Water Online

September 2017

Water Innovations gives Water and Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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By Silvia Vlad, Monique Waller, and Quirien Muylwyk I n the summer of 2016, the Region of Niagara — a regional municipality on the Canadian shore of Lake Erie serving 450,000 residents — faced the challenge of developing and implementing a cyanobacterial monitoring and response plan within a single season, while managing an active cyanobacterial event with the potential to impact one of the Region's six water treatment plants. An increasing number of municipalities are affected by cyanobacteria or cyanobacterial metabolites each year, and many utilities have noted blooms appearing earlier in the spring and lasting longer into the fall. Several risks are inherent to a drinking water supply impacted by cyanobacteria — notably metabolite toxins (cyanotoxins), which can harm human and animal health, as well as the taste-and-odor compounds 2-methylisoborneol (MIB) and geosmin. While a range of options is available to utilities managing the risks posed by these blooms, tradeoffs exist between the costs of monitoring, using temporary mitigation techniques, or implementing permanent treatment measures. These challenges are further complicated by the intermittent nature of cyanobacterial events, for which the occurrence, duration, and magnitude are not easily predicted. In Spring 2016, operators at the DeCew Falls treatment plant reported needing to clean the intake bar screens of algal debris more often than in past years. Although no toxins had yet been detected, the Region wanted to understand the potential implications of finding cyanobacteria in their source — including potential cyanotoxin production, a timeline for toxin intrusion into the plant, and barriers needed to prevent the toxin from entering the water supply. The Region of Niagara engaged CH2M to obtain answers to their questions when elevated algal activity was confirmed in the raw water storage reservoir upstream of the DeCew Falls plant. CH2M worked with the Region through the summer and early fall to: 1. Develop a proactive, cost-effective monitoring program that could generate useful data at the right time to support sound decision-making about cyanotoxin management, both during the current event and for monitoring during subsequent seasons. 2. Evaluate existing treatment capabilities already in place at the DeCew Falls plant. 3. Identify and prepare to implement seasonal or short-term treatment augmentations. Tiered Monitoring Re c o m m e n d a t i o n s w e re developed for monitoring the source, in-plant, and treated water for algae, cyanobacteria, and their metabolites across six of the Region's treatment plants, to provide supplemental information beyond what was obtained through monitoring practices already in place. The monitoring plan was used to identify both the occurrence of algae, cyanobacteria, or their metabolites, and their impact on plant performance using a variety of tools, including visual observations of the 10 wateronline.com n Water Innovations A case study from Lake Erie shows the value of adaptable monitoring plans and how to get ready to respond to dynamic situations. Navigating A Cyanobacterial Event: Lessons Learned In Balancing Risk And Cost For A Single Season While a range of options is available to utilities managing the risks posed by these blooms, tradeoffs exist between the costs of monitoring, using temporary mitigation techniques, or implementing permanent treatment measures.

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