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Methodology for Assigning Pathogen Removal Credits for Sub-Surface Desalination Intakes

Project: 14-06
Estimated Release: 2018
Type: Report

Program: Principal
Funding Partner: NA
Total Investment: $330,392 (Cash: $200,000, In-Kind cash and service: $130,392)

Principal Investigator: Dr. Zia Bukhari, Ph.D., American Water

Background

The water desalination industry does not have an established protocol for determining whether groundwater is under the influence of surface water and typically does not assign pathogen removal credits to raw water sources for drinking water facilities. This challenge is faced by many utilities that derive their source water from wells that may be under the influence and is particularly challenging for seawater projects that are considering what could be a substantial additional investment in a subsurface intake. In the United States, for example, the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) assigns log removal requirements based on bin and treatment type. However, “Alternative Filtration Technologies” log removal is determined by State. Development of a methodology for assigning pathogen removal credits for intake wells will provide guidance to state regulators.

This project will review the various techniques that can be applied to establish whether or not groundwater is under the influence of surface water and determine a recommended approach or suggested order to the preferred approached. This project will also review the various ways of establishing that these criteria are achieved and a method to reliably determine pathogen removal credits if intake wells are employed. An intake well may be a constructed engineered intake (such as an infiltration gallery) or employ buried pipes under native subsurface materials. The recommended approaches will then be demonstrated at a full-scale seawater desalination well.

Goals and Objectives

The project will:

  • Evaluate methodologies and approaches currently practiced for making a determination as to whether or not an intake well is under the influence of surface water.
  • Evaluate methodologies available for determining the pathogen removal credit that can be verified for a given intake well.
  • Make recommendations for the preferred methodologies and demonstrate the validity of these methods on a full-scale seawater well to establish whether or not it is under the influence of surface water and provide pathogen removal credits for protozoa and virus.

Research Approach

Task 1: Literature review and Utility Survey of the various approaches to establishing pathogen removal credits for a subsurface intake and determining if the groundwater is under the influence of surface water. Perform a literature review on the various methods and techniques that have been used or could be considered for establishing whether or not a groundwater is under the influence of surface water, and established regulatory frameworks that would provide guidance for this process. The final outcome should be a literature review and utility survey document to summarize the findings on the available techniques for the various types of subsurface intakes.

Task 2: Develop Recommended Approach(s) to Establishing Whether Groundwater is Under the Influence. Provide a detailed description of the necessary monitoring program, environmental conditions, groundwater hydrological conditions, and subsurface intake structure including structure material and necessary components to allow these methods to be utilized. Identify potential roadblocks or fatal flaws.

Task 3: Develop Recommended Approach(s) to Establishing Pathogen Removal Credits for a Specific Well. Provide a description of necessary monitoring program, environmental conditions, groundwater hydrological conditions, and subsurface intake structure, as well as necessary components to allow these methods to be utilized.

Task 4: Demonstrate with Full-Scale Seawater Desalination how the Proposed Methodology from Tasks 3 and 4 would be Successfully Applied – Using the recommended approaches developed in Tasks 2 and 3, demonstrate on a full-scale subsurface intake (i.e. horizontal well, slant well, or other subsurface intake) the application of these concepts to validate methods proposed.

Task 5: Final Report. This task will summarize Tasks 1 through 4 into a final report for WRRF, which will include the literature review, utility survey, recommended approaches, and documentation of method success regarding full-scale demonstration.

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