Editing Microfiltration (section)

==Characteristics of main process==
Membrane filtration processes can be distinguished by three major characteristics: driving force, [[retentate]] stream and [[permeate]] streams. The microfiltration process is pressure driven with suspended particles and water as retentate and dissolved [[solutes]] plus water as permeate. The use of hydraulic pressure accelerates the separation process by increasing the flow rate ([[flux]]) of the liquid stream but does not affect the chemical composition of the species in the retentate and product streams.<ref>Cheryan, M 1998, ''Fouling and Cleaning in Ultrafiltration and Microfiltration Handbook'' 2nd edn., CRC Press, Florida, p.1-9.</ref>

A major characteristic that limits the performance of microfiltration or any membrane technology is a process known as [[fouling]]. Fouling describes the deposition and accumulation of feed components such as suspended particles, impermeable dissolved solutes or even permeable solutes, on the membrane surface and or within the pores of the membrane. Fouling of the membrane during the filtration processes decreases the flux and thus overall efficiency of the operation. This is indicated when the pressure drop increases to a certain point. It occurs even when operating parameters are constant (pressure, flow rate, temperature and concentration) Fouling is mostly irreversible although a portion of the fouling layer can be reversed by cleaning for short periods of time.<ref>Cheryan, M 1998, ''''Fouling and Cleaning. in Ultrafiltration and Microfiltration Handbook'''' 2nd edn., CRC Press, Florida, p.1-9.</ref>

===Membrane configurations===
[[Image:Cross-flow.svg|right|300 px|thumb|Figure 2: Cross-flow geometry]]
[[Image:Dead-end.svg|right|300 px|thumb|Figure 3: Dead-end geometry]]
Microfiltration membranes can generally operate in one of two configurations.

[[Cross-flow filtration]]: where the fluid is passed through tangentially with respect to the membrane.<ref>Perry, RH & Green, DW, 2007. ''Perry's Chemical Engineers' Handbook'', 8th Edn. McGraw-Hill Professional, New York. p 2072-2100</ref>  Part of the feed stream containing the treated liquid is collected below the filter while parts of the water are passed through the membrane untreated. Cross flow filtration is understood to be a unit operation rather than a process. ''Refer to Figure 2 for a general schematic for the process.''

[[Dead-end filtration]]; all of the process fluid flows and all particles larger than the pore sizes of the membrane are stopped at its surface. All of the feed water is treated at once subject to cake formation.<ref>Perry, RH & Green, DW, 2007. ''Perry's Chemical Engineers' Handbook'', 8th Edn. McGraw-Hill Professional, New York. p2072-2100</ref>   This process is mostly used for batch or semicontinuous filtration of low concentrated solutions.<ref>Seadler, J & Henley, E 2006, ''Separation Process Principles'', 2nd Edn,  John Wiley & Sons Inc. New Jersey. p.501</ref> ''Refer to Figure 3 for a general schematic for this process.''