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Public health risks and potential nuisances associated with the generation and disposal of sludge have been the primary factors for implementing various sludge treatment and safe disposal practices at municipal sewage treatment plants. There are usually many drivers behind the evolution of these practices. The Metropolitan Water Reclamation District of Greater Chicago (District) from the dawn of modern sewage treatment has a colorful eight decades history of sludge treatment and disposal practices, the evolution of which has been driven by various factors. The various drivers that have motivated the development, implementation, and/or abandonment of various solids management practices at the District, will be examined in this paper from a historical perspective, under the following headings to delineate how the District has benefited by addressing them in a timely and appropriate manner:

Early Sludge Management Practices (Imhoff tanks, sand bed dewatering – 1920 to 1930)

Beginning and End of Heat Drying and Incineration at Calumet Water Reclamation Plant (WRP)(1932 – 1940s)

Dawn of Lagooning (1935 – to date)

Era of Nu Earth (ca. 1970 to 1979)

Resurgence and Decline of Heat Drying at Stickney WRP (1939 to 1981)

Beginning and End of Wet Air Oxidation (1961 – 1972)

Beginning of Heated Anaerobic Digestion (1964 – to date)

Prairie Plan Conceptualization and Implementation (1971 – to date)

Dawn of Centrifugal Dewatering (1981 – to date)

Air Drying and Production of Class A Biosolids (1983 – to date)

Resurgence of Heat drying? (Beginning of 21st century)

The sludge management practices at the District as they exist today have evolved over roughly eight decades. When the District was formed in 1899, there was no sludge generation, because dilution of sewage was the sole treatment practice However, as large sewage treatment plants were constructed and started functioning at the District during the 1920s and 1930s, sludge resulted from the collection and processing of sewage in the treatment plants. Hence, the treatment and disposal of sludge became a necessity for the District, because indiscriminate disposal of sludge was not only aesthetically objectionable but also posed the risk of spreading diseases in the community.

Although public health risks (e.g., occurrence and spreading of various water borne diseases and the breeding of vectors that propagate disease) and aesthetics (e.g., generation of objectionable odors, etc.,) have been the primary factors for implementing sludge treatment and safe disposal practices at municipal sewage treatment plants, there are several drivers that have motivated the evolution of the sludge management techniques and practices that are specific to the District. These are examined from a historical perspective to delineate how the District has benefited by addressing them in an appropriate manner.

Document Type: Research Article


Publication date: January 1, 2002

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