Investigation of the formation of NDMAUFC across biofilters

Ashley N. Kent, Caroline G. Russell, Jason T. Carter, William A. Mitch, Raymond M. Hozalski, Peter M. Huck

Research output: Contribution to journalArticlepeer-review


Full-scale sampling at 16 facilities illustrated that NDMA precursor concentrations, measured by adding chloramine under Uniform Formation Conditions (NDMAUFC), increased across biofiltration at 7 of 16 facilities (by 3–48 ng/L or 12%–296%) but stayed the same or decreased (by up to 5 ng/L or 24%) at the other nine facilities. Increases in NDMAUFC concentrations were attributed to both particulate and soluble precursors. Only two facilities had an increase in NDMAUFC greater than 10 ng/L. However, NDMAUFC concentrations in the biofilter effluent from five facilities exceeded 10 ng/L during one or more sampling events. For these facilities, testing at multiple scales showed that mitigation steps could include pretreatment with ozone (which resulted in overall lower NDMAUFC), increased free chlorine contact time prior to ammonia addition, and/or optimized biofilter design and operation.

Original languageEnglish (US)
Article numbere1322
JournalAWWA Water Science
Issue number1
StatePublished - Jan 1 2023

Bibliographical note

Funding Information:
The authors of this report are indebted to the water utilities, organizations, and individuals that contributed to this project. The authors thank the other project team members, including Sarah Page, PhD, Carrie Smith, EIT, Hesam Zamankhan, PhD, Allison Wheeler, EIT, Brent Alspach, PE, Zhong Zhang, Ben Ma, Michele Van Dyke, PhD, Sigrid Peldszus, PhD, and Katrine Orland Led. In addition, the support and guidance provided by the Water Research Foundation (Djanette Khiari, in memory), the Project Advisory Committee (Mike Hotaling, Lutgarde Raskin, PhD, Paul Westerhoff, PhD, PE, BCEE, and John Haley), and the many utility participants are very much appreciated.

Publisher Copyright:
© 2023 American Water Works Association.


  • biofiltration
  • biological filtration
  • NDMA
  • nitrosamines


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