Connecting the Dots: Can Climate Change Influence Algal Blooms that Lead to Disinfection By-Product Formation in Your Drinking Water?

摘要

In 2006, the City of Cleveland Division of Water (CWD) detected episodic high spikes in the five regulated halo-acetic acids (HAA5) concentrations in the treated water from their four water treatment plants (WTPs). Total tri-halomethane (TTHM) concentrations did not similarly increase. CWD typically experiences low TTHM and HAA5 concentrations of less than 40 and 30 ug/L, respectively, in their distribution system sampling locations from the months of June to October. However, in 2006, discrete HAA5 concentrations were greater than 100 μg/L. In response to the high HAA5 spikes in 2006, CWD evaluated their water quality and WTP and distribution system operations to identify any potential changes that may have caused the increase in HAA5 concentrations. No water quality or operational changes that could have caused the increase in HAA5 concentrations were identified. As a result of the initial investigations, it is hypothesized that increases in HAA5 concentrations are due to changes in the character of the dissolved organic matter (DOM) that may not be observable by measuring organic carbon concentrations and UV254 alone. Measurements taken by the National Oceanic and Atmospheric Administration (NOAA) have demonstrated an increase in Lake Erie water temperatures, a decrease in winter ice formation, and an increase in size and frequency of an anoxic zone that forms at the bottom of Lake Erie during summer. This increase in the anoxic zone may cause changes in algal growth and population, and a subsequent change in the organic carbon character released from the algae. In 2006, the Lake Erie region had an unusually warm winter followed by a subsequent warm summer and a huge algal bloom consisting of blue-green algae (cyanobacteria) species. Water Research Foundation (WaterRF) project # 4302 is a tailored collaboration project with the goal of better understanding the relationship between Lake Erie source water and the formation of HAA5. The objectives of this research project are to: a) demonstrate the relationship between ice coverage on Lake Erie and the algal population dynamics, b) develop the relationship between the algal population and the DOM character and c) relate the DOM character to DBP formation. The technical approach of this project includes characterizing DOM and algae populations in Lake Erie over a 21 month project period. Throughout the duration of this project, untreated water samples are being collected weekly from Lake Erie and analyzed for algae, DOM, and DBP formation analysis. As part of this project, several new analytical methods are being developed for better characterization of algal species and algae-generated extracellular organic matter including FlowCAM? - a state-of-the-art instrument for real-time imaging and particle counting in a water sample.