Reverse filtration

The cake may creep down along the partition due to gravity this is almost inevitable in the absence of a pressure gradient across the filtering partition. The vertical filtering partition makes these filters especially useful as thickeners, since it is convenient to remove cake by reverse filtrate flow. 

The kidneys are the sites of elimination of water-soluble chemicals that are removed from the blood by the process of reverse filtration. Two characteristics are primarily responsible for determining whether a chemical will be eliminated by the kidneys size and water solubility. 

Size. The reverse filtration process requires that chemicals to be removed from the blood are able to pass through 70 to 100 A pores. As a rule, chemicals having a molecular mass of less than 65,000 are sufficiently small to be subject to reverse filtration. 

Water Solubility. Non-water-soluble chemicals will be transported to the kidneys in association with transport proteins. Thus, in association with these proteins, the chemicals will not be able to pass through the pores during reverse filtration. Lipophilic chemicals are generally subject to renal elimination after they... 

Fig. 3. SEM micrograph of a CA microfiltration membrane fouled (A) after filtration of BSA only for 3100 s, (B) after completion of SMY deposition portion of cycle 11, and (C) after completion of backflushing portion of cycle 11. The primary feed contained 2.0 g/L of BSA, and the secondary feed contained 1.34 g/L of yeast. The cycle conditions were tf = 300 s, tsf = 15 s, and tb = 3, with an average TMP of 7.5 psi maintained during forward as well as reverse filtration.

Figure 2.1 Schematic (not to scale) of particle deposition and removal during forward and reverse filtration. (From Redkar and Davis [1]).

Sanjeev, G. R., and Davis, R. H. (2004). Cross-flow microfiltration with high flequency reverse filtration. AIChEJ. 41(3), 501-508. 

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