The objective of this research study was to statistically analyze the performance of a large number of activated sludge processes and to develop methods and procedures for introducing reliability and stability concepts into design and operation of wastewater treatment plants. Variations in the daily effluent quality of 43 activated sludge processes were examined. From an analysis of the data, it was found that the effluent variables are not distributed symmetrically, and generally their distributions are skewed further to the right than to the left of the most frequent value. The log-normal distribution was found to fit the observed effluent biochemical oxygen demand (BOD) and suspended solids (SS) date most consistently.
Performance of Activated Sludge Processes: Reliability, Stability and Variability
Authors: Salar Niku, Francisco J. Samaniego, Edward D. Schroeder, George Tchobanoglous
1981 EPA Municipal Environmental Research Laboratory