There are several ways of treating water for drinking and cooking. Some treatment methods are more effective for specific types of contamination. Some water treatment devices combine treatment methods. No single method mitigates all hazards.
A filter can be lost, batteries can flatten or the device can be damaged.
Consider using more than one water treatment method.
- To clear muddy water place a piece of charcoal (e.g. from a campfire) in the bottom of a container and let the water stand. This can be surprisingly effective for clearing suspended earth and mud. However, it has no effect against other contaminants.
- Water processed this way should undergo secondary treatment.
- Heat kills many pathogens.
- To make water safe to drink, bring water to a rolling boil for one minute.
- Muddy water doesn’t hinder the effectiveness of boiling.
- This method requires extra stove fuel and takes time.
There is no one filter system that deals effectively with every type of contaminant. Each has advantages and disadvantages.
Filtration by itself is of benefit against pathogens such as giardia and cryptosporidium, of some benefit against bacteria, but cannot remove viruses, as they are much smaller than the pores in currently available filters.
Most filters have an internal element or cartridge which requires cleaning after a certain amount of use and is usually replaceable.
- Prefilters are used for removing particles such as leaf matter, soil or silt from water prior from water before it passes through the main filter. This step helps to maintain flow rates and reduce cleaning and replacement of filter cartridges. It improves the effectiveness of chemical treatments and is essential prior to using a UV purifier when water is murky.
- Simple prefilters, such as a clean handkerchief or cloth, remove some suspended materials, but have no effect against other contaminants.
- Commercial prefilters are much more effective.
- Pump filters use mechanical pressure in combination with a cartridge with an activated-charcoal or ceramic core. Pressure is provided by a hand-operated pump and takes time. Their weight and bulk is greater than other filters.
- Gravity filters are the easiest way to treat large quantities of water, but takes time. A suitable place is needed to suspend the water reservoir.
- Bottle and squeeze filters are lighter and less expensive and are quick and easy to use. The quantity filtered is limited by the size of the bottle or bag. These are good for individuals.
- Straw-type filters are a one-person option where water is sucked up for immediate drinking through the filter from a water source.
Cartridges that form the core of water filters are either:
- Activated-carbon cartridges absorb many chemicals, including chlorine. These are best for removing blue-green algae toxins. They tend to block rapidly – prefiltration can reduce this. Chemicals can then be used to treat other pathogens. This should be done after filtering, not before.
- Ceramic cartridges rely on small pore size to remove dirt and bacteria. Some are impregnated with silver to incapacitate bacteria and prevent growth of mould and algae.
Iodine tablets can treat some common pathogens including giardia and E. coli.
However, iodine is not effective against:
- Blue-green algae as it does not neutralise the toxins.
Water treated with Iodine tablets has a strong salty, chemical taste.. Drink flavourings added after treatment can be used to counteract this taste.
Cool water should be treated then stand for at least 30 minutes before drinking.
Cold or murky water should stand for at least 1 hour before drinking.
Chlorine treatment is effective against E. coli and viruses, but not against giardia and cryptosporidium. Chlorine-treated water is also less unpalatable.
Ultraviolet light treatment
Ultraviolet (UV) light from UV purifiers is a practical option for water purification. UV light is effective in disrupting pathogen reproduction to make them far less harmful.
- Easy to use and water is quickly made safe to drink.
- No cleaning of cartridges.
- Batteries are rechargeable.
- UV purifiers do not add chemicals.
- Time taken to treat sufficient water for a group if only one device is carried.
- Suspended materials in water impacts their effectiveness – prefiltering is required.
- Does not remove contaminants such as chlorine or sediments
- A water bladder needs to be topped up from a bottle.
Choosing the best water treatment
Selection of a portable water treatment method should consider:
- expected contaminants in the area to be visited
- size of group
- ease of use and time taken for water to be drinkable
- lifespan and availability of replacements
- purchase price and cost of replacements