Strathalbyn (South Australia) – Monochloramines
27/2/06: Strathalbyn Monochloramines 4.8mg/L (highest levels only)
20/2/06: Strathalbyn Monochloramines 4.7mg/L
According to the ADWG: “Based on health considerations, the concentration of monochloramine in drinking water should not exceed 3mg/L (equivalent to 4.1mg Cl as C12/L).
Some water supplies may also be disinfected through a process called Chloramination where ammonia is added to the water prior to the chlorine, which in turn can create Monochloramines. Sunlight does not degrade Monochloramines to the same extent as chlorine, meaning that water can be stored for longer periods of time.
Between January 2000 and July 2012, SA Water recorded over 50 incidences of
Monochloramines breaching or the same as the 2011 ADWG.
“Chloramines are produced by combining chlorine and ammonia…Chloramines are weaker disinfectants than chlorine, but are more stable, thus extending disinfectant benefits throughout a water utility’s distribution system. They are not used as the primary disinfectant for your water. Chloramines are used for maintaining a disinfectant residual in the distribution system so that disinfected drinking water is kept safe.
Chloramine can also provide the following benefits:
• Since chloramines are not as reactive as chlorine with organic material in water, they produce substantially lower concentrations of disinfection byproducts in the distribution system. Some disinfection byproducts, such as the trihalomethanes (THMs) and haloacetic acids (HAAs), may have adverse health effects at high levels. These disinfection byproducts are closely regulated by EPA. EPA recently reduced the allowable Maximum Contaminant Levels for total THMs to 80 ug/L (250ug/L in Australia) and now limit HAAs to 60 ug/L. The use of chlorine and chloramines is also regulated by the EPA. We have Maximum Residual Disinfectant Levels of 4.0 mg/L for both these disinfectants. However, our concern is not from their toxicity, but to assure adequate control of the disinfection byproducts.
• Because the chloramine residual is more stable and longer lasting than free chlorine, it provides better protection against bacterial regrowth in systems with large storage tanks and dead-end water mains.
• Chloramine, like chlorine, is effective in controlling biofilm, which is a slime coating in the pipe caused by bacteria. Controlling biofilms also tends to reduce coliform bacteria concentrations and biofilm-induced corrosion of pipes. • Because chloramine does not tend to react with organic compounds, many systems will experience less incidence of taste and odor complaints when using chloramine. (12)
“Chloramine (as CI2) is a water additive used to control microbes, particularly as a residual disinfectant in distribution system pipes. It is formed when ammonia is added to water containing free chlorine. Monochloramine is one form of chloramines commonly used for disinfection by municipal water systems. Other chloramines (di- and tri-) are not intentionally used to disinfect drinking water and are generally not formed during the drinking water disinfection process. Some people who use water containing chloramine in excess of the maximum residual disinfectant level could experience irritating effects to their eyes and nose, stomach discomfort or anemia.” (13)
“Although monochloramine has been shown to be mutagenic in some in vitro studies, it has not been found to be genotoxic in vivo. In the absence of data on human cancer and on the basis of inadequate evidence for the carcinogenicity of monochloramine in experimental animals, monochloramine was evaluated by IARC as not classifiable as to its carcinogenicity (Group 3). The US EPA classified monochloramine in group D, not classifiable as to its human carcinogenicity, in that there is inadequate human and animal evidence. IPCS did not consider that the increase in mononuclear cell leukaemia was treatment-related. In the NTP bioassay in two species, the incidence of mononuclear cell leukaemias in female F344/N rats was increased, but no other increases in tumour incidence were observed”. (14)
(14) Monochloramine in Drinking-water Background document for development of WHO Guidelines for Drinkingwater Quality 2004