2015 – Clare (Queensland) – Chlorine
2 – The sample taken from Clare WTP on 10/7/2015 does reflect the hand written operator logs and are therefore believed to be an accurate recording of the sample taken, however the sample location is prior to the clear water storage and does not represent the final treated water. The sample taken on the same day on the outlet of the clear water storage shows a total chlorine of 3.52 mg/L and the next day 11/7/2015 shows 2.24 mg/L at the tank outlet. This data indicates that no water exceeding 5 mg/L of total chlorine was released by the WTP.
3 & 4 – The samples taken from Clare WTP on 3/9/2015 show 5.9 mg/L of total chlorine at the outlet of the clear water storage, and 5.3 mg/L of total chlorine at the town pool reservoir sample point. These recordings reflect the operator hand-written logs and are therefore believed to be an accurate recording of the sample taken. The logs state that on 3/9/2015 the operators identified an air lock in the chlorine dosing pump which had been preventing chlorine dosing. In order to ensure all water leaving the plant was disinfected sodium hypochlorite was added directly to the clear water storage tank. It is believed that this has resulted in the high total chlorine readings.
The two sample points above, while treated water, do not represent the final water provided to customers “at the tap”. The SunWater office, and school sample points are at customer tap locations and these two sample points showed 3.37 mg/L and 3.10 mg/L of total chlorine respectively on 3/9/2015, and 0.61 mg/L and 0.64 mg/L the following day on 4/9/2015.
At no time in any of the above instances were any customer complaints received by SunWater, and there have been no reports (suspected or confirmed) of any illnesses.
Sunwater Annual Drinking Water Quality Plan 2015/16
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
2014/15 – Clare (Queensland) – Turbidity
2014/15 – Clare (Queensland) – Turbidity 37.87NTU (max), 1.31NTU (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