From the Guidelines
Campers can effectively remove Giardia cysts from natural water sources through boiling or using filters with a pore size of 1 micron or smaller, as recommended by the USPHS/IDSA guidelines 1. Boiling water for at least one minute (or three minutes at elevations above 6,500 feet) will kill Giardia cysts by denaturing their proteins and destroying their cellular structure. For filters, only those capable of removing particles ≥ 1 µm in diameter should be considered, including those that operate by reverse osmosis, those labeled as absolute 1-µm filters, and those labeled as meeting NSF Standard No. 53 for cyst removal 1. These methods work because Giardia cysts are sensitive to heat and physical removal, which disrupt their protective outer shell and internal structures. Campers should always treat water from lakes, streams, or other natural sources, as Giardia infection causes giardiasis, a gastrointestinal illness that can ruin any outdoor adventure with symptoms like diarrhea, stomach cramps, and nausea. Some key points to consider when using filters include:
- The "nominal" 1-um filter rating is not standardized, and many filters in this category may not be capable of removing 99% of oocysts 1.
- Filters that provide the greatest assurance of oocyst removal include those that operate by reverse osmosis, those labeled as "absolute" 1-um filters, and those labeled as meeting NSF (National Sanitation Foundation) standard no. 53 for "cyst removal" 1. It's also important to note that while boiling and filtration are effective methods for removing Giardia cysts, they may not be 100% effective, and campers should always take precautions when consuming water from natural sources.
From the Research
Methods for Removing Giardia Cysts
Two methods that campers can use to remove Giardia cysts from a natural water source are:
- Filtration: This method involves using a filter with small pores to remove Giardia cysts from the water 2.
- Disinfection: This method involves using disinfectants such as chlorine, chlorine dioxide, ozonation, or ultra-violet (UV) irradiation to inactivate or remove Giardia cysts from the water 2, 3.
Effectiveness of Methods
The effectiveness of these methods in removing Giardia cysts from natural water sources has been studied in various research papers. For example, a study found that ozonation was more efficient than chlorination in removing Giardia cysts from surface water 3.
Important Considerations
It is essential to note that the removal of Giardia cysts from natural water sources is crucial to prevent waterborne diseases. Campers should always treat natural water sources before consumption to minimize the risk of infection.