2015/18 – Townsville (Queensland) – Chlorate, Turbidity, Lead

Townsville (Queensland) – Chlorate

2015/16: Townsville Reticulation – Chlorate 0.995mg/L (highest level) 0.565mg/L (av)

2017/18: January – March 2018 DWI-7-506-00054. Townsville Drinking Water Scheme. Chlorates >700 μg/L (Townsville Water’s self-imposed limit). Townsville has ongoing issues with chlorates in hot weather; compounded for the past few years by higher chlorine set points due to water restrictions. All mitigation measures available have been put in place. Old stock replaced with new stock, reducing the size of storage tanks, stock emptied before refilling, keeping chlorine residuals as low as possible, lowering of reservoir levels to turn over reservoirs. Chlorates reduced as the temperatures cooled. Investigations are underway to convert Douglas WTP to chlorine gas to reduce chlorate formation. (Chlorate levels 1057mg/L (max) in transmission reservoirs (752mg/L av.)). (Chlorate levels 869mg/L (max) in reticulation (701.5mg/L av.)).

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.” https://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…” https://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/chlorite-chlorate/indexeng.
php#sec10_1Guidelines for Canadian Drinking Water Quality.

Townsville (Queensland) – Turbidity

2014/15: Townsville (Queensland) – Turbidity 13.8 NTU (Maximum detection during year)

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
consumer’s tap

Townsville (Queensland) – Lead

1 May 2018DWI-7-506-00058: Townsville Drinking Water Scheme. Lead 0.037mg/L Lead was detected on TCC’s side of the meter. Lead was not detected in the house sample. Further investigations and sampling detected lead in a few older suburbs in Townsville. All samples taken were on TCC’s side of the network. A wide range of sampling was carried out to ensure this was not a widespread issue. Over 600 other locations were sampled. It must be noted that bad sampling technique was used and it is thought that due to no flushing occurring and meters being removed that contamination of samples occurred. Resamples (using correct technique) returned results with no lead breaches. To err on the side of caution all affected services were replaced.Lead was detected in two further samples in August. All services and meters were replaced with no lead detected upon retesting. Lead continues to be monitored throughout the network. No further lead has been detected in over 350 samples. Townsville has an ongoing capital works program to replace all old services and this will continue to be funded. This incident was not closed before the end of the financial year. (Highest level listed in report 0.5mg/L (max), 0.04mg/L mean).

Lead Australian Drinking Water Guideline 0.01mg/L

“… Lead can be present in drinking water as a result of dissolution from natural sources, or from household plumbing systems containing lead. These may include lead in pipes, or in solder used to seal joints. The amount of lead dissolved will depend on a number of factors including pH, water hardness and the standing time of the water.

Lead is the most common of the heavy metals and is mined widely throughout the world. It is used in the production of lead acid batteries, solder, alloys, cable sheathing, paint pigments, rust inhibitors, ammunition, glazes and plastic stabilisers. The organo-lead compounds tetramethyl and tetraethyl lead are used extensively as anti-knock and lubricating compounds in gasoline…ADWG 2011