Microfiltration prefilters

The technology is a combination of biodegradation, adsorption onto activated carbon, and microfiltration. It uses microbes grown on active powdered carbon as a prefilter and to degrade organics and a cross-flow membrane filter to remove biomass, viruses, and suspended impurities. 

Regarding water filtration procedures first, prefilters should be provided to prevent large particulates from entering the system and microfiltration to remove bacteria. Prefilters are usually the replaceable cartridge type with porosities ranging as high as 25 pm. Microfiltration follows and is generally accomplished with 0.2-pm absolute filters, which will remove most bacteria. 

To extend its life, a microfiltration cartridge may contain two or more membrane filters in series, or as shown in Figure 7.13, a coarse prefilter cartridge... 

Recently, some membrane manufacturers have attempted to produce anisotropic microfiltration membranes in which the open microporous support is a built-in prefilter. Unlike most other applications of anisotropic membranes, these membranes are oriented with the coarse, relatively open pores facing the feed solution, and the most finely microporous layer is at the bottom of the membrane. The goal is to increase filter life by distributing the particle load more evenly across the filter than would be the case with an isotropic porous membrane. 

Clarification of apple juice. Inorganic membranes have been utilized in two ways in the production of apple juice. One is to clarify pressed or prefiltered apple juice and the other is to extract clarified apple juice directly from apple puree or pomace. Microfiltration of apple juice has been one of the most successful commercial applications of inorganic membranes. 

Tangential microfiltration has been used in many wine treatment applications over the past 10 years. Suitable membranes are now available for clarifying must or untreated wines, as well as the final clarification of prefiltered wines. This technique may also provide an alternative to filtration through diatomaceous earth precoats, especially in cases where waste discharges could lead to excessive pollution. Tangential microfiltration is still. 

Examples of such nonwoven filters comprising one or more layers of microfibres and nanofibres for microfiltration of specific biological contaminants were reported in US patents 2004/0038014, 2007/0075015, and 2007/0018361. Prefilters are commonly pleated or wound filter fabrics. Prefilters have a large band of retention ratings. The most common retention rating of these filters is 20 or 50 nm, and it can be engineered to all necessary apphcations. 

---