Document Type

Dissertation - Open Access

Award Date

2024

Degree Name

Doctor of Philosophy (PhD)

Department / School

Civil and Environmental Engineering

First Advisor

Guanghui Hua

Abstract

Nonpoint source pollution (NPS) from stormwater runoff, carrying a variety of contaminants, presents substantial challenges to water treatment processes and public health. Among the primary pollutants, phosphate and nitrate significantly contribute to the degradation of water quality, resulting in issues such as eutrophication and methemoglobinemia. Tree leaves, which are a major source of dissolved organic carbon (DOC) in forested watersheds and serve as a key fuel for wildfires, further exacerbate these challenges. Post-wildfire, the altered DOC is mobilized by precipitation, leading to stormwater runoff that impacts natural water bodies and complicates treatment processes, particularly through the formation of hazardous disinfection by-products (DBPs). The first objective of this dissertation was to develop and evaluate novel methods for coating water treatment residuals (WTR) onto woodchips, aiming to simultaneously remove phosphate and nitrate from stormwater runoff. Three distinct coating techniques were tested, with phosphate adsorption effectiveness ranked as follows: Wet WTR Direct Coating > Wet WTR Glue Coating > Dry WTR Glue Coating. Despite variations in phosphate removal efficiency, all WTR-coated woodchips demonstrated similar nitrate reduction capabilities and exhibited long-term stability under appropriate hydraulic retention conditions. The second objective focused on assessing the leaching behavior of DOC from four types of raw and thermally treated leaves, as well as their potential for DBP formation. The results indicated that DOC release significantly decreased as thermal treatment temperatures increased. Among the kinetic models applied, the intraparticle diffusion model provided the most accurate explanation of the DOC release mechanisms. Additionally, the potential for DBP formation was reduced in thermally altered leaves, with specific formation patterns differing between chlorination and chloramination processes. The third objective was to evaluate the treatability of DOC leached from raw and heat-treated maple leaves and assess their potential for DBP formation. The study revealed that DOC treatability decreased as the temperature of heat treatment increased. The efficiency of DOC removal followed the order: powdered activated carbon (PAC)/coagulation > PAC > coagulation. A strong correlation was observed between DOC concentration and DBP formation potential, which was notably reduced following PAC adsorption and PAC/coagulation treatments.

Publisher

South Dakota State University

Download

Share

COinS
 

Rights Statement

In Copyright