Full Description

Seattle Public Utilities has chosen ultraviolet (UV) disinfection as part of a multi-barrierstrategy for disinfecting drinking water at the 180 mgd Cedar Treatment Facility. Two UVreactors underwent full-scale bioassay challenges and on-line dose monitoring confirmationtesting. The test protocol was one of the most extensive of its kind for UV treatmentequipment and had objectives related to dose delivery, log-inactivation, and energyoptimization. Specific testing was designed to cover the design parameters for the CedarTreatment Facility: reactor flow rates spanned a range of 7.0 - 15.0 USMGD; UVtransmittances spanned a range of 88 - 96 %/cm; and, aged lamps were operated at 60 - 100% power. Two challenge organisms were used: MS2 bacteriophage to determine UV dosedelivery; and, PhiX174 bacteriophage was chosen as a non-pathogenic surrogate forCryptosporidium to demonstrate log reductions. Two transmittance-altering substances withdifferent absorbance characteristics were tested, coffee and ligno-sulfonic acid (LSA).Performance results for the two reactors are presented, along with the results of dosemonitoring that utilized on-line flow, UV transmittance and UV sensor inputs. Therationale for determining an appropriate safety factor for the control system based on thelevel of agreement between the bioassay and dose-monitoring results are also discussed. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 16File Size: 1 file , 430 KB