In the fifth part of our series on backcountry water treatment methods, we focus on activated carbon filters. These filters use adsorption to remove chemicals, viruses, and other contaminants from water. This article explores the principles, effectiveness, and practical considerations of using activated carbon filters in backcountry settings.
Introduction to Adsorption and Ion Exchange
Adsorption is a process where contaminants adhere to the surface of a filter medium, such as activated carbon. This method differs from absorption, where substances are absorbed into the filter medium. Activated carbon is particularly effective at removing organic chemicals, chlorine, and heavy metals from water. Ion exchange involves replacing undesirable ions in the water with harmless ones, further enhancing water quality.
Activated Carbon
Activated carbon is created by heating organic material, such as wood, in a low-oxygen environment to produce charcoal. This charcoal is then treated with steam or chemicals to create a porous structure with a large surface area, making it highly effective for adsorption.
Effectiveness and Limitations
While activated carbon filters are excellent for removing chemicals and improving taste and odor, they do not kill microorganisms. In fact, bacteria can sometimes be protected by the charcoal, which absorbs disinfectants that might otherwise kill them. Therefore, activated carbon is often used in conjunction with other filtration methods to ensure comprehensive water treatment.
Practical Applications and Examples
Household Use
Activated carbon filters are commonly used in household systems, such as refrigerator filters, faucet attachments, and water pitchers. These systems improve water taste and remove chlorine and other chemicals.
Improvised Filtration
In survival situations, crushed charcoal from a campfire can be used as an improvised water filter. While this method can reduce bacteria and viruses by 50-85% and larger parasites by 99%, it is far less effective than commercial filters.
Commercial Filters
Commercial activated carbon filters, such as those found in Brita pitchers, are designed to remove a range of contaminants. For example, Brita’s standard filter reduces chlorine, mercury, and cadmium, while the Longlast filter also removes lead, asbestos, and benzene.
Filtration Standards and Certifications
NSF Standards
The American National Standards Institute (ANSI) and NSF International provide standards for water filter performance. NSF Standard 42 covers aesthetic effects, such as taste and odor, while NSF Standard 53 addresses health effects by certifying the reduction of harmful contaminants.
Importance of Data Sheets
It’s essential to refer to the data sheets provided by filter manufacturers to understand what contaminants are reduced and by how much. Certifications alone may not give a complete picture of a filter’s effectiveness.
Backpacking Options
Several options are available for backpackers seeking activated carbon filtration:
Platypus Carbon Element
The Platypus carbon element is a lightweight, hiking-specific filter that removes flavors and odors from water. It is designed to be used in conjunction with a primary microbiological filter.
Katadyn Bottle Adapter
The Katadyn bottle adapter fits on standard containers and uses activated carbon to reduce chemicals and improve taste. It is refillable, making it a cost-effective option for frequent use.
Sawyer S3 Select Water Purifier
The Sawyer S3 combines a microfilter with a proprietary foam that adsorbs viruses, heavy metals, chemicals, and pesticides. This filter is effective for up to 62 gallons of water.
Grail Geopress
The Grail Geopress uses a combination of mechanical filtration and ion exchange to remove a wide range of contaminants, including viruses, bacteria, and heavy metals. It is effective for up to 65 gallons of water.
Adventure Medical RapidPure Straw
The RapidPure straw is an ultralight option that provides virus protection for up to 25 gallons. It uses electroadsorptive technology to remove biological contaminants and activated carbon to improve taste and odor.
Conclusion
Activated carbon filters are a valuable tool for backcountry water treatment, particularly for removing chemicals and improving taste and odor. While they do not provide comprehensive microbial protection on their own, they are highly effective when used in conjunction with other filtration methods. Understanding the capabilities and limitations of activated carbon filters can help ensure safe drinking water during outdoor adventures.
Stay tuned for the next installment in this series, where we will explore additional methods and tools for backcountry water treatment.