Date of Award

Spring 1-1-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil, Environmental & Architectural Engineering

First Advisor

R. Scott Summers

Second Advisor

Eric Dickenson

Third Advisor

JoAnn Silverstein

Abstract

Organic constituents at the low to sub-microgram per liter level derived from wastewater effluents represent precursors to previously undetected disinfection by-products (DBPs) in drinking water utilities. N-nitrosodimethylamine (NDMA) is an emerging DBP of particular concern due to its suspected genotoxicity and carcinogenicity an order of magnitude greater than currently regulated DBPs. Granular activated carbon (GAC) has been shown to be a potential control technology for removing NDMA precursors from wastewater effluent, but adsorption behavior of specific precursor material is still poorly understood. The goal of this research is to expand knowledge of the GAC adsorption behavior of NDMA and other DBP precursors in wastewater effluent, including understanding the effect of different activated carbon types, the effect of varying GAC column Empty Bed Contact Time (EBCT), the effect of source water blending on NDMA precursor sorption, and the breakthrough of NDMA precursors relative to trihalomethane, haloacetic acid, and haloacetonitrile precursors. Lignite-based and wood-based activated carbon were found to remove NDMA precursors better than coconut-shell and bituminous carbons, presumably due to larger mesopore volumes. NDMA precursors are thought to be larger molecular weight compounds or behave in water such that adsorption occurs in the mesopore region. A distinct non-adsorbable fraction in powdered activated carbon batch tests suggests a range of different precursor compounds. In Rapid Small-Scale Column Tests (RSSCTs), a simulated 20-minute bench-scale EBCT performed better than a 10-minute column, thus longer EBCTs are suggested when optimizing GAC control for NDMA precursors in wastewater. NDMA precursors were also found to adsorb independently of bulk organic matter and other DBP precursors, suggesting its precursors are distinct from currently regulated and other nitrogenous DBPs. As a result, Overall Fluorescence Intensity was proposed as a possible surrogate for NDMA precursors due to its similar adsorption behavior in RSSCTs using blended influent waters. Evidence is also presented for considering NDMA precursors as similar to micropollutants due to rapid sorption in batch testing distinct from DOM, and diminished impacts of influent concentrations on fractional RSSCT breakthrough.

Available for download on Sunday, September 27, 2020

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