AWWA ACE58265

Cryptosporidium parvum oocysts have emerged as the microbial water contaminant withgreatest resistance to chemical disinfectants. There is particular concern because both thefree and combined forms of chlorine, the most common disinfectant in the United States,when used as primary inactivation agents are considered practically ineffective incontrolling C. parvum oocysts under typical drinking water conditions (Gyurek et al.,1997; Rennecker et al., 2000, 2001; Driedger et al., 2000, 2001; Corona-Vasquez et al.,2002a,b). In contrast, ozone and chlorine dioxide are both considered viable chemicaldisinfectants (Rennecker et al., 1999, 2000, 2001; Gyurek et al., 1999; Ruffell et al.,2000; Driedger et al., 2000, 2001; Li et al., 2001; Corona-Vasquez et al., 2002a,b) butthere is concern about potentially high disinfection requirements (Rosen et al., 2002).The resistance of C. parvum oocysts to ozone and chlorine dioxide, though known to varywith various factors (Clark et al., 2002; Sivaganesan et al., submitted), can be 20 to 50times higher than that of Giardia lamblia cysts (Corona-Vasquez et al., 2002a), themicrobial contaminant with highest resistance to chemical disinfection regulated underthe current version of the Enhanced Surface Water Treatment Rule.A promising alternative for more efficient control of C. parvum oocysts is the sequentialapplication of certain combinations of disinfectants. Recent studies have shown that theefficiency of C. parvum oocyst inactivation by both free and combined chlorine can beincreased significantly after limited exposure to ozone (Li et al., 1999, 2001; Finch et al.,2000; Rennecker et al., 2000, 2001; Driedger et al., 2000, 2001; Corona-Vasquez et al.,2002b; Rochelle et al., 2002). In contrast, pretreatment with chlorine dioxide does notappear to enhance as much the rate of secondary inactivation by free or combinedchlorine (Corona-Vasquez et al., 2002a)The goal of this paper is to review the current status of synergistic sequentialdisinfection technologies for the control of C. parvum oocysts and to providerecommendations for additional research that might be needed to complete thedevelopment and possible implementation of sequential CT requirements. Includes 20 references.

Product Details

Edition:

Vol. - No.

Published:

06/15/2003

Number of Pages:

7

File Size:

1 file , 250 KB