RO Membrane Cleaners

“The truth is most membrane installations do not address the causes of potential membrane foulants before the system is installed.”

Flag City Water Systems can assist you with the products, services and solutions of the worlds most effective support chemicals and technology for the care and preservation of any type of membrane technology.  Through our water analysis and membrane autopsy services we can analyze the issues for any membrane installation before or after the installation.  These services will determine the cause and effect of all membrane degradation.  Once the fouling mechanisms are understood we can offer the best products to control everything from biological problems to scaling issues.

Membrane Cleaning Tips

RO membrane centerEffective membrane cleaning involves proper procedures combined with chemistry that is specifically formulated to remove the target foulant. One without the other can result in ineffective cleaning.

Use proper chemical dilutions- When diluting cleaners, take into consideration the total volume of water in the system including: tanks, pipes and/or hoses and vessels. Table 1 gives a guide to membrane vessel volumes.

Use proper flow rates- The velocity of the solution across the membrane surface is critical. Clean 4” membranes at 10 to 12 gpm and 8” membranes at 35 to 40 gpm. Full-fit membranes require higher flow rates, 60 gpm for an 8” element.

Always clean membranes in parallel- If necessary, separate the vessels to achieve this. Never clean the vessels in series as it is difficult to ensure proper flow rates and pressures.

Minimize cleaning pressure- Clean at pressures less than 60 psi. This will minimize or eliminate foulants being pulled down to the membrane surface by water permeating during the
cleaning procedure.

Heat the cleaning solution- Heat to the maximum temperature allowed by the membrane manufacturer.

Additional Tips

  • Use only DI or RO permeate water to dilute cleaning solutions.
  • Reduce cleaner foaming by placing return lines below the water level in the CIP tank.
  • Use a combination of low and high pH cleaning solutions.
  • Recirculate the cleaning solution for a minimum of 45 minutes.

Membrane Installation

Interconnector
Used to connect the permeate tube of one membrane to another, or the permeate tube of a membrane to the end cap of the pressure vessel. The interconnector uses o-rings to provide the seal.

Casing or Outer Wrap
Provides a rigid construction to maintain to the shape of the membrane element under pressure and to prevent membrane damage during handling. This is generally constructed from fiber reinforced plastic. Some 4” membranes are simply tape wrapped. The membrane manufacturer model number and serial number are typically visible on or through the outer wrap.

U-Cup Brine Seal
Forms a seal between the membrane element and the pressure vessel. The design is such that the pressure of the feed water opens the “u-cup” and forms the seal. This ensures that the feed water passes through the element and not around it.

Pressure Vessel
Pressure vessels house the membranes, typically from one to seven membranes per tube depending on the length of the vessel. Vessels are typically made of stainless steel or fiberglass reinforced plastic (FRP).

Loading of Membranes

Membranes should be loaded and removed in the same direction as the water flow. Glycerin (a water-soluble lubricant) should be used on the U-Cup seals and o-rings during the installation. When installing membranes, record the membrane serial numbers and the location of each membrane within the vessel.