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USING MICROELECTRODES AND LIVE/DEAD BACLIGHT TO COMPARE PENETRATION, ACTIVITY, AND VIABILITY WITHIN NITRIFYING BIOFILM SUBJECTED TO FREE CHLORINE, MONOCHLORAMINE, AND PHOSPHATE - Abstract
Citation:
Lee, W. H., D. WAHMAN, P. L. Bishop, AND J. G. PRESSMAN. USING MICROELECTRODES AND LIVE/DEAD BACLIGHT TO COMPARE PENETRATION, ACTIVITY, AND VIABILITY WITHIN NITRIFYING BIOFILM SUBJECTED TO FREE CHLORINE, MONOCHLORAMINE, AND PHOSPHATE - Abstract. Presented at Association of Environmental Engineering and Science Professors Education and Research Conference, Tampa, FL, July 10 - 12, 2011.
Impact/Purpose:
To inform the public.
Description:
Many utilities have used monochloramine as a secondary disinfectant for regulation compliance. Along with the addition of chloramine comes the risk of nitrification. Nitrification in drinking water distribution systems may result in degradation of water quality and non-compliance with existing regulations. It is well known that nitrifying bacteria biofilms are involved in nitrification episodes in water utilities. Unfortunately, our understanding of distribution system nitrification biofilm and its control is incomplete. In addition, orthophosphate (PO43-) is often used to prevent corrosion in drinking water distribution systems. However, relatively little is known about its effect on nitrifying biofilm. The purpose of this research is to address knowledge gaps in our understanding of biofilm control in chloraminated drinking water distribution systems experiencing nitrification. The research primarily used microelectrode sensors (~10 μm diameter), which are capable of probing the full depth of a model distribution system biofilm, determining the profile of the relevant water quality parameters (e.g., monochloramine (or total chlorine), phosphate, ammonia, dissolved oxygen, nitrate, and pH), and enabling calculations of the relative contribution of biofilm activity. Combined with confocal laser scanning microscopy observation using LIVE/DEAD BacLight, this research demonstrated monochloramine’s greater penetration than free chlorine, the quantification of possible nitrifying biofilm recovery, and the positive act of phosphate on nitrifying biofilm development and nitrification. Overall, this research provide an improved insight into nitrifying biofilm subjected to free chlorine, monochloramine, excess ammonia, and phosphate, thus allowing further development of better strategies to prevent and control nitrification in water utilities.