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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.
The primary threats in water collected from rural, relatively pristine sources are Bacteria and Protozoa, the likelihood of Viruses being present is very low.
| Type | Method |
| Pump Filtration | Water is pumped through a filter unit |
| Effectiveness | Drawbacks |
| Effectively removes Protozoa, Parasites and Bacteria | Most do not remove Viruses |
| Type | Method |
| Gravity Filtration | Gravity provides the force to move the water through the filter unit |
| Effectiveness | Drawbacks |
| Effectively removes Protozoa, Parasites and Bacteria | Most do not remove Viruses |
| Type | Method |
| Bottle/Squeeze Filtration | Convenient but most have limited capacity and flow rate |
| Effectiveness | Drawbacks |
| Some models effectively remove Protozoa, Parasites and Bacteria | Most do not remove Viruses. Many do not remove organisms |
| Type | Method |
| UV Light Treatment | Uses Ultra Violet light rays to destroy Bacteria, Protozoa and Viruses. Lightweight & convenient |
| Effectiveness | Drawbacks |
| Effectively removes Protozoa, Bacteria and Viruses | Water MUST be clear, may not be reliable unless water is pre-filtered Not effective against metazoa (multi celled parasites eg nematode worms, flukes) |
| Type | Method |
| Chemical Treatment | 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. |
| Effectiveness | Drawbacks |
| Effectively kills or deactivates most Protozoa (some don't kill cryptosporidium), Parasites, Bacteria & Viruses. | Reduced effectiveness in cloudy water. |
| Type | Method |
| Boiling | One of the most effective ways to purify water, requires a rolling boil for 1 minute |
| Effectiveness | Drawbacks |
| Effectively removes Protozoa, Parasites, Bacteria and Viruses | Does not remove chemicals or inorganic matter |
| Type | Method |
| Mechanical Purification – Ultra Filtration | Purifies water using the same 'process' as a filter |
| Effectiveness | Drawbacks |
| Removes Protozoa, Parasites, Bacteria and Viruses | Greater initial expense |
With thanks to MSR, who have a much more in depth article here: https://thesummitregister.com/complete-guide-to-water-treatment/
