Water is considered as one of the most essential commodities for us. Its everyday necessity, however, comes with the challenge of accessing clean and pure water for drinking and cooking. With the persistently increasing levels of contamination of underground water sources due to a variety of factors like rapid industrialization warrant use of treated water employing different types of water purification systems. Water can be contaminated through biological, physical, chemical, or radiological contaminants. In simple terms, contaminants are referred to very broadly as being anything apart from the water molecules present in water.
Given below is a general classification of types of water contaminants and some examples of each type:
- Biological contaminants are simply organisms in water. These are also known as microbiological contaminants. Examples include bacteria, parasites, viruses, and protozoa.
- Physical contaminants affect the physical properties of water. These contaminants may change the appearance of water. Examples include sediments and organic materials in water bodies.
- Chemical contaminants are the compounds or molecules other than water molecules. These contaminants may occur as a result of human activities or naturally. Some examples of chemical contaminants are pesticides, arsenic, salts, bleach, nitrogen, and toxins produced by human or animal drugs.
- Radiological contaminants are considered the most lethal of all types of contaminants and a major reason behind life-threatening diseases, such as cancer. This sort of contamination happens because of the presence of unstable atoms, which can emit radiation. Such contaminants include uranium, plutonium and cesium.
Not only the above contaminants affect water quality but problems of discolouration or foul odour also hit the quality of drinking water. To purify water by removing such a classified range of contaminants requires different water purification systems. This blog, therefore, discusses the popular types of water purification systems based on contaminants present in water and their functional mechanism.
What are the Stages of Water Purification?
Before getting to know about the different types of water purification systems, it is good to know about the stages of water purification systems. Given below are different stages of water purification:
- Ion exchange and coagulation – This is the first step of the water purification process. In this step, water is demineralised or softened by separating substances.
- Sedimentation – In this process, the dissolved solids are settled or deposited which result in cleansing of water from large-sized suspended solids.
- Filtration and granular activated carbon – At this stage, the suspended solids are filtered or separated with the help of activated carbon. The activated carbon works as a magnet that helps stick the impurities and allows clean water.
- Disinfection – Through disinfection, bio contaminants are separated from the water molecules.
- Reverse osmosis – Those impurities which may have been left at the earlier stages are removed through reverse osmosis process. This is a complex water purification technique that is capable of eliminating the smallest of impurities present in the water.
- Storage – At the last stage of water purification, water is stored in a clean container or a designated storage tank for domestic use.
Types of Water Purification System
Water purification systems are chosen in response to the quality or rather type of contaminants or impurities present in water. As discussed above, contaminants are classified into four broad categories. The selection of a particular type of water purification method is made once the kind of impurity present in water is determined. Let’s take a sneak peek into some of the widely prevalent types of water purification methods and the purposes they serve.
Reverse Osmosis (RO)
A gradual decline of sources of pure drinking water all over the world, in general, and complexity of water contaminants at different places due to increased industrial interference, in particular, have led to a major transformation in water purification technology. With years of R&D in the field, reverse osmosis has emerged as a viable solution to treating complex water impurities which can hardly be removed by simple purifiers.
RO water purification system is based on reverse osmosis technology. This technology is used to demineralise or deionise water. It works on the principle of reverse osmosis or reversing the natural osmosis process. Using this technique, water is pushed through a semipermeable membrane which allows pure water molecules to pass through while leaving the impurities behind. Besides blocking impurities, the RO technology minimizes hardness of water to improve the taste of drinking water. The purified water pushed through the membrane is collected in a tank for use.
RO water purifiers are designed to remove dissolved impurities, bacteria, viruses and pyrogens. The major benefits of RO water purifiers are that such purifiers remove physical as well as chemical contaminants. Besides, they also remove biological contaminants to ensure pure drinking water. Due to the increased efficiency, the major RO water purifier uses are both in domestic and commercial settings. The RO water purification method is suitable for purifying water at home or in public places where the system is installed with water dispensing machines.
Though a revolutionary technology that is potent enough to clean the most complex impurities which could not be removed using conventional purification methods, RO is costlier and results in significant wastage of water. However, new innovation in the technology has found a way to redirect the waste water into the overhead tank and reintroduce the same into the purification system, thus, reducing water wastage.
Another problem with the RO system is that it tends to remove the healthy minerals in water, thereby, reducing the health benefits of drinking water. But with functions, such as TDS (total dissolved solids) controller, you can maintain a certain percentage of mineral contents in water. Another new innovation is remineralization technology in RO systems by which minerals can be re-inducted into the drinking water.
Ultraviolet (UV) Water Purification System
Ultraviolet water purification systems employ ultraviolet light to remove microorganisms, such as bacteria, viruses, microbes, cysts, and pathogens present in water. This technology is suitable for purifying water which is infested with organic impurities. UV technology prevents the proliferation of microorganisms by using UV radiation. The radiation penetrates the cells of microbes and disables their reproduction ability. Once the proliferation of microorganisms is stopped the water is eventually cleaned. The dead germs are removed through a filter and the purified water is collected in a tank for drinking purposes.
For water contaminated with biological, physical and chemical impurities, a combined UV+RO filtration system is used for purifying water. UV water purifiers are also used in combination with activated carbon filters for more efficient removal of contaminants.
Activated Carbon Purification System
Activated charcoal removes toxic chemicals, like chlorine and pesticides in water. Activated carbon employs the adsorption technique for purifying water. Through this technique, the heavy metals, chemicals and other contaminants are attracted to the activated carbon surface. It removes the major impurities in water and protects the membranes of RO water purifiers by pushing less contaminated water for reverse osmosis. It blocks chemical impurities that may cause damage to the RO membranes.
For impurities, such as arsenic or fluoride in water, activated alumina is a preferred choice. It consists of aluminium oxide which is a highly porous ceramic compound with good outstanding adsorption capability. It means that when AA attracts chemicals to its porous zone, the chemicals are not only blocked inside the pores but, in fact, they are bonded together. This technique is very cost-effective for removing the water contaminants, such as heavy metals and toxins with the added features of preventing the harmful substances from leaking back into the environment. This technology is remarkable for purifying water for domestic use as well as for water treatment facilities.
Ultrafiltration (UF) Water Purifier
Ultrafiltration water purifying system is one of the most used systems for purifying water. This technology efficiently separates pure water molecules and contaminants present in water. In such systems, the UF membrane traps suspended heavy metals, solids, viruses, and other microbes when water is passed through it. The system is best suited for places where chemical contamination is low.
Which type of water purifier is best for home?
Different purifiers have different advantages. Selection of the water purification system depends on the nature of contamination. It is recommended that before installing a purification system, you should use a water testing kit to determine the type of contaminants present in water. Once the type of contamination in water is established, you can choose the best quality RO water purifier or other type of purifier to meet your requirements. Choosing the best type of water purifier for home is a challenging task. Nonetheless, as discussed above, selecting the best water purifier is not a very cumbersome task. As a first step, determine the type of contaminant present in water with the help of a water testing kit. Knowledge about the type(s) of contaminants in water makes the selection work easier. However, it has been often noted that most recommend the usage of RO or UV water purifiers, which has given rise to a fractured opinion among experts on an ongoing RO water purifier vs UV water purifier debate. This has ultimately led to technological innovation that sought to combine these different purification methods. That is the reason, nowadays, some water purifiers come in a combination of UV+UF+RO technology to deal with a broad range of impurities in water.