH). Includes 5 references, figures.

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Edition: Vol. - No. Published: 06/16/2002 Number of Pages: 9File Size: 1 file , 430 KB