December 7, 1916: Engineering News article. Activated Sludge Results at Cleveland Reviewed. “A comprehensive review of nearly a year’s operation of one of the two largest activated sludge plants in the United States. Cleveland’s activated-sludge installation has now been in operation over nine months. Within 10 days after passing sewage through the plant, activated sludge was produced, but it took about two months to get all the recording apparatus tested out and the plant in shape for continuous operation….
The first experiments at Cleveland with the activated-sludge process indicated that two important requirements of an ideal method of sewage treatment were being satisfied: The process produced a clear sparkling effluent and there was an absence of odors….
The theory of the activated-sludge process involves properly conditioning a bacterial growth and bringing the growth into the most intimate contact wit the suspended particles of the crude sewage. The plant, therefore, was divided into six compartments in order that the results obtained at the end of each step could be definitely studied and that, if necessary, the solid matter of the sewage could be aerated longer than the liquid itself.”
Reference: “Activated Sludge Results at Cleveland Reviewed—I.” (1916). Engineering News. 76:23(December 7, 1916): 1061-2.