April 30, 2018

Lessons learned from the largest waterborne outbreak in U.S. history

Carrie Lewis, General Manager at the Portland Water District and previous Superintendent at Milwaukee Water Works

Twenty-five years ago 400,000 people fell ill and 50 people died in one of the deadliest waterborne disease outbreaks in U.S. history.  This April marks the 25th anniversary of the Cryptosporidium outbreak in Milwaukee WI. Cryptosporidium is a parasite that can be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals.

So what happened in April 1993? Deep snow had built up over the winter; it was all released into the watershed during a rainstorm early that spring.  The wastewater plant was overloaded and combined sewer overflows were pouring into Lake Michigan.  The discharge from the plant and the combined sewer overflows flowed over the intake to one of Milwaukee’s two drinking water treatment plants.  Because Cryptosporidium is resistant to chlorine, the pathogen was unaffected by the plant’s disinfectant.  Then, the filtration plant failed to remove the tiny microorganisms and the pathogen passed through the plant and into the distribution system.

Customer complaints of dirty and smelly water started to trickle in. Symptoms begin to appear 2 to 10 days after ingestion, so soon there were many people out of work and school with gastrointestinal illnesses. Pharmacies couldn’t keep Imodium in stock. City and state health agencies conferred and concluded that the drinking water was the likely source of the illness. After the State Health Director said he would not drink Milwaukee water, the plant was shut down and a city-wide boil water advisory was issued.

In the years that followed, water quality monitoring was increased and SCADA controls were improved. Drinking water treatment processes and wastewater systems were upgraded, including the use of deep tunnel storage.  Green infrastructure was implemented to absorb storm water runoff, and the utility hired its first ever Water Quality Manager to help get things back on track.

The outbreak was a huge wake-up call for the drinking water profession and had lasting effects nationwide.  The crisis solidified the water industry’s understanding that we are in the business of protecting public health, not just treating and distributing water. We began to view operators as highly skilled positions and realized the importance of maintenance and reinvestment in our infrastructure. The importance of multiple barriers to prevent contamination came into focus. We also learned that regulations need to be considered in relation to each other, not in isolation, and optimal performance of wastewater systems is essential.  Federal rules were enacted to address the health effects associated with Cryptosporidium in surface water used as a drinking water supply and improved treatments were implemented across the country.  Today, water quality data and information are widely used to guide adjustments that better protect public health and the environment.

Twenty-five years later, the water industry is clear, the importance of quality drinking water to protect public health is a key component to the success of any community.