CHARACTERIZATION OF LEACHABLE DISSOLVED ORGANIC MATTER FROM BIOSOLIDS AND IMPLICATIONS FOR NUTRIENT RELEASES, MODELING, AND EMERGING CONTAMINANTS

Abstract

Treated wastewater residuals are utilized as a soil amendment to recycle nutrients to agricultural soils. Due to international application, biosolids are also a significant source of anthropogenic dissolved organic matter (DOM) to the environment.

The first contribution of this dissertation characterized DOM and nitrogen mineralization rates of anaerobically digested (AnD) biosolids with variable pre-treatments, such as the thermal hydrolysis pretreatment coupled to anaerobic digestion (THP-AnD). There was not strong evidence that differently pretreated-AnD material had largely different aerobic inorganic nitrogen releases when incubated in a sandy loam soil. Variable pools of DOM decayed in soil treatments over time. Biosolids-DOM was then characterized from a greater representation of full-scale stabilization processes including (i) limed stabilization (LT), (ii) aerobic digestion (AeD), and (iii) anaerobic digestion (AnD). These different final stabilization processes produced substantially different leachates characterized by organic carbon content, size-exclusion chromatography, and fluorescence spectroscopy. Traditional optical metrics previously defined for aquatic DOM did not consistently capture fluorescence maxima of the anthropogenic material. Therefore, boundary-based excitation emission matrix (EEM) analyses were re-defined based on local fluorescence maxima. Novel parallel factor analysis (PARAFAC) and spectral database comparisons confirmed that biosolids-DOM contain both common high energy stimulated components and low energy stimulated components that are unique to digested leachates.

The third research contribution applied fluorescence suppression experiments to measure interactions of halogenated ECs with contrasting biosolids-DOM types. Despite digested biosolids-DOM containing different humic acid-like or fulvic acid-like signatures than limed leachates, antimicrobial triclocarban and industrial compound 2-4 dichlorophenol suppressed similar high energy fluorescent signatures in all biosolids-DOM. This suggests TCC and 2-4 DCP electronically interacts with smaller aromatic compounds, such as amino acids, and this interaction is not unique to DOM from different waste stabilizations. This study contributes to future bioavailability assays modeling complex effects of leachate quality on halogenated contaminants.

This thesis also confirmed the presence of dehalogenating microbes in the anaerobic microbial community structure of a THP-AD system. These results contribute to on-going work assessing solids treatments, where halogenated emerging contaminants can be dehalogenated before land application. This work advances understanding of biosolids DOM leachates, modeling EEM data, and fate of ECs during full-scale solids treatment processes.