Grantee Research Project Results

2024 Progress Report: Winning the Race Against Competing Risks: Optimizing Drinking Water Disinfection to Minimize Opportunistic Pathogen & DBP Risk

EPA Grant Number: R840604
Title: Winning the Race Against Competing Risks: Optimizing Drinking Water Disinfection to Minimize Opportunistic Pathogen & DBP Risk
Investigators: Mitchell, Jade , Karanfil, Tanju , Rose, Joan B. , Haas, Charles N. , Dreelin, Erin , Gim Aw, Tiong , Weir, Mark , Lauper, Ursula , Mraz, Alexis , Wanjugi, Pauline , Chowdhury, Zaid , Palmer, Patrick
Institution: Michigan State University , The Ohio State University , Tulane University , Drexel Univeristy , Clemson University , The College of New Jersey , New York State Department of Health
EPA Project Officer: Harper, Jacquelyn
Project Period: August 1, 2023 through May 12, 2025
Project Period Covered by this Report: August 1, 2023 through July 31,2024
Project Amount: $2,123,000
RFA: National Priorities: Research on Disinfectants, Disinfection By-products (DBPs), and Opportunistic Pathogens in Drinking Water Distribution Systems Request for Applications (RFA) (2022) RFA Text |  Recipients Lists
Research Category: Harmful Algal Blooms , Drinking Water, Disinfection Byproducts , Water Quality

Objective:

This project has four main objectives. They are to (1) Develop a strategic sampling program based on health data and DWDS characteristics; (2) Assess the occurrence and co-occurrence of DBPs and OPs and evaluate contributing factors in nationally representative DWDS through field sampling; (3) Characterize risks and system risk factors associated with DBP and OP occurrence and concentrations; and their risk tradeoffs for multiple communities and populations; and (4) Engage and collaborate with stakeholders and partners to support risk management within the water quality community of practice. 

Progress Summary:

Key project accomplishments can be summarized by objective. For objective 1, utilizing historical public health and water quality data, we conducted a preliminary analysis comparing NYC DWDS water quality and Legionella occurrence in nearby healthcare facilities (HCFs). Preliminary results indicate that the effect of HCF-specific supplemental drinking water treatments may be greater than the effect of DWDS water quality parameters. Both water quality parameters and HCF supplemental treatments may influence Legionella concentration, as well. We expect to refine this analysis as we extract additional data. Also under objective 1, we acquired comprehensive descriptions of our 25 utility partners’ DWDS, via numerous virtual calls and an in-person workshop, which 13/25 utility partners attended. This information facilitated development of a first-year strategic sampling program with five to eight sampling locations per utility, targeting influent and effluent water quality, average and maximum water residence times, and two low disinfectant residual areas for each utility. 

For objective 2, we completed two rounds of DWDS pilot sampling at two utilities, followed by two rounds of full-scale sampling at 24 utilities (one utility is yet to be scheduled). We analyzed samples for water quality indicators (e.g., DOC, DN, SUVA254, Br-, I-, Cl-, SO42-, NO2-, NO3-, etc.), levels of 39 regulated and unregulated DBPs (354 samples), and presence/concentration of numerous OPs (300-307 samples, depending on the test). We began a preliminary analysis of pilot data and found that chloramine plants may have lower DBP concentrations than chlorine plants, and that there may not be significant trends associated with sampling locations, CAT, or calculated genotoxicity. The most common DBPs in pilot data were THMs, HAAs, and HALs. For the full-scale data, we know that 42/307 samples (13.7%) and 36/300 samples (12%) tested positive for P. aeruginosa (mainly in source water) and L. pneumophila (mainly in the DWDS), respectively. Lastly, we developed a utility information database, corresponding data dictionary, and R scripts to import sampling data and utility information in order to expedite statistical analysis and modeling efforts once sample processing is complete. 

For objective 3, we conducted a literature search for DBP ingestion dose-response data in animals. We successfully generated 159 unique combinations of DBPs and endpoints for 11 DBPs (five regulated and six unregulated). We also compared benchmark dose-response modeling results for select datasets in EPA’s online BMDS tool, the R software package ToxicR, and the BBMD online tool and are in the process of choosing the preferred software. For collaboration and engagement objectives, we held the previously described in-person workshop with utility partners. We determined utility partners’ long-term needs and concerns, how they would like us to address said needs/concerns, and necessary information for improving their communication with their stakeholders and the public. We also maintained our website, presented at two AWWA meetings, submitted a session proposal for ACE25, and will present project work at the upcoming WQTC meeting. 

Future Activities:

We are prepared to perform numerous future activities. One pivotal item will be water quality, DBP, and OP sampling data analysis. This will include correlation tests, principal component analysis, and multivariate regression. Second, we plan to create our 2025 sampling plan, which will capture temporal variation (across seasons) in water quality, DBP, and OP occurrence. Third, using our 2024 sampling data, we will develop exposure assessments for inhalation, ingestion, and dermal exposure to DBPs, and inhalation and ingestion of OPs in drinking water. We also plan to collect dose-response data for inhalation and dermal exposure to DBPs. Our existing DBP ingestion dose-response data will be pooled (if applicable) and fit to dose-response models using our preferred fitting software. Several collaboration and engagement activities are planned. First, we aim to host a webinar to share sampling findings and the year two sampling plan with partners and stakeholders. Additionally, in January we will submit individual abstracts to the 2025 AEESP Annual Meeting. 

Supplemental Keywords:

Risk assessment, risk management, water, DBPs, pathogens

Relevant Websites:

Department of Biosystems & Agricultural Engineering Exit

Progress and Final Reports:

Original Abstract

Final