2015/2016 – Mt Morgan (Queensland) – Giardia
As part of the annual verification monitoring program, samples were collected from the Mount Morgan WTP (potable water) and No. 7 Dam (raw water source) for Giardia analyses. The result obtained for the potable water sample was 1 cyst per 20L while the raw water sample had <1 cyst per 20L. The test results for the potable sample did not contain any other unusually high or non-compliant results for a range of physical-chemical parameters including turbidity.
At the day of sampling, the daily in-house water testing results measured a turbidity of 0.62 NTU, a free chlorine residual of 1.61 mg/L and a pH of 7.53. There were no known excursions to normal operations at the WTP during days prior to the time of sampling. The telemetry data were also within the normal operating range. There was no known immediate impact for the Giardia detection within and downstream of the WTP.
“Although known as a human parasite for 200 years, Giardia has been regarded seriously as an agent of disease only since the 1960s. It has been identified as an important waterborne pathogen, and linked to many outbreaks of illness associated with drinking water, particularly in North America. Although the importance of this organism has been established, there are large gaps in knowledge about it, and there are no tests for identifying the presence of human infectious species in water.
Giardia has a relatively simple life cycle involving two stages: a flagellate that multiplies in the
intestine, and an infective thick-walled cyst that is shed intermittently but in large numbers in faeces. Concentrations of cysts as high as 88,000 per litre in raw sewage and 240 per litre in surface water havebeen reported (Wallis et al. 1996). Giardia is typically present in larger numbers in Australian sewagethan Cryptsoporidium. Cysts are robust and can survive for weeks to months in fresh water.
There are a number of species of Giardia, but human infections (giardiasis) are usually assigned to one, G. intestinalis (= G. lamblia and G. duodenalis). G. intestinalis infections have been reported from domestic and wild animals, but the host range of human infectious species is uncertain. Although substantial advances have been made in the sampling and counting of cysts, there are currently no established methods to identify human infectious organisms in water. Waterborne outbreaks of giardiasis have generally been linked to consumption of untreated or unfiltered surface water and contamination with human waste.
Consumption of contaminated drinking water is only one of several mechanisms by which transmission (faecal-oral) can occur. Recreational waters, including swimming pools, are also emerging as an important source of giardiasis. However, excluding outbreaks, by far the most likely route of transmission is by direct contact with a human carrier. Transmission of Giardia can also occur by contact with infected animals and occasionally through contaminated food.” ADWG 2011
2014 June – Mt Morgan (Queensland) – E.coli
A reticulation sample collected on 22 June 2014 from the Mt Morgan water supply scheme tested positive (1 MPN/100ml) for E. coli. At the time of the sampling the free chlorine residual
measured from the sampling point and supply reservoir were 0.48 mg/L and 1.63 mg/L, respectively. A second split (parallel) sample collected on the 22 June for general physico-chemical testing was also analysed for E. coli but tested negative for the bacteria. All follow-up samples taken from the sample site, supply reservoir, and other reticulation sampling points tested negative for E. coli.
“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