Award Date

5-15-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering and Construction

First Committee Member

Daniel Gerrity

Second Committee Member

Sajjad Ahmad

Third Committee Member

Haroon Stephen

Fourth Committee Member

Krystyna Stave

Fifth Committee Member

Kaushik Ghosh

Number of Pages

232

Abstract

In recent years, potable reuse applications have become more common due to population growth and increased water demand, especially in communities with limited or variable water resources. However, there are concerns about potential exposure to pathogens and chemical compounds in treated wastewater. Therefore, advanced wastewater treatment processes are of paramount importance in any potable reuse system. The overall aim of this study was to develop and implement static and dynamic QMRAs to compare public health risk in various potable reuse scenarios. Cryptosporidium, norovirus, adenovirus, and Salmonella were chosen as the target pathogens. The research evaluated the performance of full advanced treatment (FAT) trains consisting of reverse osmosis (RO) and advanced oxidation processes (AOPs), which are required in California for planned IPR systems that directly inject recycled water into local aquifers or discharge to surface water. The study also explored ozone-biological filtration as an alternative for FAT trains by comparing its public health risk to that of the RO-based treatment train. Treatment process performance and resultant public health risks were modeled using the STELLA 10.1 system dynamics software package. The system dynamics model accounted for the possibility of unit process failure and subsequent effects on downstream treatment process performance (i.e., ‘domino effects’). The model also compared typical vs. outbreak scenarios and identified the components and operational conditions that were most critical to minimizing public health risks in each of the potable reuse paradigms. The dynamic disease transmission model incorporated secondary transmission and immunity through implementing different epidemiological states. In this study, dynamic disease transmission model was focused on norovirus which is the most common cause of acute gastroenteritis diseases in the US. This study indicated that combined annual risk of infection was lower in DPR systems with direct distribution (median risk= 5.4×10-8 and 1.2×10-6 for ozone-based DPR and RO-based DPR, respectively) compared to the IPR systems and DPR with blending. Generally, potable reuse treatment trains with surface water utilization resulted in similar risk of infection which exceeded the benchmark risk of 10-4. The model also identified 120 days and 150 days of storage time at 10°C and 20°C of temperature as the most critical parameters in de facto reuse systems when targeting Cryptosporidium and adenovirus, respectively. Included secondary transmission and immunity resulted in up to 8 orders of magnitude higher risk of norovirus than the static framework (depending on the treatment train). However, results of this study indicated that potable reuse systems were sufficiently robust to handle the high concentration of norovirus during outbreak conditions and that disease incidence of norovirus was mainly attributed to secondary transmission pathway. However, these results may change if other pathogens are considered in dynamic disease transmission model.

Keywords

Alternative technologies; Pathogens; Public health; Risk assessment; Water reuse

Disciplines

Environmental Engineering | Water Resource Management

Language

English


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