In this first part of the series on backcountry water treatment methods, we explore the effectiveness of boiling and pasteurization for disinfecting water in the wilderness. Both methods have their advantages and limitations, and understanding these can help ensure safe drinking water on your outdoor adventures.
Introduction to Boiling
Boiling is often considered the gold standard for disinfecting water. It is effective against all three main categories of biological threats: cysts (like Cryptosporidium and Giardia), bacteria (such as E. coli and Salmonella), and viruses (including Norovirus and Hepatitis A). Boiling water kills these pathogens through heat, making it a reliable method for ensuring safe drinking water.
However, boiling has its drawbacks. It is time-consuming and fuel-intensive, which can be a significant disadvantage in the backcountry. Despite the availability of ultralight microfilters, there are situations where boiling might be necessary:
- Filter Failure: Filters can fail due to gasket issues, physical damage, or clogging. In such cases, boiling serves as an effective backup method.
- Untreatable Water Sources: Some water sources may contain contaminants that filters cannot handle, such as water contaminated with heavy bacterial loads or viruses. Boiling ensures that these pathogens are effectively neutralized.
Conventional Wisdom on Boiling
The conventional advice for boiling water is to bring it to a rolling boil for one full minute. At elevations above 6,500 feet, this time increases to three minutes. This guidance comes from agencies like FEMA and the CDC, ensuring that the water is safe to drink. While effective, this method is considered overkill and can waste time and fuel.
Pasteurization as an Alternative
Pasteurization involves using heat to eliminate pathogens at temperatures well below boiling. This method has been thoroughly studied and is widely used in the food industry, particularly for milk processing. The FDA’s Grade A Pasteurized Milk Ordinance provides a comprehensive guide on pasteurization temperatures and times.
Key Concepts in Pasteurization
- Temperature vs. Time: Pasteurization can be achieved at lower temperatures given sufficient time. For example, 145°F for 30 minutes is sufficient for commercial-grade pasteurization.
- Efficiency: Heating water to boiling consumes more fuel and time than necessary. Pasteurizing water at lower temperatures can save fuel and provide sufficient disinfection.
Practical Considerations for Pasteurization
The temperature at which pasteurization is achieved varies with the time the water is held at that temperature. For instance, at 191°F, pasteurization can be achieved in just one second. This efficiency is crucial for backcountry applications where fuel conservation is important.
Log Reduction Rates
Log reduction rates measure the effectiveness of a disinfection method. A one log reduction means a 90% reduction in contaminants. The goal for pasteurization is typically a five log reduction, which translates to a 99.999% reduction in pathogens.
Temperature Thresholds
Studies show that heating water to 150°F for five minutes can achieve the necessary five log reduction. This temperature covers the disinfection needs for cysts, bacteria, and viruses, making it an efficient target for pasteurization.
Using the Water Pasteurization Indicator (WAPI)
The WAPI is a small, lightweight device that indicates when water has reached pasteurization temperature. It contains soybean wax that melts at 150°F. Once the wax melts and falls to the bottom of the tube, it confirms that the water has been pasteurized.
Water Pasteurization Indicator (Amazon, $17)
Field Testing the WAPI
Experiments show that the WAPI effectively indicates water pasteurization under various conditions. By using the WAPI, you can avoid the need for a thermometer and ensure your water is safe to drink without wasting fuel.
Fuel Efficiency in Heating Water
Experiments comparing different flame levels for heating water to 160°F show that lower flame settings are more fuel-efficient. Higher flames may heat water faster but waste more fuel. Using lower flames can conserve fuel while still achieving the necessary pasteurization temperature.
Conclusion
Boiling and pasteurization are both effective methods for disinfecting water in the backcountry. While boiling is a reliable method, it is often overkill and can waste valuable resources. Pasteurization offers a more fuel-efficient alternative, achieving the same level of disinfection at lower temperatures. Tools like the WAPI can help ensure water safety without the need for a thermometer, making pasteurization a practical option for backcountry water treatment.
Stay tuned for the next installment in this series, where we will explore other methods and tools for backcountry water treatment.