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OHA Drinking Water Services
Contact Report Details |
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| PWS ID: | OR41 00152 | ||
| PWS Name: | BROWNSVILLE, CITY OF | ||
| Who Was Contacted and Phone: | Scott McDowell (541) 466-5666 | ||
| Contact Date: | 05/31/2007 | ||
| Contacted By: | BYNUM, ROBERT (DWP) | ||
| Contact Method/Location: | Office | ||
| Assistance Type: | CIRCUIT RIDER ASSISTANCE | ||
| Reasons: | N/A N/A |
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| Details: | SUMMARY: Filter media assistance DETAILS: Contacted by Scott McDowell, city administrator, and asked for assistance in slow sand filter media replacement. Reviewed original sand specification and proposed replacement sand specification. New sand specification was a close match to original and should work equally well. Made some suggestions for higher performance sand if available. "The specification looks pretty good. Sand should be clean and meet AWWA B100 and the specs require this. For slow sand filters, the specific gravity should be greater than 2.6 which the spec calls for. The uniformity coefficient should always be less than 3 and preferably between 1.5 to 2.0. The spec calls for UC of 2.5 or less which is fine but the old spec was a little better with a UC of 2.1 or less. The normal range for the effective size is 0.15 to 0.35 mm. The spec calls for an ES of 0.28-0.35 mm which is at the high end of the acceptable range but matches exactly the original spec. If possible, it would be nice to get an ES of 0.20 to 0.28 mm but this might be difficult and it may tend to increase the headloss across the filter. Essentially the new spec matches the original sand spec close enough and it should perform as good as the original did when new. If performance has always been acceptable there should be no reason to change. If available a slightly finer sand (ES of 0.25-0.28 mm) with a UC of 1.5 to 2.5 may perform better. The City of Westfir changed their sand a few years ago with sand from the Morse Bros. Stayton sand and gravel plant. Their sand had an ES of 0.28 mm and a UC of 2.46. Remember that performance will not be optimal until the biological growth (schmutzdecke) forms on the new sand." ACTION NEEDED: None | ||