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theses

Nonylphenol (NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), octylphenol (OP), and bisphenol A (BPA) are endocrine disrupting compounds (EDCs) that are present in wastewater. Studies of fate of these compounds have primarily focused on aquatic environments but EDCs are transferred from aquatic to terrestrial ecosystems through land-based sludge and biosolids applications. Biosolids are applied to land as a source of fertilizer, liming material, and soil conditioning. The main hypotheses of this work were that biosolids are important source of alkylphenolic compounds and bisphenol A in soils, and that these compounds are persistent in the soil over extended period of time. The goal of this work is to study the fate of these EDCs in sludge, biosolids and soils that have been treated with biosolids. Sludge and biosolids from 14 wastewater treatment plants (WWTP) comprising of 5 sludge stabilization processes, and operating under a wide range of physical, chemical and biological parameters were studied to examine the effect of sludge stabilization on the EDCs in biosolids destined for land uses. Subsequent to that, the fate of these contaminants was examined in 21soils of contrasting management and geomorphic characteristics 10 years after biosolids amendment. Finally, the ability of environmental models to predict the concentration of EDCs from which environmental fate can be deduced was evaluated using PhATE model. The results showed that NP, the recalcitrant end product of NPEO degradation, was detected at a range of 0.73-501µg kg-1 in sludge, 0.2-564 µg kg-1 in biosolids, and 0.12-28 µg kg-1 in soil. The effect of sludge stabilization process, or treatment was statistically significant (p<0.05) for NP and BPA, nearly significant (p=0.064) for OP, but not for NP1EO and NP2EO. Composting produced the highest reduction followed by alkaline stabilization, lime stabilization, anaerobic and aerobic digestion processes. Thus, EDC load being transferred to the soil was minimized through sludge stabilization prior to the actions of soil and environmental processes that eventually determine their fate in soil. After 10 years of biosolids amendment, EDC concentrations in the amended soils were 0.01-28 µg kg-1, and 0.01-2.3 µg kg-1 in control soils. EDCs were present in higher concentrations in the topsoil (2-28 µg kg-1) than in the subsoil (0.03-7 µg kg-1), and statistically significant difference (p<0.05) exists between the two sets of concentrations. However, the APEOs might have being from both sludge and biosolids, and pesticides sources as most of the sites studied were likely managed with pesticides. The EDCs studied show soil persistence at concentrations of 0.01-28 µg kg-1 in 3 soils that were amended with biosolids only. Soil concentration was dependent on the biosolids application rate and the concentration of EDCs in the biosolids. Modeling fate of these EDCs using PhATE model indicate that these compounds are depleted in biosolids-amended soils within 4 years of such amendment.

ETD_6431

Ph.D.

Includes bibliographical references

by J. Adewale Adewunmi

doi:10.7282/T3BZ67V7

ETD doctoral

The author owns the copyright to this work.