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Watershed Sources and Long-term Variability of BDOC and NOM as Precursors

AWWA Research Foundation, 11/1/2002-10/31/2005

PIs: Reckhow, Rees & Nusslein
Research Staff: Alison Boutin, Gladys Makdissy
Students: Greg Devine, Darleen Bryan, Teresa Conneely

The purpose of this study was to: (1) to investigate sources, nature, and long-term variability of natural organic matter (NOM) and biodegradable organic matter (BDOM) in source waters, and (2) to evaluate their impact on the formation of disinfection byproducts (DBPs). This work was conducted in three major phases. In the first phase an extensive literature review was conducted on DBP precursors and BDOM in source waters.  For the second phase, we identified about a dozen utilities for in-depth watershed analysis.  These utilities were asked to share their raw water data, as well as a broad range of ancillary information.  Bulk raw water samples were shipped to UMass for some advanced characterization tests.  At UMass, a suite of organic analyses were conducted (e.g., TOC, DOC, UV abs, CHON, precursor analysis), along with biodegradability test, and a detailed set of NOM fractionation and characterization tests.  This information along with the utility-supplied data was used to help develop a set of NOM watershed models.  These models made use of modern GIS-based data, and span the range from the empirical to the semi-mechanistic. 

Proposal, Plans and Reports

  • Progress Reports: #1, #2, #3

Project Data

  • lab notebook?
  • Chlorination of Amino Acids and Proteins


Unpublished manuscripts based on this work

Publications based on this work

  • Reckhow, DA, PL Rees, G Makdissy, “Management of Water Supplies for Control of Disinfection Byproduct Precursors,” Proceedings of the conference, Safe Drinking Water: Where Science Meets Policy, March 16-17, 2006, Chapel Hill, NC.

Theses/Dissertations based on this work


Additional Background: One of the key issues in watershed management for NOM control is an understanding of the origin and genesis of aquatic organic matter.  In many cases the discrimination between those organics termed allochthonous versus those called autochthonous is the goal.  Some have framed this in the context of aquogenic versus pedogenic organic matter.  In either case, the underlying goal is worth pursuing, although the articulation may be overly simplistic.  We are now coming to an agreement that humic substances are a complex mixture of plant and bacterial products that have been partly degraded and then recombined through a mixture of covalent bonding (e.g., by nearly random, non-enzymatic reactions) and weaker associations supported by hydrophobic forces and hydrogen bonding.  On average, these humic substances are quite refractory, a property which has been attributed to non-enzymatic processes.  They also tend to be the single most important reservoirs of the THM and HAA precursors.

In contrast, the non-humics are largely natural plant products that may have undergone some degree of biodegradation or biosynthesis.  One newly recognized and prominent group of non-humics is the acylheteropolysaccharides (APS).  These are high-molecular weight (>1000 daltons), algal derived polymers of simple sugars, acetate and lipids.  They are recalcitrant, much like the humic substances.  Recent reports have placed this material at 10%-35% of the DOC in lakes and rivers.  The APS pool probably constitutes the majority of what has often been characterized as the hydrophilic neutral fraction of NOM.  This fraction is abundant in large reservoirs, and it is known to have a substantial THM and HAA precursor content, albeit somewhat lower than the humic fractions.  This fraction has also shown itself to be high in BDOC.




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