Diamite and High Flux A Liquid Membrane Cleaners

No matter how good the feed water, or how effective the pretreatment before the membrane system, the membrane surface of the system’s elements will eventually be covered with enough foulant to reduce the membrane flow below a useful rate. In almost all cases a good membrane cleaning requires low and high pH cleaners.

The Diamite Series and High Flux A are liquid membrane cleaners designed to remove inorganic, silica, and organic foulants. They are all highly concentrated and formulated for easy mixing. The mix ratio is one gallon of cleaner with 39 gallons of good quality water.

Diamate and HFA Liquid Membrane Cleaners

Cleaner For Removing Membrane Solution pH Info Sheet Safety Data Sheet
Diamite LpH Mineral Scale, Hardness TFC 4
Diamite ZpH Mineral Scale, Hardness TFC 2
High Flux A Silica TFC 4
Diamite AFT Organic, Biological TFC 11
Diamite BFT Organic, Biological TFC 13

When should you clean?

It’s time to clean when the system’s normalized flow and/or salt rejection has decreased 15% or differential pressure has increased 15%.

Suggested Cleaning Procedure

To clean your own membrane system you will need to have a clean-in-place (also known as CIP) system. A CIP system consists of:

CIP Tank > Filter > Pump > Membrane System > Back to CIP Tank

Next you need to determine the total volume of cleaner needed to clean your system. You need 15 gallons of cleaning solution per 8×40 membrane element, and 7 gallons per 4×40 membrane element. For example for a 100- 8×40 element system you would need 15*100 = 1500 gallons at a minimum.

This total volume includes the water in the membrane system (including pressure vessels, pipes, and pumps) and the CIP tank. To calculate the system volume, add one gallon for each 4×40 element, and 3.5 gallons for each 8×40 element, then add 10% to account for the volume of pipes and pumps. For example for a system with 100- 8×40 elements the calculated system volume is 100*3.5 = 350 gallons.

Above we calculated the total volume of cleaner needed for a 100-8×40 element system was 1500 gallons. Since the system volume is 385 gallons, the volume of water to add to the CIP tank is 1500 – 385 = 1115 gallons.

The next step is to determine how many gallons of cleaner are needed. Use one gallon of cleaner per 39 gallons of good quality water. For our example of a 100-8×40 element system requiring a total volume of 1500 gallons, the number of gallons of liquid cleaner is 1500/40 = 37.5 gallons.

Now you know how to calculate cleaning volume and amount of cleaner to mix up. You will probably be cleaning your system with both low and high pH cleaners. These would be Diamite LpH and Diamite AFT respectively. (If your system is very heavily fouled, you may wish to substitute Diamite ZpH and Diamite BFT). You may also need to clean for silica. The cleaner for that is HFA. The usual cleaning order is Diamite LpH (ZpH) > Flush > HFA (if required) > Flush > Diamite AFT (BFT) > Flush.

If you are using the silica cleaner High Flux A, you MUST clean first with Diamite LpH to remove any calcium scale. You can substitute Diamite ZpH for LpH. Call us if you have any questions on this point.

The stepwise procedure is:

  1. Mix the liquid cleaners in the ratio of 1 gal to 39 gallons of clean water (either permeate water potable water) in the CIP tank.
  2. You do not need to heat the low pH or silica cleaning solutions. The water temperature should be no colder than 70°F or 20°C and no hotter than 115°F or 45°C. For high pH cleaning where there is a good deal of organic material on the membrane, heating the solution to not more than 110°F or 42°C can be beneficial. It is very important not to expose membranes to solutions hotter than 115°F or 45°C. Call us if you have any questions on this point.
  3. Circulate cleaning solution from the CIP tank to the system and back to the CIP tank. Circulate a minimum of 7 gpm per pressure vessel for 4×40 elements, and a minimum of 20 gpm per pressure vessel for 8×40 elements. Use as low a pressure and high a flow as possible. Keep differential pressures across membrane stages below 60 psi.
  4. For low and high pH cleanings, monitor the pH of the cleaning solution pH. For Diamite LpH, add additional powder to keep pH from raising above 4.5. For Diamite AFT, add additional powder to keep the pH from dropping below 11. Keep circulating through each section of system until the pH has stabilized for 30 minutes. Membrane systems very heavily fouled with organic material can benefit by inserting an overnight soak into the cleaning schedule.
  5. As said above you must first clean using Diamite LpH before cleaning for silica using HFA. Mix and circulate as with Diamite LpH and Diamite AFT. The pH of the High Flux A will not change during cleaning. Circulate cleaning solution for at least one hour.
  6. After each cleaning dump the cleaner and fill the CIP tank with good quality water. Circulate though system for 5-15 minutes and dump flush water to drain.

Determine the effect of each cleaning periodically

It is very useful to know how each cleaning step improves productivity. You can get this information by running the system for a short time after each cleaning step. This information can be used to tweak the procedure and spot any cleaning problems early on. It is not necessary to do this every time you clean. Call us to discuss.