Surface modified polymeric membranes to reduce (bio)fouling: a microbiological study using E. coli

Membrane bio(fouling) is the main problem during an operation of membrane elements for water treatment processes. In an attempt to reduce a bio(fouling) affinity, commercial polyvinilidene fluoride (PVDF) microfiltration membranes (Millipore) were surface modified via photoinitiated graft polymerisation with quaternized 2(dimethylamino) ethyl metacrylate (qDMAEM) or 2-acrylamido-methyl-propane sulfonic acid (AMPS) as functional monomers. Membranes with different degrees of modification were obtained by varying the time of polymerisation and concentration of the monomer solution. Another set of PVDF membranes was modified using interfacial polymerisation between polyethyleneimine (PEI) and toluene diisocyanate. The affinity of modified membranes to biofouling was studied using E. coli bacteria. It was found that membrane samples modified with qDMAEM as well as with PEI have a strong bactericide effect towards E. coli. The possible mechanism of antimicrobial action of modified membranes has been discussed.

In an attempt to produce membrane surfaces with potentially low biofouling properties, PVDF microfiltration membranes were surface modified by a photoinitiated grafting technique with quaternary 2-dimethylaminoethylmethacrylate (qDMAEM) and 2-acrylamido-2-methyl-1propanesulfonic acid (AMPS) as functional monomers varying the concentrations of the monomers and the time of polymerisation. Another set of PVDF membranes was modified using an interfacial polymerisation method with different concentrations of polyethileneimine (PEI) as a potential biocide agent. We have shown that membrane samples with grafted qDMAEMA as well as ones modified with PEI poses a strong antimicrobial action towards E.coli bacteria. The antimicrobial action of modified membrane samples can be explained by the penetration of polymeric polycationic chains at the wall of the bacteria cell. This destroys the outer cell membrane layer, causing leakage of cytoplasmic components that leads to the death of the cell. The modified membranes possessing biocide properties could be potentially more resistant to biofouling in water treatment applications.