Innovative installation saves money while advancing sustainability
The Metropolitan Sewer District (MSD) of Greater Cincinnati serves an Ohio population of more than 850,000 spread out across 290 square miles. Like many large cities, Cincinnati MSD operates combined stormwater and sanitary sewer systems, some of which were constructed more than a century ago. These systems were built to collect rainwater runoff, domestic sewage and industrial wastewater in the same pipe. Whether by design, or due to infiltration and inflow of stormwater, they have the tendency to overflow, discharging untreated sewage into local waterways or flooding streets and basements.
Cincinnati’s sewers were discharging an average of 14.4 billion gallons of combined sewage every year into the Ohio River, and its tributary streams within Cincinnati’s urban watershed. In 2002, the US Environmental Protection Agency entered into a federal consent decree with MSD, mandating the elimination of sanitary sewer overflows and mitigation of combined sewer overflows into receiving waterways. Engineers estimated the cost to mitigate the sewer overflows through capital investments such as deep tunnel construction, at US$3.1 bullion, an “unacceptable” capital expense to pass along to MSD’s customers.
To overcome these challenges, MSD partnered with Xylem to optimise the performance of their existing assets through advanced digital optimisation solutions. Xylem worked with MSD to implement Xylem’s Wastewater Network Optimisation solution, which utilises a combination of sensors and weather data to create a real-time decision support system (RT-DSS). This platform delivers automated, optimised control of existing assets to reduce sewage overflows, improve storage and maximise treatment plant operations during wet weather.
The project was a success. After MSD implemented a coordinated real-time control (RTC) programme, overflow volumes were reduced by 247 million gallons annually, based on 2015 rainfall, a 45% reduction in overflow compared to the original design. Additionally, operational enhancements from the project increased treatment facility utilisation by more than 100%, as a result of using the existing assets more efficiently.
MSD continues to expand the wastewater network optimisation solution across their system, delivering savings to rate-payers, while protecting the local watershed to make the city more sustainable.