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Study focuses on the removal of assimilable organic carbon and total organic carbon during desalination pretreatment
American Water Works Co. Inc. presented the results of a study regarding pretreatment for desalination of seawater. American Water Director Mark LeChevallier reported the results at the 26th Annual WateReuse Symposium in Phoenix.
Funded by the Water Research Foundation and the subsidiary companies of American Water, the study specifically concerned the removal of assimilable organic carbon (AOC) and total organic carbon during desalination pretreatment. Pretreatment for seawater desalination typically focuses on removal of particles but many of the problems with membrane fouling are due to natural organic matter in water.
American Water developed a novel method to measure the AOC that bacteria feed upon in order to grow on the desalination membrane filters. The test uses a naturally bioluminescent marine organism for the assessment and monitors its growth by tracking the increase in light produced by the bacterium.
“The results of these studies suggest that when terrestrial organic matter enters highly saline water, it undergoes complexation by manganese and/or calcium to form soluble complexes that control its subsequent surface chemistry,” LeChevallier said. “When absorbed onto silts, these complexes become difficult to remove by charge neutralization and may require separation by enmeshment requiring high coagulant doses or coagulation at extremes of pH that impact the surface charge and allow for removal.”