“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.
Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG 2011
Based on health considerations, the guideline value for total chlorine in drinking water is 5 mg/L.
Chlorine dissociates in water to form free chlorine, which consists of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion. Chlorine and hypochlorites are toxic to microorganisms and are used extensively as disinfectants for drinking water supplies. Chlorine is also used to disinfect sewage and wastewater, swimming pool water, in-plant supplies, and industrial cooling water.
Chlorine has an odour threshold in drinking water of about 0.6 mg/L, but some people are particularly sensitive and can detect amounts as low as 0.2 mg/L. Water authorities may need to exceed the odour threshold value of 0.6 mg/L in order to maintain an effective disinfectant residual.
In the food industry, chlorine and hypochlorites are used for general sanitation and for odour control. Large amounts of chlorine are used in the production of industrial and domestic disinfectants and bleaches, and it is used in the synthesis of a large range of chemical compounds.
Free chlorine reacts with ammonia and certain nitrogen compounds to form combined chlorine. With ammonia, chlorine forms chloramines (monochloramine, dichloramine and nitrogen trichloride or trichloramine) (APHA 2012). Chloramines are used for disinfection but are weaker oxidising agents than free chlorine.
Free chlorine and combined chlorine may be present simultaneously (APHA 2012). The term totalchlorine refers to the sum of free chlorine and combined chlorine present in a sample.
Chlorine (Free) ADWG Guideline: 5mg/L (Chlorine in chloraminated supplies 4.1mg/L). Chlorine dissociates in water to form free chlorine, which consists of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion.
Chlorine (Total) ADWG Guideline 5mg/L (chloraminated supplies 4.1mg/L): The term total chlorine refers to the sum of free chlorine and combined chlorine present in a sample
Isisford (Queensland) – Turbidity
2009-11: Isisford (Queensland) – Turbidity 14 NTU (Maximum detection during year), 2.4NTU av.
Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.
Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
2011 Aug-Dec: Isisford (Queensland) – Chlorate
15 Aug 11: 0.33mg/L
13 Dec 11: 1.22mg/L
Chlorite: ADWG Health 0.3mg/L.
Chlorite and chlorate are disinfection by-products of chlorine dioxide disinfection process.
“… industry are having serious problems meeting chlorite/chlorate limits that were proposed in the new Australian Drinking Water Guidelines, especially for disinfection in long distance pipelines that are dosed with sodium hyptochlorite” pers comm 18/5/11.
“Chlorite occurs in drinking water when chlorine dioxide is used for purification purposes. The
International Agency for Research on Cancer (IARC) has concluded that chlorite is not classifiable as carcinogenic to humans and is listed in the Group 3 category. Changes in red blood vessels due to oxidative stress are a major concern with excessive levels of Chlorite in drinking water. According to the US EPA, potential health problems for people drinking Chorite above safe drinking water guideline include: Anemia in infants and young children and nervous system effects.” http://water.epa.gov/drink/contaminants/index.cfm
“Chlorine dioxide (chlorite) is rarely used as a disinfectant in Australian reticulated supplies.
When used, the chlorite residual is generally maintained between 0.2mg/L and 0.4mg/L. It is
particularly effective inthe control of manganese-reducing bacteria. Few data are available on
chlorate levels in Australian water supplies….Chlorine dioxide, chlorite, and chlorate are all
absorbed rapidly by the gastrointestinal tract into blood plasma and distributed to the major
organs. All compounds appear to be rapidly metabolised. Chlorine dioxide has been shown to
impair neurobehavioural and neurological development in rats exposed before birth. Experimental studies with rats and monkeys exposed to chlorine dioxide in drinking water have shown some evidence of thyroid toxicity; however, because of the studies’ limitations, it is difficult to draw firm conclusions (WHO 2005) The primary concern with chlorite and chlorate is oxidative stress resulting in changes in red blood cells. This end point is seen in laboratory animals and, by analogy with chlorate, in humans exposed to high doses in poisoning incidents (WHO 2005).” Australian Drinking Water Guidelines – National Health and Medical Research Centre
“…Subchronic studies in animals (cats, mice, rats and monkeys) indicate that chlorite and chlorate cause haematological changes (osmotic fragility, oxidative stress, increase in mean corpuscular volume), stomach lesions and increased spleen and adrenal weights… Neurobehavioural effects (lowered auditory startle amplitude, decreased brain weight and decreased exploratory activity) are the most sensitive endpoints following oral exposure to chlorite…” http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/chlorite-chlorate/indexeng.
php#sec10_1Guidelines for Canadian Drinking Water Quality.