Water Purification Systems
- Water Purification – a process which removes specified contaminants from a water source.
- Water Disinfection – a purification process which kills or removes biological contaminants such as cysts, bacteria, viruses, protozoa, etc. from a water source.
- Water that has been disinfected may still be polluted with contaminants that are not affected by the disinfection treatment.
- In some cases, additional contaminants may actually be added to the water during the disinfection process.
- For instance, the process of chlorination nearly always adds some disinfection byproducts.
- Boiling water will actually concentrate inorganic contaminants.
Granular Activated Carbon Filters (GAC):
Activated carbon is particles of carbon that have been treated to increase their surface area and increase their ability to adsorb a wide range of contaminants – activated carbon is particularly good at adsorbing organic compounds.
Contaminant reduction in GAC filters takes place by two processes: physical removal of contaminant particles, blocking those that are too large to pass through the pores (obviously, filters with smaller pores are more effective). There is also a process called adsorption by which a variety of dissolved contaminants are attracted to and held (adsorbed) on the surface of the carbon particles. The characteristics of the carbon material (particle and pore size, surface area, surface chemistry, density, and hardness) influence the efficiency of adsorption.
GAC is a highly porous material; therefore, it has an extremely high surface area for contaminant adsorption. One reference mentions “The equivalent surface area of 1 pound of GAC ranges from 60 to 150 acres (over 3 football fields).” Another article states, “Under a scanning electron microscope the activated carbon looks like a porous bath sponge. This high concentration of pores within a relatively small volume produces a material with a phenomenal surface area: one teaspoon of activated carbon would exhibit a surface area equivalent to that of a football field.
GAC is made of tiny clusters of carbon atoms stacked upon one another. The carbon source is a variety of materials, such as peanut shells, coconut husks, or coal. The raw carbon source is slowly heated in the absence of air to produce a high carbon material. The carbon is activated by passing oxidizing gases through the material at extremely high temperatures. The activation process produces the pores that result in such high adsorptive properties.
The adsorption process depends on the following 5 factors:
- Physical properties of the GAC, such as pore size distribution and surface area
- The chemical nature of the carbon source
(the amount of oxygen and hydrogen associated with it)
- Chemical composition and concentration of the contaminant
- The temperature and pH of the water
- The flow rate or time exposure of water to GAC
It is important to replace the cartridge according to the manufacturer’s instructions.
Advantages of GAC filters:
- GAC filters are used for aesthetic water treatment, since they can reduce chlorine and particulate matter as well as improve the taste and odor of the water.
- Loose granules of carbon do not restrict the water flow to the extent of Solid Block Activated Carbon (SBAC) filters, which makes them suitable in situations, like whole house filters, where maintaining a good water flow rate and pressure is important.
- Simple, economical maintenance. Typically an inexpensive filter cartridge needs to be changed every few months to a year, depending on water use and the manufacturer’s recommendation.
- GAC filters do not require electricity, nor do they waste water.
- The bottom line is that GAC filters are effective and valuable water treatment devices, but their limitations must be considered. A uniform flow rate, not to exceed the manufacture’s specifications, needs to be maintained for optimal performance and the filter cartridge must be changed after treating the number of gallons the filter is rated for.
Ultra Violet Light:
Water passes through a clear chamber where it is exposed to Ultra Violet (UV) Light. UV light effectively destroys bacteria and viruses. However, how well the UV system works depends on the energy dose that the organism absorbs. If the energy dose is not high enough, the organism’s genetic material may only be damaged rather than disrupted.Advantages of using UV:
- No known toxic or significant nontoxic byproducts introduced
- Removes some organic contaminants
- Leaves no smell or taste in the treated water
- Requires very little contact time (seconds versus minutes for chemical disinfection)
- Improves the taste of water because some organic contaminants and nuisance
- Microorganisms are destroyed
- Many pathogenic microorganisms are killed or rendered inactive.
- Does not affect minerals in water
Disadvantages of using UV:
- UV radiation is not suitable for water with high levels of suspended solids, turbidity, color, or soluble organic matter. These materials can react with UV radiation, and reduce disinfection performance. Turbidity makes it difficult for radiation to penetrate water and pathogens can be ‘shadowed’, protecting them from the light.
- UV light is not effective against any non-living contaminant, lead, asbestos, many organic chemicals, chlorine, etc.
- Tough cryptosporidia cysts are fairly resistant to UV light.
- Requires electricity to operate. In an emergency situation when the power is out, it will not work.
- UV is typically used as a final purification stage on some filtration systems. If you are concerned about removing contaminants in addition to bacteria and viruses, you would still need to use a quality carbon filter or reverse osmosis system in addition to the UV system.
The formation of oxygen into ozone O3 occurs with the use of energy. This process is carried out by an electric discharge field as in the CD-type ozone generators (corona discharge simulation of lightning).
Ozone is a naturally occurring component of fresh air. It can be produced by the ultraviolet rays of the sun reacting with the Earth’s upper atmosphere (which creates a protective ozone layer), by lightning or it can be created artificially with an ozone generator.
The ozone molecule contains three oxygen atoms whereas the normal oxygen molecule contains only two. Ozone is a very reactive and unstable gas with a short half-life before it reverts back to oxygen. Ozone is the most powerful and rapid acting oxidizer man can produce, and will oxidize all bacteria, mold and yeast spores, organic material and viruses given sufficient exposure.
In the home, ozone is often combined with activated carbon filtration to achieve a more complete water treatment.
Advantages of using Ozone:
- Ozone is primarily a disinfectant that effectively kills all biological contaminants.
- Ozone also oxidizes and precipitates iron, sulfur, and manganese so they can be filtered out of solution.
- Ozone will oxidize and break down many organic chemicals including many that cause odor and taste problems.
- Ozonation produces no taste or odor in the water. Since ozone is made of oxygen and reverts to pure oxygen, it vanishes without a trace once it has been used.
Disadvantages of using Ozone:
- Ozonation requires electricity to operate. In an emergency situation when the power is out, it will not work
- Ozone is not effective at removing dissolved minerals and salts.
In an emergency, boiling is the best way to purify water that is unsafe because of the presence of protozoan parasites or bacteria.
If the water is cloudy, it should be filtered before boiling. Filters designed for use when camping, coffee filters, towels (paper or cotton), cheesecloth, or a cotton plug in a funnel are effective ways to filter cloudy water.
Place the water in a clean container and bring it to a full boil and continue boiling for at least 3 minutes (covering the container will help reduce evaporation). If you are more than 5,000 feet above sea level, you must increase the boiling time to at least 5 minutes (plus approx. one minute for every additional 1,000 feet) Boiled water should be kept covered while cooling.
Advantages of Boiling Water:
- Pathogens that might be lurking in your water will be killed if the water is boiled long enough.
- Boiling will also drive out some of the Volatile Organic Compounds (VOCs) that might also be in the water. This method works well to make water that is contaminated with living organisms safe to drink, however because of the inconvenience, boiling is not routinely used to purify drinking water except in emergencies.
Disadvantages of Boiling Water:
- Boiling should not be used when toxic metals, chemicals (lead, mercury, asbestos, pesticides, solvents, etc.), or nitrates have contaminated the water.
- Boiling may concentrate any harmful contaminants that do not vaporize as the relatively pure water vapor boils off.
- Energy is needed to boil the water
In many ways, distillation is the reverse of boiling. To remove impurities from water by distillation, the water is usually boiled in a chamber causing water to vaporize and the pure (or mostly pure) steam leaves the non-volatile contaminants behind. The steam moves to a different part of the unit and is cooled until it condenses back into liquid water. The resulting distillate drips into a storage container.Salts, sediment, metals – anything that won’t boil or evaporate – remain in the distiller and must be removed. Volatile organic compounds (VOCs) are a good example of a contaminant that will evaporate and condense with the water vapor. A vapor trap, carbon filter, or other device must be used along with a distiller to ensure the more complete removal of contaminants.
Advantages of Distillation:
- A good distillation unit produces very pure water. This is one of the few practical ways to remove nitrates, chloride, and other salts that carbon filtration cannot remove.
- Distillation also removes pathogens in the water, mostly by killing and leaving them behind when the water vapor evaporates.
- No drop in quality over time – As long as the distiller is kept clean and is working properly the high quality of treated water will be very consistent.
- No filter cartridges to replace, unless a carbon filter is used to remove volatile organic compounds.
Disadvantages of Distillation:
- Distillation takes time to purify the water. It can take two to five hours to make a gallon of distilled water.
- Distillers uses electricity all the time the unit is operating
- Distillers remove all of the oxygen from the water
- Distillers require periodic cleaning of the boiler, condensation compartment, and storage tank.
- Countertop Distillation is one of the more expensive home water treatment methods, using $0.25 to $0.35 of electrical energy per gallon of distilled water produced – depending on local electricity costs. The cost of ownership is high because you not only have the initial cost of the distillation unit to consider, but you also must pay for the electrical energy for each gallon of water produced. If it cost you $0.25 to distill each gallon and you purified 10 gallons per week, you would pay $130 for your 520 gallons of distilled water each year.
- Most home distillation units require electricity, and will not function in an emergency situation when electrical power is not available.
Reverse Osmosis (RO):
Reverse Osmosis is a separation process which uses water pressure to force water molecules through a membrane that has extremely tiny pores, leaving the larger contaminants behind. Purified water is collected from the “clean” side of the membrane, and water containing the concentrated contaminants is flushed down the drain from the “contaminated” side. This is the reverse of the “normal” osmosis process, where water moves naturally . . . through a semi-permeable membrane . . .
from an area of low solute concentration . . . to an area of high solute concentration (with no external pressure applied).The average RO system is a unit consisting of a sediment/chlorine pre filter, the reverse-osmosis membrane, a water storage tank and an activated-carbon post filter. They cost approx. $150 to over $1,500 for point of use systems.
Advantages of Reverse Osmosis:
- Reverse osmosis significantly reduces salt, most other inorganic material present in the water, and some organic compounds. With a quality carbon filter to remove any organic materials that get through the filter, the purity of the treated water approaches that produced by distillation.
- Microscopic parasites (including viruses) are usually removed by properly functioning RO units, but any defect in the membrane would allow these organisms to flow undetected into the “filtered” water – so they are not recommended for use on biologically unsafe water.
- Though slower than a carbon or sediment water filter, RO systems can typically purify more water per day than distillers and are less expensive to operate and maintain.
- Reverse Osmosis systems also do not use electricity, although because they require relatively high water pressure to operate, they may not work well in some emergency situations.
Disadvantages of Reverse Osmosis:
- Point of Use RO units make only a few gallons of treated water a day for drinking or cooking.
- RO systems waste water. Two to four gallons of “waste” water are flushed down the drain for each gallon of filtered water produced.
- Some pesticides, solvents and other volatile organic chemicals (VOCs) are not completely removed by RO. A good activated carbon post filter is recommended to reduce these contaminants.
- Many factors impact the RO membrane’s efficiency in reducing the amount of contaminant in the water. These include the water’s pH, temperature and pressure; the contaminant’s concentration and chemical properties as well as the membrane type and condition.
- Although RO filters do not use electricity, they depend on a relatively high water pressure to force the water molecules through the membrane. In an emergency situation where water pressure has been lost, these systems will not function.
- RO systems require maintenance. The pre and post filters and the reverse osmosis membranes must be changed according to the manufacturer’s recommendation, and the storage tank must be cleaned periodically.
- Damaged membranes are not easily detected, so it is hard to tell if the system is functioning normally and safely.
Atmospheric Water Generators (AWG):
Atmospheric Water Generators represent an incredible technological breakthrough. Drinkable Air AWG machines create pure, fresh drinking water out of the air we breathe. AWG units are humidity and temperature driven; meaning the higher the humidity in the atmosphere the more water the machine will produce. Humidity is part of the earths hydrologic cycle. The water that is produced by the AWG converting moisture in the air to water contains no contaminates, bacteria or other microorganisms.
Drinkable Air patented EnviroGuardTM purification system uses Ozone and GAC filters to ensure 100% pure water at all times. Drinkable Air AWG units carry the name “Chameleon”1 for branding and customer awareness.
How Atmospheric Water Generators work
- The Drinkable Air AWG first pulls air through an electrostatic filter, removing 99% of all air born particles.
- A condensation unit receives this clean humid airflow and condenses water vapor into liquid.
- As the machine collects the water, it drops into a collection tank where it is immediately Ozonated to kill all bacterial contaminates.
- The entire tank is chilled and this cool refreshing water is then pumped through a granulated activated carbon (GAC) filter which filters out any excess Ozone and makes the water taste great.