UCLA

Biofilm formation is a concerning issue for many industrial processes, especially for water treatment membranes, because it leads to fouling and poor performance of the system. Combinations of physical and chemical cleaning methods are commonly used to remove the deposited biofilms. However, there is little understanding of the interactions between chemical cleaning agents and the biofilm. Therefore, companies perform a series of iterations whereby a certain cleaning product or process is applied to the surface with the hope of dislodging the biofilm. This leads to indiscriminate use of cleaning agents and inconsistent results of biofilm removal. The goal of this project is to give insights to the impact of representative cleaning agents on individual biofilm components and ultimately, to design an efficient microbial cleaning strategy for biofouled surfaces, which will help to ensure a safe and sustainable operation of water supply and enhance the performance of membrane-based water treatment processes.

In this study, the interaction between a homogeneous layer of a single biofilm component (polysaccharides, proteins, nucleic acids) and different cleaning solutions (base, oxidizer, surfactant, chelating agent) was evaluated by comparing permeate flux of an ultrafiltration membrane and frequency shift measured by a quartz crystal microbalance. The efficacy of cleaning agents towards model biofilm component mixtures designed to mimic gram-negative and gram-positive bacterial biofilms and an actual bacterial biofilm component extracted from Pseudomonas aeruginosa (a gram-negative bacteria) were tested. The presence of calcium in the feed solution hindered the ability of the cleaning solutions to completely remove the foulants except when a chelating agent was used. The usage of a base and an oxidizer showed the best performance yet did not fully removed the model biofilm component mixtures or the bacterial biofilm component. Overall, it was determined that the presence of proteins in biofilms determines their susceptibility to cleaning.