This project developed a technical framework for (1) the evaluation of direct potable reuse facility performance using a probabilistic assessment of treatment train performance, and (2) the use of quantitative microbial risk assessment to assess the level of treatment required to achieve risk-based targets. This framework was built into a tool, DPRisk, that allows for the quantification and characterization of pathogen risk in direct potable reuse applications. Details on how to access DPRisk can be found in the DPR Research section of the California State Water Resource Control Board’s website at https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/direct_potable_reuse.html. Research partners: California State Water Resource Control Board and Metropolitan Water District of Southern California. Published in 2021.