Statewide (PA) Chlorine Contact Time Tracer Study - Gwin, Dobson ...

• Ensure disinfection contact time complies with the goals established under
the Interim Enhanced, Long Term 1 and Long Term 2 Surface Water
Treatment Rules and Stage 1 and 2 of the Disinfectants/Disinfection
Byproducts Rule.
• To prepare water suppliers for the “balancing act” of maintaining adequate
pathogen (ex.,giardia) and virus inactivation while avoiding “over
disinfection” that can lead to byproduct formation
• Surface water suppliers may be unaware of the actual short‐circuiting that is
occurring in chlorine contact basins. By default, DEP’s field staff or the water
suppliers had assigned a “rule‐of‐thumb baffling factor” (i.e. short circuiting
estimate) that may not realistically reflect conditions
• Many of the suppliers do not have the technical expertise to conduct tracer
studies, hence PADEP’s efforts to perform studies of select systems.
• This presentation will provide a general overview of tracer studies, selected
methodologies, findings and importance of such efforts to thoroughly
evaluate ones water system