Chemically enhanced backwash

A typical UF pilot plant has been used in this study. Examples of application for these membranes can be found in the literature [40, 58]. The UF unit woks in deadend mode (2.5 m h ) and it can be operated in filtration, backwash and chemically enhanced backwash (CEB) modes as described in the literature for similar UF systems [40]. The specifications of the hollow fiber UF modules and the operating conditions are summarized in Table 5. 

Chemical enhanced backwashes (CEB) are also used to minimize the cleaning frequency of hollow fiber membranes. Chemical enhanced backwashes include the use of chemicals, such as hypochlorite, acid, and caustic in relatively high doses, to affect a mini chemical clean of the membranes without a full membrane cleaning. Concentrations of up to 1000 ppm acid, 500 ppm caustic, and 1000 ppm hypochlorite are typically used in a CEB. 

Cieaning Maintenance cleaning by backwash or chemically enhanced backwash is an option for contained and submerged modules and easier for hollow fibers. Clean-in-place may be easier for contained systems and smaller volumes of chemicals may be required. 

The enhanced backwash comprises three steps first, a backwash with permeate (approx 30 s) to remove accumulated particles from the hollow fiber. Second, a short soak (10-15 min) with alow dose of oxidant/disinfectant to remove adsorbed foulants fiom the membrane, and finally another short backwash (with permeate) to remove the chemicals from the systems. 

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