What are the reasons for treating water and when to do it?
Learning from a teacher who has stopped learning
is like drinking water from a stagnant pond. Indonesian proverb
The aim of water treatment is to remove contaminants or reduce them to a concentration that means the water is safe to drink. Safe drinking water does not have to be sterile, and can contain organic and inorganic matter that the body can tolerate. Contaminants include sediments and pathogens (bacteria, viruses, protozoa, larger organisms (worms) or salts and toxins (fertilisers, heavy metals). Most commonly, water supplies are contaminated by human or animal excrement, or occasionally a dead animal carcass ends up in the water supply (e.g. cattle crossing a river). Contamination can also occur in the form of pollutants from human infrastructure such as mining or farming.
Typical water borne diseases Signs and symptoms of typical water borne diseases
Common pathogenic parasitic infections in humans include Giardia, Cryptosporidium (protozoans) and E. coli (a common bacteria), all of which are transmitted via contaminated water of poor hygiene. Symptoms vary from stomach cramps and fatigue though to bloating and diarrhoea.
A pathology test can quickly distinguish Giardia from Cryptosporidium, but on a bushwalk the symptoms of stomach and intestinal upset are very similar. Instead, these types of infections are generally referred to as Traveller’s diarrhoea. Good hygiene practice and care of food and water are the best ways to prevent getting sick in the bush. Prevention is better than cure!
Water, to treat or not to treat? The decision process involved
There are a few rules that can be applied to assess if water should be treated. In general, on day walks that start from home or a base such as a caravan park near the walk area, take all water from a tap. Day walks like this are often close to farms, houses, mines or other places that make the water quality questionable. Also, on most day walks there’s no need to collect water on the trip. The exception is a day walk when it’s hot. Ask the leader about water collection.
On overnight and longer walks, it’s probable that water will be of a higher quality. Nearly all remote places have good water. As the number of people walking or travelling through the region increases, so does the chance of water being polluted. For example, parts of Tasmania’s Overland Track have water pollution, from human wastes. Provided there are no more campsites, tracks, huts or other potential pollutant sources, further upstream, going upstream from campsites will usually be enough. Huts have long been associated with poor-quality water. The remedy is to get water well away from the hut, and upstream. Rivers and creeks that are flowing strongly are usually safe, as are ponds in off-track areas.
Some land management authorities say that all water should be treated. While there are places where treatment is necessary, the advice to treat all water seems to be based more on avoiding successful litigation than science. Short of carrying out a microbiological study for every water source encountered on a bushwalk, however, when collecting water it’s necessary to make an assessment of the risk involved in drinking that water source without treatment. This assessment involves weighing up the likelihood of a water source being contaminated from infrastructure, toileting such as from popular campsites and tracks, or farm animals. Although impossible to be 100% confident of water quality, it’s possible to make an informed decision by determining the water source by looking at the land and a map.
Part of this assessment involves an understanding of contamination dosage. The amount of concentration of the pathogen necessary to cause illness water varies. Potable tap water is certainly not sterile: it contains some level of contaminants that water authorities have assessed are in sufficiently low quantities for the vast majority of people to handle. So on a bushwalk, it’s okay to drink water that isn’t sterile.
Individual health and immune strength is also a factor: everyone’s immune system is different, and tolerance levels to pathogen contaminants vary. Diseases that affect the immune system like HIV and diabetes mean that infected people may be more susceptible to pathogens. Pregnant women are also at higher risk. Therefore, individuals who are immunocompromised (i.e. an impaired immune system) would be wise to treat all water, even in wilderness areas where the risk of contamination is low. Likewise, overseas travellers often don’t risk drinking the same water supplies as locals because their immune systems have not had time to build adequate resistance. This is often why travellers are advised to drink bottled water only.
Infection of waterborne pathogens can also occur from using contaminated water to wash or cook or from physical contact with an infected person, ”hand to mouth” transmission. According to a study of the risk of giardiasis from consumption of wilderness water in North America, the incidence of giardia in wilderness walkers is high, however, the infections are more likely caused by poor hygiene rather than contaminated water1. Regular use of antibacterial gels after toileting and before food preparation and consumption on a bushwalk can reduce the likelihood and spread of infection.
But while the body can fight some pathogens to some degree, it’s a different story for some materials that can accumulate in the body. Long-term use of water contaminated with heavy metals can have severe health implications because the metals can bind to cellular matter and interfere with essential processes2. Heavy metals have carcinogenic properties and can interfere with respiratory and circulatory systems. Unlike water sources that are pathogen-infected, water sources that contain heavy metals cannot easily be treated to make them safe in the field and should therefore be avoided unless in an emergency.
In short, choosing to treat water comes down to good judgement of the water source, personal health and the general hygiene practices used by the group.
- Welch TP (2000). Risk of giardiasis from consumption of wilderness water in North America: a systematic review of epidemiologic data. International Journal of Infectious Diseases 4 (2): 100–103
- Landis, WG; Sofield, RM; Yu, M-H (2000). Introduction to Environmental Toxicology: Molecular Substructures to Ecological Landscapes. 4th: CRC Press