Date of Award
Spring 2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil, Construction, and Environmental Engineering
First Advisor
Zitomer, Daniel H.
Second Advisor
Mayer, Brooke
Third Advisor
McNamara, Patrick
Fourth Advisor
Downing, Leon
Abstract
Sewer overflows discharge 850 billion gallons of untreated sewage into U.S. lakes and rivers every year during high-intensity precipitation events. Common approaches include storage tanks or rapid solids removal followed by chlorine disinfection. These approaches can be capital intensive and only achieve partial treatment. A decentralized, end-of-pipe sewer overflow treatment system would eliminate detrimental overflow effects while handling highly variable flow and pollutant loading. Specifically, the rapid reaction rate of chemical oxidation can achieve soluble organics removal and disinfection of chlorine-resistant pathogens in a small footprint. To address the overflow issue, an advanced high-rate treatment system (AH-RTS) was developed and evaluated at two scales: bench and pilot. The AH-RTS combined rapid solids removal with ozonation for chemical oxidation. Three processes were investigated for compatibility with chemical oxidation: chemically enhanced primary treatment (CEPT), conventional primary treatment (CPT), and cloth media filtration (CMF). The performance goal was to meet Clean Water Act discharge permit requirements for biochemical oxygen demand (BOD), total suspended solids (TSS), and Escherichia coli (E. coli). The bench-scale batch AH-RTS achieved discharge permit limits for BOD, TSS, and E. coli in 35 total minutes of treatment, while the bench-scale continuous flow AH-RTS only met TSS and E. coli requirements. The pilot-scale AH-RTS was designed using data from bench-scale system testing. The pilot-scale AH-RTS met the performance goal with a pseudo-first order k of 0.046 min-1 at 24°C for COD removal during oxidation in a total treatment time of 32 minutes. The pilot-scale AH-RTS had a specific ozone utilization efficiency (SOUE) of 1 gram of ozone to remove 1 gram of COD. Pilot-scale SOUE was influenced by whether CPT, CEPT, or CMF was employed. Finally, pilot-scale AH-RTS pseudo first-order rate constant (k) value was significantly affected by water temperature and the method of solids removal before chemical oxidation. In additional to the technical research described herein, Rapid Radicals Technology, LLC, was founded to commercialize the AH-RTS. A perspective on the entrepreneurship and technology transfer experience is included. Rapid Radicals received a $1M National Science Foundation Small Business Innovation Research program grant and other grants to build and test a larger pilot-scale AH-RTS at remote overflow locations.