Transparent exopolymer particles (TEP) and their potential effect on membrane biofouling.

Transparent exopolymer particles (TEP) have been described as a class of particulate acidic polysaccharides, which are large, transparent organic particles, and commonly found in seawater, surface water, and wastewater. Due to their unique physicochemical characteristics, more and more attention has recently been given to the effects of TEP on membrane fouling. In this review, the characteristics and determination methods of TEP as well as its potential effect on membrane biofouling are discussed. It appears that the analytical methods for TEP available in the literature are still debatable, and there is room for further improvement. Nevertheless, evidence suggests that TEP might be involved in the development of membrane fouling, especially at the early stage of biofilm development on membranes.

Quorum quenching bacteria can be used to inhibit the biofouling of reverse osmosis membranes.

Over the last few decades, significant efforts have concentrated on mitigating biofouling in reverse osmosis (RO) systems, with a focus on non-toxic and sustainable strategies. Here, we explored the potential of applying quorum quenching (QQ) bacteria to control biofouling in a laboratory-scale RO system. For these experiments, Pantoea stewartii was used as a model biofilm forming organism because it was previously shown to be a relevant wastewater isolate that also forms biofilms in a quorum sensing (QS) dependent fashion. A recombinant Escherichia coli strain, which can produce a QQ enzyme, was first tested in batch biofilm assays and significantly reduced biofilm formation by P. stewartii. Subsequently, RO membranes were fouled with P. stewartii and the QQ bacterium was introduced into the RO system using two different strategies, direct injection and immobilization within a cartridge microfilter. When the QQ bacterial cells were directly injected into the system, N-acylhomoserine lactone signals were degraded, resulting in the reduction of biofouling. Similarly, the QQ bacteria controlled biofouling when immobilized within a microfilter placed downstream of the RO module to remove QS signals circulating in the system. These results demonstrate the proof-of-principle that QQ can be applied to control biofouling of RO membranes and may be applicable for use in full-scale plants.