Date of Award

Spring 2016

Document Type


Degree Name

Master of Science (MS)


Civil & Environmental Engineering

Committee Director

Charles B. Bott

Committee Member

Gary Schafran

Committee Member

Peter Pommerenk


The Adsorption/Bio-oxidation (A/B) process accomplishes carbon capture via bio-flocculation in the adsorption stage (A-stage) to maximize energy recovery while simultaneously providing an optimal carbon to nitrogen (C/N) ratio for denitrification in the Bio-oxidation stage (B-Stage). The present study evaluated the influence of the solids retention time (SRT), dissolved oxygen (DO) concentration, and production of extracellular polymeric substances (EPS) on bio-flocculation and subsequent carbon capture using a pilot-scale A-stage process. A mixed liquor suspended solids (MLSS)-based control strategy was implemented to manage carbon capture by maintaining a constant MLSS concentration of 3,000 mg/L in response to diurnal variations in organic loading. Bio-flocculation, in terms of colloidal organic matter removal and concentration of effluent suspended solids, was enhanced by operating at a 0.56 day SRT compared to a 0.26 day SRT regardless of the DO concentration. Increasing the DO concentration from 0.5 to 1.0 mg/L at a longer SRT resulted in maximum bio-flocculation and carbon capture without significantly increasing the amount of COD lost to mineralization. These operating conditions coincided with a large reduction in loosely bound EPS (LB-EPS) and slight reduction in tightly bound EPS (TB-EPS) leading to the lowest LB-EPS to TB-EPS (LB/TB) ratio. Further increasing the DO concentration to 1.5 mg/L did not enhance bio-flocculation or carbon capture. Although EPS may have contributed to enhancing bio-flocculation, correlations found between EPS production and bio-flocculation were not as strong compared to operating conditions such as the SRT, DO concentration, MLSS concentration and influent wastewater characteristics. On the other hand, EPS production showed strong correlations for suspended solids removal and subsequent carbon capture in the A-stage pilot, especially when operated at a longer SRT.