For thousands of years, people have treated water intended for drinking to remove particles of solid matter, reduce health risks, and improve aesthetic qualities such as appearance, odor, color, and taste. The treatment needs of a water system are likely to differ depending on whether the system uses a groundwater or surface water source. Common surface water contaminants include turbidity, microbiological contaminants (Giardia, viruses and bacteria) and low levels of a large number of organic chemicals. Groundwater contaminants include naturally occurring inorganic chemicals (such as arsenic, fluoride, radium, radon and nitrate) and a number of volatile organic chemicals (VOCs) that have recently been detected in localized areas.

Types of home drinking water treatment devices:

• Ultraviolet Light Disinfection Systems
• Mecanical Filters
• Activated Carbon and Activated Alumina Filters
• Reverse Osmosis Systems
• Ion Exchange (softners) and Ion Exchange Water Conditioner
• Distilation Systems
• Aeration Systems
• Chlorination Systems

List of Devices for Treating some of the more common contaminants and undesirable minerals

Contaminant / minerals	UV Light	Mechanical Filters	Activated Carbon	Activated Alumina	Reverse Osmosis	Ion Exchange	Distaltion	Aeration	Chlorination
Bacteria and Viruses	*								*
Taste and Odor			*		*		*
Lead			*	*	*	*	*
Nitrate					*	*	*
Chlorine and Trihalomethanes			*
Radon			*					*
Hardness						*
VOCs and other Organics			*					*
Pesticides and PCBs			*				*
Iron and Magnese					*	*			*
Sulfate					*	*	*
Giardia and Crytosporidium Cysts		*			*		*
Sediment and Turbidity		*
Total Disolved Solids					*		*
Aluminium					*		*
Arsenic				*	*		*
Barium					*	*	*
Cadmium					*	*	*
Chloride					*		*
Chromium					*		*
Copper					*		*
Fluoride				*	*		*
Mercury					*		*
Radium					*	*	*
Selenium				*	*		*
Silver					*		*
Zinc					*		*

Summary of advantages, disadvanteges and costs of various types of entry / use treatment devices

Ultraviolet Light

Advantages: Effective for destroying bacteria and viruses and disinfecting drinking water.

Disadvantages: Will not remove contaminants other than bacteria and viruses. Not effective for Giardia and Cryptosporidium cyst removal.

Costs: Units typically cost between $300 and $700.

Ion Exchange (excluding manganese greensand)

Advantages: Effective for removing minerals such as hardness, barium, radium, nitrate, sulfate, calcium and magnesium. Effective for removing iron (provided concentrations do not exceed about 1 mg/L).

Disadvantages: Requires regeneration (usually with sodium chloride or potassium chloride).

Costs: Typical costs vary from $500 to $1200 depending on the resin (anion exchange resins cost more than cation exchange resins) and type of equipment.

Mechanical Filters

Advantages: Effective for removing suspended particles such as rust, dirt and sediment. Filters tested and approved for Giardia and Cryptosporidium cysts are available.

Disadvantages: Not effective for removing dissolved contaminants such as lead, nitrate, VOCs, etc.

Costs: Use-device mechanical particulate filters typically cost between $30 and $100, with filter  replacement cost of $15 to $40.

Activated Carbon Filters

Advantage: Effective at removing a wide range of organic contaminants such as VOCs and pesticides. Carbon block and precoat designs have been validated as effective for lead reduction. Often effective for reducing taste and odor problems. Does not use electricity or generate wastewater.

Disadvantages: Not effective at removing inorganic materials such as hardness, iron, nitrate or fluoride. Bacteria growth may occur in the carbon filter if not maintained properly. May require post-disinfection

facilities.

Costs: Point-of-Use activated carbon filters typically cost between $75 and $350. Replacement filter cost is in the $20 to $40 range. Point-of-Entry treatment devices typically cost between $500 and $1,250. Replacement filters cost $200 to $400.

Activated Alumina Filters

Advantages: Effective for removal of arsenic, fluoride and lead. Does not use electricity and does not waste water.

Disadvantages: Will usually not remove minerals other than those listed above.

Costs: Similar to activated carbon.

Reverse Osmosis

Advantages: Can remove a wide variety of inorganic and organic contaminants including lead, nitrate and sodium. Normal household water pressure provides good performance.

Disadvantages: Uses from three to five liters of water for each liter produced. Some membranes are damaged by chlorine.

Costs: Under the sink use-devices that include a mechanical prefilter and an activated carbon post filter typically cost $400 to $1,000. Replacement membranes cost $30 to $100.

Distillation

Advantages: Removes the greatest variety of contaminants.

Disadvantages: Uses approximately three kilowatts of electricity per five liters of water. Water-cooled units waste a considerable amount of water. Will require frequent cleaning, especially where the water is hard. Removal of minerals may leave bland taste to the water. Process is slow.

Costs: Between $99 and $500 for a countertop model.

Aeration

Advantages: Effective for removing radon and volatile organic chemicals.

Disadvantages: Expensive to purchase and install. Requires secondary pumping and pressurization.

Costs: Between $2,200 and $3,800.

Chlorination

Advantages: Only effective way of dealing with large amounts of iron, hydrogen sulfide and colloidal  iron. Is also an excellent disinfectant.

Disadvantages: Requires handling and storage of hazardous chemicals. Requires time to insure that chemicals are mixed properly and available when needed.

Costs: Between $800 and $1,500.