Groundbreaking water treatment research advances potable reuse technologies

WALNUT CREEK, Calif., June 17, 2025 – A pioneering research study by a multidisciplinary team of researchers, engineers, and utilities has been completed, providing clear guidance for pathogen reduction in carbon-based advanced treatment (CBAT) water systems. Funded by The Water Research Foundation (WRF), project 5129 focuses specifically on innovative approaches to ozone and biologically activated carbon (BAC) filtration processes for potable reuse applications.

The project titled “Demonstration of Innovation to Improve Pathogen Removal, Validation, and/or Monitoring in Carbon-Based Advanced Treatment for Potable Reuse” was led by Principal Investigator Andrew Salveson of Carollo Engineers. The comprehensive study delivers critical insights for water utilities seeking alternatives to reverse osmosis-based treatment systems.

The research was conducted in collaboration with Hampton Roads Sanitation District (HRSD) in Virginia, and Mekorot, Israel’s national water company, providing international perspective and extensive operational data. The study was further strengthened by the participation of key water reuse utilities, including the Clay County Utility Authority, Polk County Utilities, and the City of Altamonte Springs (Florida), as well as the City of South Jordan (Utah). This cross-section of utilities contributed to the broad applicability of the findings.

The multi-year study validated a novel approach using an ozone to total organic carbon ratio after accounting for the nitrite demand on ozone [(O₃-NO₂):TOC] as an effective dose control method. This innovative approach optimizes energy use by reducing the required ozone dose while achieving effective pathogen reduction, resulting in lower utility operational costs. Furthermore, it minimizes bromate formation, a regulated disinfection byproduct that must be controlled in drinking water systems to meet public health standards, while maintaining robust virus disinfection levels.

Key research findings:

• The (O₃-NO₂):TOC approach proved to be an efficient and more accurate control strategy for ozone disinfection compared to traditional methods.
• Operating parameters such as pH, temperature, nitrite spikes, and peroxide addition did not significantly impact the effectiveness of this control approach.
• Upstream coagulation/flocculation/sedimentation significantly enhanced pathogen removal by BAC.
• Machine learning models were successfully developed as “soft sensors” for total organic carbon, enabling more frequent measurement updates.
• A tiered ozone validation protocol was developed allowing for different levels of virus reduction credit based on site-specific information.

“The findings from this comprehensive study represent a significant advancement for ozone and BAC systems used for potable reuse,” said Salveson. “The validated ozone dosing methodology provides utilities with a pathway to implement carbon-based advanced treatment systems that are more energy-efficient and environmentally sustainable than traditional approaches, particularly for inland communities where concentrate disposal poses challenges.”

The research team compiled extensive datasets from existing studies and conducted bench and pilot-scale testing at the utilities. They confirmed the effectiveness of the (O₃-NO₂):TOC dose control mechanisms and developed a validation protocol that can be used by utilities and regulators to implement this optimized operational approach.

The scope and success of this study reflect the significant collaborative effort across the water industry. In addition to the participating utilities, substantial contributions came from HRSD through its SWIFT initiative, which provided extensive data and parallel research support.

For more information on this research, visit WRF project 5129.

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Media Contact:
Cameron McWilliam
Senior Public Relations Manager // Carollo
[email protected]