Cryptosporidium was the cause of 65.6% of the reported waterborne disease outbreaks in swimming pools between 1993 and 2002, and Cryptosporidium continues to pose a significant threat to public health in these venues. Cryptosporidium is very resistant to chlorine disinfection (surviving several days to a week under typical free chlorine and pH levels found in swimming pools) because it is protected by thick-walled outer shell, called an oocyst wall. This leaves filtration to serve as the primary means of safeguarding public health against cryptosporidiosis. This research work was focused on sand filtration as barrier to Crypotosporidium in swimming pools. In addition to straight sand filtration, multiple doses and types of chemical polymers (or clarifiers) were used in an innovative approach to optimize Cryptosporidium removal from swimming pool water and to better understand the removal of Cryptosporidium oocysts via commonly-used sand filters. In Phase I, the electrostatic surface charge (or zeta potential) of oocysts was measured under a range of water conditions, coagulant types, and coagulant dosages applicable to swimming pool systems to identify optimum coagulant dosages for subsequent experiments. In Phase II, both uncoagulated and a variety of batch coagulated water samples were filtered through sand filters under simulated swimming pool conditions, and the oocyst removals were calculated after the first and successive passes through the bench-scale filter. Phase III involved determining oocyst removals under uncoagulated and optimally coagulated conditions (based on Phase II results) in a 1:25 scale model swimming pool with water continually recirculated through the filter and with periodic filter backwashes over 5-day experimental periods. Finally, in Phase IV, a polystyrene microsphere surrogate (also carried through the preceding three experimental phases) of the same size, shape, and density as Cryptosporidium oocysts were evaluated for removal at 2 local swimming pools during normal operating conditions and bather use for 10-day periods, and the optimum conditions identified in Phase III were also evaluated in subsequent 10-day periods on the full-scale swimming pools. Cryptosporidium removal results will be reported for oocysts in swimming pools under normal conditions and under a variety of optimized coagulation/treatment conditions. Regulators, pool designers, and pool operators will gain a much better understanding of the oocyst removal capabilities of sand filters in the swimming pool environment with and without clarifier use. They will be better able to develop enhanced standard operating procedures and remediation strategies to reduce the risk of future waterborne disease outbreaks thereby protecting public health and increasing participation in aquatic activities. James E. Amburgey, Ph.D. is currently an Assistant Professor at the University of North Carolina at Charlotte for the Department of Civil and Environmental Engineering. In addition, he is the President and Director of Research for Water Treatment Research, Inc. in Kannapolis, NC. Prior to his current positions, he was an Emerging Infectious Diseases Postdoctoral Research Fellow at the Centers for Disease Control and Prevention (CDC). He received his Bachelor of Science in Civil Engineering from the University of North Carolina at Charlotte. He received his Master of Science and his Doctorate in Civil and Environmental Engineering from the Georgia Institute of Technology. Dr. Amburgey has authored many articles and presented at numerous conferences. His research interests include granular media filtration, coagulation, backwashing, filtration modeling, pathogen removal, pathogen and bioterrorism detection methods, UV disinfection, bioadhesion, interparticle forces, membrane treatment processes, and dispersant and surfactant treatment technologies. He currently has two patents pending.
|
