This post was most recently updated on May 4th, 2021
According to a 2017 report by the United Nations (UN) World Health Organization (WHO), 2.1 billion people lack access to a safe and reliable drinking water supply at home. Eighty-eight percent of the four billion annual cases of diarrhea reported worldwide have been attributed to a lack of sanitary drinking water.
Each year approximately 525,000 children under age five die from diarrhea, the second leading cause of death, and 1.7 million are sickened by diarrheal diseases caused by unsafe water, coupled with inadequate sanitation and hygiene.
We all know that we need to drink pure water; we are less sure of how various water filters work – either as standalone water filters or as a part of a water purifier.
How is a water filter different from a water purifier?
Did you know that a water filter is different from a water purifier? Both of them use the same principle of mechanical filtration, but in addition to removing inorganic material, water purifiers remove bacteria and viruses. To achieve this, they use chemical treatment of water and/or electrostatic charges to deactivate viruses.
However, note that different water filters have different functions. Some can make your water taste better, while others can filter out harmful chemicals or germs. No single filter can keep every type of contaminant out of your drinking water, and not everyone needs a water filter.
If that is not intriguing enough, chemicals such as chlorine, when used in the right quantities are actually beneficial as they kill the germs present in water. Others like Fluorides are useful to prevent tooth decay. What is definitely harmful are ions of heavy metals like Arsenic, Mercury, Cadmium, and Lead in any quantity whatsoever. The presence of microbes like bacteria, viruses, and protozoa makes the water further contaminated, which creates the demand for high-end purification systems.
Filters used for water purification
Active Carbon Filters
Active carbon filters are used to purify soluble gases such as chlorine, carbon monoxide, nitrogen, ammonia, and organic material like dead algae that make it to your water source. Activated carbon is typically used in filters as it has been treated to have a much higher surface area than non-treated carbon. This allows for adsorption, the phenomenon of the adhesion of atoms, ions, or molecules from a gas, liquid or dissolved solid to a surface. Generally, household carbon filters come with a lining of activated silver that kills bacteria.
A biosand filter (BSF) is used to remove pathogens and suspended solids from water using biological and physical processes that take place in a sand column covered with a biofilm. BSFs have been shown to remove heavy metals, turbidity, bacteria, viruses, and protozoa. BSFs also reduce discoloration, odor, and unpleasant taste in the water supply. Due to the lack of recurring costs, they are much recommended to be used, especially in developing countries like India.
Reverse Osmosis Filters
Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules, and larger particles from drinking water. Reverse Osmosis is recommended when the Total Dissolved Solids quotient of your water supply exceeds 500 ppm. However, be aware that the process does not differentiate between good and bad mineral content, so it produces water that is purified to the extent of more than 95% with minimal mineral content.
Ultraviolet light (UV) is very effective at inactivating cysts and deactivating viruses as it directly attacks the DNA of the microbes. UV light’s disinfection effectiveness decreases as turbidity increases, a result of the absorption, scattering, and shadowing caused by the suspended solids. The main disadvantage to the use of UV radiation is that, like ozone treatment, it leaves no residual disinfectant in the water; therefore, it is sometimes necessary to add a residual disinfectant after the primary disinfection process. They are usually used in conjunction with other water filters like RO membrane etc.
Ion exchange systems use ion exchange resin- or zeolite-packed columns to replace unwanted ions. The most common use case is water softening consisting of removal of Ca2+ and Mg2+ ions replacing them with benign (soap friendly) Na+ or K+ ions. Ion exchange resins are also used to remove toxic ions such as nitrite, lead, mercury, arsenic, and many others.
Usually used as part of the pre-filtration process, it works very well in removing sediments like rust, sand, dust, silt, heavy metals, and other large particles in water. Usually, a sediment filter is made from Polypropylene (PP) or pleated polyester (washable) with a size ranging from 1 to 100 microns. It can be used alone as a point of entry (POE) whole house filtration solution or used in conjunction with other filters to provide greater filtration.