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The impact of ozonation on the reduction of chlorinated disinfection by-products formation was investigated in 15 full-scale and lab-scale drinking water facilities of Québec (Canada). Total trihalomethanes (TTHM) and the sum of six haloacetic acids (HAA6) were measured after chlorination under uniform formation conditions (UFC). Results showed that before ozonation TTHM and HAA6 average concentrations were 89.4 and 45.3 μg/L, respectively. In full-scale ozonation conditions TTHM-UFC and HAA6-UFC reductions averaged respectively 27 and 32%. After lab-scale ozonation at a O3/C of 1:1, a decrease of only 9% of TTHM was calculated, while for HAA6, reduction was not significantly impacted (30%). For BDOC, average concentrations of 0.13, 0.46, and 0.69 mg C/L were measured before and after and lab-scale ozonation, respectively. Chlorine demand (Cl2D) and immediate ozone demand (IOD) were found to be the most appropriate indicators to evaluate NOM reactivity after ozonation. [ABSTRACT FROM PUBLISHER]

There is a renewed interest in predicting RCT following growing evidence that AOP is effective against many emerging contaminants. Five surface waters were investigated to evaluate the OH-radical activity using the RCT concept, predict RCT using traditional water quality characteristics and predict contaminants removal by ozonation and peroxone. It was shown that RCT was dependent on water quality characteristics and could be modeled (R2 = 0.92), using water characteristics and treatment conditions. Predictions of MIB oxidation closely matched the published data of Kawamura (2000) and bench-scale assays performed on one of the water under investigation. [ABSTRACT FROM AUTHOR]

Endotoxins are a component of most Gram negative bacteria, and some cyanobacteria. They may be toxic to humans when inhaled or injected, but the effects are unclear when they are ingested. In fact, low concentrations may protect children against certain allergies. Data for endotoxins in Quebec waters are unavailable, hence this study mapped levels in the waters around Montreal, using two commercial test methods. The recently developed factor C method had a greater linear range and was more convenient to use than the widely used Limulus amebocyte lysate (LAL) method. Although the methods gave endotoxin values of the same order, a consistent relationship between the two could not be established. Endotoxin concentrations in the untreated waters varied from 32 to 1,188 EU/mL, comparable in the literature from pristine waters to wastewaters. Values were generally lower in the summer. Filtration is known to be partially effective at removing endotoxins, but the effects of disinfection are not well established. Accordingly, chlorination, ozonation, and ultraviolet light were tested for the destruction of endotoxins in water, at doses found during drinking water disinfection. While chlorine and ultraviolet light had minimal effects on endotoxin levels, ozone could achieve up to 60% reductions at Ct values (concentration x contact time) as low as 2.5 mg-min/L. [ABSTRACT FROM AUTHOR]

The occurrence of the most prevalent chlorinated disinfection by-products (DBPs) was investigated in three Quebec City distribution systems that deliver drinking water subjected to different treatment strategies. Trihalomethanes (THMs), haloacetic acids (HAAs), and other complementary parameters were monitored in several locations representing variable water residence times over 16 months. The occurrence of chlorinated DBPs levels was considerably lower in the system where raw water is subjected to pre-ozonation instead of pre-chlorination (as pre-treatment) or direct chlorination. Seasonal analysis of the data showed that according to the system and to the group of chlorinated DBPs, the average DBP concentrations in winter were two to four times lower than the average DBP levels of the entire period under study. Considerable variations of both DBP groups were observed according to the water residence time in the distribution system, but the behavior was not the same for THMs as for HAAs. In fact, correlations between THM and HAA levels were good only for cold water and low residence time conditions. Seasonal and spatial variations of DBPs documented in this study have important implications on regulatory issues and from an epidemiological point of view. [ABSTRACT FROM AUTHOR]