EVALUATION AND INHIBITION OF BIOFILM ATTACHMENT TO MEMBRANE SURFACES IN WATER AND WASTEWATER TREATMENT SYSTEMS

As engineers’ understanding of the biological treatment systems in water and wastewater systems increased, advanced technologies have emerged. These included combining biological systems with other treatment systems such as membrane technologies. The overall objective of this research was to evaluate the impacts of bacterial attachment to membranes during treatment operations and propose an antimicrobial coating to maximize membrane performance. Membranes from a small scale, membrane aerated biological unit were removed and analyzed for continued performance after an extended operational period. Afterwards, a selenium based antimicrobial coating was developed to prevent microbial attachment without harming membrane performance. This coating was applied to reverse osmosis membranes and the coating’s efficacy to prevent biofilm growth on the reverse osmosis membrane surface was investigated. Ultimately, the selenium coating displayed a strong inhibition against bacterial attachment and biofilm formation. Selenium’s capability to catalytically generate superoxide molecules was effective in damaging bacterial cell membranes resulting in lysis. Both Gram positive (S. aureus) and Gram negative (E. coli) bacteria showed high susceptibility to the superoxide attack. Attachment utilizing the selenocystamine molecule via peptide bond to a modified membrane surface was selected as the desired attachment method. Selenocystamine allowed for the RO membrane to maintain its higj permeate flux without overly diminishing membrane rejection. Attachment of selenium to membrane surfaces may be a valuable technology to allow for continuous performance even in the harsh operating conditions present in biological reactors.