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Journal of Water and Health In Press, Uncorrected Proof © IWA Publishing 2013  |  doi:10.2166/wh.2013.198

Laboratory validation of an ozone device for recreational water treatment

Robert S. Donofrio, Sal Aridi, Ratul Saha, Robin Bechanko, Kevin Schaefer, Lorelle L. Bestervelt and Beth Hamil

NSF International, 789 Dixboro Road, Ann Arbor, Michigan 48105, USA E-mail: Donofrio@nsf.org
Del Ozone, 3428 Bullock Lane, San Luis Obispo, CA 93401, USA

First received 8 October 2012; accepted in revised form 10 March 2013. Available online 8 April 2013


Obtaining an accurate assessment of a treatment system's antimicrobial efficacy in recreational water is difficult given the large scale and high flow rates of the water systems. A laboratory test system was designed to mimic the water conditions and potential microbial contaminants found in swimming pools. This system was utilized to evaluate the performance of an in situ ozone disinfection device against four microorganisms: Cryptosporidium parvum, bacteriophage MS2, Enterococcus faecium, and Pseudomonas aeruginosa. The sampling regimen evaluated the antimicrobial effectiveness in a single pass fashion, with samples being evaluated initially after exposure to the ozone unit as well as at points downstream from the device. Based on the flow dynamics and log reductions, Ct values were calculated. The observed organism log reductions were as follows: >6.7 log for E. faecium and P. aeruginosa; >5.9 log for bacteriophage MS2; and between 2.7 and 4.1 log for C. parvum. The efficacy results indicate that the test system effectively functions as a secondary disinfection system as defined by the Centers for Disease Control and Prevention's Model Aquatic Health Code.

Keywords: Cryptosporidium parvum; Ct value; disinfection; ozone; recreational water

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