RO membranes will need to be cleaned on a regular basis, anywhere from once a year to three times a year, depending on the quality of the feed water. It's time to clean the RO membranes if the normalized permeate flow has fallen by 15%, as a general rule.
Outcome of cleaning RO Membranes
The outcome of a membrane cleaning is as much a function of the technique as it is of the cleaning chemical's quality. Netsol Water scan offer advice on procedures for improving RO membrane cleaning performance.
How to clean RO Membranes?
Forward flush, backward flush, and air flush are three distinct membrane cleaning methods. Chemicals can also be used to help in flushing.
1: Cleaning RO Membranes with a Forward Flush
Membranes are flushed with feed water in a forward direction when forward flush is used. During the permeate flow or feed water phase, permeate or water flows through the system more quickly, than during the production phase. Particles that have been absorbed by the membrane are liberated and discharged as a result of the faster flow and turbulence.
2: Cleaning RO Membranes with a Backward Flush
It is a filtration method that works in the other direction. Under pressure, permeate is flushed through the feed water side of the system. The pores of membrane are flushed, from the inside out, when a backward flush is used. As the pressure, on the permeate side is greaterthan the pressure inside the membranes, therefore, the pores are cleansed.
3: Cleaning RO Membranes with Air Flush or Water/Air Flush
The so-called air flush or air/water flush is a modern cleaning method. This is a kind of forward flush that involves, injecting air into the supply line. Because air is used, air bubbles occur, resulting in increased turbulence. Fouling is eliminated from membrane surfaces as a result of the turbulence.
4: Cleaning RO Membranes with Chemicals
1: Examine the cleaning tank, hoses, and cartridge filters to ensure they are in good working order. Clean tank and clean hoses if necessary. Install new cartridge filters.
2: RO permeate should be used to fill the cleaning tank. Turn on the recirculation pump or agitator in the tank.
3: Slowly pour (your chosen RO cleaning product) into the cleaning tank, based on the total volume of the CIP and the product strength required, and properly mix.
4: Check the temperature of the solution. If in case, the temperature of the solution is below the specified level, you should adjust the heating control to get the desired temperature.
5: The pH of the solution should be checked, which should be around 12 or whatever the manufacturer recommends. Adjust the pH with sodium hydroxide (NaOH) or similar chemical as indicated by the membrane manufacturer if the pH is too low. Adjust the pH using hydrochloric acid (H2O:HCl) if it's too high.
6: For 30 minutes, circulate the solution through one stage at a time in the feed flow direction. Circulate at the flow rate advised by the membrane or system manufacturer. If the manufacturer's recommendation isn't available, contact the friendly staff at Netsol Water Solutions. Pressure should be kept low enough, during cleaning to produce minimal permeate, but it should never exceed 60 psig [4.2kg/cm2].
7: To avoid redeposition of removed materials, the first return flow (up to 15% of the cleaning tank volume) should be routed to drain in cases of high fouling. In a multistage system, every stage must be cleaned independently for better performance.
8: Before continuing, dump the tank and create a new cleaning solution if the first stage cleaning solution becomes turbid or discolored. If pH or temperature of the solution deviates, from the prescribed range, a new solution should be made. In any case, for each stage, a new cleaning solution should be created.
9: Before putting the system back in service, give it a good rinse with RO permeate.
10: Divert product water to drain until any remaining cleaning solution has been removed from the system before resuming service.
What do we have to offer?
Membrane cleaning solutions, from Netsol Water are extremely successful at removing even the toughest scales and foulants from RO membranes. Our membrane cleaning systems are designed for a wide range of RO membranes, from those used in food and beverage to those used in water reuse.