Predicting chlorine decay and THM formation in water supply systems

Abstract

In 1976, the US Environmental Protection Agency (USEPA) published the results of a national survey that showed that chloroform and other trihalomethanes (THMs) were ubiquitous in chlorinated drinking water. Also in 1976, the US National Cancer Institute published results linking chloroform to cancer in laboratory animals, thus giving rise to an important public health issue. Although numerous disinfection by-products (DBPs) have been reported in the literature since that time, with more than 700 confirmed species to date, only a small number have been addressed in either quantitative or health effects studies. The DBPs that have been quantified in drinking water are generally present at low to mid lg/ l levels or below. Approximately 50% of the total organic halide (TOX) formed during the chlorination of drinking water and more than 50% of the assimilable organic carbon (AOC) formed during ozonation of drinking water is still not accounted for and little is known about the potential toxicity of many of the vast number of DBPs present in drinking water. The presence of free chlorine is a prerequisite to THM formation. Therefore, a robust understanding of the mechanisms of both chlorine decay and THM formation are fundamental to the management of THMs in water supply systems. This paper presents a review of work undertaken to improve our understanding of these key phenomena and highlights areas of vulnerability in our knowledge and so recommends areas of future research.

Seasonal and spatial evolution of trihalomethanes in a drinking water distribution system according to the treatment process

“…In addition to the direct effects of temperature, seasonal variations in the characteristics and 308 composition of organic precursors have also been found to be significant (Brown et al 2011 …”

“…In addition to the direct effects of temperature, seasonal variations in the characteristics and 308 composition of organic precursors have also been found to be significant (Brown et al 2011). The THM occurrence in 309 urban distribution systems is highly variable with the ambient temperature, but also with the localization.…”

Contact Tank Design Impact on Process Performance

“…Table 1 summarises the mathematical models used to compute: chlorine decay, pathogen (Giardia lamblia) inactivation and by-product (total trihalomethanes -TTHM) formation during the disinfection process. The general form of the source terms for both the disinfectant decay and by-product formation is detailed in Brown et al, [10,11], with further information available in associated studies (e.g. [9,38]) guiding the selection of appropriate model inputs (Table 1).…”

“…Empirical chlorine decay model based on the experimental findings of Brown et al [9] Brown et al [10], Brown et al [11], Brown et al [9], Angeloudis et al [5], Angeloudis et al [7] Model input:…”

Characterization of dissolved organic matter for prediction of trihalomethane formation potential in surface and sub-surface waters

“…Besides organic matter, the physical and chemical factors of water also influence the formation of THM. These include bromide (Br) ion concentration, pH and temperature [26].…”