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Microfiltration

Microfiltration (MF) is a process which removes contaminants from a liquid by passage through a microporous membrane, physically excluding particulate matter. A typical MF membrane pore size range is 0.1 to 10 µm.

Microfiltration membranes were first introduced to the municipal water treatment market in 1987 and applied primarily to waters that were relatively easy to treat. These were cold, clear source waters that were susceptible to microbial contamination. Low pressure membranes were selected to remove turbidity spikes and pathogens without chemical conditioning. As low pressure membranes increased in acceptance and popularity, users began to apply the technology to more difficult waters which contained more solids and higher levels of dissolved organics. Some of these waters required chemical pretreatment, including pre-chlorination. These shifts in water quality triggered change in low pressure Membrane Technology.

Increasingly used in drinking water treatment, MF effectively removes major pathogens and contaminants such as Giardia lamblia cysts, Cryptosporidium oocysts, and large bacteria. For these applications, a miniumum absolute micron rating of 0.2 µm is required. For potable water applications (mineral and drinking water), the most commonly used membrane geometry is pleated cartridges usually made from Polythersulphone (PES) media. The PES is asymmetric with larger pores being on the outside and smaller pores being on the inside of the filter media.