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MICROBIAL GROWTH IN DISTRIBUTION SYSTEMS
Citation:
Meckes*, M C. MICROBIAL GROWTH IN DISTRIBUTION SYSTEMS. Presented at Water Distribution Workshop, Columbus, OH, 12/11-12/2002.
Description:
Drinking water is not sterile. Microbes are commonly found in delivered water. Some survive treatment, while others may be introduced due to cross connections, line breaks, or by other means. Biofilm forms in drinking water pipes when bacteria and other organisms adhere to pipe walls and begin producing an extracellular polysaccharide envelope. That glue-like substance can anchor the bacteria to surfaces, where they can reproduce and grow. Increased temperature and rainfall (and the resulting increase in turbidity) are both factors contributing to the growth of biofilm, as are structural features of pipes and the velocity of the water running through them; biofilm growing in usually stagnant pipes can also be released with a sudden increase in flow. Nutrients and residual disinfection agents present in the water, and the material pipes are made of also play roles in creating an environment favorable for biofilm growth. Furthermore, the presence of biofilm as pioneer organisms provides an environment for other organisms to colonize - including, possibly, pathogenic bacteria.
Studies currently being conducted to understand the problem include the development of rapid, cost-effective methods for detecting the groups of bacteria specifically associated with biofilm, and for obtaining quantitative information as well. One of the specific organisms studied is Mycobacterium - both its detection and enumeration in water samples.
Studies are ongoing to determine the effects of the following factors on biofilms:
1. Effect of pH
2. Effect of disinfecting agents
3. Effect of nutrients
4. Effect of a cross-connection
Another study, in the planning stage, will look at the survival and growth of Aeromonas spp. in biofilm. Studies on the control of these organisms will be developed from some of the work mentioned above, in order to minimize potential health risks with microbial growth in distribution systems