microfiltration

Microfiltration is a membrane filtration process that uses a semi-permeable barrier to separate solids and large molecules from a liquid. The membranes employed have pore sizes roughly in the range of 0.1 to 10 micrometers, allowing water and small solutes to pass while retaining larger particulates, bacteria, and some oil droplets.

Membranes used for microfiltration are typically made from polymeric materials such as polypropylene, polyethersulfone, polyvinylidene fluoride, or cellulose derivatives, as well as ceramic options for more demanding applications. Modules are arranged in configurations that promote tangential flow (crossflow) to reduce fouling, though dead-end flow designs are still used in some processes. Operating conditions commonly involve transmembrane pressures from about 0.1 to 0.5 MPa (roughly 15 to 75 psi) and temperatures tailored to the liquid and membrane material.

The technology is used to remove bacteria, suspended solids, and emulsified fats from liquids, while allowing dissolved salts and most small organic molecules to pass. It is widely applied in water and beverage clarification, dairy processing (milk, whey, cream), beer and wine stabilization, and in biotechnology and pharmaceutical manufacturing for clarifying cell cultures and sterilizing solutions prior to downstream processing. Microfiltration can also serve as a pretreatment step to protect downstream processes such as ultrafiltration, nanofiltration, or reverse osmosis.

Key considerations include fouling and concentration polarization, which reduce flux over time, and the need for cleaning-in-place and sanitization. While effective for particle and microbial removal, microfiltration does not remove dissolved solutes or small molecules, which may require complementary treatment steps.