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Drink Dilemma – the facts about water treatment

The Dangers

Drinking water directly from streams and rivers can be hazardous because such sources could contain Pathogens; a Pathogen is a disease causing organism commonly referred to as a germ.

There are four types of water-borne pathogens that are of concern:

• Protozoa – single cell organisms often transferred through human and animal faeces. They are highly resistant to chemical treatments but are easily filtered because they are relatively large. They can also be treated with UV Light and heat. Giardia, Cryptosporidium.
• Bacteria – single cell organisms that can reproduce in water. Medium sized, they can usually be removed by filters though not all will have this capability. Can also be treated with UV and heat. E. Coli, Salmonella, Cholera.
• Viruses – these are spread through water but only reproduce in a host. They can be difficult to filter because they are Small, they are sensitive to chemical, UV and heat treatments. Hepatitis A, Norwalk, Rotavirus.
• Multi-cellular parasites – Large and can be easily filtered, can also be treated by boiling. Resistant to UV and chemicals. Hookworm and Roundworm.

Location, location, location

The primary threats in water collected from rural, relatively pristine sources are Bacteria and Protozoa, the likelihood of Viruses being present is very low.

Water Treatment Options:

Pump Filtration

• Effectiveness - Effectively removes Protozoa, Parasites and Bacteria
• Method - Water is pumped through a filter unit
• Drawbacks - Most do not remove Viruses

Gravity Filtration

• Effectiveness - Effectively removes Protozoa, Parasites and Bacteria
• Method - Gravity provides the force to move the water through the filter unit
• Drawbacks - Most do not remove Viruses

Bottle/Squeeze Filtration

• Effectiveness - Some models effectively remove Protozoa, Parasites and Bacteria
• Method - Convenient but most have limited capacity and flow rate
• Drawbacks - Most do not remove Viruses. Many do not remove organisms

UV Light Treatment

• Effectiveness - Effectively removes Protozoa, Bacteria and Viruses
• Method - Uses Ultra Violet light rays to destroy Bacteria, Protozoa and Viruses. Lightweight & convenient
• Drawbacks - Water MUST be clear, may not be reliable unless water is pre-filtered
  

  Not effective against metazoa (multi celled parasites eg nematode worms, flukes

Chemical Treatment

• Effectiveness - Effectively kills or deactivates most Protozoa (some don't kill cryptosporidium), Parasites, Bacteria & Viruses.
• Method - Liquid or tablets added to water. Can impart a taste to the water, effectiveness reduced for cloudy water. Lightest, most compact option. Waiting period is required, 30 minutes up to 4 hours
• Drawbacks - Reduced effectiveness in cloudy water

Boiling

• Effectiveness - Effectively removes Protozoa, Parasites, Bacteria and Viruses
• Method - One of the most effective ways to purify water, requires a rolling boil for 1 minute
• Drawbacks - Does not remove chemicals or inorganic matter

Mechanical Purification - Ultra Filtration

• Effectiveness - Removes Protozoa, Parasites, Bacteria and Viruses
• Method - Purifies water using the same 'process' as a filter
• Drawbacks - Greater initial expense