Reverse Osmosis (RO) vs. Nano Filtration (NF)

Question

Which configuration is more green? A 3passes RO or a combination of a NF as first pass followed by 2 passes RO? Treating intermediate age leachate.
Thank you!

Terry Scheurman · Answer

A lot of this depends on the ultimate use of the filtrate, reject and permeate. You can make the output from a MF much cleaner so that you use less energy in an RO and get cleaner reject and permeate from the RO with a lot less total energy and possibly end up with a usable filtered solids. The ultimate answer to green is what do you mean? Plugging a nano is not any better than plugging an RO. Neither becomes very green when you need to clean.  The rhymes will help you as silly as they are.

IOANNIS GLARAKIS · Answer

sorry for being my question so vague. treating liquid=medium age leachate. Permeat low limits drive us to at least 2 passes RO. TNinput=0-80mg/L (almost complete nitrif & denitrif depending on temprature ), TP=1-2mg/L, COD=5,5g/L & EC=21-23mS/cm. 3rd pass is usefull after a heavy rain when RO is loaded with raw leachate or mixed biological treated and raw leachate. ABy the term 'green" i used, i meant lower energy consume. Steady state recovery= 0.7, flowrate=7.5 m3/h. Thank u all for answering.

Joseph Cotruvo · Answer

Why do you need 3 passes? What is your essential target spec?

Moon KIM · Answer

You may consider " Operating Energy / Waste Generated by Treatment / Life Cycle of  Product for Green Solution. I wonder what kind of water you use it for. The two system would have differentiation in green aspect by treating water.

Allan McElroy · Answer

By "green" presumably you mean lowest specific energy consumption (kW.h/m3).
However which stream(s) are you optimising for, and on what parameters (water quality, recovery and flow rates). 
How much waste are you generating (brine, CIP chemicals, consumables, cartridge filters, and NF/RO membrane replacements).
As others have mentioned, your "green" notion is vague, and it depends on where you define your system boundary for your "green" assessment.

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