Invisible Particles Foul Up Desalination Plants

Several years ago, former KLL Director Dr. Tom Berman conducted a 3 year pioneering study of small transparent organic particles (Transparent Exopolymer Particles (TEP)) in Lake Kinneret. This research showed that the lake water contained as many as 25 million tiny sugar and/or protein containing particles per liter regardless of the season and that these organic particles were important players in the lake’s ecosystem. In fact, since their discovery in the ocean in 1993, TEP have been found in almost all naturally created bodies of water: seas, lakes and rivers.

Now it seems that TEP could also have a down side. These microscopic particles are ubiquitous, very numerous, small and sticky. Many of them carry loads of bacteria. Consequently, they have just the characteristics needed to cause biofouling–the attachment of biofilm, a thin usually resistant layer of bacteria, on all kinds of wet surfaces. Biofilm means big headaches in various types of water treatment plants. For example, both desalination plants and water treatment facilities generally use filtration through membranes as a final water purification step. During operation, layers of biofilm develop on these membranes and eventually clog them. To minimize biofilm build up on these surfaces, source water is filtered and chemically treated prior to final filtration through the membranes. This additional process makes biofilm a major and very expensive problem for the desalination and water treatment industry.

Based on the probable involvement of TEP in biofilm formation, Dr. Berman proposed that checking TEP levels would be a good way to monitor the efficiency of pretreatment in these plants. KLL researchers are working together with IDE Technologies Ltd on a new approach called Microbial Support Capacity to measure how effectively various pretreatments lower the potential for biofilm to develop on sensitive filtration membranes. The Microbial Support Capacity index is based on measuring the levels of TEP and a few other “biologically based” parameters in treated water. This new evaluation procedure is being tested at the KLL using water samples from the newly commissioned Ashkelon Desalination facility, which is presently the world’s largest operating desalination plant. The KLL team hopes to simplify the tests and make them more user-friendly and suitable for application in the filtration and water treatment industries. Optimizing the Microbial Support Capacity index for industrial use will allow plant designers, managers and operators to routinely evaluate the efficiency of various treatment stages in plants that are susceptible to problems caused by microbial build up.