Applications Invited for Reducing Nitrification Risks Through Collaboration Between Drinking Water Wholesalers and Consecutive Systems

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About the Organization

The Water Research Foundation (WRF) is the leading research organization advancing the science of all water to meet the evolving needs of its subscribers and the water sector. WRF is a 501(c)(3) nonprofit, educational organization that funds, manages, and publishes research on the technology, operation, and management of drinking water, wastewater, reuse, and stormwater systems—all in pursuit of ensuring water quality and improving water services to the public.

WRF was formed in 2018 through the integration of three highly respected research collaboratives: WateReuse Research Foundation, Water Environment Research Foundation, and Water Research Foundation. Separately, these organizations focused on research to support varied segments of the water sector—water reuse, wastewater and stormwater, and drinking water, respectively. Now a One Water organization, WRF delivers the research programming the sector needs to address the most pressing water issues holistically.

About the Grant

This project is funded by The Water Research Foundation (WRF) as part of WRF’s Emerging Opportunities Program. The Emerging Opportunities Program has unique proposal requirements.

Project Objectives:

The objective of this research project is to improve nitrification risk management in consecutive drinking water distribution systems. The specific objectives are:

• To catalog the roles and responsibilities of wholesale and consecutive systems—including regulatory requirements, water quality, and operations—and to develop best practices for roles and responsibilities of wholesale and consecutive systems.
• To identify and share strategies that promote communications and collaborations between drinking water wholesale and consecutive systems.
• To develop best practices for effective collaboration between wholesale and consecutive systems in managing nitrification risks.
• To provide guidance to consecutive utilities on preventing, detecting, and responding to nitrification events, including low-level nitrification events.

Budget:

Applicants may request up to $100,000 in WRF funds for this project. In-kind support is encouraged, though not required.

Background and Project Rationale:

The use of chloramine as a secondary disinfectant for drinking water has significantly increased in the United States (U.S.) since the U.S. Environmental Protection Agency (EPA) implemented its Microbial and Disinfection Byproduct Rules (MDBP) under the 1996 Safe Drinking Water Act Amendments. Today, approximately 30 percent of U.S. drinking water systems use chloramine (Khiari, 2019).

Chloramine is widely adopted because it helps reduce risks associated with regulated chlorine disinfection byproducts, such as haloacetic acids and trihalomethanes, and provides a stable disinfectant residual. Chloramine is also more effective at controlling biofilms that may harbor pathogens, including Legionella.

Despite these benefits, the use of chloramine poses challenges, particularly in the promotion of nitrification in the distribution system. If not carefully managed, nitrification can degrade water quality, reduce disinfection residual, increase bacterial growth, and lead to customer complaints, operational difficulties, regulatory violations, and public health concerns. Approximately two-thirds of systems using chloramine experience nitrification (Khiari, 2019).

Managing nitrification risks can be especially challenging for consecutive systems, which often face unique challenges due to limited control over the quality of water they receive and fewer options for addressing nitrification events. Higher temperatures and prolonged water age in distribution systems increase these risks, especially in warmer climates and during summer months. Even if wholesalers deliver water that complies with regulatory standards, external factors—such as climate and water retention time—can still render it vulnerable to nitrification in the consecutive systems' distribution networks.

Effective nitrification management requires a clear understanding of the roles and responsibilities of both wholesalers and consecutive systems. These roles are often defined by the terms of the contract between the two entities, which can vary depending on the specific system and location.

Wholesalers should maintain an adequate disinfectant residual and proper chloramine formation as they deliver potable water to consecutive systems. The regulatory minimum disinfectant residual at the entry point to the distribution system is 0.2 mg/L, and a disinfectant residual cannot be less than this concentration for more than four hours in any 24-hour period. However, wholesalers should maintain levels above this threshold. This residual may be collaboratively negotiated or adjusted temporarily to address specific events or risks, and these adjustments should be clearly defined in the contractual agreement or through event-related discussions.

Once the water reaches the consecutive system, it becomes the responsibility of the consecutive system to manage nitrification risks throughout its distribution network. Consecutive systems are tasked with compliance with all regulatory standards, including monitoring water quality, performing booster disinfection if needed, ensuring that distribution system operation does not compromise water quality, and maintaining the system through flushing. Storage tanks require additional operation and maintenance efforts, including limiting water age, providing adequate cycling and mixing, and routine cleaning. These activities are crucial in ensuring that nitrification does not compromise water quality or lead to excessive disinfectant decay and increased bacterial growth.

Currently, there is a lack of clear guidance on how wholesale and consecutive systems can communicate, collaborate, and manage these risks effectively. Utilities have identified this gap as a critical need, especially in light of anticipated revisions to the MDBP rules. EPA is expected to propose updates to these rules in 2025, and as part of its rule review process, the agency has sought recommendations from the National Drinking Water Advisory Council (NDWAC). Among its 11 proposed revisions, NDWAC highlighted three key areas directly relevant to wholesalerconsecutive system relationships and the use of chloramine:

• Developing a numeric disinfectant residual requirement.
• Addressing data gaps related to disinfection byproducts of emerging concern.
• Creating model contracts and improving communication between wholesalers and consecutive systems.

If implemented, these recommendations will necessitate stronger collaboration and communication between wholesale and consecutive systems to proactively mitigate nitrification risks. NDWAC also emphasized the importance of establishing communication channels and technical support to enhance utilities' collective ability to manage nitrification and ensure the delivery of high-quality drinking water to consumers.

This project focuses on collaborative efforts between wholesalers and consecutive systems, including treatment, monitoring, operation, reporting, and communication. It will provide actionable guidance to wholesale and consecutive water systems to effectively manage nitrification risks, support public health, improve water quality and operational efficiency, and enhance the overall resilience of drinking water systems.

Expected Deliverables:

• Literature review
• Workshop
• Final report
• Practical guidance documents based on insights from the literature review, survey, and workshop discussion.
• Webcast

Project Duration:

The anticipated period of performance for this project is 12 months from the contract start date.

Eligibility

Proposals will be accepted from domestic or international entities, including educational institutions, research organizations, governmental agencies, and consultants or other for-profit entities.

How to Apply

Proposals are accepted exclusively online in PDF format, and they must be fully submitted in 1 PDF file, before 3:00 pm Mountain Time on Wednesday, May 7, 2025.

The online proposal system allows submission of your documents until the date and time stated in this RFP. To avoid the risk of the system closing before you press the submit button, do not wait until the last minute to complete your submission. Submit your proposal at https://forms.waterrf.org/cbruck/rfp-5348.

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