Microfiltration

Microfiltration (MF) is the most basic form of thin layered semi-permeable membrane based process to treat water and wastewater. MF process can be used to remove bacteria, pathogens, suspended solids and other particulate matters which are responsible for bad taste, odor or color. The main driving force for the separation is hydraulic pressure (typically 1-4 barg) applied to the feed side. The pore size of MF membranes is in the range of 0.03 to 10 microns.

Microfiltration membranes are made from a variety of materials including organic polymers, such as polypropylene, ceramics and metal alloys.

There is growing concern over effective pretreatment of influent stream prior to inlet to water recovery stages of Nanofiltration (NF) and Reverse Osmosis (RO). Having MF as pretreatment helps in limiting number of chemicals that are added to feed stream. By removing pathogens, MF process can help achieve the objective of reducing chemical addition processes such as chlorination and dichlorination.

To prevent excessive membrane fouling and to achieve better permeate passage Microfiltration (MF) uses high cross flow rates and the rejected quantities are flushed away in the concentrate stream. Operational pressure of these membrane is lower than NF and RO.

The feed flow is pressurized through the membrane and accumulated solids are captured on the membrane surface until back-washing is performed, during the process of back-washing the accumulated solids are pushed out from the membrane surface and disposed.

• Examples of Microfiltration Applications:
• Cold sterilization of beverages and pharmaceuticals
• Purifying of fruit juice, wines and beer.
• Removing bacteria from the water (biological wastewater treatment)
• Effluent treatment
• Segregation of oil/water extract
• Pre-treatment of water for nanofiltration or reverse osmosis
• Solid-liquid segregation for pharmaceuticals and food industries