Impact of Physical and Chemical Cleaning Agents on Specific Biofilm Components and the Implications for Membrane Biofouling Management

A homogeneous layer of a single biofilm component (polysaccharides, proteins, and nucleic acids) was studied on an ultrafiltration membrane and its interaction with different cleaning solutions (base, oxidizer, surfactant, and chelating agent) was evaluated by comparing permeate flux, with the base and oxidizer showing the best cleaning performance. The presence of calcium in the feed solution hindered the ability of the cleaning solutions to completely remove the foulants in the absence of a chelating agent. Backwashing the membranes fouled with polysaccharides and DNA resulted in full flux recovery but had little effect on recovering the flux of protein-fouled membranes. The efficacy of cleaning agents toward model biofilm component mixtures designed to mimic Gram-negative and Gram-positive bacterial biofilms were tested. Flux recovery was enhanced by the usage of a base and oxidizer. However, full recovery was never achieved using chemical cleaning agents. It was determined that the presence of proteins in biofilms determines their susceptibility to cleaning.