Date of Award

Summer 2022

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Micheal R Collins

Second Advisor

Paula Mouser

Third Advisor

Jeffrey Hall

Abstract

The application of slow sand filtration (SSF) has conventionally proven to be a reliable and relatively inexpensive means of producing potable drinking water for decades. As technologies in drinking water treatment continue to advance, innovations to the design and operation of slow sand filtration have the ability to transform its contribution in municipal and industrial settings. SSF amended with granular activated carbon (GAC) has been on the rise in recent decades due to its ability to improve the removal of organic material, while allowing SSF to maintain its innate treatment simplicity.

A slow sand filter amended with granular activated carbon in Winthrop, Maine has demonstrated the potential to preserve the life span of the GAC sublayer for over one and a half decades. From the time when GAC was initially installed in 2005, it has not required the addition of human regenerative interferences to maintain elevated removals of organic precursor measured by dissolved organic carbon (DOC). This study aimed to investigate the biologically active components and seasonal microbial patterns within filter sublayers that may contribute to the GAC bioregenerative process. Specific goals of this study were to explore mechanisms contributing to the maintenance of GAC adsorption sites, explore impacts of seasonal temperature variations on biodegradable and non-biodegradable organic carbon removals by slow sand filters amended with GAC, and to explore impacts of seasonal temperature variations on microbial communities.

Removals associated with biodegradable organic carbon (BDOC) and non-biodegradable organic carbon (BDOC) showed significant removals after several years of filter run-time, as well as differences in removals based on various GAC “ages.” Biomass and microbial community composition showed sensitivity to filter media type, location within the filter, and influence of temperature variations. Metals accumulations and content on various media showed significant accumulations of Iron on sand media and Calcium on GAC media. Results suggest calcium cation accumulation on the GAC sublayer may be correlated to higher removals of organic carbon on GAC.

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