Treatment Techniques and Devices
Once contamination is detected in a drinking water supply it is important to use the proper treatment device to remove the contaminant. The following section is intended as a guide to help in the selection of a treatment device. Before buying a treatment device have the water supply tested for contamination and consult a specialist when selecting the best treatment device. If the specific contaminant is known the information in the following sections will indicate the possible treatment devices and link to more detailed information on this web site.
ACTIVATED ALUMINA
Activated Alumina is a granulated form of aluminum oxide. In this process, water containing the contaminant is passed through a cartridge or canister of activated alumina. The alumina absorbs the contaminant and freshwater continues to the service faucet. The cartridge of activated alumina has to be replaced periodically. It is important to determine by testing when the contaminant removal capability of the device is exhausted, so the treatment technique will remove, not contribute to, the contaminant. Also, activated alumina devices will accumulate bacteria, so treated water will have higher bacteria counts than raw water.
Contaminants Removed: Arsenic, Fluoride.
ACTIVATED CARBON
Activated carbon filters absorb impurities from water as it passes through a carbon cartridge or tank. Such filters are used to eliminate or remove undesirable odors, tastes, organic compounds, and residual chlorine. Carbon filters also remove some potentially, hazardous contaminants such as radon gas, hydrogen sulfide, many dissolved organic chemicals and trihalomethanes. Most inorganic chemicals are not removed by these filters.
Contaminants Removed: Hydrogen Sulfide, Radon, Chlorine, Volatile Organic Compounds, Pesticides, Benzene, Colors, Odors.
AERATION
Aeration systems spray the water through an air-filled chamber then use a fan to move the contaminated air out of the area.
Contaminants Removed: Hydrogen Sulfide, Radon.
ANION EXCHANGE
Anion exchange units use a resin that exchanges chloride, or in some cases hydroxide, for the contaminant anions. Most use chloride which increases the chloride content of water as it removes anions such as nitrate, sulfates and bicarbonates.
Contaminants Removed: Nitrate, Sulfate, Fluoride, Tannins.
CHEMICAL PRECIPITATION
In chemical precipitation certain compounds are added to the water that chemically react with the contaminate. The products of the reaction will then either sink to the bottom or float to the top of the holding tank, so that they can be removed. This method is primary used in public water supplies and is not a viable solution for private water supplies. If contaminant is detected in a private water supply use an alternate method or contact you local water authority.
Contaminants Removed: Arsenic, Barium, Cadmium, Chromium, Lead, Mercury, Selenium, Silver.
CHLORINATION
The most common, oldest and relatively inexpensive method used to disinfect water is chlorination. A chemical feed pump continuously dispenses chlorine into the water supply. Chlorine, an oxidizing agent, kills most bacteria and some viruses. In the proper concentrations and under adequate exposure time, chlorine is an excellent disinfectant.
Chlorine reacts with certain metals and organic matter in the water to form hazardous, chlorinated, organic chemicals. Use of an activated carbon filter after chlorination will remove excess chlorine and limited amounts of any chlorine compounds formed. Chlorination may also oxidize and remove some color and odor causing substances, including iron and hydrogen sulfide.
Contaminants Removed: Bacteria, Iron, Hydrogen Sulfide, Some Viruses.
DISTILLATION
Distillation heats water until it vaporizes as steam. Minerals, bacteria and other substances are left behind when the steam recondenses into relatively pure water. Distillers remove bacteria, minerals, trace amounts of metals, many volatile organic chemicals and nitrate. The distillation process is very slow (daily capacity is usually between two and five gallons). Approximately five gallons of tap water is required to produce one gallon of distilled water.
Contaminants Removed: Bacteria, Lead, Nitrate, Sodium Chloride, Organic Chemicals, Many Pesticides.
ION EXCHANGE
Ion exchange systems soften hard water by removing the minerals (calcium and magnesium that cause hardness. This system also efficiently removes iron, manganese and many heavy metals. The hard water is pumped through a tank containing an exchange resin. Sodium on the resin replaces the hardness minerals. The sodium remains in a soluble form in the softened water.
Contaminants Removed: Iron, Magnesium, Calcium, Manganese.
MECHANICAL FILTRATION
Mechanical filters, or microfiltration, removes suspended material from water including sand, silt, clay or organic matter. These filters do not remove dissolved or very fine particles and are often used in combination with other treatment equipment. Filters are commonly of fabric, fiber, ceramic or other screening material.
Contaminants Removed: Sediment
NEUTRALIZING FILTERS
Neutralizing filters treat acidic water. The filter treats all of the home water supply by passing it through granular calcite (marble, calcium carbonate or lime) or by chemically feeding in soda ash, sodium carbonate or caustic soda (sodium hydroxide).
Contaminants Removed: Acidity.
OXIDIZING FILTERS
Oxidizing filters use a zeolite coated filter to oxidize dissolved iron, manganese and hydrogen sulfide. The contaminants then form large particles that the filter can catch.
Contaminants Removed: Hydrogen Sulfide, Iron, Manganese.
REVERSE OSMOSIS
Reverse Osmosis (RO) units remove substantial amounts of most inorganic chemicals (such as salts, metals, minerals) most microorganisms, and many organic chemicals. They do not effectively remove some organic compounds. Mechanical filters and activated carbon filters are almost always used with a RO unit. First, the mechanical filter (1) removes dirt, sediment and other impurities, that would otherwise clog the reverse osmosis membrane. The RO (2) unit is installed next. The water is held in a pressurized water storage container (3). An activated carbon filter (4) then removes organic compounds which pass though the RO unit. A separate water tap (5) is used for this water.
Reverse Osmosis uses large amounts of water. Typically, about 75% or more of the water is discarded with the contaminants.
Contaminants Removed: Lead, Sulfate, Calcium, Magnesium, Sodium, Potassium, Manganese, Aluminum, Chloride, Nitrate, Fluoride Boron, Most Microorganisms, Organic Chemicals.
ULTRAVIOLET
Low-pressure mercury arc lamps produce ultraviolet light which has germicidal properties. The radiation kills or deactivates pathogens. Bacteria are killed with relatively low amounts of radiation, viruses are more resistant, and cysts and worms are unaffected. Radiation leaves no residual product that continues to disinfect beyond the treatment period.
Contaminants Removed: Bacteria, Viruses, Cysts such as Cryptosporidium and Giardia.
Once contamination is detected in a drinking water supply it is important to use the proper treatment device to remove the contaminant. The following section is intended as a guide to help in the selection of a treatment device. Before buying a treatment device have the water supply tested for contamination and consult a specialist when selecting the best treatment device. If the specific contaminant is known the information in the following sections will indicate the possible treatment devices and link to more detailed information on this web site.
ACTIVATED ALUMINA
Activated Alumina is a granulated form of aluminum oxide. In this process, water containing the contaminant is passed through a cartridge or canister of activated alumina. The alumina absorbs the contaminant and freshwater continues to the service faucet. The cartridge of activated alumina has to be replaced periodically. It is important to determine by testing when the contaminant removal capability of the device is exhausted, so the treatment technique will remove, not contribute to, the contaminant. Also, activated alumina devices will accumulate bacteria, so treated water will have higher bacteria counts than raw water.
Contaminants Removed: Arsenic, Fluoride.
ACTIVATED CARBON
Activated carbon filters absorb impurities from water as it passes through a carbon cartridge or tank. Such filters are used to eliminate or remove undesirable odors, tastes, organic compounds, and residual chlorine. Carbon filters also remove some potentially, hazardous contaminants such as radon gas, hydrogen sulfide, many dissolved organic chemicals and trihalomethanes. Most inorganic chemicals are not removed by these filters.
Contaminants Removed: Hydrogen Sulfide, Radon, Chlorine, Volatile Organic Compounds, Pesticides, Benzene, Colors, Odors.
AERATION
Aeration systems spray the water through an air-filled chamber then use a fan to move the contaminated air out of the area.
Contaminants Removed: Hydrogen Sulfide, Radon.
ANION EXCHANGE
Anion exchange units use a resin that exchanges chloride, or in some cases hydroxide, for the contaminant anions. Most use chloride which increases the chloride content of water as it removes anions such as nitrate, sulfates and bicarbonates.
Contaminants Removed: Nitrate, Sulfate, Fluoride, Tannins.
CHEMICAL PRECIPITATION
In chemical precipitation certain compounds are added to the water that chemically react with the contaminate. The products of the reaction will then either sink to the bottom or float to the top of the holding tank, so that they can be removed. This method is primary used in public water supplies and is not a viable solution for private water supplies. If contaminant is detected in a private water supply use an alternate method or contact you local water authority.
Contaminants Removed: Arsenic, Barium, Cadmium, Chromium, Lead, Mercury, Selenium, Silver.
CHLORINATION
The most common, oldest and relatively inexpensive method used to disinfect water is chlorination. A chemical feed pump continuously dispenses chlorine into the water supply. Chlorine, an oxidizing agent, kills most bacteria and some viruses. In the proper concentrations and under adequate exposure time, chlorine is an excellent disinfectant.
Chlorine reacts with certain metals and organic matter in the water to form hazardous, chlorinated, organic chemicals. Use of an activated carbon filter after chlorination will remove excess chlorine and limited amounts of any chlorine compounds formed. Chlorination may also oxidize and remove some color and odor causing substances, including iron and hydrogen sulfide.
Contaminants Removed: Bacteria, Iron, Hydrogen Sulfide, Some Viruses.
DISTILLATION
Distillation heats water until it vaporizes as steam. Minerals, bacteria and other substances are left behind when the steam recondenses into relatively pure water. Distillers remove bacteria, minerals, trace amounts of metals, many volatile organic chemicals and nitrate. The distillation process is very slow (daily capacity is usually between two and five gallons). Approximately five gallons of tap water is required to produce one gallon of distilled water.
Contaminants Removed: Bacteria, Lead, Nitrate, Sodium Chloride, Organic Chemicals, Many Pesticides.
ION EXCHANGE
Ion exchange systems soften hard water by removing the minerals (calcium and magnesium that cause hardness. This system also efficiently removes iron, manganese and many heavy metals. The hard water is pumped through a tank containing an exchange resin. Sodium on the resin replaces the hardness minerals. The sodium remains in a soluble form in the softened water.
Contaminants Removed: Iron, Magnesium, Calcium, Manganese.
MECHANICAL FILTRATION
Mechanical filters, or microfiltration, removes suspended material from water including sand, silt, clay or organic matter. These filters do not remove dissolved or very fine particles and are often used in combination with other treatment equipment. Filters are commonly of fabric, fiber, ceramic or other screening material.
Contaminants Removed: Sediment
NEUTRALIZING FILTERS
Neutralizing filters treat acidic water. The filter treats all of the home water supply by passing it through granular calcite (marble, calcium carbonate or lime) or by chemically feeding in soda ash, sodium carbonate or caustic soda (sodium hydroxide).
Contaminants Removed: Acidity.
OXIDIZING FILTERS
Oxidizing filters use a zeolite coated filter to oxidize dissolved iron, manganese and hydrogen sulfide. The contaminants then form large particles that the filter can catch.
Contaminants Removed: Hydrogen Sulfide, Iron, Manganese.
REVERSE OSMOSIS
Reverse Osmosis (RO) units remove substantial amounts of most inorganic chemicals (such as salts, metals, minerals) most microorganisms, and many organic chemicals. They do not effectively remove some organic compounds. Mechanical filters and activated carbon filters are almost always used with a RO unit. First, the mechanical filter (1) removes dirt, sediment and other impurities, that would otherwise clog the reverse osmosis membrane. The RO (2) unit is installed next. The water is held in a pressurized water storage container (3). An activated carbon filter (4) then removes organic compounds which pass though the RO unit. A separate water tap (5) is used for this water.
Reverse Osmosis uses large amounts of water. Typically, about 75% or more of the water is discarded with the contaminants.
Contaminants Removed: Lead, Sulfate, Calcium, Magnesium, Sodium, Potassium, Manganese, Aluminum, Chloride, Nitrate, Fluoride Boron, Most Microorganisms, Organic Chemicals.
ULTRAVIOLET
Low-pressure mercury arc lamps produce ultraviolet light which has germicidal properties. The radiation kills or deactivates pathogens. Bacteria are killed with relatively low amounts of radiation, viruses are more resistant, and cysts and worms are unaffected. Radiation leaves no residual product that continues to disinfect beyond the treatment period.
Contaminants Removed: Bacteria, Viruses, Cysts such as Cryptosporidium and Giardia.
