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Permanent link (DOI): https://doi.org/10.7939/R3K386

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Physics of wastewater flow and pathogen transport processes from a soil-based at-grade effluent treatment system and associated groundwater contamination risks in Alberta, Canada Open Access

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Other title
Subject/Keyword
Groundwater hydrology
Hydrologic response to effluent infiltration
Electromagnetic Induction
Threshold values
7-day effluent travel depth
Groundwater contamination risk assessment
Pressure transducer
Vadose zone thickness
Groundwater flow and gradient
Environmental Site Assessment
Wastewater flow and pathogen transport processes
Hydrological processes
Safety Code Council
Septic system
On-site Wastewater Treatment System
Bromide and nitrate plume
Process based modeling
Alberta Standard of Practice
Nest of wells
Wetaskiwin Rest Stop
Soil physics and hydrology
Soil-based effluent treatment
Groundwater mounding
Soil adsorption field
Onsite Wastewater Treatment System
Mapping
Multidimensional saturated and unsaturated flow and transport
Spectral and wavelet signal analysis
Field investigation
Soil absorption field
Wastewater plume center of mass
Hydrogeology
Ultraviolet disinfection
E.coli and Virus transport
Aspen
Moment analysis
Monitoring wells
E.coli attenuation
LFH At-grade effluent dispersal lines
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Weldeyohannes, Amanuel Oq
Supervisor and department
Dr. Dyck, Miles (Renewable Resources, University of Alberta)
Dr. Kachanoski, Gary (President's Office, Memorial University of Newfoundland)
Examining committee member and department
Dr. Chang, Scott (Renewable Resources, University of Alberta)
Dr. Parkin, Gary (School of Environmental Sciences, University of Guelph)
Dr. Kachanoski, Gary (President's Office, Memorial University of Newfoundland)
Dr. Carl Mendoza, Carl (Earth and Atmospheric Sciences, University of Alberta)
Dr. Landhausser, Simon M. (Renewable resources, University of Alberta)
Dr. Dyck, Miles (Renewable Resources, University of Alberta)
Department
Department of Renewable Resources
Specialization
Soil Science
Date accepted
2015-03-20T14:50:25Z
Graduation date
2015-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Understanding of wastewater flow and transport processes and treatment effectiveness through the soil-absorption field of soil-based wastewater treatment systems remains a challenge. In addition, Alberta regulators and the on-site wastewater industry wanted to quantify the effectiveness of the new LFH At-grade soil-based wastewater absorption and treatment system design. An extensive field research program was executed at Wetaskiwin Rest Stop, Central region of Alberta, a site that has been receiving secondarly treated and ultraviolet disinfected effluent via pressurized effluent distribution at-grade laterals since 2007. The specific objectives were to investigate: i) hydrologic response to effluent infiltration from at-grade line sources under shallow groundwater conditions, ii) fate and transport of pathogens under boundary conditions typical of on-site water treatment systems (OWTS), and iii) groundwater contamination risks associated with OWTS. Following site characterization, field-scale tracer experiment was conducted using E.coli and Bromide as step and pulse inputs respectively. Groundwater response to effluent infiltration, wastewater plume movement, E.coli and virus concentrations were monitored in nests of monitoring wells over time. Finally, using the field measurements, HYDRUS 2D was used to investigate groundwater contamination risks associated with OWTS. Considering the existing regulatory requirement of 7-day effluent travel depth through the vadose zone that has been established in Alberta, a residence time assumed to be enough for pathogens attenuation in the vadose zone, weekly cycle hydrologic responses were interpreted. Findings indicated: i) significant hydrologic response to effluent infiltration from at-grade line sources at a weekly scale, ii) effluent reaching the groundwater for approximately 15% of the time in the spring and summer periods when effluent loading rate of ≥5 cm3 cm-2 d-1 encountered a groundwater at ≤0.5 m below the ground surface. These conditions also coincided with the significant 7-day cycle of the effluent input function due to traffic on the highway and use of the facilities. The results suggest consideration of both surface effluent loading and regional hydrologic conditions when designing at-grade wastewater treatment systems to minimize potential groundwater contamination risks; iii) the vadose zone of ≥0.88 m thick, the vertical separation between the at-grade lines and the top of the groundwater level, filtered E.coli bacteria that were present in the infiltrating effluent to acceptable levels achieving the 7-day effluent travel depth design criteria, however it didn’t perform well for some viruses, and iv) initial groundwater depth from the surface is critical for designing at-grade effluent treatment systems. Under the prevailing site boundary conditions and assuming a homogenous medium, a loading rate up to 15 cm3 cm-2 d-1 poses less threat when the initial depth to groundwater is at ≥2 m. In practical terms therefore, matching effluent loading rate vis-a-vis the effluent receiving site characteristics is critical particularly during the spring snow melt and summer period. In addition to the design criteria of OWTS, inclusion of performance criteria as standard of practices for these systems is suggested. The findings presented in this thesis contribute significantly to the understanding of wastewater flow and transport under boundary conditions typical of OWTS and shallow groundwater conditions.
Language
English
DOI
doi:10.7939/R3K386
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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