2013/23: Lake Monduran – Queensland – Trihalomethanes
Lake Monduran can contain varying elevated levels of natural organics. The current configuration of the Lake Monduran WTP struggles to deal with the elevated levels and therefore at times the THM levels in the treated water can exceed the ADWG, health value of 250μg/L. Three (3) of four (4) samples taken at Lake Monduran WSA throughout the year exceeded the ADWG, health value. The average exceedance was around 326μg/L
Bundaberg Regional Council Drinking Water Quality Annual Report 2013/14
Lake Monduran WSA: In the 2014/15 water year four (4) samples were taken for THM analysis. One (1) of these samples exceeded the ADWG health value. The average THM value was around 233μg/L.
Bundaberg Regional Council Drinking Water Quality Annual Report 2014/15
A total of Sixteen (16) samples were taken for THM analysis over the year within the Gregory River WSA. Nine (9) of these exceeded the ADWG, health value. The average exceedance was around 290μg/L.
Bundaberg Regional Council Drinking Water Quality Annual Report 2015/16
A total of four (4) samples were taken for THM analysis throughout the year. Two (2) of these slightly exceeded the ADWG health value. Both samples returned a result of 255μg/L
Bundaberg Regional Council Drinking Water Quality Annual Report 2016/17
A total of eighteen (18) tests were undertaken for THM analysis over the year within the Gregory River WSA. Eight (8) of these exceeded the ADWG, health value. The average of these exceedances was around 300ug/L
Bundaberg Regional Council Drinking Water Quality Annual Report 2017/18
Lake Monduran (Fred Haigh Dam) can also contain elevated levels of natural organics. The existing configuration of the Lake Monduran WTP can have difficulty in treating elevated levels of these organics and therefore, at times, the THM levels in the treated water can exceed the ADWG Health limit of 250ug/L. A total of four (4) samples were taken for THM analysis throughout the year. Three (3) of these tests exceeded the ADWG Health limit. The average of these exceedances was 297ug/L.
Bundaberg Regional Council Drinking Water Quality Annual Report 2018/19
Lake Monduran (Fred Haigh Dam) can also contain elevated levels of natural organics. The existing configuration of the Lake Monduran WTP can have difficulty in treating elevated levels of these organics and therefore, at times, the THM levels in the treated water can exceed the ADWG Health limit of 250μg/L. A total of four (4) samples were taken for THM analysis throughout the year. Two (2) of these tests exceeded the ADWG Health limit. The average of these exceedances was 310μg/L.
Bundaberg Regional Council Drinking Water Quality Annual Report 2019/20
The Monduran WTP has difficulty in treating elevated levels of organics in the source water and therefore, at times, the THM levels in the treated water can exceed the ADWG Health limit of 250ug/L. The WTP only services the Lake Monduran Caravan Park which has a seasonal consumer demand. Council is assessing various strategies including other treatment technology options. Updates have been provided to QWSR throughout the 2022-2023 period. Closure advice for incident DWI-476-22-09526 was received
to QWSR on 15/09/2023.
Value of Exceedences: 420, 345, 428ug/L
Bundaberg Regional Council Drinking Water Quality Annual Report 2022/23
Trihalomethanes Australian Guideline Level 250μg/L (0.25mg/L)
Why and how are THMs formed?
“When chlorine is added to water with organic material, such as algae, river weeds, and decaying leaves, THMs are formed. Residual chlorine molecules react with this harmless organic material to form a group of chlorinated chemical compounds, THMs. They are tasteless and odourless, but harmful and potentially toxic. The quantity of by-products formed is determined by several factors, such as the amount and type of organic material present in water, temperature, pH, chlorine dosage, contact time available for chlorine, and bromide concentration in the water. The organic matter in water mainly consists of a) humic substance, which is the organic portion of soil that remains after prolonged microbial decomposition formed by the decay of leaves, wood, and other vegetable matter; and b) fulvic acid, which is a water soluble substance of low molecular weight that is derived from humus”. US EPA
2022/23 – Lake Monduran (Chlorate)
Chlorate levels were recorded greater than 0.8mg/L (ADWG interim health limit) in the reticulation network. In response to these exceedances’ operators undertook routine tank cleaning. Council continues to dilute the sodium hypochlorite. The investigation report for incident DWI-476-22-09717 was submitted to QWSR on 05/09/2022. Updates for incident DWI-476-23-10158 were provided to QWSR throughout the 2022-2023 period. Closure advice for incident DWI-476-23-10158 was received from QWSR on
20/09/2023.
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 in the 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.