Date of Award

Spring 2022

Document Type


Degree Name

Master of Science (MS)


Civil, Construction, and Environmental Engineering

First Advisor

McNamara, Patrick

Second Advisor

Zitomer, Daniel

Third Advisor

Newton, Ryan


Activated sludge is a conventional treatment process for biochemical oxygen demand (BOD) and total suspended solids (TSS) removal at water resource recovery facilities (WRRFs). A common operational issue that arises is activated sludge foaming on top of the aeration basin and secondary clarifier. Foaming events in activated sludge may lead to decreased treatment efficiency, maintenance issues, and potential environmental health risks. Stable foaming events are caused by biological and chemical drivers (i.e., microbes and surfactants) during the aeration process. However, foaming events are difficult to predict and quantify. This research developed an inexpensive and easy-to-use method to quantify foaming potential that can be applied at WRRFs. Subsequently, the novel technique was applied to investigate the microbial community composition and functional parameters associated with foaming potential from activated sludge samples at South Shore Water Reclamation Facility (WRF) in Oak Creek, WI, USA. Results from the development of the foaming potential method using linear alkylbenzene sulfonate (LAS) showed that the method is reproducible (RSD < 15%) and able to capture changes in foam inducing constituents. The method was tested further using wastewater samples with varying percentages of recycled activated sludge (RAS) and primary effluent (PE) from South Shore WRF that yielded standard deviations < 5%, which confirmed the method was reproducible. Using full-scale activated sludge samples from South Shore WRF, the following genera were identified as being associated with foaming events: Zoogloea, Flavobacterium, Variovorx, and Bdellovibrio. This is the first report that Variovorx and Bdellovibrio are correlated with foaming events in activated sludge. Furthermore, the foaming potential positively correlated (p ≤ 0.05) with soluble total nitrogen. Characterizing foaming events through frequent sampling in activated sludge may allow for prediction and mitigation efforts by monitoring the microbial community composition and functional parameters.

Available for download on Friday, April 14, 2023

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