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Opening Pandora’s Box – Disinfection Data Accuracy for Water Systems

This webinar was broadcast on January 22nd, 2018

Slide Deck: Evaluating the Integrity of Water System Monitoring

In 2014 – 2015 the Washington State Department of Health conducted the Disinfection Data Integrity Project. The yearlong study investigated disinfection measurement, recording and reporting practices in 33 surface water treatment plants located in the Northwest Region of Washington State. Deficiencies were identified in all 33 treatment facilities that affect the accuracy of the calculated pathogen inactivation achieved by the disinfection processes. Pathogen inactivation level errors of over 100% were identified when more accurate data was used.

Accurately determining chlorine disinfection inactivation levels is complex. Three water quality (WQ) parameters: chlorine residual, pH, and temperature are used along with the time the disinfectant is in contact with water before the first customer (contact time) to determine disinfection efficiency. Contact time is dependent upon three more parameters: the volume of the contact vessel, the baffling efficiency of the contact vessel, and the water flow rate. Each one of these components (three WQ parameters, contact vessel size, efficiency, and flow rate) can and do affect data integrity and impact the accuracy of calculated disinfection inactivation levels used to ensure public health protection.

An average of eight issues that affect data accuracy were found at each utility suggesting that water monitoring data integrity is not robust. This presentation will share study findings and explore ways to improve practices at your utility.

Our Presenters:

Nancy is a professional engineer with 29 years’ experience with the Washington State drinking water program, where she coordinates statewide implementation of surface water treatment rules.  Three years living among the Mossi people in the Sahel region of West Africa sparked a lifelong interest in safe drinking water.  She received her MS degree in environmental engineering from Stanford University and her BS degree in civil engineering from the University of Washington.

Steve is a professional engineer with 29 years’ experience in water and sanitation issues. He works for the Washington State drinking water program and is a consultant for Water 1st International, a non-profit water and sanitation development organization. His experience encompasses a myriad of settings, from the Kurdish refugee camps in Northern Iraq to post-war rehabilitation in Bosnia Herzegovina, and from simple pipe systems in the slums of Dhaka, Bangladesh, to development efforts on onsite non-potable water systems for urban buildings in the USA. He received his MS degree in civil and environmental engineering from the University of Washington and his BS in civil engineering from Marquette University.