Algae are single-celled or simple multi-cellular photosynthetic organisms. Found in both salt and fresh water, algae range from microscopic to giant seaweed over one hundred feet long. Most species of algae are not dangerous though harmful algae blooms (HABs) can form when certain types of microscopic algae grow in water. HABs appear to be increasing along the coastlines and surface waters of the U.S.
Bacteria are single-celled organisms that can be divided into two groups: (1) pathogenic (disease causing) and 2) non-pathogenic (non-disease causing). The most abundant life form on earth, bacteria can be shaped like a rod, spiral, or sphere and can exist individually or in chains or pairs. Some bacteria can form protective spores. Bacteria commonly found in water include Legionella, Salmonella, and E. coli.
Bacteriostatic filters inhibit or prevent the growth of bacteria ("bactericidal" kills bacteria outright). Ceramic filters, such as the Katadyn Drip Ceradyn filter, have incorporated a silver compound throughout the ceramic that acts as a bacteriostatic agent.
Biological contaminants in drinking water include bacteria, viruses, and protozoa. They can occur naturally or as a result of human or animal waste contamination.
BPA or bisphenol A is an industrial chemical used in most types of plastic bottles and other consumer products, such as cups, can liners, baby products, and food containers. Studies have shown that even low levels of BPA act as an endocrine disruptor, which have been linked to reproductive damage, heart disease, diabetes, cancer, and obesity
Capacity generally refers to the lifespan of a filtering media. In other words, it measures how long a filter can effectively remove contaminants from drinking water. It is important to note that while the filter may keep working after its capacity has been reached, that is, the designated amount of water has passed through the filter, the filter may not work as effectively.
Carbon granules have a slight electro-positive charge that attracts the negative ions of contaminants. They can remove chemical contaminants, some heavy metals, and odors. However, carbon filter elements are not as effective at removing sediment, particulates, and microorganisms.
Ceramic filtration is a filtration element made from ceramic with small pores capable of filtering contaminants down to 0.2 microns. Ceramic filters are capable of removing bacteria, protozoa, cysts, algae, and spores from fungi. Ceramic filters can be cleaned with a brush, which means they can be easily serviced in the wilderness. However, ceramic filters are not ideal in below freezing temperatures because any water left in the ceramic can freeze and crack it. Dropping the filter also create holes in the ceramic which may compromise its quality. Some ceramic filters have used iodine as a post treatment, but newer ceramic filters have begun to use bonding silver metal nanoparticles to prevent the growth of pathogens in the filter.
Chemical contaminants in drinking water include mineral salts (nitrates, sulfates, copper), pesticides, heavy metals, and volatile organic compounds (phenols). Chemical contamination can occur as a result of incorrect use of pesticides, chemical spills, improper water treatments, and improper disposal of waste.
Chlorine dioxide is a powerful oxidizer that disinfects without chlorinating, consequently, produces less harmful byproducts than chlorine. Capable of killing pathogenic microorganisms such as fungi, bacteria, and viruses, chlorine dioxide also prevents and removes biofilm. While it doesn’t leave an after taste, chlorine dioxide can take anywhere between 15 minutes to 2 hours to completely disinfect. It comes in both tablet and liquid form.
Cryptosporidium is a single-celled microbe in the protozoan group that live in the intestines of mammals, such as humans. Cryptosporidium enters water through fecal material and can form a protective shell resistant to disinfectants, such as iodine. The icrobe can cause illnesses ranging from a mild stomachache to life-threatening diseases.
Cysts are parasites that have formed an egg-like, chlorine-resistant covering after they leave a host. Capable of surviving outside the host for long periods of time, cysts “hatch” when they are ingested by humans and can cause diarrhea, abdominal cramping, nausea, vomiting, fever, headache, and loss of appetite. Common disease-causing cysts include giardia and cryptosporidium
Giardia lamblia (Giardia) is a single-celled microbe in the protozoa group which causes a gastrointestinal disease called giardiasis. Symptoms include diarrhea, fatigue, and cramps. For those with compromised immune systems, giardia can be deadly. Symptoms typically appear 1 to 2 weeks after infection.
Glass fiber filtration uses fibrous material made from glass, usually in blanket or tube form to filter water. The glass fibers easily fold to create a large filter surface that can fit into small spaces. Glass fiber filters can filter down to the same micron level as ceramic filters, but unlike ceramic filters, glass fiber filters cannot be brushed clean, which means they would be difficult to service in the wilderness. Additionally, while glass fiber filters are more lightweight than ceramic filters, glass fiber filters need to be replaced more often.
Gravity fed systems are simply filters that use gravity as pressure to filter water. The water to be filtered is either placed above the filter and allowed to drip down into the filter, or by placing the filter in the water and running a siphon hose to a collection container that is the below the filer. Gravity fed systems require no electricity and are highly portable.
Hollow-fiber filtration is relatively new in wilderness filtration products. Hollow fiber filters can filter down to 0.2 microns, which effectively filters bacteria and protozoa but not all viruses, so a secondary purifier might be needed. In contrast to ceramic and glass fiber filters, hollow fiber filtration has a significantly higher flow rate at three liters per minutes. It also weighs less than both ceramic and glass fiber filters.
Hydration packs have a pouch and a lightweight water bladder. Hydration packs typically have a tube running from the water bladder to the outside of the pack where it is easily accessible, even while on the go.
Iodine is usually applied in crystal form or iodine based purification tablets and can remove many viruses, bacteria, and protozoa. Because iodine has an aftertaste, most iodine disinfectant kits also include a vitamin C pill to neutralize the iodine taste. However, because Vitamin C compromises iodine, it should be added only after the recommend amount of time for treatment. There are questions regarding the health effects of long-term ingestion of iodine, and pregnant women and those with thyroid problems should not drink water treated with iodine. Additionally, iodine works slower in colder water and is not effective against cryptosporidium.
Microfilters are small-scale filters that are often used for camping and other outdoor use. They are designed to remove cysts, protozoa, sediment, and some bacteria from water. They are less effective at removing viruses. Most microfilters use ceramic, glass, or hollow-fiber filtration elements and work with a hand pump or with gravity. Because microfilters are susceptible to bacterial growth, newer filters are including bacteriostatic technology.
Microorganisms are living organisms (such as bacteria, viruses, and protozoa) so small, they can only be seen with a microscope. Many infectious microorganisms can be found in drinking water, including Norwalk virus, rotavirus, Entamoeba, giardia, and cryptosporidium. Because they are highly resistant to disinfectants, giardia and cryptosporidium are the most common cause of water borne illness in the U.S. Infectious microorganisms enter the drinking water supply through human or animal waste, storm water run off from roadways and farms and discharges from sewage treatment plants or septic system discharges.
MSR MIOX water purifiers use a potent mix of oxidants (MIOX) to inactivate viruses and bacteria, including giardia and cryptosporidium, without pumping or iodine. Ultralight yet rugged, the purifiers simply require batteries and salt to work.
Particulates are particles of sediment, sand, rust, and dirt in drinking water. Particulates contribute to water turbidity and may make water taste and smell “dirty.” They not only make water harder to filter, but they may also carry toxic contaminants.
Physical contaminants include particles of sand, clay, and sediment that can cause turbidity or cloudiness in drinking water as well as a foul taste or odor. Physical contaminants are dangerous because they encapsulate contaminants and protect them from disinfectants. When the physical contaminant is later swallowed, the pathogen is released and can cause illness.
Protozoa are single-celled animals, usually microscopic that feed on bacteria. Many protozoa are spread in a protected form called a cyst or oocyste. The three most common protozoa that are found in water are cryptosporidium parvum, giardia, and Naegleri fowler. Protozoa are often resistant to chemical filtration, such as chlorine.
Pump filters are filters in which one end of the filter is placed into water supply, such as a lake or stream. The water is then pumped through a filter out the other end of the pump, usually into an attached water container. While pump filters are usually lightweight, they may not filter all small viruses and can easily become plugged.
Sediment includes sand silt, loose scale, clay, or organic material that can cause turbidity or cloudiness in water. Sediment may carry harmful microbiological, organic, and inorganic contaminants.
Spores are highly resistant, single-celled asexual reproductive particles that are typically released by algae and fungi. A single mold growth can spawn literally millions of spores. Common spores found in drinking water include cryptosporidium spores, which are unaffected by chlorine disinfectant.
UV lamp filtration scrambles the DNA of contaminants by exposing them to UV light rays, effectively killing microorganisms such as bacteria, viruses, molds, algae, yeast and cysts such as cryptosporidium and giardia. UV filters are also lightweight, do not add chemicals to the water, and work quickly without changing the taste or pH of the water. However, water turbidity must be low for UV to work well. Additionally UV filters won’t remove chemical pollutants.
Viruses are shaped like a spear, wire, or sphere and are smaller than bacteria, which means they can slip through filters that otherwise catch bacteria. Unlike bacteria, viruses cannot reproduce, but instead they use the host cell to replicate. Waterborne viruses include the noroviruses, hepatitis A, and enteroviruses. In North America, waterborne viruses are far less common than bacteria or protozoan cysts; however, in poorer, less developd countries, waterborne viruses can be more of a problem.
Water purification drops, such as iodine drops or chlorine dioxide drops, are a liquid form of disinfectant. Because drops are usually less effective in cloudy or murky water, it is advisable to find the cleanest water possible to filter.
Water purification tablets are small pills, such as iodine and sodium dichloroisocyanurate (NaDCC) used to treat water. Easy to dispense and highly portable, tablets usually take at least 30 minutes to make the water drinkable.
