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AWWA WQTC65773
- Total Coliform Monitoring: Lessons from a Monitoring Program Using Large Sample Volumes and Large Number of Samples
- Conference Proceeding by American Water Works Association, 11/01/2007
- Publisher: AWWA
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In order to comply with impending Stage 1 Disinfection/Disinfection Byproduct Rule,Tampa Bay Water implemented chloramination in its regional system in May 2002. InSeptember 2002 and March 2003, two newly treated surface water sources were brought online to meet growing demand and regulatory decreases in permitted groundwater use.Historically, the Tampa Bay region relied solely on treated groundwater. Pinellas Countyalso instituted a unidirectional flushing program in April 2002 (roughly). Following thesemajor operational changes, Pinellas County Utilities (PCU) observed a significantincreases in the number of positive Total Coliform samples for both their routinecompliance sampling and special auxiliary monitoring. County staff related the increaseto the change in disinfectant and/or the introduction of the new sources. The apparenttemporal correlation between these events and the sudden increase in positive totalcoliform samples led to the hypothesis that some or all of these changes led to theincreased positive samples. In order to evaluate possiblecausal relationships between the new water sources or new treatment and thebacteriological issues, PCU and Tampa Bay Water initiated an intensive, year longmonitoring program at eight locations in the regional transmission system and at connectionpoints between the wholesale and retail systems. Preliminary monitoring by PCUsuggested that larger volume samples were more likely to detect total coliform positiveresults when total coliform bacteria were present (Pryor et al, 2005). Preliminarystatistical monitoring using bootstrap analyses supported that larger sample sizes weremore effective at detecting total coliform bacteria when they were present.Since the objective of the sampling was to identify sources of total coliform, theparticipants agreed that larger sample volumes would be appropriate. Due to methodlimitations and to help the entire industry address the effectiveness of the larger samplevolumes, the larger volume samples were taken as multiple 250 ml samples. In order forthese results to be comparable with historical total coliform samples a 100 ml sampleswas also taken at the same time so that the results of 100 ml samples could be comparedwith progressively increasing volumes ranging from 250 mls up to two liters. Includes reference.
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