Edward (Eddie) Campbell of the Portland Water Bureau gave an excellent presentation to a small but enthusiastic group at our 18 July 2012 ORAWRA dinner meeting at the Lucky Lab Beer Hall in Portland, OR.
Campbell spoke on PWB's recent successful variance request to avoid filtration of the Bureau's primary drinking water source - the Bull Run Watershed - because of potential Cryptosporidium contamination. Cryptosporidium is a chlorine-resistant protozoan that causes potentially fatal gastrointestinal distress. Recall the 1993 disaster in Milwaukee, when over 100 people died and about 400,000 became ill. The elderly and those with compromised immune systems are especially vulnerable.
Campbell gave more than a Cryptosporidium talk as he recounted the history of Portland's municipal water system and the Bull Run source in particular. I also learned that PWB's groundwater source - a wellfield on the south bank of the Columbia River - is not only used in the summer but also whenever the turbidity from the Bull Run source exceeds 5 NTU, which can happen during the winter rainy season.
Here is a PDF of his PPT:
Here is a little publication about the organism.
Upshot: PWB was granted a 10-year variance (effective 1 April 2012) with conditions and avoided the expense of an ultraviolet system. Campbell noted that among large and mid-sized cities Portland is one of six without a filtered surface water supply system; the others are Tacoma, Seattle, San Francisco, New York, and Boston. PWB is also the first public water system ever granted a variance from a SDWA treatment requirement.
Even if you're not interested in Cryptosporidium, give Campbell's presentation a look. Lots of good information.
Note added: Funny thing: the PWB just issued a 'boil water advisory' for its service area west of the Willamette River, but it was for E. Coli, not Cryptosporidium (which can also be killed by one minute of boiling).
"When water chokes you, what are you to drink to wash it down?" - Aristotle (thanks to C.W. Fetter's Applied Hydrogeology, 2/e, 1988)