Award Date

8-1-2012

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Civil and Environmental Engineering

First Committee Member

Jacimaria Batista

Second Committee Member

Sajjad Ahmad

Third Committee Member

David James

Fourth Committee Member

Spencer Steinberg

Number of Pages

127

Abstract

Endocrine-disrupting compounds (EDCs), such as estrogen, are known to be present in the aquatic environment at concentrations that negatively affect fish and other wildlife. Wastewater treatment plants (WWTPs) are major contributors of EDCs into the environment. EDCs are released via effluent discharge and land application of biosolids. Estrogen removal in WWTPs has been studied in the aqueous phase; however, few researchers have determined estrogen concentration in sludge. This study focuses on estrogen concentration in wastewater sludge as a result of secondary treatment types and sludge handling processes. Grab samples were collected before and after multiple treatment steps at two WWTPs receiving wastewater from the same city. The samples were centrifuged into aqueous and solid phases and then processed using solid phase extraction. Combined natural estrogens (estrone, estradiol and estriol) were measured using an enzyme-linked immunosorbent assay (ELISA) purchased from a manufacturer. Results confirmed that activated sludge treatments demonstrate greater estrogen removal compared to trickling filters and estrogen load (mass estrogen per mass solid) was measured for the first time on trickling filter solids. Physical and mechanical sludge treatment processes, such as gravity thickeners and centrifuges, did not significantly affect estrogen removal based on mass balance calculations. Dissolved air flotation demonstrated a slight decrease in estrogen concentration, while anaerobic digestion resulted in increased estrogen load on the sludge and a high estrogen concentration in the supernatant. Although there are no state or federally mandated discharge effluent standards or sludge application standards for estrogen, implications from this study are that trickling filters would need to be exchanged for activated sludge treatment or followed by an aeration basin in order to improve estrogen removal. Also, anaerobic digestion may need to be replaced with aerobic digestion for sludge that is intended for land application.

Keywords

Endocrine disrupting chemicals in water; ELISA; Estrogen; Secondary treatment; Sewage – Purification; Sewage sludge; Sludge handling; Wastewater sludge; Wastewater treatment

Disciplines

Environmental Engineering | Environmental Health and Protection

Language

English

Comments

Related poster:

http://digitalscholarship.unlv.edu/celebration/2012/april27/20/


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