Optimizing the Activated Sludge Process by Encouraging Futile Cycling

by Westley K. C. Chun, CH2M Hill, United States,
Edward D. Schroeder, CH2M Hill, United States,
Wiltraud Pfeiffer, CH2M Hill, United States,

Document Type: Proceeding Paper

Part of: Environmental Engineering


A study was conducted to demonstrate that cell yield in activated sludge processes can be decreased without increasing oxygen consumption by applying operating conditions that encourage 'futile cycling'. Laboratory-scale activated sludge reactors were used and operated as sequencing batch processes. When these reactors were either fed or aerated intermittently during the reaction step of the activated sludge process to induce 'futile cycling', cell yield was 24 percent lower and oxygen consumption was as much as 18 percent lower than when the reactors were fed once and aerated uniformly during the reaction step. The results anticipated when applying intermittent operating schemes to full-scale systems are significant reductions in the operating costs for an activated sludge wastewater treatment facility.

Subject Headings: Activated sludge | Water treatment plants | Wastewater management | Sewage | Benefit cost ratios | Aeration | Wastewater treatment plants

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