ContaminantsContaminantsContaminants are found in all public and private water sources. Find out what they are and what their effect is.
Private Water SuppliesPrivate Water SuppliesPrivate water supplies such as tanks, creeeks, rivers and bores can suffer from contamination which may result in gastric upsets.
Public Water SuppliesPublic Water SuppliesEach state in Australia has its own water authorities responsible with providing drinking water that meets the criteria outlined in the Australian Drinking Water Guidelines. However it is impossible to avoid events such as floods that may cause localised contamination and so "Boil water alerts" are issued for affected areas. In addition, the process of treating water to make it potable can result in other contaminants being added to the water, e.g., chlorine.
Approved ChemicalsApproved ChemicalsThere are more than 35 chemicals approved for use in treating drinking water, including salts of aluminium, copper, iron, and sodium.
Risk AssessmentRisk AssessmentBriefly discusses the difficulty of assessing risks to water quality.
Water AlertsWater AlertsThroughout Australia each year, public water authorities issue alerts for residents of affected areas to boil water in order to avoid waterborne diseases.

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Risk Assessment Public Water Risk Assessment

The Federal Government Department of Environment, Water, Heritage and the Arts produced a technical paper on Drinking Water Quality (PDF file) in which the authors noted: 

"...While multi-barrier systems have been engineered into water supplies and increasingly stringent standards are being applied to sewage discharge, these systems can and do fail. Pathogenic microorganisms disseminated by water still present one of the greatest risks to public health—risks far greater than those resulting from exposure to chemicals...

...Specific pathogens and pathogen groups of concern in Australia include enteric viruses, environmental protozoans (e.g. Naegleria fowleri), faecal protozoans (e.g. Cryptosporidium and Giardia) of human and probably animal origin, environmental bacteria (normally opportunistic pathogens) including Legionella spp., Aeromonas and Pseudomonas, and faecal bacteria (Salmonella spp. excluding S. typhae; Compylobacter, Shigella, Vibrio cholerae (now low risk), and enteropathogenic E. coli).
There is difficulty in quantifying risks due to specific pathogens as none are routinely monitored. Routine monitoring is confined to faecal bacterial indicators (total coliforms and E. coli or thermotolerant coliforms). While these indicator bacteria are reasonable surrogates for assessing faecal pollution episodes, they generally fail to establish the absence of non-faecal pathogens. They are also of limited value in assessing the presence of disinfectant-resistant enteroviruses and faecal protozoans.

Rapid urbanisation and increasing intensity of animal production are leading to concerns about decreasing security of water supplies, especially those supplies which are untreated or which are only disinfected. Increasing wastewater discharges and limited control, and virtually no treatment of stormwater discharges to lakes and streams, will increasingly be viewed as threats to public water supplies...
...Many rural water supplies are of generally unsatisfactory quality—poor surveillance and high frequency of detection of faecal coliforms (see for example Department of Conservation and Natural Resources (1991), Queensland Department of Water Resources (1991))...

...One emerging water supply issue of concern is the growing awareness that previously undetectable organisms, including enteric viruses and Cryptosporidium parvum, may be present even in fully treated supplies...." (my emphasis)

As this report indicates, the risk of disease from bacteria, cysts and viruses in drinking water is not insignificant.  The Queensland Department of Health in its publication Cryptosporidium and Giardia in Drinking Water Interim Management and Response Protocol (PDF file) highlights the impossibility of complete testing of drinking water.  The report states in part:

"...Cysts and oocysts tend to clump and are likely to be unevenly distributed throughout water. Routine sampling only tests a tiny fraction of the water and it is unlikely to detect  intermittent or unevenly distributed contamination...

...Testing of water supplies should be limited to the investigation of cases/outbreaks of confirmed human disease where the epidemiological investigation of cases by public health authorities indicates that the ingestion of drinking water is a likely risk factor....

...the scientific limitations of currently available tests for Giardia and Cryptosporidium are substantial and to act only on the results of such tests may create unnecessary community concern and costs to water authorities and ultimately, the community." (my emphasis)

What this means is that there are technical and cost limitations regarding water testing and that the testing does not ensure drinking water will be free of parasites.  

 While the water authorities have a number of active processes, such as filtration and disinfection, to produce potable water, they can never entirely eliminate the possibility of machine failure or human error.  Further, water testing is limited and even if it shows the presence of pathogens, there is no way to recall the water that is already in the distribution system.  It would seem that a reasonable option to ensure good quality drinking water is to install a water purifier at the point of use.  The Seagull IV water purifiers are independently certified to meet US EPA standards for the removal of bacteria, cysts and viruses leaving you with pure drinking water so you no longer have to worry about water treatment plant failures.

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