In order to provide safe drinking water, utilities must have accurate knowledge of how pathogens are removed by various treatment approaches and be able to predict treatment effectiveness. Many investigations on this subject have been conducted for systems whose source waters have relatively higher turbidity, because contamination by protozoa is considered more likely in such systems. There is a need for additional research on pathogen removal by filtration of high-quality source waters with low turbidity and low dissolved organic carbon. This project will (1) demonstrate the inadequacy of settled/clarified or filtered water turbidity; and (2) identify design, operational, and/or monitoring strategies for ensuring that the minimum Cryptosporidium oocyst removal assumptions of various regulations are reliably and cost effectively achieved. Research partner: City of Calgary.