Project Type

Direct Potable Reuse Research Initiative


Water Research Foundation



Current Status

Ongoing since 2018

Key Features

  • Direct potable reuse pathogen risk assessment
  • Quantitative microbial risk assessment
  • Probabilistic assessment of treatment train performance
  • Pathogen quantification in wastewater
  • Chemical peak protection

Project Overview

The California State Water Resources Control Board is currently developing DPR regulations in California. Prior to undertaking this effort, six priority research topics were studied to support regulatory development. The State is pursuing these research themes by engaging small (4- to 5-person) Technical Work Groups (TWGs) composed of subject experts. Trussell staff served leadership roles in three of the six research topics.

Trussell’s Dr. Brian Pecson is the Chair of the TWG overseeing DPR-1, one of the research efforts. The goal of the DPR-1 project was to develop a sound technical framework for: 1) the evaluation of DPR facility performance using a probabilistic assessment of treatment train performance (PATTP), and 2) the use of quantitative microbial risk assessment (QMRA) to assess the level of treatment required to achieve risk-based targets. This framework was built into a tool—called DPRisk—that allows the State Water Board’s Division of Drinking Water to quantify and characterize pathogen risk in DPR applications. These processes are critically important in identifying the log reduction values (LRVs) necessary for adequate protection of public health from waterborne pathogens. The TWG overseeing the effort completed a literature review of previous PATTPs and QMRAs and developed a framework for the consistent application of these approaches. The Research Team used the framework to develop the web based DPRisk tool and an accompanying Guidance Document. Together, the TWG and Research Team provided training to the State Water Board on the use of DPRisk.

DPR-2 is the second of the State Water Board’s six research topics that is focused on gathering high-quality data on the concentrations of drinking water pathogens in raw wastewater. This effort will help the State Water Board verify the required log removal values necessary for public health and enable them to develop recommendations for the collection and analysis of pathogen data in future monitoring efforts. As Project Manager, Dr. Brian Pecson led a literature review and methods development phase to create optimized standard operating procedures. The resulting quality assurance project plan (QAPP) was used for a 14-month monitoring campaign that evaluated multiple viral and protozoon pathogens over 120 sampling events at five large wastewater facilities in California. The study will produce one of the largest datasets ever collected on pathogen concentrations in wastewaters.

Dr. Shane Trussell is leading a TWG in collaboration with Orange County Water District and Kennedy Jenks to address DPR-4: how to provide protection against potential peaks of chemicals coming through the treatment train. The primary objective of the project is to present a case study that investigates the families or groups of chemicals with similar characteristics that should be targeted for reduction/removal that are not sufficiently reduced/removed by full advanced treatment processes. The project team conducted research and reviewed three utilities performing potable reuse via advanced water treatment facilities: The City of San Diego, the Singapore Public Utilities Board, and the Orange County Water District. Dr. Trussell and the TWG presented their findings to the State Water Board to help inform their DPR regulations.

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