Providing Financial Assistance to States for Testing and Treatment Act of 2020 or the PFAS Testing and Treatment Act of 2020 This bill expands the allowed use of existing grants for certain water systems to address emerging contaminants, including perfluoroalkyl and polyfluoroalkyl substances, commonly referred to as PFAS. These substances are man-made and may have adverse human health effects. Specifically, these grants may be used for activities such as investing in compliance for public water systems and underground sources of drinking water, and to provide household water quality testing. The bill also establishes additional grants for states to address groundwater contamination by certain perfluoroalkyl substances.