There is wide spread potential for human exposure to disinfection byproducts (DBPs) in drinking water because everyone drinks, bathes, cooks and cleans with water. Chlorine can cause eye, nose, stomach problems and sinus irritation when ingested via drinking water. Inhalation of chlorine leads to asthma, showering of Chlorinated water can magnify the effects of chlorine inhalation, due to the enclosed nature of shower stalls.
In 1976, the U.S. National Cancer Institute Published results showing that Chloroform, one of the trihalomethanes (THM) that occurs as a by product of drinking water disinfection, was carcinogenic in rodents (U.S. NCI Report). Since that time, there has been a concern that disinfection against microbial risks could also pose chemically induced cancer risks for humans (Melnick et al. 1994). Further more, several epidemiology studies have suggested a weak association between drinking chlorinated water and the occurrence of bladder rectal, and colon cancer (Doyle et al. 1997). In addition, disinfection alternative to chlorination, such as ozo-nation, produce byproducts for e.g. bromates that are carcinogenic to rodents (Balmier et al. 1995). Recently, it has been shown that consumption of drinking water with high THM levels is associated with adverse reproductive outcomes (Wailer et al. 1998; Xie 2004).
Problems associated with chemical disinfectants on human body are of significance considering the water disinfection scenario. Not only this, pathogenic bacteria found in water bodies are now-a-days becoming resistant to the action of chemical disinfectants. Chlorine resistance was progressively increased in E. coli. O157:H7 and thereby adapting to starvation (John et al. 1998). Microbes differ greatly in their sensitivity to disinfectants. Specific protozoa, viruses and bacteria are known to be highly resistant to chemical disinfectant and pose a unique challenge to the water treatment industry.
Micro-organisms produce a gelatinous material known as exopolysaccharide to form biofilms. Biofilm associated bacteria have been reported as being up to 3,000 times more resistant to free chlorine (Lechevallier et al. 1998). One study showed that Staphylococcus aureus isolated from healthy and sick persons showed resistance to chloramines (Balakliets et al. 1989) . Chlorine resistance in Salmonella typhi was recognized 70 years ago (Heathman et al. 1936). Bacterial spores of Genus Bacillus and Clostridium have been the most resistance (Sagripanti and Bonifacino 1996; Russell 1997). Pseudomonas aeruginosa strains show resistance
Table 14.6 Characteristics of bacteriophage as disinfectant
Sr. No. Characteristics
1. Cost of production
4. Non corrosive
5. Safety concern
7. Non toxic to higher forms of life
8. Effect on pathogenic bacteria
Cost effective production Liquid and powder formulations can be possible
They are replicate at the site of its host and are thus available where they are most needed
They are non-corrosive
They are highly safe, no serious side effects have been found
Lytic phages are found to be highly effective in killing pathogenic bacteria. Phage resistant bacteria remain susceptible to other lytic phages having similar target range to repeated disinfectant exposure (Lakkis and Fleiszig 2001). In one study, Pseudomonas aeruginosa strains showed resistance to quaternary ammonium compounds used to disinfect contact lenses (Sundheim et al. 1998).
Therefore, to overcome all the above mentioned problems associated with the use of chemical disinfectants, an alternative strategy could be to use bacteriophage as biological disinfectant. Bacteriophages fulfill most of the characteristics of ideal disinfectants. Table 14.6 summarizes characteristics fulfilled by bacteriophages as ideal disinfectant.
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