A drought cycle began in Salt Lake City in 1999 and persisted through 2004. In 1999, the reserves in the Upper
Reservoir were drawn down to provide drinking water. It was anticipated that runoff
would happen again sometime in the foreseeable future and fill it back up. The next four
years did not see much in the way of runoff. The decision was made in 2000 to
minimally utilize Parleys Treatment Plant and purchase water from neighboring utilities
that had more storage. The flow through volumes in the Lower Reservoir went from
20,000 acre-ft to less than 5,000 acre-ft annually. The Upper Reservoir did not fill until
the spring of 2005 after a heavy winter. No water was released and
very little was treated from the Lower Reservoir during 2000 through 2004. Very small
releases were made from the Upper to the Lower Reservoir to provide what was
absolutely necessary for treatment during 2000 to 2004. The Lower Reservoir became an
essentially closed system, and water quality problems started to occur in 2002. In late October of 2002 Parleys Treatment Plant was called upon to produce water after
being off for about nine months. The algae counts in the raw water
were about 202,000,000/100L. The predominant organism was Oocystus Gigal. While
this organism is not a taste and odor problem, it forms a slime coating which made it very
difficult to coagulate and remove in the treatment process. Good floc appeared to form
just fine. Then the floc broke up across the sedimentation basin, and unfilterable water
resulted at the end. Eventually, 60 mg/L of ferric chloride produced a settleable and
filterable floc. The normal dose for the treatment plant was 5-10 mg/L. This incident
prompted a closer look at what had been happening to water quality on the reservoir
during the drought. In general, DO decreased and TDS increased as the reservoir annual flow through
amounts decreased. This paper discusses improvements
due to measures that were taken during the summer of 2004. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 540 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 11/01/2005 |
