Requires Electricity: A high-pressure electric water pump can be used to apply external pressure on the input water, hence RO purifiers cannot operate without electricity.
Wastes Water: A significant area of the input water is discharged together with the dissolved impurities, which leads to unnecessary wastage of water. Normally, RO purifiers produce 3 litres of waste water for every 1 litre of water that is purified.
As its name implies, Ultraviolet or UV purification uses ultraviolet rays for the purification of water. A UV purifier operates by throwing high-intensity UV rays on the water that kills or inactivates the disease-causing bacteria and viruses.
But, UV purifiers can't remove any dissolved or un-dissolved impurities or compounds from water. Because of which most of the UV purifiers that are available in the marketplace use some kind of external sediment pre-filters to get rid of un-dissolved impurities and activated carbon filter to remove Chlorine and some dissolved impurities.
Therefore, UV water purifiers are only suggested for areas where the water source has a low degree of TDS.
In case the water has reduced TDS level but it is contaminated with germs and viruses and looks muddy then it is possible to utilize UF+UV water purifier.
Much like RO, Ultrafiltration additionally uses a semi-permeable membrane to purify water. After reading the very first sentence, you must now be thinking if both RO and UF use the same method to purify the water then what's the difference between RO and UF. Ultrafiltration or UF uses a membrane with much bigger pores (appx. 0.01 microns) as compared to RO that uses a membrane with very small pores (appx. 0.0001 microns).
The benefit of using Ultrafiltration is UF purifiers can operate without electricity since the membrane has considerably larger pores and water can pass through it obviously utilizing the force of gravity. Which means no outside water or pressure pump is necessary. Also, since UF vacuums do not hold any water back, there is no wastage of water.
But there are some limitations of using UF purifiers, because of larger pore size, UF can simply remove un-dissolved solids and larger impurities. It can't get rid of the dissolved solids or lessen the TDS amount. So, UF purifiers are not acceptable for elimination of high TDS water or hard water.