Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Mark T. Hernandez

Second Advisor

Joseph Ryan

Third Advisor

Sherri Cook

Fourth Advisor

Wil V. Srubar

Fifth Advisor

Dennis Grubb

Abstract

Concrete is the most common material used to transport storm water and sewage in the world. It is used for pipes, culverts, tunnels and variety of other subterranean appurtenances. Municipalities, water utilities, and many agencies recognize that concrete corrosion is emerging as one of the most serious problems plaguing this critical infrastructure. The dominant form of concrete deterioration in wastewater conveyance systems is microbially mediated (Microbial Induced Concrete Corrosion: MICC). This type of corrosion occurs as a result of ubiquitous microbiological sulfur cycling within sewers: Below the waterline, sulfate present in wastewater is reduced to sulfide (H2S) under anoxic conditions; this partitions into the headspace of pipes and other wastewater structures as H2S gas, which serves as a substrate for biofilms of acidogenic sulfur-oxidizing bacteria (SOBs) above the waterline. These biofilms produce sulfuric acid, which chemically dissolve the cement binder and compromise the concrete structure. While current mitigation technologies focus their attention on developing acid resistant materials, little research has been done on limiting acidophile development in these environments. In response to the current research gaps in this arena, the central aim of my work was to study the effects of substituting metal-impregnated sorbents for a fraction of the fine aggregates traditionally used in cements ─ for the express purpose of inhibiting the bacterial communities responsible for the corrosion in sewer systems. Laboratory investigations evaluated the inhibition potential of selected heavy metals against SOB communities, and resolved minimum inhibitory concentrations, individually and in combinations. Parallel studies characterized different sorbents along with their metal desorption profiles in response to biogenic acid. Field studies in the Denver Metropolitan wastewater collection system, then assessed anti-corrosion performance of cement mortar formulations with different loads of metal-impregnated sorbents.

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