Point-of-Use Water Purifiers

A point-of-use water purifier is installed under a kitchen sink to filter your drinking and cooking water. POU filters generally use combinations of string-wound sediment, carbon, ion exchange and redox filters.


Activated carbon and reverse osmosis (RO) systems can remove lead, chlorine, organic odors, pathogens, cryptosporidium, giardia and other contaminants.

Reverse Osmosis (RO)

Reverse Osmosis (RO) is an effective water filtration technology. It utilizes semi-permeable membranes to separate salts and other contaminants from freshwater. RO systems typically include multiple pre- and post-treatment filters to reduce the likelihood of fouling (when dissolved contaminants form scale on the membrane) and prevent bacteria and other organic contamination.

The RO system begins with a sediment filter to remove large particles such as sand, clay and plant matter. A carbon filter removes organic contaminants including pesticides and algae and granular activated carbon (GAC) filters out chlorine and disinfectants in the water as they are oxidizers and can cause degradation of the thin film-material RO membranes. RO systems are also equipped with antiscalants and scale inhibitors to prevent a build-up of calcium carbonate on the membrane.

After these initial steps, the water passes through a series of pressure vessels which contain the RO membranes. Each vessel has a number of RO membranes (usually from 1 to 6 membranes). The pressure vessels are connected in an array so that the reject water from the first one feeds the next RO membrane in the array. The clean water is collected in a pressurized storage tank for future use.

The water then goes through a final stage that includes a carbon post-filtration to remove aesthetic taste and odors from the treated water as it makes its way to the faucet. This last step is often referred to as the “polishing phase” of the RO process.

Activated Carbon (AC)

Activated carbon (AC) filters remove organic contaminants from drinking water. It adsorbs organic compounds from the water by diffusion and chemical reactions within its pores. The pore size and surface area are important factors in the ability of AC to remove specific organic chemicals from water. In general, smaller molecules diffuse deeper into the AC pores and are more likely to adsorb. Conversely, larger molecules may be trapped in the larger pores and not removed from the water. The effectiveness of an AC filter to remove a particular organic compound can also be affected by water temperature and pH levels.

Typically, AC is made from wood, coal, nut shells, peat, or other carbon-heavy materials that have been heated, creating a porous structure with microscopic holes, or pores. The pore size can be controlled to create different types of AC, depending on the application.

Most water applications for AC are related to odor and taste control and the removal of organics, such as heavy metal ions. There are two main forms of AC used for these purposes: granular activated carbon (GAC) and powdered AC. GAC filters are commonly used in conjunction with other water filtration processes. Powdered AC is added as a slurry to the water and left for a specified contact time before being clarified or filtered.

Some GAC is regenerated on-site and reprocessed into a new batch of carbon. This process is generally called “steam activation.” The regenerated GAC can be used in packed-bed columns downstream of other non-GAC filtration or membrane processes to adsorb organic DBP precursors, which are then filtered out.

Ultraviolet Disinfection (UVD)

UV light disinfection is a chemical-free process that uses radiation to kill microorganisms in water. It is effective in removing bacteria, viruses and parasites that are resistant to chlorine (like cryptosporidium). UV is a very safe treatment for your home water supply. It is a good choice for well water, spring water, lake and surface water as well as municipally treated water.

Like chlorine, UV kills disease-causing organisms by scrambling their DNA. It does this in a much faster way and is far more effective than chlorination. This makes it a better choice for municipally treated water and for those concerned about the potential for heavy metals and other contaminants in their drinking water to cause health problems.

A UV system requires a permanent power source to operate. It also needs a constant flow of water and is not effective during a power outage. It is best installed as a point-of-entry (POE) system, where it is connected before the water enters the home.

The system should be pretreated with a sediment or carbon block filter before water reaches the UV lamp. This will remove color, turbidity and suspended particles that can shield the microorganisms from UV radiation. It will also help prevent mineral build-up on the quartz sleeve of the lamp. It is important to clean and maintain the sensor regularly as well. Failure to do so will cause the sensor to inaccurately read incoming UV energy.


Using the membrane, water is filtered to remove harmful contaminants from drinking water. In addition to improving taste, odor, and clarity, some advanced systems can also add healthy dissolved minerals back into the water in a process called remineralization. Remineralizing the water provides a variety of health benefits that many people desire, including an alkaline pH value similar to that of most bottled water.

While calcium and phosphate naturally form protective fluorapatite on teeth, there are some circumstances when they cannot do so, such as xerostomia or certain dental conditions. Remineralization is a process where calcium, phosphate, and fluoride ions are deposited into crystal voids in demineralized enamel. This helps to prevent the sensitivity associated with non-cavitated tooth lesions, which can eventually lead to decay if left untreated.

A remineralization cartridge allows the beneficial minerals in water to be absorbed into the enamel, which results in healthier, stronger, and more resilient teeth that resist damage from hot or cold foods or beverages. This is an important benefit for patients with xerostomia, as the extra minerals may help to reduce dry mouth symptoms. In addition to reintroducing the healthy minerals, the remineralization filter raises the overall alkalinity of the water, helping to improve taste and promote hydration. A remineralization filter can be purchased separately or as part of a complete point-of-use water purification system. The Neo-Pure QCRO system includes a remineralization filter and offers 6-month and 12-month maintenance kits to keep the system up and running. Each kit contains a carbon block filter, a reverse osmosis membrane, and an inline remineralization cartridge. The system’s quarter-turn cartridge replacement design makes routine maintenance quick and easy.