AWWA ACE95295

Metcalf & Eddy used on-line particle counting to determine the particle count and log removal of Giardia- and Cryptosporidium- sized particles, in order to optimize and compare the performance of different pilot and full-scale processes. Four types of water treatment processes were evaluated with on-line particle counting: direct filtration, one full-scale and one pilot version of different types of sludge blanket clarification with filtration, and dissolved air floatation (DAF) with filtration. A direct filtration water treatment plant using deep bed granular activated carbon was evaluated to determine if filtration performance could be improved. From the particle counting data it was concluded that a change in coagulant and a change to a slightly smaller GAC media would greatly improve the effectiveness of filtration. A pilot study was conducted comparing: sludge blanket clarification with and without tubes and coupled with deep bed GAC filtration and single media sand filtration; to an existing up-flow sludge blanket clarification and GAC filtration process. The effect of high and low dose pre-ozonation and pre and intermediate ozonation on particle removal was evaluated. A pilot study was conducted evaluating the performance of dissolved air flotation (DAF) and dual media filtration for treating two different raw water qualities, and comparing alum, sodium aluminate and polyaluminum chloride coagulants. Performance was compared under different clarifier and filter surface loading rates. These studies illustrate the effectiveness of using on-line particle counting in real time, to optimize and document the performance of clarification and filtration unit processes taken separately or together as an overall process. Various ways of managing, analyzing, and interpreting particle count and log removal data are discussed. Conclusions are drawn about the performance of the various unit processes and the application and effectiveness of on-line particle counting for process optimization with respect to removal of Giardia- and Cryptosporidium- sized particles. Recommendations for further study are also discussed.