Date of Award:

5-2022

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Michael McFarland

Committee

Michael McFarland

Committee

David Stevens

Committee

Ronald Sims

Committee

Alfonso Torres

Committee

Joan McLean

Abstract

Some municipal wastewater treatment (MWWT) facilities have adopted magnetite in their treatment processes through a technology called BioMag® to meet effluent regulatory requirements for total nitrogen and total phosphorus. However, there is limited information on the mechanisms and efficiency of magnetite in the removal of nitrogen (N) and phosphorus (P) from wastewater. This research, therefore, estimated its effectiveness in the removal of these nutrients, with a case study of the Marlay-Taylor Water Reclamation Facility in Maryland. The intervention analysis model was used, but a new forecasting approach to the model was proposed to fit the data in this study and other similar data. Results showed a significant improvement in both N and P removal. Graphical analyses showed an improvement in operating parameters like the mixed liquor suspended solids and sludge volume index. An account of the N and P removal mechanisms by the magnetite was also provided.
Some MWWT facilities using magnetite in their treatment process stabilize their waste sludge using anaerobic digestion (AD) and produce biogas. Therefore, laboratory studies were conducted to determine the effect of magnetite on biogas production (mainly methane and carbon dioxide) and on hydrogen sulfide (H2S) gas reduction. Results showed no significant differences in biogas production, contrary to some studies which reported increases in methane yield with magnetite addition. H2S in the biogas reduced below the concentration that is immediately dangerous to life and health (IDLH). An increase in dissolved iron was also noted.

Some recent studies that used magnetite and other conductive materials in AD experiments reported elemental sulfur (So) formation in the digesters. However, previous research that used iron compounds reported iron sulfide (FeS) formation as the mechanism of H2S reduction. Therefore, a bioenergetics model was used to determine if the oxidation of H2S to So is theoretically possible in the AD environment. So formation could also occur due to air presence or leakage in the digesters. Results showed that the reaction leading to So formation was exothermic, implying that energy was produced which could support microbial growth. However, conductive material may be required to initiate this reaction by facilitating electron transfer.

Checksum

a12d8284b32c5c5a8fc648aa25f633cf

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .