| The primary objective of this research was to determine the capability of an emerging drinking water clarification process, dissolved air flotation (DAF), to remove waterborne Cryptosporidium, an environmentally resistant, parasitic pathogenic protozoa, considered ubiquitous in U.S. surface waters. A secondary goal was to compare removal via DAF with other processes, including conventional sedimentation clarification.;A series of bench-scale, pilot-scale and full-scale experiments achieved these objectives. Two high quality, northeastern U.S. surface waters served as the source waters for the bench- and pilot-scale experiments. The non-inactivated Cryptosporidium-spiked bench-scale experiments evaluated three coagulants: alum and ferric chloride in both warm (;The bench-scale results showed that DAF outperformed sedimentation for all coagulation strategies and for both water temperatures. DAF clarification alone consistently achieved bench-scale removals ;Pilot-scale DAF results confirmed bench-scale results, achieving 2.0 and 3.0 log reduction, using alum and ferric chloride coagulation, respectively. DAF followed by dual media filtration achieved 4.2 to 5.1 log removal for the three coagulation strategies evaluated depending on coagulant and filtration rate. The full-scale experiments demonstrated sedimentation removal of ;Bench- and pilot-scale DAF removal was significant. Environmental professionals should consider DAF clarification as an effective barrier in the multiple-barrier approach to public health protection of drinking water. |
