From The Editor | January 15, 2015

Everything You Need To Know About Microbial Risk Assessment


By Kevin Westerling,

The answer to the question “How bad could it be?” is within your grasp, compliments of the U.S. EPA.

Whenever and wherever there’s a chance for waterborne pathogen exposure, whether in tap water, recreational waters, or within food and beverage products, the degree of risk needs to be addressed … but first it must be calculated.

Methods for conducting microbial risk assessments (MRAs) have long been scattershot — different per industry, source water, and pathways to exposure (e.g., ingestion, inhalation, or skin contact) — but the EPA, which does more risk assessment than anyone, has recently published best practices that are standardized for all. Titled Microbial Risk Assessment Tools, Methods, and Approaches for Water Media, it is the new bible for risk assessors.

If you simply follow regulations and don’t make them, you might wonder what use the document may be to you. Assessing the potential risk for human exposure to known pathogens — a critical step in rulemaking — is only the most obvious reason. Here are some other good reasons for performing a microbial risk assessment:

  • Watershed protection – to determine critical points for control;
  • Treatment process evaluation – to specify techniques for reduction, removal, or inactivation of pathogens;
  • Research – to identify and prioritize needs;
  • Managerial – to help predict the consequence(s) of various management options available to risk managers.

As risk management goes, risk assessment is only one criterion to consider, but it’s an important first step against which all other, sometimes competing, factors are weighed. Other considerations include legal and regulatory requirements, economic factors, technological factors, and political, public, and social factors.

Within its intended scope of risk assessment, however, the EPA document is quite comprehensive, with tools designed for compatibility across all types of water media. Even the risk of inhaling aerosolized biosolids, falling under the umbrella application of water reuse, can be assessed. In fact, the rise of water reuse should lead to many more MRAs being conducted, as water managers seek to preserve safety and ease public concerns.

The new MRA framework fits right in with the trend toward water reuse and the “one water” philosophy that is (rightly) taking over. While risk assessors would previously follow guidelines designed for clean water or wastewater — those that correlated to either the Safe Drinking Water Act (SDWA) or the Clean Water Act (CWA) — the EPA has now provided them a one-size-fits-all option.

Access the full document here, and learn more from the EPA about the nature and control of waterborne pathogens here. For technology solutions to microbial contamination, visit Water Online’s Drinking Water Disinfection and Wastewater Disinfection Solutions Centers.