School of Mechanical Engineering Seminar
Wednesday, March 6, 2013 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Biofilm control in water by Ultraviolet (UV) irradiation and Advanced Oxidation Processes (AOPs)

Anat Lakretz

PhD Student of Dr. Hadas Mamane - Faculty of Engineering

And Prof. Eliora Ron - Faculty of Life Science

Biofouling is the undesired accumulation of microorganisms on surfaces (i.e. microbial biofilms) which in turn interferes with technical, economical, and hygienic requirements. Biofouling is ubiquitous in all water systems, and create a major problem in all of its sectors. Ultraviolet (UV) irradiation is being increasingly applied as a primary disinfection process for water, effectively used for inactivation of suspended cells. However, this information may not be relevant when evaluating this process as a strategy to control biofouling. Advanced Oxidation Processes (AOPs) are processes where pollutants are chemically oxidized by free hydroxyl radical (•OH). Many studies have demonstrated the efficiency of AOPs for removal of organic contaminants, including micro-pollutants. However, these processes were hardly investigated in the context of water disinfection and prevention of biofilms.

The goal of this study was to investigate the potential of UV and UV-based AOPs as preventive strategies to control biofouling in water. The AOP process used was UV added with hydrogen peroxide (H₂O₂/UV). The H₂O₂/UV process includes two direct reactions with the microorganism: UV direct photolysis and H₂O₂ oxidation; and an indirect reaction: oxidation by •OH radical generated from the direct photolysis of H₂O₂.

It was shown that UV irradiation alone controls biofilm formation but up to limited time post-treatment. H₂O₂/UV controlled biofilm better than both UV irradiation and H₂O₂ alone and required lower H₂O₂ concentrations than H₂O₂ treatment alone. In water containing organic constituents H₂O₂/UV showed improved biofilm control compared to UV irradiation alone. In addition, it was found that the ratio of surviving bacterial concentration to the residual H₂O₂ concentration post-treatment plays an important role in controlling biofilm formation. In summary, UV and especially H₂O₂/UV has a high potential to act as preventive strategies to control biofouling in water. The final stage of this study included investigation of both processes in tow pilot scale systems: (1) Control of biofouling on pipe materials in Lake Kinneret water distribution pilot; (2) Control of biofouling on reverse osmosis (RO) membranes in brackish water desalination pilot plant.