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The goal of this study was to provide pilot-scale information about the ability of ultraviolet (UV) todisinfect unfiltered surface water. A pilot-scale low pressure UV system was operatedwith raw water from the Pardee Reservoir at the East Bay Municipal District inCalifornia. Monitoring of particle counts, turbidity, and UV transmittance at 254 nm was performedfor 12 months with data recorded hourly. The online particle count data were collected in8 different size ranges between 2 m and 50 m, but for reporting purposes the data wasdivided into two: greater than and smaller than 10 m in diameter. In addition to monitoring the water quality properties for evidence of particulate matterthat could conceivably inhibit UV disinfection (i.e. particle counts and turbidity), theinactivation of indigenous total coliform bacteria, total aerobic spore-formers (TAS), andsomatic coliphages across the pilot UV reactor was periodically monitored in an effort todetermine if inactivation was achieved at a level consistent with expectations based onUV treatment in particle-free water, and if not, to try to correlate impaired inactivationwith turbidity or particle counts. These three groups of organisms were selected toinclude those that are of a size consistent with Giardia and Cryptosporidium and mighttherefore experience a similar degree of particle shielding (i.e. coliforms and TAS), andvirus-sized organisms (i.e. somatic coliphage). Previous work had also indicated thatthese organisms might be present in surface waters at high enough ambientconcentrations to allow several log inactivation to be measured across the UV system.Total coliform bacteria were enumerated using the membrane filtration technique basedon Standard Method 9222 (APHA et al. 1998). TAS were enumerated using a membranefiltration technique (Rice et al. 1996, Verhille et al. 2003). Somatic coliphage wereenumerated using the spread plate technique, Standard Method 9224 (APHA et al. 1998). The pilot UV system was a 5 to 15 gpm low pressure high output (LPHO) TrojanUVMax. The reactor had been biovalidated by the manufacturer with fluences availableas a function of flow rate, UVT, and lamp age. The UV fluence was confirmed onsite bybiovalidation using MS-2 phage on three occasions over the study period, and rangedfrom 90 to 100 mJ/cmsup2/sup. Methods for the biovalidation procedure followed Bolton andLinden (2003) for the collimated beam work. Includes 8 references, figure.

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Edition: Vol. - No. Published: 11/01/2005 Number of Pages: 4File Size: 1 file , 170 KB