Hydraulic Regime and Activated Sludge Performance

by Robert M. Sykes, (M.ASCE), Assoc. Prof.; Dept. of Civ. Engrg., 470 Hitchock Hall, 2070 Neil Ave., Columbus, Ohio 43210,

Serial Information: Journal of the Environmental Engineering Division, 1982, Vol. 108, Issue 2, Pg. 286-296

Document Type: Journal Paper

Discussion: Droste Ronald L. (See full record)
Closure: (See full record)


The standard bio-kinetic theory used to describe the activated sludge process predicts that the soluble organic matter (SOM) concentration in the effluent of plug flow aeration tanks will be less than the SOM concentration in the effluent of completely mixed aeration tanks, if both contain the same total biomass and are operated at the same solids' retention time (SRT). Large-scale field studies indicate that this prediction is false. An alternate model of the process is presented that identifies the effluent SOM as a product synthesized and excreted by the microbes of the activated sludge. This model predicts that all aeration tanks treating a given wastewater will produce the same effluent SOM concentration if they contain the same total biomass and are operated at the same SRT. The alternate model also predicts that the effluent SOM concentration will be proportional to the influent organic matter concentration, that the apparent microbial decay rate will vary as different nutrients are considered, and that plots of the specific uptake rate vs. the effluent SOM concentration will show a positive SOM intercept. All these predictions are supported by experiment.

Subject Headings: Hydraulics | Activated sludge | Effluents | Professional societies | Wastewater treatment | Aeration | Biomass | Organic matter

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