ORCID Identifier(s)

0000-0002-5037-564X

Graduation Semester and Year

2019

Language

English

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering

Department

Civil Engineering

First Advisor

Melanie Sattler

Abstract

Sewer systems are a principal element of infrastructure in modern cities, accounting for massive amounts of public investments made over many decades and can be considered as an asset of the nation. Many concrete manholes in the sewer system are deteriorating due to the attack of sulfuric acid produced by microorganisms in a process termed as Microbial Induced Concrete Corrosion (MICC). The life span of concrete sewer elements significantly reduces from 100 years to 30–50 years, in extreme cases even down to 10 years. The primary aim of this study is to enhance the understanding of the correlation between gas-phase hydrogen sulfide concentrations, which lead to MICC, and sewer environmental factors, including dissolved oxygen (DO), biochemical oxygen demand (BOD), sulfide, sulfate, temperature, and pH. In addition, the effects of seasonal variations on hydrogen sulfide concentrations and the impact of manhole categories including the depth, velocity, turbulence and drop are also studied. For 130 manholes in the City of Arlington, Texas, the wastewater characteristics in the gas phase such as temperature, relative humidity and hydrogen sulfide were measured in-situ using various instruments and the liquid phase parameters like dissolved oxygen (DO), pH and temperature were also measured in-situ. The samples for measuring the biochemical oxygen demand (BOD), sulfate, total and dissolved sulfide were collected in-situ and were analyzed in the laboratory using standard methodology. The sewer system characteristics like slope and velocity were obtained from the city. In each manhole studied, hydrogen sulfide concentration, liquid phase temperature, and liquid phase pH showed similar hourly trends in consecutive days of sampling. The trend in rise and fall of concentration of these parameters over time showed slight variations depending on the manhole’s location and category. The manholes with hydraulic jump generated the highest average hydrogen sulfide concentration, and the lowest was observed in manholes with subcritical flow in upstream and downstream. The average liquid phase temperature was always greater than the ambient temperature inside a manhole, with a variation of 3°F on an average. In all the manholes studied for seasonal variation, the concentration of hydrogen sulfide was found to be maximum during the summer, when the temperature was elevated. Due to involvement of multiple parameters affecting each factor, no strong linear correlations were obtained between the factors studied.

Keywords

Manhole corrosion, MICC, Concrete sewer corrosion, Hydrogen sulfide corrosion

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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