Water Innovation, Surveillance, and Toxicity Ranking Tools for Characterization and Prioritization of Drinking Water Disinfection By-products and Contaminants

Principal Investigator - Xing-Fang Li, Professor, University of Alberta, 2008 - 2012

Challenge

Drinking water disinfection is essential to human health, however disinfection processes can lead to the formation of disinfection by-products (DBPs).  This is due to reactions between the disinfectants and natural organic matter or other precursors in the water.  Studies have found some evidence of a possible association between consumption of chlorinated drinking water and elevated risk of bladder cancer with less consistent evidence of other adverse health effects. However, the regulated DBPs do not account for the magnitude of human cancer risk estimated, which highlights gaps in terms of determining which DBPs are of toxicological relevance. There is a need to develop better testing technologies to characterize DBPs and their toxicity, determine their precursors, and provide approaches to minimize toxic DBPs.

The project team, led by Dr. Xing-Fang Li, has developed highly sensitive analytical techniques enabling the detection of new toxic DBPs, and techniques to remove DBP precursors.

Project

To uncover which DBPs may be of health concern, this team has developed highly sensitive analytical techniques which 1) enable the detection of new toxic DBPs, 2) characterize the formation of these compounds under water disinfection conditions, and 3) investigated the removal of natural organic matter precursors to reduce the toxic DBPs in treated water.

To detect and characterize the formation of DBPs, nine drinking water treatment plants were surveyed for novel, unregulated DBPs.  Each drinking water treatment plant used some form of chlorination or ozonation.  Researchers found one novel DBP in all treatment plants (2,6-dichlorobenzoquinone) and another novel DBP in 72% of treatment plants (2,6-dibromobenzoquinone).  Additionally, researchers found that DBP toxicity testing showed these novel DBPs can damage DNA and proteins.

Natural organic matter can interact with treatment processes, such as chlorination, to form DBPs.  Therefore, natural organic matter is a precursor to DBP formation.  To find useful approaches for reducing DBP formation, researchers used liquid chromatography–organic carbon detection (LC-OCD) to separate and quantify natural organic matter into six fractions which are based on size, ionic character and water solubility. By providing coagulation (clumping) of natural organic matter, DBP precursors were reduced.  However, future studies will need to address means of  further reducing these precursors.

The common occurrence and relatively high toxicity of some novel DBPs indicate the importance of monitoring and understanding the mechanisms of toxicity, and assessment of human exposure and health effects. Further research is warranted for a comprehensive survey for risk assessment, identification of the factors controlling DBP formation, and feasible treatment for reducing DBP formation.

Outputs

• Development of new analytical tools for monitoring, new toxicity testing tools for prioritization of DBPs for monitoring, and regulatory consideration in the future.  This was made possible because of the effective dissemination of knowledge via publications, conferences, workshops, and seminars.
• This project has resulted in several partner and end-user oriented publications.  These include:
  • Book “Disinfection By-Products – Relevance to Human Health”. Hrudey, S.E; Charrois, J.W.A. (Eds). IWA Publishing. 2012
  •  “Occurrence and formation of chloro- and bromo-benzoquinones during drinking water disinfection” Water Research, 46, 4351-4360 (2012)..
  • “Removal of halobenzoquinone (emerging disinfection by-product) precursor material from three surface waters using coagulation” Water Research 47, 1773 -1782 (2013).
  • Monograph “Analytical Methods for Predicted DBPs of Probable Toxicological Significance” Water Research Foundation. Denver, CO. 2011.
  • “Application of automated solid-phase microextraction to determine haloacetonitriles, haloketones and chloropicrin in Canadian drinking water” Water Quality Research Journal of Canada, 48.1, 85-98, 2013.

Publications in Academic journals such as Environmental Science and Technology, Analytical Chemistry, Trends in Analytical Chemistry.  Additionally, this research has developed new techniques in the field which are being taught at both conferences and academic institutions.

Outcomes

• Enhanced understanding of the likelihood of substantial human cancer risks being attributed to drinking water exposure to DBPs.  The improved perspective on human cancer risks from DBPs has allowed development of an over-arching perspective for addressing health risks from DBPs in relation to the more pervasive and certain health risks from microbial pathogens.
• Potential changes to practice and policy for regulatory agencies in Canada, the USA, and Australia.  The drinking water guidelines committee of the Australian National Health and Medical Research Council has established a working group to explore developing guidelines for disinfection by-products.