Algae and Algal Toxins - Impacts on Treatment and Control Strategies


  • Erik Rosenfeldt, Ben Stanford, Bill Becker - Hazen and Sawyer

Learn more about our resources for algae and cyanotoxins.

The shut-down of the Toledo, Ohio water system in 2014 due to detected algal toxins has brought national attention to a water quality issue that has been increasing in recent years and is expected to become an even bigger issue for more utilities as our climate changes and extreme events like droughts and intense rainfalls occur more frequently. These factors have resulted in the issuance of health advisories by the EPA for two cyanotoxins, microcystins and cylindrospermosin, in the summer of 2015, and a legislative mandate by Congress and the President for EPA to fully evaluate risks to public health from cyanotoxins in drinking water by November 5, 2015.

Utilities have been left with conflicting information to date about how to best respond to this issue. Many utilities (outside of Ohio which has instituted required algal toxin testing for surface water utilities) are adopting a conservative approach to monitoring for algal toxins, given the variability and uncertainty in the regulatory landscape for these contaminants at this time. However, a few utilities with historical drivers to do so have taken strong proactive positions, developing algae monitoring and management strategies, surveying their water resources for algal toxins, and developing understanding of their treatment capabilities for algae, taste and odor (T&O), and algal toxins.

This paper will present two sets of results. First, the results of a survey of six eastern US water treatment plants located on different water supplies who have experienced algae related issues will be presented, highlighting the range of utility approaches for reacting to algae issues and concerns. Second, case studies from two utilities will be presented outlining the development of holistic algae toxin and T&O control strategies, incorporating a tiered approach to algae monitoring and management, and developing treatment SOPs targeted for algae toxin and T&O control. The utilities profiled in the case study have algae sensitive water sources, and as such have maintained a significant database of historical algae quantity and identification data, along with water quality data, which facilitated the development of the tiered monitoring and management strategies. AWWA Cyanotoxin Testing and Treatment Resources, including the Cyanotoxin Oxidation Calculator and Powdered Carbon Testing Protocols were used to assess treatment capabilities for algal toxins and T&O at each of the facilities.

The presentation will provide an opportunity for utilities to learn about how to work through the process of developing these plans, using readily available resources, as they prepare for the 2016 algae season across the United States.

For more information, please contact the author at

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