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Evaluation for Source Water Control Options and the Impact of Selected Strategies on DPR

Project: 13-12
Type: Decision Making Tool
Estimated Release: 2016

Program: Principal
Funding Partner: Metropolitan Water District
Total Investment: $231,130 (Cash: $149,980, In-Kind cash and service: $ 81,150)

Principal Investigator: Alan Rimer PE, DEE, Black & Veatch


Many regions across the Unities States are facing water crises, which will challenge current concepts of water supply management. A paradigm shift to expand the use of traditional recycled water use to potable reuse is inevitable. Specific drivers for direct potable reuse (DPR) include: lack of suitable hydrogeology for groundwater storage or large reservoirs to meet indirect potable reuse (IPR) requirements, high costs associated with tertiary recycling for irrigation and other non-potable applications, lower energy costs for production than other water supply alternatives (i.e. sea water desalination), and advancements in advanced water treatment (AWT) and monitoring technologies.

To date, no regulations for DPR have been adopted in the United States. Recently, the need and opportunity for DPR have gained local and national recognition, and the development of regulations are under consideration. In the State of California, Governor Jerry Brown recently signed Senate Bill 322 on October 8, 2013, which requires the California Department of Public Health (CDPH), in consultation with the State Water Resources Control Board (SWRCB), to convene an expert panel to investigate the feasibility of developing uniform criteria for DPR. While the final report is due December 31, 2016, Governor Brown emphasized the urgency for DPR in a statement “This information is past due…The three year time frame mandate in the bill is too slow. California needs more high quality water and recycling is key to getting there.” WRRF’s project gains increased significance in the face of the current drought crisis in California.

Goals and Objectives

The project will:

  • Evaluate upstream wastewater treatment impacts on DPR source water and downstream advanced treatment processes.
  • Assess the impact of hydraulic control mechanisms on influent water quality and flow variations that may stress advanced treatment process for DPR applications.

Variable influent water quality and extent of source control strategy implemented have a direct impact on the performance of an IPR/DPR treatment process train. In addition, utilities that own and operate wastewater treatment plants (WWTP) and advanced water purification facilities (AWPF) are often separate entities with different treatment objectives (e.g. WWTP treats to comply with ocean discharge requirements and AWPF treats to meet drinking water requirements). A successful, reliable DPR treatment system requires two entities working together, not only to meet their individual treatment objectives, but also to complement each other to provide a safe potable reuse supply.

Research Approach

Task 1: Literature Review. The literature review for this project involves an in-depth review of a wide variety of topics that will meet the project objectives of: 1) quantifying upstream wastewater treatment impacts on DPR source water quality and treatment processes and 2) evaluating the impact of flow equalization and source water storage buffers on treatment reliability. In addition to a traditional literature review and data available from the project team and Foundation’s previous and current work, a questionnaire on systems operation will be developed to obtain information from our utility partners.

The current, documented challenges posed from each “type” of source (e.g. activated sludge process, membrane bioreactor [MBR], nitrified/denitrified effluent versus non-fully nitrified effluent, and others) must be identified in this literature review. In addition, hydraulic and load variations observed at wastewater treatment plants (WWTPs) that would impart variations in source water quality and potentially “stress” downstream IPR/DPR facilities will be investigated when reviewing the literature and conducting statistical characterization of effluent and performance data from our utility partners. The literature review, case study results, and discussions with partner utilities will form the foundation for the development of guidelines.

Task 2: Development of Guidelines. While Task 1 provides a historical look at the challenges in blending WWTP objectives with DPR objectives, Task 2 develops part of the pathway forward by showing what should be done through Hazard Analysis and Critical Control Points (HACCP) and what could be done with controls. This forms the basis for the draft Guidance Document which will be further refined in Task 3 by going into specifics on what it would take to implement these strategies for specific utilities/treatment/infrastructure.

The approach to developing source control strategies for DPR will build on the following information and specific information gathered from the utilities (data collection and statistical characterization work in Task 1). Guideline development will be built upon information obtained from the review of WRRF 11-01 Online sensor Monitoring, OCSD’s Expanded Source Control Program for Constituents of Emerging Concern (CEC), WERF Research on WWTP Security and Emergency Response Strategy (WERF Project 03-CTS-7S and WERF Project 04-CTS-11S), and HACCP Principles.

Task 3: Case Studies. Four case studies that cover a wide range of source waters delivered to an existing IPR treatment system were chosen for analysis. The RFP only required one case study, but four different case studies were selected where B&V has on-going working relationships with the utility and the understanding of their operations is very high. This will streamline case study development in support of the development of the overall Guidance Manual.

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