Abstract:
The surrogates (e.g., Escherichia coli) commonly used to monitor drinking water treatment are useless indicators of ozonation efficiency, as they are too sensitive to oxidants. Therefore, alternative indicators have been proposed (Toenniessen and Johnson, 1970; Payment and Franco, 1993). Among these, the endospores of aerobic bacteria (ABE) appear as the most appropriate. In addition to having a resistance to ozone comparable to that of Cryptosporidium oocysts (Owens et al., 2000; Kaymak and Haas, 2005), ABE are non pathogenic, occur abundantly in surface waters (Rice et al., 1996; Facile et al., 2000) and are easily enumerated.
Along with water turbidity, pH and natural organic mater, temperature is the parameter that influences ozone disinfection more importantly (Elovitz et al., 2000; Dow et al., 2006). According to Driedger et al. (2001) and Larson and Mariñas (2003) the temperature influences the Chick Watson equation rate constant (k) of ABE inactivation according to the Arrhenius relation.
However, most studies on this subject were done under conditions not reflecting site specific kinetics of inactivation and, in addition, there is a need to differentiate the temperature effects on disinfection by ozone (Finch et al., 2001; Dow et al., 2006).
In this study the impact of temperature on ABE inactivation by Beliche drinking water treatment plant (DWTP) primary disinfection with ozone was examined over a three-month period. The DWTP, with a treatment capacity of 12 960 m3/day, is located in Algarve (Portugal) and treats surface water. During the study, the influent raw water temperature decreased gradually from 19.1ºC to 12.9ºC. However, its matrix composition did not vary significantly.
