Facilities Managers: Are you wondering when to change your dairy membranes? In this article, we’ll walk you through the signs and symptoms that let you know it’s time.

Feed Quality

Feed quality is a huge factor in the life of your membranes. You will want to look for the following:

  • Entrained air feeds oxygen to bacteria and also contributes to flux loss. Look for leaky seals.
  • Temperature — for whey, and whole and skim milk, you will have more microbial growth at 120 degrees F. Temperatures below 70 degrees F are ideal.
  • Pre-treatment can be essential — make sure you know the prefiltration specs for your unique situation.
  • UF Permeate
    • Check for cloudiness and repair/seal membranes if present. Cloudiness indicates you are losing protein.
  • RO Permeate
    • Same as above regarding cloudiness
    • Also, clean the CIP storage tanks and lines regularly (every 1-2 days) to remove organics and avoid microbial issues.

CIP Considerations

See our previous article on CIP Best Practices.

Clean Water Flux Test

This test determines the effectiveness of your CIP. The test should be done at the conclusion of every CIP cycle. Record permeation rate of the system at base temperature and pressure. Normalize temperatures and pressures outside of the baseline. Additional washes may be needed if not within 5% of the previous test. When you graph these tests, there should be a stable line.

Records Are Your Friend

Records are very important. On install, record dates, lot numbers, manufacturer information and plant location. Record daily CIP logs and production logs. Maintain a record of your clean water flux tests (see above).

Visual Checks

Take permeate samples regularly and check for signs of leakage. RO permeate should be clear and colorless. MF/UF/NF permeate will normally have color but should not appear cloudy.

Analytical Checks

  • RO Polishers — regularly record permeate conductivity. For new membranes, this typically would be 10-30 micro-mhos.
  • RO conductivity is usually a lot higher (~100-1,000 micro-mhos). Record when new and use that as your baseline. Results are dependent on the ash content in your feed.
  • NF — test the permeate for sugar content to determine if leaks are present.
  • UF — test the permeate for protein. There should be less than 1% loss for new membranes. For membranes 6 months or older, approximately 2-4% loss. Change out your membranes before it gets to 4%.

Find Your Sweet Spot

The below graphs illustrate a hypothetical situation — your results will depend on your product.

Chart the cost of your membranes over the membrane lifetime.

Next, chart protein loss over the membrane lifetime.

Where the two graphs intersect is the sweet spot — that’s when you should change your membranes in order to get the biggest bang for your buck.

When to Change Your Dairy Membranes?

Here are additional scenarios that mean it’s time to change your dairy membranes:

  • Visual permeate checks show obvious leaks and those leaks aren’t coming from seals.
  • The membrane plant no longer meets production requirements.
  • The membrane plant no longer meets product quality requirements and CIP doesn’t correct the issue.
  • Membrane leakage causes excessive downstream issues (for example, with your wastewater plant) and those costs are worse than the cost of replacing your membranes.

Do I Need a Full Set of Replacement Membranes On-Hand?

We recommend having 10% on-hand in case a replacement is needed. Replacements can normally be obtained within one week.

A Better Process

Caloris is here to help if you are in need of assistance with your membrane systems. Contact us today to discuss your filtration needs. Call 410-822-6900 or send email to problem.solved@caloris.com to be connected to a membrane system specialist.

Did you miss our previous post on Membrane CIP Best Practices?


About Caloris

Caloris transforms process systems design for the better with unexpected, future-focused solutions that solve real operational problems. We engineer efficient, dependable and productive solutions that also improve environmental sustainability where practical. Designed with the end user in mind to drive plant productivity. Caloris offers evaporation, membrane filtration and spray drying process systems for food and dairy industries, as well as for water reuse and wastewater treatment applications. Both Caloris’ custom and pre-engineered packaged systems are designed to meet our customers’ specific concentration/purification needs utilizing the most cost effective and energy efficient technologies available. Whether concentrating dairy, food or juice products at a high-volume production facility, or processing industrial wastewaters to reduce transportation and treatment costs and recover re-usable water, Caloris provides a range of options and technologies.