Ultra-filtration and Micro-filtration Membrane Autopsies

Ultra-filtration (UF) and micro-filtration (MF) membranes differ significantly from RO membranes both in their applications and their construction and usage. 

The first key difference is that UF and MF membranes are constructed of much more robust materials than RO membranes. From a construction perspective, they are frequently made from polymers such polysulfone, polypropylene, cellulose acetate, polyvinylidene fluoride (PVDF) but may also be made from ceramics for higher temperature applications.  This leads to a key difference in their application where they are used to remove suspended organic and inorganic materials (such as clays) and are then cleaned using oxidizing agents like hypochlorite. 

As a result, UF and MF membranes are often cleaned on a much more frequent basis than RO membranes and can involve rapid chemical cleans such as Chemically Enhanced Backwashing where a dilute chemical solution is flushed through the system to remove deposits. Our low-pressure membrane autopsies thus focus not only on the identification of membrane foulants, but also on their removal, allowing you to restore flux and meet production goals.

Like other membrane processes, UF membranes are susceptible to fouling when particulate matter adheres to the membrane surface. Unchecked, this build-up will eventually decrease water production as well as increasing operating pressures, energy consumption and result in more frequently cleaning.

There are a few different types of fouling that can occur, some are reversible and others are irreversible.

Solids fouling: Suspended solids and colloidal particles can collect on the membrane surface and within its pores, preventing the flow of water through the membrane. They are normally removed during cleaning, but some types may be hard to remove, making the existing cleaning program ineffective.

Biological fouling: Biological contaminants like algae and bacteria are often found in surface water and in MBR systems. These microorganisms can attach themselves to the membrane and begin multiplying and form a film that will prevent water from passing through the membrane.

Scaling: Scaling occurs when minerals precipitate on the membrane surface when they exceed their solubility or are oxidized. Once these minerals crystalize, they can be nearly impossible to remove without specific chemical cleaning.

Filtered water contamination: If either solids or bacteria are detected in the filtrate, this usually indicates a damaged membrane. This can be caused by high temperature, pH, oxidants or physical damage. Unfortunately, once this occurs and water is no longer meeting your specifications, replacement is the generally the only option. 

Autopsy options

We have developed several different autopsies to help suite a range of different needs. Our Standard Autopsy identifies the cause of failure and is valuable where there is a suspected issue or as part of a maintenance optimisation. Our Advanced Autopsy identifies cleaning strategies when the existing cleaning program is not working and our Premium Autopsy works to evaluate your whole process including pre-treatment and operational procedures to wholistically improve the operation.