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EFFECT OF VARYING FLOW REGIMES ON BIOFILM DENSITIES IN A DISTRIBUTION SYSTEM SIMULATOR
Citation:
Meckes*, M C., R M. Clark*, M Dosani, S. Li, AND P. Biswas. EFFECT OF VARYING FLOW REGIMES ON BIOFILM DENSITIES IN A DISTRIBUTION SYSTEM SIMULATOR. Presented at AWWA's Water quality Technology Conf, Salt Lake City, UT, 11/5-9/2000.
Description:
Maintenance of a free chlorine residual within water distribution systems is used to reduce the possibility of microbial contamination. However, it has been demonstrated that biofilms within water distribution systems can harbor coliforms. In laboratory scale studies, others have shown that biofilms can harbor pathogenic microorganisms. It has also been demonstrated that the number of viable biofilm organisms remains relatively high within distribution systems which maintain chlorine residuals at typical levels. High chlorine residuals within distribution systems can contribute to formation of undesirable disinfection by-products. As a consequence of low levels of chlorine, and with adequate nutrients, biofilm growth within distribution systems remains a concern. Biofilms are commonly found growing at relatively high densities on surfaces within water distribution systems. The presence of biofilms within a distribution system does not necessarily indicate that the quality of the treated water has been compromised during tansmission. Such films may be in monolayers or held within extra polymeric materials secreted by the bacteria which make up the film. As the film grows, the shear force of the water separates some of the film which can then be adsorbed to downstream surfaces or which becomes a part of the bulk water moving through the distribution system. Relatively little is known regarding the effect of flow regimes on biofilm densities. Of particular interest are those sections of a water distribution system which maintain low flow conditions due to limited use. This study was designed to determine the effects of varying flow regimes on culturable biofilms and planktonic bacteria in system dead ends in the presence and absence of free chlorine residuals.