A few years ago I worked with American Water (the USA company with the largest number of water utilities) on an AWWARF project on pathogen intrusion due to low pressure transients in drinking water systems. Not surprisingly low pressure transients were measured following power outages resulting in pump trips. The low pressures result in the intrusion (sucking in) of dirty and often contaminated water into the drinking water distribution system. As an engineer who has been doing transient analysis for 45 years I fully expected that low pressure transients would develop following a pump trip. Any engineer doing transient analysis would expect this result. However, the study was directed at determining the health hazards resulting from low pressure transients in drinking water systems. The results of this extensive study was that low pressure transients could result in the intrusion of pathogens which pose serious health risks to the users of the drinking water system. This study clearly documented serious potential health risks if measures were not taken to protect public drinking water systems from inevitable transient events (pump trips. I fully expected that an effort would have been made to implemented Federal and/or State guidelines or regulations to protect the public from this well known public health risk. To my knowledge this has not happened and our public drinking water systems continue to be at risk from inevitable pump trips following power outages. Consider the fact that several European Countries mandate that drinking water systems be protected from low pressure transients following a pump trip. In the USA we have the data documenting this serious problem but no such mandate to address it. I also find it interesting that a paper generated by a study in Canada just published (March 2010) in Drinking Water Engineering Science (Negative Pressures in Full Scale Distribution Systems etc.) revisits the issue of measuring and predicting low pressure transients following pump trips with, of course, the same conclusions. These events pose a serious risk to the public health. Nothing new here but the lack of action to protect the USA public drinking water systems is puzzling and disturbing. We see great concern that a terrorist event could contaminate our drinking water systems and yet we do not take action to address a known problem with well tested solutions to prevent the inevitable occurrence of events leading to contamination of many of our drinking water systems.
Dr. Don J. Wood |
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Let’s Protect our Drinking Water Systems from Low Pressure Transients!
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