Zeolite Incorporated Materials for Targeted Biomass Retention and Pollutant Removal
2022-04
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Zeolite Incorporated Materials for Targeted Biomass Retention and Pollutant Removal
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2022-04
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This dissertation describes the assessment and treatment of pollutants, namely nutrients, in waste streams. Nutrients such as nitrogen, are of major and growing concern because nitrogen removal from waste streams is energy and cost intensive; yet, without treatment cause eutrophication in aquatic systems. The aquatic health of the Volta River in Ghana was assessed by monitoring pollutants including water quality parameters, contaminants of emerging concern, antibiotic resistance, and the microbial community. While Ghana is a low- to middle- income country, inadequate sanitation infrastructure and environmental regulations contribute to environmental and human health issues. In this highly collaborative work, common (e.g., nitrogen) and emerging contaminants (e.g., DEET, PFAS) were detected and the microbial community was analyzed from samples collected along the length of the lower Volta River. Spikes in microbial detection (16S rRNA gene) and antibiotic resistant genes were associated with anthropogenic activities indicating adverse effects of human activities on the health of the Volta River.
Additionally, novel biofilm technologies were explored to enhance nitrogen removal from waste streams. Specifically, zeolite-coated hollow fiber membranes and zeolite-coated biofilm carriers were designed to facilitate the partial nitritation-anammox (PNA) processes in mainstream wastewater, where significant cost savings and improved treatment could be realized. Zeolite particles and zeolite coated membranes in batch systems fed with mainstream-like synthetic wastewater demonstrated that anammox bacteria could be enriched and total nitrogen removal enhanced when compared to control systems without zeolite. By varying the mass of zeolite in the system it was discovered that a minimum amount of zeolite, or ammonium sorption capacity, was needed to achieve anammox retention. Zeolite-coated materials were further tested in flow-through systems to determine under what wastewater-relevant conditions nitrogen treatment enhanced. Zeolite-coated carriers in reactors under anaerobic conditions significantly retained anaerobic ammonia oxidizing (anammox) bacteria over systems with uncoated carriers; however, identical reactors operated under aerobic conditions did not retain aerobic oxidizing bacteria (AOB) on the carriers themselves. In both anaerobic and aerobic conditions, AOB were preferentially retained in the liquid of the reactors containing zeolite-coated carriers. Unexpectedly, denitrifying genes (specifically nirS, nirK, and nosZ) were also retained in systems with zeolite-coated carriers, indicating the nitrite-shunt process maybe another application. Zeolite-coated membranes were configured in flow-through membrane-aerated reactors and subject to varying operating lengths, inter-lumen oxygen concentrations, and influent nitrite with mixed results. Anammox bacteria were only detected in high quantities on zeolite membranes when operated for two weeks with 100% oxygen with and without nitrite in the influent. AOB were not enriched under any conditions at a 95% confident interval. Further exploration is needed to better understand the lack of AOB retention on both zeolite-carriers and membranes. Finally, zeolite-coated carriers were tested in stormwater-like systems both in the field and in laboratory reactors for retention of anammox, AOB, and feammox bacteria. Anammox bacteria and AOB were detected in increased quantities on zeolite-coated carriers over uncoated carriers when deployed in a raingarden, but not when deployed in a stormwater pond outlet structure. Carriers were also pre-seeded with anammox biofilm prior to field deployment in order to monitor biomass retention, and at the 2.5-month time scale tested, both control and zeolite carriers in both stormwater systems demonstrated excellent retention of biomass. Biomass was also well retained when both carrier types were pre-seeded and tested in laboratory reactors with simulated storm events. When pre-seeded, both reactors also demonstrated high rate of ammonium removal. Systems containing zeolite carriers inoculated with pond-water, however, had much higher rates of ammonium removal over control carriers indicating that under some conditions, zeolite coating did improve reactor performance. Finally, zeolite particles and zeolite-coated carriers were explored to determine if they also would preferentially retain feammox bacteria, the only known microorganism to defluorinate per- and polyfluorinated alkylated compounds. Reactors with zeolite particles and zeolite-coated carriers, had increased feammox bacteria and higher rates of ammonium removal. Overall, this research has demonstrated that zeolite-incorporated technologies are promising solutions to retaining anammox, AOB, and feammox bacteria and enhancing nitrogen removal in waste streams if applied under the right conditions. Treating waste streams to reduce the impacts of excess nutrients and other pollutants from human sources is important to protecting the health of aquatic systems.
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University of Minnesota Ph.D. dissertation. 2022. Major: Civil Engineering. Advisor: Paige Novak. 1 computer file (PDF); 334 pages.
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Chester, Anndee. (2022). Zeolite Incorporated Materials for Targeted Biomass Retention and Pollutant Removal. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/250423.
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