Chemical foam cleaning as an alternative for flux recovery in dynamic filtration processes

In this study, the suitability of a new foam cleaning method for dynamic filtration modules was investigated. Foam was produced from a commercially available cleaning agent in a foaming device constructed in house. First, characterization experiments proved the ability to produce foams of a defined quality and stability. In subsequent lab-scale cleaning experiments, the optimal cleaning parameters such as pH, incubation time, temperature and NaOCl concentration were evaluated with image analyses of filter samples. Based on these results the best composition of the cleaning foam was chosen.Foam from 5000 ppm NaOCl liquid solution (or ∼270 mg NaOCl/L foam volume) was successfully applied to clean a flat-sheet mesh-filter module established in a pilot plant. It was shown that even after consecutive application the initial filtration performance could be recovered after chemical foam cleaning. No difference in cleaning efficiency was observed compared to a reference method using a liquid cleaning agent.The newly developed foam cleaning method shows high potential for dynamic filtration processes, particularly in the large scale where CIP cleanings with liquid cleaner cannot be performed due to the large pore size of the filter.

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► Operation of a 500 L pilot plant using flat-sheet dynamic filtration modules.
► A new on air foam cleaning method for dynamic filtration modules was investigated.
► Characterization of foams with regards to density, stability and bubble size.
► Foamed NaOCl solutions were successfully used to recover flux and TFP after fouling.
► Promising alternative for MBR cleaning to reduce amount of hypochlorite required.