Oct 20, 2022

Presence Absence (PA) Demo

Presence-absence (P-A) is a test that depends on a colour change to indicate the presence of contamination. If the test turns out to be positive, meaning the indicator bacteria is present, the water sample will change to a specific colour. P-A tests will not tell you the number of indicator bacteria in the water sample.

This demo will show how to conduct a PA test using Hach Pathoscreen medium.

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CAWST is a Canadian charity and licensed engineering firm. We address the global need for safe drinking water and sanitation by building local knowledge and skills on household solutions people can implement themselves.

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Development of this website and creation of collections of emergency themed tools on Water Treatment, Water Quality Testing, Behavior Change and Sanitation funded by Bureau of Humanitarian Assistance - USAID.

This project is made possible by the generous support of the American people through the United States Agency for International Development (USAID). The contents are the responsibility of CAWST (Centre for Affordable Water and Sanitation Technology) and do not necessarily reflect the views of USAID or the United States Government.

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