Celebrating Decades of Wastewater Treatment Excellence

Four Rivers Sanitation Authority (Four Rivers) was formed under the Illinois Sanitary Four Rivers Act of 1917 and voted into existence by election in 1926. A board of three trustees was appointed by the Winnebago County Judge to oversee the affairs of Four Rivers. 

In 1926, a $2.5 million bond issue was approved by voters and construction of the primary treatment plant on Kishwaukee Street and intercepting sewers were begun. It is interesting to note that today, that establishing sum would be worth nearly $36.5 million. 

The construction process was largely by hand and featured the use of horse and donkey-drawn hauling and the efforts of hundreds of skilled craftsmen and laborers. 

Our initial plant was declared operational four years later – on February 1, 1932. The grounds consisted of an administration building, main pumping station, two primary clarifiers, two digesters, two storage tanks and sludge drying beds. 

In 1940, regional growth necessitated a major upgrade to the initial system and two digesters, one sludge storage tank, four sludge drying beds, two lagoons and a short connection line of sewers were added to the treatment plant. 

The costs of the addition were shared by the United States Government, the Federal Works Progress Administration (W.P.A.) and Four Rivers itself. A second bond issue was presented to the voters and passed April 9, 1946 for the amount of $1.5 million. In the ensuing four years, another primary digester, four additional clarifier tanks and major trunk sewer extensions were added. 

On November 2, 1954, a third substantial bond issue was approved by voters for $3 million. The funds covered completion of all the trunk lines within the original Four Rivers boundaries. A secondary treatment process was added to the plant through the additions of an automatically operated bar screen, two additional primary clarifiers, automated gas mixing for the primary digesters, four trickling filters and additional sludge drying lagoons. 

The trickling filters were placed in operation in 1958, but were shut down as obsolete 20 years later. During the 20-year period beginning in 1958, several technological advancements in wastewater treatment took place. For instance, chlorination was begun in May, 1967 to disinfect the final treated water before it was discharged to the Rock River. Vacuum filtration of sludge replaced sand filter drying beds and sludge drying lagoons in 1968.  The activated sludge process was started in May, 1969 as a replacement for trickling filters. Further expansion of the Kishwaukee Street plant during that time included adding four sludge thickening tanks, six additional primary clarifiers and expansion of the activated sludge process to accommodate daily wastewater flows of greater than 50 million gallons each day. 

Industrial expansion necessitated much of the expansion as much flow coming from manufacturers contained high concentrations of toxins such as cyanide and heavy metals like zinc, cadmium and copper. In 1963, Four Rivers was fined by the State of Illinois for fish kills in the Rock River relating to cyanide discharged by industrial users. 

Four Rivers worked with the State, Rockford Area Chamber of Commerce and local industrial plating manufacturers to have much of the plating wastes collected in a common facility and hauled to a cyanide destruction plant. Due to such industrial contaminants, Four Rivers’s anaerobic digestion process failed – resulting in the need to dispose of sludge processed by vacuum filtration in a special landfill. 

Federal regulations including the Water Pollution Control Act of 1972 and the Water Pollution Control Act of 1977, better known as the “Clean Water Act,” raised the standards of treatment for wastewater and implemented new pollution control methods. In 1972, local industry produced about 50% of Four Rivers’s flow and 25% of that share came from metal finishing and electroplating shops. The metal plating process produced wastewater with dangerous concentrations of cyanides and heavy metals and to comply with Federal regulation in response, Four Rivers began an Industrial Protection Program by creating a formal industrial waste surveillance department and establishing local limits for heavy metals and cyanide discharge. In 1984, Four Rivers’s pretreatment program became the first in Illinois to achieve United States Environmental Protection Agency approval. 

Many additional plant upgrades have been made to meet expanding regulatory requirements and to improve efficiency. For instance, an additional biological process called “nitrification” was added in 1997 to reduce ammonia in our discharged waters. The activated sludge process was also expanded by 33% and mechanical aeration was replaced by fine bubble diffusion that same year. Vacuum filtration for biosolids drying was replaced in 2000 by higher efficiency centrifuges. 

Also in 2000, anaerobic digestion was brought online to stabilize biosolids and reduce the  amount sent to the centrifuges. Due to the success of our industrial pretreatment program and with added efficiencies, Four Rivers Sanitation Authority now creates and applies super-clean biosolids to farm fields as fertilizers. We burn and convert methane to energy, meeting 70% of our needs with three co-generation engines doing two megawatts in total. Using this technology alone, we saved $800,000 in 2020. 

Continued regulatory requirements defined by the Environmental Protection Agency (EPA) and the Illinois Environmental Protection Agency (IEPA) mandate that Four Rivers meet the standards defined by the Illinois Nutrient Loss Reduction Strategy by January 1, 2030.  These requirements demand that Four Rivers significantly reduce nutrient flows to the four watersheds we influence:Rock River, Sugar River, Kishwaukee River and the Pecatonica River.  To achieve these goals, Four Rivers is expanding the Kishwaukee plant to include better phosphorus removal, replace aging infrastructure, and to reduce Four River’s carbon footprint.