How to choose the right water purifier based on water quality?

A water purifier is one of the domestic sources for water purification and it is an electric appliance. Water purifier filters toxic metals being dissolved in water, organic and inorganic components present in the water, provides sufficient temperature, provides mineral content which we are required, maintains alkalinity (Alkalinity is a chemical measurement of a water‘s ability to neutralize acids. Alkalinity is also a measure of its ability to resist changes in pH upon the addition of acids or bases) and gives the sufficient calcium and magnesium concentration.

There are different types of water purifiers available in the present market. such as,

  • UF+UV water purifier
  • RO+UF+UV water purifier

And also provides extra qualities water purifier like maintenance of TDS of water (TDS meter).

TDS Meter to check quality of water
TDS Meter

So, now for the selection of water purifier for our home depends upon the availability of water source like water supply from well, water supply from the municipality, water supply from the ground, water supply from storage tanks and like that so many ways. So for that available water, we need to check the TDS of available water.

TDS ( Total dissolved solids ) meter is available in the market. Standards of TDS meter reading is provided by our government. If water has 500 mg/litre TDS we can drink that water provided by BIS (Bureau of Indian Standards) and 500mg/litre is the benchmark for water quality and taste.

While coming to the WHO,  water with<300mg/litre TDS was deemed excellent by a WHO panel, water with TDS between 300 to 600mg/litre was good, water with TDS between 600 to 900 was fair, water with TDS between 900 to 1200mg/litre was poor and water with TDS >1200mg/litre was unacceptable.

And also water with low concentrations of TDS may also be unacceptable due to flat and insipid (lacking flavour) taste of water.

UF+UV Water Purifier

According to my knowledge people who are living in town, villages (far away from farming lands) can select these type of filters because most of them get water supply from the storage tank ( like overhead tanks, sumps) and from the municipality (municipal water supply). People who are getting water supply from municipality water supply are not needed the water purifier because they supply the water within the permissible limits of TDS  further if they want to consume the pure water they can use these type of water purifier.

Parts and operation

  • Pre sediment filter
Parts under filtration
  • Inline sediment filter
  • Inline carbon block filter
  • UF membrane cartridge
  • UV disinfection cartridge
Parts under operation
  • Adapter
  • Float switch
  • Solenoid valve
  • UV lamp
  • Storage tank

The pre sediment filter is gone through mechanical filtration. Sediment filter filters out particulates, solids, debris, dirt and et cetera (etc.).

Sedimentation is the deposition by settling of suspended particles present in the water.pre sedimentation filter is used frequently for protecting downstream appliance.

There are several types of sediment filters but usually, we prefer the spun type of sediment filter. And also we need to select the micron, nominally 5-micron sediment filter is used A 5-micron filter, for example, removes particles as small as 5 microns. Spun type sediment filter has transparent cloth rolled up on the roller which contains holes, while water is injected into the sediment filter water passes through cloth first and then next filtered water goes into the roller by holes and then that water is going to next system, dirt is deposited on the cloth. But, it can not remove dissolved solids, things that are in the solution and attached to the water molecule as a liquid.

Water is injected to next stage contains inline sediment filter inline, inline activated carbon filter, ultrafiltration UV chamber and solenoid valve. Now, water is injected into the Inline sediment filter through the inlet if the Inline sediment filter, water is further filtered by the Inline sediment filter and then water is injected into the Inline activated carbon filter. Carbon filtering is a method of filtering that uses a bed of activated carbon to remove contaminants and impurities, using chemical absorption. Activated carbon filters are small pieces of carbon, typically in granular or powdered block form, that have been treated to be extremely porous. Activated carbon works via a process called adsorption (the process by which a solid holds molecules of a gas or liquid or solute as a thin film ), whereby pollutant molecules in the fluid to be treated are trapped inside the pore structure of the carbon substrate.

Now water is injected into the UF (Ultrafiltration). It has a bunch of narrow pipes which is having 0.05-micron size holes like a tree is having roots, and it filters the water like tree absorbing the impure water from the ground.

Now, water is injected into the UV chamber (made with stainless steel). UV light has provided of wavelength 190nm-400nm, when water passes through the UV light all germs, microorganisms are killed by UV light.

Now the purified water fills the container, Now, we can drink this water. when the tank is full  Float switch open and cuts the main supply. The float switch is an electromechanical device and it contains airbag and spring, as soon as the airbag  is filled up with water it exerts the pressure against the switch and cuts main supply.

A solenoid valve is fixed at the outlet of the inline sediment filter. It is an electromagnetic device. It prevents the overflow of water due to inlet water pressure.

RO+UF+UV water purifier

RO means Reverse osmosis.

Simple Reverse Osmosis Schematic
Simple Reverse Osmosis Schematic

Osmosis is a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.

Reverse osmosis is a process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure.

A membrane is a selective barrier, it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles.

Reverse osmosis system in which a membrane is present. When pressurised water pumped through the membrane which is having 0.0001 micron-sized holes filters the water in such a way that only water is ejected, that water does not contain anything even the mineral content which is required by our body also that water does not contain a taste. But, the companies manufacture the RO water purifier provision of minerals not naturally.

Next ejected water is pumped through the UF filter and UV chamber. Now the ejected water fills the container we can drink that water but does not contain anything even the mineral content which is required by our body also that water does not contain a taste.

RO water purifiers are effective especially in places where pesticide use contaminates groundwater, in dessert regions where the salt content is high, in industrial areas where effluents ( liquid waste or sewage discharged into a river or the sea ) are discharged without proper treatment or where seawater is the main source of supply.

The problem starts when RO purifier is pitched (throw roughly) as household solutions for optimal TDS in places other than the above-mentioned areas like municipality water supply, groundwater stored in an overhead tank in towns and et cetera (etc.). So, RO water purifier is not advisable in these areas.