Features of the Hyperfiltration System

Conventional membranes rely on rigid polymeric, ceramic, or porous stainless steel membranes. These membranes are available in discrete pore sizes and cannot be customized to the characteristics of the feed. Furthermore, once installed on-site it is difficult and costly to modify their separation properties in response to variable feed characteristics. 

The formed-in-place membrane is compatible with a wide variety of contaminants often encountered in hazardous wastewater steams. Many ccmventional reverse osmosis membranes are made from materials such as cellulose acetate and exhibit poor conqmtibility with reactive substances often encountered in hazardous wastes. These cmventiaial membranes will degrade and become inoperative when challenged with many organic cmnpounds. The compatibility problem becomes more critical as the level of concentration increases. The formed-in-place membrane is stable under most chemical environments and will not degrade even at high contaminant concentrations. 

A major limitatimi of many membrane systems is their propensity to irreversibly foul. Fouling is the uncontrolled build up of materials on the surface of the membrane. Fouling leads to a loss of flux and eventually results in cessation of flow. If a membrane fouls, it must be cleaned in order to restore flux. If cleaning is unsuccessful, then the membrane is replaced. 

The technology discussed in this chapter utilizes a cross-flow filtration mechanism to continuously clean the surface of the membrane, hence minimizing fouling. In this mode, the feed stream is directed parallel to the membrane s surface resulting in a cleaning action which minimizes the buildup of materials on the membrane s surface. 

Since all membranes eventually foul, a cleaning cycle is necessary to restore flux and operability. Many membrane systems have limited abilities to be regenerated due to restrictions in the chc ce of cleaning chemicals. Hie formed-in-place membrane is compatible with a wide rai e of chemical cleaning methods, enabling in-place regeneration of flux. In situatimis where the membrane becomes irreversibly fouled, the formed-in-place membrane can be stripped and reformulated on-site. 

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