A point-of-use water purifier is installed at a single water connection like your kitchen or bathroom sink. These lower capacity systems are designed for light usage.
They don’t protect your pipes or appliances from contaminants known to clog, crack, or damage them. They also do not treat your shower water.
Reverse Osmosis (RO)
A reverse osmosis system uses high pressure to force water through a semipermeable membrane. Clean drinking water (called permeate) flows through the membrane and contaminated waste water (called brine) goes to the drain. The RO system’s pre-filters remove large particles from the water and its RO filter removes most other contaminants. Some systems also add post-filters to address off-tastes or odors.
When shopping for an RO, look for a model with a flow restrictor and a storage tank to minimize waste. Also, make sure the system you choose is certified by NSF or WQA. That way, you’ll be sure that it meets the standards to treat specific contaminants such as arsenic, chromium-6, disinfection byproducts, lead and nitrates from fertilizers.
You might be surprised to learn that a reverse osmosis system sends 4 gallons of water down the drain for every gallon of clean drinking water produced. However, that wastewater is useful for other purposes, such as washing dishes or cleaning clothes. It can also be returned to riverbeds for filtration through the hydrologic cycle.
The most popular point-of-use RO systems are installed under the kitchen sink, although they can be placed elsewhere if you have more space. Some RO systems include a final polishing filter for even more contaminant removal, but that increases the cost and requires extra maintenance.
Activated Carbon
Activated Carbon (AC) is a highly porous material that acts like a sponge soaking up unwanted chemicals. It removes organic chemicals from vapor or liquid streams through a process called adsorption. When contaminants pass through the carbon bed, they are drawn to the surface of its pores by a magnet-like force and then trapped inside its microporous structure. Once the contaminant is bound, it becomes immobilized and the filtered water flows through to the next stage of treatment, if needed.
Typical raw materials for AC include coal, coconut shells and lignocellulosic plant wastes. The raw material is then activated for use in a variety of applications by thermal or chemical treatments. Thermal activation involves reducing moisture, dehydrating and carbonizing the raw material. Chemical activation adds a powerful dehydrating agent to the raw material and heats it up. This makes the pore structure more open, which is better suited for adsorption of larger molecules.
Typically, AC is used for two main purposes: taste and odor control and the removal of organic compounds from water. In the former, granular AC is added to the water to adsorb unpleasant taste and odor compounds. In the latter, AC is used to treat industrial wastewater discharged as effluent from fabric dyeing factories, rubber thread factories, chlorinated solvent plants and other similar processes. By adsorbing contaminants, the treated water can be upgraded for reuse in the plant or can be released into waterways without causing environmental damage.
Micron Filtration
Water filters with micron ratings are the best way to remove heavy metals, chlorine and other contaminants from a water supply. These filters can also eliminate bad taste from contaminated or chemically treated water. The result is energizing, healthy filtered water that helps boost energy levels and maintains proper hydration, especially in hot environments.
Microns are tiny holes in the filter media. Unlike a mesh door that allows air to pass through but prevents flies and bugs from entering, a filter with a micron rating will allow water to pass through while blocking microscopic impurities from getting into the water supply.
The smaller the micron rating, the more impurities will be filtered. However, smaller micron ratings can cause a loss of flow rate and may need to be replaced more often due to clogging.
Boshart offers a wide range of micron ratings to suit any filtration need, from basic to industrial. The micron rating is indicated in two ways – nominal or absolute. A nominal micron rating indicates the percentage of particulates at a given size that will be retained by the filter under specific test conditions while an absolute micron rating indicates the smallest particle that can fit through the filter’s pores.
Systems with a micron rating of around 1 micron or 1/2 a micron are the most effective option for removing bacteria and other pathogens but they can cause clogging problems in rare cases. Products with a 50-micron rating have larger pores that will retain anything bigger than a white blood cell without causing major clogging issues.
UV Light
Ultraviolet (UV) light is a region of the electromagnetic spectrum that lies between visible light and X-rays. UV radiation is divided into three segments based on its interaction with biological materials: UVA (400-315 nm), also known as black light; UVB (315-280 nm); and UVC (288-100 nm), which does not reach Earth’s surface and can cause sunburns and skin cancer.
The water treatment process in a POU system typically includes string-wound sediment and carbon filters for removing large particles and organic chemicals; reverse osmosis membrane technology for separating and removing nearly all suspended and dissolved contaminants; UV disinfection to inactivate pathogens; and remineralization to add back essential minerals after RO (especially calcium, magnesium, and potassium)11.
When UV radiation is applied to water, it interacts with ribonucleic acid molecules in bacteria and viruses, changing the structures of their DNAs, causing them to break down and inactivate. The most effective UV systems for POU applications utilize a combination of UV-LED and medium pressure mercury lamps, allowing for the selection of optimum wavelengths to achieve the highest level of germicidal effectiveness. A pulsed irradiation mode maximizes the effectiveness of UV by allowing for more frequent, shorter exposures to the water11.