NF is the abbreviation for Nano-Filtration and is a membrane water purification process similar to RO membrane water purification. Nanofiltration membranes have slightly bigger pore size than RO which has led to Nanofiltration sometimes being called a “loose RO” membrane process.
NF water purifiers will remove salts of larger valency 2 or divalent elements, but will let monovalent salt molecules like Sodium Chloride to pass through. It should be noted that even though NF will let through monovalent Sodium Chloride, it will not allow the passage of a divalent salt of Sodium like Sodium Sulphate. All salts of heavier atoms like those of the toxic heavy metals are blocked by NF water purifiers. One of the main uses of NF membranes in industrial applications is to soften water or remove water hardness.
Difference between Nanofiltration and Reverse Osmosis
The main difference between nanofiltration and reverse osmosis is that RO blocks monovalent salts like sodium chloride, whereas nanofiltration allows them to pass through. Because Nano filtration pores are bigger than RO, NF water purifiers can work on lower pressure than RO. Also NF water purifiers have a lesser tendency of fouling of its membranes. The image below shows graphically how water is purified by an NF membrane by showing what it will let through and what it will not allow to pass through.
NF Water Purifier will purify water from all toxic dissolved chemicals including like heavy metals and all organic compounds. NF will completely remove all microorganisms from water including the smallest of viruses. NF water purifier will remove upto 60% of hardness salts of calcium and magnesium in water. With these advantages of NF water purifiers some water purifier manufacturers in India have started making NF water purifiers. Some examples of Indian NF water purifiers are Aquaguard Total NF water purifier, Aquaguard water purifier Reviva NF and Permionics Pureflo NF water purifier.
Advantages of Nano NF water filter
- Works on lower pressure than RO and so requires much less energy
- Recovery in NF water purifiers is more than RO and so NF does not waste as much water as an RO
- Ideal for drinking water purification of any water source with TDS less than a 1000ppm
- Softens hard water
- Removes toxic Heavy metals from water
- Removes toxic and other organic compounds from water and thus removes bad odours and taste from water
Capacity of whole house Nano Filter NF water purifiers
Nanfiltration water purification plants or NF water purifiers meant as whole house water purifiers are usually classified as having a flow of so many Liters Per Day or LPD. To calculate the amount of water required per day, you could use an average of 200 liters required per day per person. So for example, a family of 6 will need a 6×200=1200 liters per day.
You would not require the NF water purifier permeate or product water to flush toilets and for cleaning floors, etc., since it is very safe to use the reject water from the NF water purifier for these jobs. The reject water from the NF water purifier is filtered and disinfected water. This is because all water sent to the membranes of a Nanfiltration water purifier has to be clean to protect the Nanfiltration membranes in a Nanfiltration water treatment plant. So the reject water from the NF water purifier can be sent to a separate tank from which water for toilet flushing, cleaning the floors, etc. can be taken.
The quantity of reject water from a NF water purifier is not as much as from an RO water purifier, but still it will be sufficient for toilet flushing, floor cleaning etc. If there is excess reject water from the NF water purifier it is best disposed of far from you intake water source, because it will have very high content of Hardness.
For cleaning, initially you could use the NF water purifier reject water and a final rinse with the NF water purifier permeate or product water. This is because the reject water of the NF water purifier contains a lot of salts, and when the water dries, these salts would leave a whitish colored stain marks on the cleaned surface. You avoid this by a final flush with the NF water purifier permeate pure water.