Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Chemical Engineering

Major Professor

Paul D. Frymier

Committee Members

Curtis Lajoie, Chris Cox, Paul Bienkowski


Influent wastewater toxicity causes upsets in the operations of biological wastewater treatment systems. Toxic compounds cause the loss of higher life forms in activated sludge, the formation of pin floes that settle poorly in downstream clarifiers and increase the addition of costly polymers. Ultimately, these effects lead to the degradation of effluent quality. In the most severe circumstances, influent toxicity can lead to a plant shut-down and the discharge of untreated wastewater into the environment. These effects can be avoided if influent wastewater is screened for toxicity and protective actions are taken to prevent damage to the activated sludge. Possible methods for the assessment of influent wastewater toxicity are chemical analysis, microscopic examination, respirometric methods, and bioluminescence-based microbiological methods. Chemical analysis is slow and requires a priori knowledge of wastewater components. The complexity of domestic wastewater constituents and the limited amount of time available for protective actions to be taken make chemical analysis unsuitable for the purpose of influent toxicity screening.

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