Coping with Climate Change and Extreme Weather: On-line raw water NOM/DBP precursor monitoring

Authors:

  • William Becker PhD, PE, Justin Irving, Ben Wright PE, Ben Stanford PhD, Allison Reinert – Hazen and Sawyer
  • Kenan Ozekin – WaterRF
  • David Reckhow

Utilities throughout the US and Canada are looking for ways to cope with climate change and extreme weather events. While much research has been conducted on water quantity issues associated with a warming climate and more frequent extreme droughts and flooding events, much less has been conducted on water quality issues. The purpose of this paper is to report on changes in raw water quality, specifically changes in the concentration and character of natural organic matter (NOM), that is occurring and the development of monitoring tools that can be used to track these changes. NOM is a particularly important parameter because is usually drives the optimum coagulant dose, consumes GAC and PAC, fouls membranes, and most importantly, is the precursor to disinfection byproducts (DBPs). Many utilities have observed increasing concentrations of DBPs in recent years and this trend is likely to continue in many areas of the country.

Results from Water Research Foundation Project #4422 will be presented. Two on-line monitoring tools are being developed that can accurately monitor the precursors to both trihalomethanes (THM) and haloacetic acids (HAA) for a variety of source waters. These tools use either UV-visible absorbance or fluorescence technology applied to in-situ probes. Results show that both technologies work well – can predict THM and HAA formation potential with an r-squared value of 0.85 or greater for a wide variety of source waters. These tools can provide utilities with real-time data so they can optimize treatment at the plant and where possible, select the intake level or raw water source in a manner that the best quality water from a DBP perspective is used.

The paper will provide utilities with recommendations regarding the best way to monitor changes in NOM concentration and character in an economically feasible way and how to best use the resulting information.

For more information, please contact the author at wbecker@hazenandsawyer.com.

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