Modeling Effects of DO and SRT on Activated Sludge Decay and Production


The effect of dissolved oxygen (DO) on the endogenous decay of active heterotrophic biomass and the hydrolysis of cell debris were studied. With the inclusion of a hydrolysis process for the cell debris, mathematical models that are capable of quantifying the effects of DO and sludge retention time (SRT) on concentrations of active biomass and cell debris in activated sludge are presented. By modeling the biomass cultivated with unlimited DO, the values of endogenous decay coefficient for heterotrophic biomass, the hydrolysis constant of cell debris, and the fraction of decayed biomass that became cell debris were determined to be 0.38 d-1, 0.013 d-1, and 0.28, respectively. Results from modeling the biomass cultivated under different DO conditions suggested that the experimental low DO (~0.2 mg/L) did not inhibit the endogenous decay of heterotrophic biomass, but significantly inhibited the hydrolysis of cell debris with a half-velocity constant value of 2.1 mg/L. Therefore, the increase in sludge production with low DO was mainly contributed by cell debris rather than the active heterotrophic biomass. Maximizing sludge production during aerobic wastewater treatment could reduce aeration energy consumption and improve biogas energy recovery potential.


Civil, Architectural and Environmental Engineering


This research was partially supported by grants from the Army Research Lab (ARL) through the Leonard Wood Institute (LWI) and Frontier Environmental Technology, LLC (Contract Numbers LWI 281173 and LWI-191-059).

Keywords and Phrases

Biomass; Cells; Cytology; Debris; Decay (organic); Dissolved oxygen; Energy utilization; Hydrolysis; Wastewater treatment; Cell debris; Endogenous decay; Heterotrophic biomass; Low DO; Sludge production; Activated sludge process; Dissolved oxygen; Oxygen; Sewage; Waste water; Activated sludge; Biomass; Dissolved oxygen; Heterotrophy; Hydrolysis; Numerical model; Wastewater; Water treatment; Activated sludge; Aeration; Article; Biomass; Chemical parameters; Energy consumption; Energy recovery; Kinetics; Priority journal; Sludge retention time; Waste water management; Algorithm; Biomass; Chemistry; Heterotrophy; Metabolism; Microbiology; Parasitology; Procedures; Sewage; Theoretical model; Time factor; Waste water; Algorithms; Heterotrophic Processes; Models; Theoretical; Oxygen; Sewage; Time Factors; Waste Disposal; Fluid; Waste Water; Cell debris; Endogenous decay; Heterotrophic biomass; Low DO; Sludge production

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Article - Journal

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© 2015 Elsevier, All rights reserved.

Publication Date

01 Sep 2015

PubMed ID