Thesis
Effectiveness of aluminum based coagulants after a wildfire
Washington State University
Master of Science (MS), Washington State University
12/2019
DOI:
https://doi.org/10.7273/000003991
Handle:
https://hdl.handle.net/2376/124972
Abstract
Wildfires are a concern to drinking water utilities located within or downstream of forested watersheds due to potential post-fire changes in source water quality. After subsiding, the aftermath of wildfires can impact the surrounding watershed. Fire-induced alterations to the forest floor can result in elevated erosion and runoff which can lead to degraded water quality. These changes in water quality can pose challenges to a water treatment plant's (WTP) existing treatment processes. To address the concerns of potentially increased and variable turbidity and dissolved organic carbon (DOC) levels following a 2017 wildfire in Washington state, the Naches River water intake was monitored from April - November 2018. The objectives of this study were to evaluate post-fire changes to the Naches River water quality and to address challenges to treatment processes by comparing the efficacy of two aluminum coagulants: aluminum sulfate (alum) and aluminum chlorohydrate (ACH). Results showed increased and more variable DOC concentrations were observed the year immediately after the fire. Overall, post-fire source water remained treatable by direct filtration with ACH. Although alum and ACH showed comparable DOC removal, ACH showed higher specific ultraviolet absorbance (SUVA) reduction, which could be beneficial for meeting disinfection byproduct regulations. Currently, the unintentional effects of post-fire land treatments, such as mulches, on surface water quality parameters such as DOC have not been well researched. The purpose of the second study was to assess the impacts that post-fire applied mulch may have on raw water quality and coagulation treatment of drinking water. Three different varieties of mulch were leached and water quality of the leachates was characterized. Coagulation tests were performed for the evaluation of alum and ACH using conventional treatment. Conventional treatment struggled to remove the DOC leached from the wood mulch. However, conventional treatment provided adequate DOC removal for the two straw mulches, but the leachates remained more aromatic than the wood leachates following treatment. While wood mulch proved difficult to treat, it would require a much greater mass of wood mulch to reach a water source to result in the same levels of DOC as a straw mulch.
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Details
- Title
- Effectiveness of aluminum based coagulants after a wildfire
- Creators
- Elizabeth Crain
- Contributors
- Amanda Kay Hohner (Advisor) - Washington State University, Department of Civil and Environmental Engineering
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890798201842
- Language
- English
- Resource Type
- Thesis