I am a student of IIT Kharagpur doing a project on water purification.
We are using a RO purifier system to make the water potable and safe for drinking. But since the reject water is having more than 1.25 to 1.5 times TDS as that of the raw water, we think that it will be unethical to dispose off the reject water as such.
We are using medium-scale water purifying systems which produce product water at 500 litres per hour rate.
I have planned to put in a nanofiltration stage just before reverse osmosis. This will help reduce the TDS of the reject water as well as help increase the lifespan of the RO membrane.
My question is: Should I use the nanofiltration membrane before the RO stage, is it economically viable?
And what are the other ways to reduce the TDS of the reject water, especially in these medium-scale water purifying systems?