Dissolved Contaminant Reduction

Dissolved contaminents in water, such as Arsenic, Perchlorate, Lead, Calcium and Magnesium (Calcium and Magnesium are referred to as hardness) can be removed a number of ways.

Reverse Osmosis

Reverse osmosis is a process that removes particulates, bacteria, viruses and most dissolved ions by passing water through a membrane while rejecting unwanted consituents to a waste stream. Undersink RO systems have become very popular over the last few years because they are effective and affordable. The cons to an RO drinking water system are that they require maintenance, there is some water wastage and they remove all minerals, even those considered health beneficial.

Filtration

Calcium and Magnesium (referred to as hardness) as well as small amount of iron can be removed from water through ion exchange technology in a process called "softening". Generally water softening on a full house scale is done using a whole house water softener. Water softeners exchange the hardness ions with sodium ions and require food grade coarse salt in order to recharge the resin. Because the resin used in a water softener is a media, a water softener can help to remove larger size particles in water (>20 micron). Water softeners cannot remove higher iron levels (in fact higher iron levels foul the resin) and are not helpful in altering water pH or in removing things like organics, nitrates, perchlorates and other harmful substances. Water softeners are also affordable and effective and require little maintenance other than refilling with salt. The downside to water softeners are the initial expense of the unit and the sodium added to the water adds to the daily sodium intake of individuals drinking the water which may be an issue for some. Because the salt discharge from a water softener causes problems for municipal waste water treatment, salt softening may be banned in your area.

Iron and manganese reduction is handled as a separate topic.