AWWARF Project # 2900


Paul Westerhoff (PI)

Paul Westerhoff, Heath Mash, Peter Fox
Department of Civil and Environmental Engineering, Arizona State University,
Tempe, AZ  85287-5306

Gary Amy
Department of Civil, Environmental and Architectural Engineering
University of Colorado, Boulder, CO 80309

Jean-Philippe Croue, Hervé Gallard
Laboratoire de Chimie de l’Eau et de l’Environnement
Universite de Poitiers, 86022 POITIERS Cedex – France

AWWARF Project Officer: Djanette Khiari

Participating Entities

City of Phoenix (Phoenix, AZ); Shimadzu Scientific (Columbia, MD); Louisville Water Company (KY), American Water Works Service Company (Vorhees, NJ), Southern Nevada Water Company (Las Vegas, NV); US Filter / Vivendi (Atlanta, GA); Contra Costa Water District; Milwaukee Water Works; City of Ann Arbor (MI); City of Fort Worth (TX); City of Philadelphia (PA); City of Gilbert (AZ); Indianapolis Water Works (IN); Central Lake County Joint Action Water Authority

Project Description

Organic nitrogen is commonly the dominant form (>50%) of dissolved nitrogen in water, but comprises a relatively small portion (0.5% to 10% by weight) of the mass of natural organic matter (NOM) or dissolved organic matter (DOM).  Dissolved organic carbon (DOC) has traditionally been used as a surrogate for NOM; NOM contains roughly 30% to 50% carbon by weight.  Conceptual models for NOM structures include aromatic and aliphatic carbon with carboxyl, hydroxyl or carbonyl function groups, but often lack significant inclusion of org-N structures.[1]   While exclusion of org-N structures may be associated with the generally low elemental N composition of NOM, other than amine functionality very little is known about org-N structures in NOM (e.g., pyroles, amides, nitriles, purines, pyrimidines, nitro compounds). Despite considerable information on various aspects of DOC cycling in the environment or fate during water treatment, little is known about the nitrogenous fraction of NOM. [2]   Org-N exerts oxidant / disinfectant demands (e.g., chlorine, ozone) and can play the role of disinfection by-product (DBP) precursors.  Removal of particulate organic nitrogen (PON) poses treatment challenges (e.g., removal of algae cells), as does dissolved organic nitrogen (DON).  During water treatment, biological treatment processes can produce DON (e.g., soluble microbial products (SMPs)), and DON can affect the performance of other physico-chemical processes (e.g., contribution to membrane fouling).  Very few direct measurements of DON are available from drinking water systems. Kjeldhal nitrogen measurements (org-N + NH) in wastewater are not sensitive at < 1 mgN/L.

An abundance of information has been published on the occurrence of org-N in marine and freshwater ecosystems.  However, a detailed study of the occurrence and treatability of org-N during drinking water treatment is not available.  Planning workshops organized over the past decade by American Water Works Association Research Founding all identified org-N as a potentially critical issue for drinking water treatment. [3, 4]   The European Community directive has a maximum admissible concentration for org-N of 1 mg Kjeldhal-N/L, but the US has no similar guideline related to org-N.  Emerging concerns over increased contribution of potentially elevated DON levels from upstream wastewater or agricultural sources in drinking water supplies and identification of potent carcinogenic org-N disinfection by-products (e.g., nitrosamines, nitromethanes) increases the need to better understand the concentrations, structures and reactivity of nitrogenous organic components in drinking water systems.

Research Objectives and Approach

The goal of this first AWWARF project focused on dissolved organic nitrogen (DON) is to document DON occurrence and provide information on its chemical characteristics and reactivity towards metal hydroxides and oxidants/disinfectants.  Relatively minor attention has focused on DON despite observations that both low and high molecular weight molecules containing organic nitrogen (e.g., simple amino acids, algal-derived humic substances) have been implicated as DBP precursors, oxidant/disinfectant demanding substances, and membrane foulant materials.  Furthermore, while higher organic nitrogen (org-N) content is associated with increasingly polar natural organic matter (NOM) fractions, there are no publications of DON removal during coagulation.  The proposed research will use both well-developed DON analytical methods from the fields of ecology and marine biology and innovative DON quantification methods tailored for the drinking and reclaimed wastewater industry to meet the following specific objectives:

  • Develop a direct DON quantification method, rather than DON computation by differences between dissolved nitrogen (DN) and dissolved inorganic nitrogen (DIN)
  • Develop a comprehensive assessment of DON occurrence in raw/finished drinking waters and reclaimed wastewaters identified for potential indirect potable reuse
  • Evaluate a suite of analytical tools for characterizing DON structure, and providing well-characterized DON material for future research studies
  • Quantify DON removal by sorption processes (coagulation, activated carbon)
  • Investigate role of DON on THM and NDMA formation during disinfection
  • Assess future organic-nitrogen research needs.

Project Update

The project initiated in October 2002.  Periodic reports were submitted in January and April 2003, and can be made available through the AwwaRF Project Officer (Djanette Khiar).

Related Publications

“Dissolved organic nitrogen in drinking water supplies: A review”, P. Westerhoff and H. Mash, Journal of Water Supply Research and Technology-Aqua, 51(8), 415-448 (2002).

“DOC and DBP precursors in western US watersheds and reservoirs.” Nguyen, M. L., Baker, L. A., and Westerhoff, P., Journal American Water Works Association, 94(5), 98-112 (2002).

“Characterization and Copper Binding of Humic and Nonhumic Organic Matter Isolated from the South Platte River: Evidence for the Presence of Nitrogenous Binding Site” J.P. Croue, M.F. Benedetti, D. Violleau, J.A. Leenheer, Environmental Science and Technology 37:2:328-336

“Occurrence and Treatment of DON in Water Supplies”, P. Westerhoff and M. Esparza-Soto, AWWA Annual Conference (ACE), Anaheim, CA, June (2003-accepted).

“Dissolved organic nitrogen Removal during coagulation and PAC treatments”, M. Esparza-Sota, Lee, W., Mash, H., Westerhoff, P., AWWA Annual Conference (ACE), Anaheim, CA, June (2003-accepted).

“Organic nitrogen in drinking water: occurrence, characteristics, and reactivity (a review and research needs)”, P. Westerhoff, H. Mash, M. Esparza, AWWA Annual Conference and Exposition, June 16-20, New Orleans, CDROM Paper# ACE02-THUR07-1, 8 pages (2002).