From Green Dye to Clean Water: The Evolution of Wastewater Treatment 

By: Charles Hardy, PE, Wastewater Treatment Specialist 

This article contains and answers the following:

Dyeing the Chicago River green tradition: Contributions to the tradition of dyeing the Chicago River green for St. Patrick’s Day.

Upgrades to wastewater treatment plants: improvements made to existing wastewater treatment facilities to meet modern standards and be more sustainable

  • What is the history behind dyeing the Chicago River green for St. Patrick’s Day?
  • What advancements have been made in wastewater treatment since the 1960s?

When visiting Chicago one Spring Break, I was amazed by waves of ice on Lake Michigan. Sadly, I was a little late for seeing a green Chicago River. Every year, the Chicago River transforms into a vibrant green spectacle for St. Patrick’s Day, enchanting locals and visitors alike. Did you know this tradition has its roots in a practical effort to clean up the river? 

Tracing Pollution to Tradition 

The tradition of dyeing the Chicago River green began in the early 1960s when City officials and collection system workers were looking for a way to identify sources of pollution to the river. Using brightly colored dye was employed in that effort and sparked an idea for celebrating a cherished holiday to the City’s population. Leveraging this practical application thus evolved into a beloved St. Patrick’s Day tradition, with the Chicago Journeymen Plumbers Local 130 continuing the ritual each year. 

From Murky Waters to Clear Solutions 

In the 1960s, efforts to clean the Chicago River and protect Lake Michigan also included constructing wastewater treatment plants and reversing the river’s flow to divert polluted water away from Lake Michigan. These measures significantly improved water quality for the City’s drinking water, but the methods used then for wastewater treatment were rudimentary compared to today’s advanced technologies. 

“Transition from a pond-based treatment system to a new more conventional, nutrient removal process to achieve reliable and cost-effective wastewater treatment. “

Innovations in Wastewater Treatment 

Fast forward to 2025, and the landscape of wastewater treatment has dramatically evolved. Modern methods leverage advanced technologies to enhance efficiency and sustainability. Here are some key advancements: 

  1. Nutrient Recovery: One of Chicago’s wastewater treatment plants includes processes to produce high-value fertilizer product from the nutrients in the incoming wastewater. 
  1. Membrane Bioreactors (MBRs): These systems combine biological treatment with filtration through plastic, porous membranes, achieving high levels of water purity while reducing energy consumption compared to more conventional treatment methods. 
  1. Advanced Oxidation Processes (AOP): These processes break down persistent organic pollutants providing high quality effluent for such applications as potable reuse. 
  1. Decentralized Treatment Systems: Smaller, location-specific systems are gaining traction, offering efficient solutions for industries, tech campuses, hospitals and residential areas. 

In 2017, the City of Davis completed a multi-year effort with owner’s advisory engineering support from West Yost for a $90 million design-build procurement of treatment facilities upgrades to the Davis Wastewater Treatment Plant.  This wastewater facilities planning and procurement process incorporated Davis’ evolving vision for wastewater treatment to transition from a pond-based treatment system to a new more conventional, nutrient removal process to achieve reliable and cost-effective wastewater treatment. 

The Davis plant upgrades included new secondary biological treatment and clarification systems, advanced filtration and coagulation facilities, and upgraded disinfection systems. These improvements are in compliance with stringent regulatory requirements and enhance the plant’s capacity to handle future demands. 

“The landscape of wastewater treatment has dramatically evolved. Modern methods leverage advanced technologies to enhance efficiency and sustainability.“

The journey from using green dye to trace pollution into the Chicago River to employing advanced technologies in modern wastewater treatment highlights the progress made in protecting our water resources. We no longer need luck to make sure our water is treated properly. West Yost instead brings our expertise to deliver for you high-quality, green solutions from both a cost-savings and enhanced environmental benefit perspective. As we continue to innovate and improve, we can look forward to a future where clean water is accessible to all, and our natural environments are preserved for generations to come.  

Charles Hardy is an environmental engineer specializing in water quality permit applications and compliance, and wastewater and recycled water planning and modeling. He routinely performs both project management and technical tasks to ensure projects meet strict regulatory requirements. Charles works closely with clients, often on long-term contracts, and is skilled in using BioWin process modeling software and MS Excel and statistical tools for data analysis. 

He has prepared various studies related to wastewater discharge permits, including treatment alternatives analysis, pollution prevention plans, and source control studies. Charles also works regularly on projects involving the reuse of treated effluent on agricultural lands, developing water balance assessments, data management tools, and plans for recycled water and biosolids reuse. ty posture, reach out to West Yost to discuss how we can support your team in securing your operations against emerging threats. environmental, and mechanical engineering, as well as geology, hydrogeology, and wastewater treatment.