FOULING OF A MICROFILTRATION MEMBRANE BY 2 GRAM-NEGATIVE BACTERIA

In this study a method is described to assess fouling of microfiltrati on membranes based on aggregation and redispersion of bacteria from fi lter cakes. Fouling by the hydrophobic Gram-negative marine bacterium SW8, grown in continuous culture under conditions of carbon- and nitro gen-limitation was compared to fouling by the hydrophilic, batch grown Escherichia coli. Effects of ionic strength and dissolved protein on cake stability were investigated. Cake redispersion was found to depen d on the solution ionic strength and on the presence of dissolved prot eins. Redispersion was also found to depend on bacterial physiology. H owever, it was not possible to discriminate between carbon- and nitrog en-limited bacteria based on measurements of surface charge and cell s urface hydrophobicity. This work shows that studies which rely on bact erial surface charge and cell surface hydrophobicity to describe membr ane surface fouling overlook bacterial surface interactions which cont rol cake stability.