Graduation Year

2022

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Sarina Ergas, Ph.D.

Co-Major Professor

Kebreab Ghebremichael, Ph.D.

Committee Member

Zeev Ronen, Ph.D.

Committee Member

Sylvia Thomas, Ph.D.

Committee Member

Sennai Habtes, Ph.D.

Keywords

Wastewater, Water Quality, Constructed Wetlands, Life Cycle Assessment, U.S. Virgin Islands, Food, Energy, Water Systems

Abstract

Changes in water use, climate, and urbanization have shifted how water resources are used and defined. Wastewater is increasingly regarded as a viable resource to address challenges in non-potable and potable water applications. When dealing with water reuse, water quality and quantity are of the utmost importance; and the final product must be suitable for its intended purpose and acceptable to users. The first portion of this research analyzed the performance and environmental impacts of pilot-scale Hybrid Adsorption Biological Treatment Systems (HABiTS) for onsite wastewater treatment and reuse. Various configurations were investigated to increase HABiTS performance and ability to produce high quality effluent for onsite reuse. Water quality parameters were monitored to determine which HABiTS configurations could achieve effluent of sufficient quality for reuse. Pilot-scale results showed that a single-stage nitrifying biofilter, with added zeolite, recirculation to a pre-denitrification tank followed by disinfection using a chlorine tablet feeder could achieve consistently low effluent E. coli levels for onsite irrigation reuse. Two HABiTS scenarios, one with recirculation and one without, met guidelines for reuse. These systems were then theoretically scaled up and evaluated using a life cycle assessment (LCA). These two systems were compared to two baseline scenarios: a conventional septic system with surface irrigation and a conventional septic system with subsurface irrigation. For the LCA, the ReCiPe impact characterization method was used, and two functional units were considered (m3 of potable water used and log E. coli removal). Normalized impact results showed that freshwater eutrophication, marine and freshwater ecotoxicity, and human ecotoxicity were the most important impact categories. Results from the impact assessment showed that HABiTS had similar or lower environmental impacts compared with the baseline systems for both functional units. HABiTS is a promising onsite wastewater reuse system that can be adapted for homeowners to reduce pollutants in water and to mitigate negative health impacts while preserving water resources.

In the second project, research was conducted on different type of OWTS, constructed wetlands (CWs), and different type of wastewater (greywater) in the Negev desert, Israel. There is a growing body of knowledge on the persistence of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) in greywater and effluents from greywater treatment systems such as constructed wetlands (CWs). This research quantified ARGs (sul1, qnrS, and blaCTXM32), a class one integron (intI1), and bacterial marker (16S), in four recirculating vertical flow CWs in a small community in the Negev desert, Israel using quantitative polymerase chain reaction (qPCR). The greywater microbial community was characterized using 16S rRNA amplicon sequencing. Results showed that CWs can reduce ARG in greywater by 1-3 log, depending on the gene and quality of the raw greywater. Analysis of other water quality parameters (suspended solids, organic carbon, biochemical oxygen demand, pH, and conductivity) showed that the performance of the CW was sustained over years of treatment and satisfies reuse standards. Community sequencing results showed that the bacterial community composition was not significantly altered after treatment, and that Proteobacteria, Epsilonbacteraeota, and Bacteroidetes were the most dominant phyla before and after treatment. Pseudomonas, Citrobacter, Achromobacter, Enterobacter, and Aeromonas were the most identified genera of the extended spectrum beta lactamase (ESBL) colonies. Some of the ESBL bacteria identified have been linked to clinical infections (Acinetobacter nosocomialis, Pseudomonas fulva, Pseudomonas putida, and Roseomonas cervicalis). This research further emphasizes and adds to the body of knowledge, the importance of monitoring intI1 and other mobile genetic elements for the potential transfer of ARGs to commensal or pathogenic bacteria.

In the last phase of this research the food, energy, water system (FEWS) approach was used in the U.S. Virgin Islands to determine users’ perception of water reuse related to food, energy, and water. Similarly, to Israel, the U.S. Virgin Islands are a water stressed region, which has prompted innovative ways to reuse water. Residents of St. Thomas are required to collect rainwater for household water use but even with rainwater collection, St. Thomas faces issues of drought. Water scarcity is not the only issue facing St. Thomas or the other U.S. Virgin Islands as the combination of high food and electricity prices necessitate new approaches to food production and water conservation. Alongside these concerns, the U.S. Virgin Islands were also hit with two category 5 hurricanes in the same year which elevated the concern for securing resources as small island communities face the brunt of climate change. The first two research projects highlighted the physical and biological benefits of water reuse for varying types of wastewaters (sewage and greywater) and wastewater treatment systems (hybrid adsorption biological treatment system and recirculating vertical flow constructed wetlands). Drawing from the experiences in the first two research projects with OWTS, community perceptions were examined as an additional component of water reuse. The involvement of stakeholders and users in water research provided a more comprehensive view of water reuse. To determine perceptions of water reuse, interviews, participant observations, and surveys were used to determine issues related to food, energy, and water, and individuals’ familiarity and perception of water reuse. Results showed that individuals familiar with the idea of water reuse were more open to water reuse. Individuals were open to water reuse for crops that would and would not be eaten but more open to water reuse for nonfood crops. Further research is needed on how wastewater reuse systems can be designed to meet the needs of household communities in small island nations while addressing FEWS concerns.

The novelty of this research lies in the value of water reuse. This research viewed various types of onsite wastewater treatment systems, different types of wastewaters (sewage and greywater), and uncovered user perceptions to view water reuse from different lenses. Overall, this research demonstrates that environmental engineering projects can encompass technological advancements, microbiological innovation, and anthropological perspectives for sustainable change.

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