Browsing by Subject "Wastewater"

Now showing 1 - 4 of 4
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    Effects of Organic Carbon on the Biodegradation of Estrone in Multiple Substrate, Mixed-Culture Systems
    (2014-08) Tan, Tat Ui
    This dissertation describes the study of the effect of organic carbon on the biodegradation of estrone (E1) in multiple substrate, mixed-culture systems. In exploring this topic, important degradation mechanisms related to organic carbon were tested to determine which, if any, play an important role. Additionally, the effects of organic carbon concentrations, loads, and quality on E1 degrading activity of cultures from a wastewater treatment system were determined. Catabolic repression effects on E1 degradation was studied by adding synthetic septage to an E1 degrading culture to determine if degradation rates were affected. No differences in first-order E1 degradation rates between test and control reactors were observed in the 2 h or 8 h period following the addition of synthetic septage, ruling out catabolic repression as an important mechanism in E1 degradation in wastewater treatment-like conditions. Cultures were grown in membrane bioreactors (MBRs) with and without exposure to E1 to determine if (i) E1 exposure is necessary for E1 degrading ability, and if so (ii) whether multiple substrate utilization and/or cometabolism play an important role in the degradation of E1. These cultures were capable of degrading E1 regardless of prior exposure. Higher rates of E1 degradation were observed in cultures with prior E1 exposure, and a lag phase of 6 h was observed in cultures without prior E1 exposure. These results indicate that E1 was degraded metabolically, demonstrating that multiple substrate utilization is the key mechanism for E1 degradation. Longer term effects of organic carbon concentrations on E1 degrading activity were explored by comparing cultures operating under starvation conditions and cultures operating on a daily feeding cycle. Cultures fed daily showed a large initial increase in E1 degradation activity, attributable to a corresponding increase in biomass. Subsequently, however, E1 degradation activity dropped substantially even though biomass continued to increase, suggesting that E1 degraders were outcompeted when subjected to repeated exposure to high organic carbon concentrations. Conversely, starvation cultures had moderate but sustained increases in E1 degradation rates. Another experiment using MBRs to distinguish organic loads from organic concentrations confirmed the positive effect of organic carbon loads on E1 degradation via biomass growth, indicating that high organic carbon concentrations rather than loads were responsible for the drop in E1 degradation rates. A follow-up study was carried out to determine if altering the duration between feeding cycles could mitigate the negative effects of high organic carbon concentrations on E1 degradation. When cultures were exposed to high organic carbon concentrations (600 mg COD/L over a 6 d period), increasing the duration between feeding cycles improved performance. Conversely, at lower organic carbon concentrations (180 mg COD/L over a 6 d period), no differences in E1 degrading activity was observed. Effects of organic carbon quality on E1 degradation were explored using aged synthetic septage and waters from various treatment and natural sources to culture mixed communities. In these experiments, spectrophotometric methods (specific UV absorbance, spectral slope ratios, excitation-emission matrices, and fluorescence index) were used to characterize organic carbon. Additional analyses and experiments were conducted to rule out organic carbon, nitrogen species, and trace element concentrations as complicating factors. These experiments showed that microbially-derived organic carbon was associated with E1 degrading ability, while organic carbon from natural water sources (river and lake) was not. Furthermore, the experiments with aged synthetic septage suggest that products from cell lysis and/or microbial products under stress by starvation may be important for E1 degradation. Overall, this work shows that multiple substrate utilizing bacteria are important for E1 degradation in wastewater treatment-like systems and indicates various organic carbon parameters that are vital for the selection of these bacteria.
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    Estrone Removal In Treatment Systems Designed For Nitrogen Removal
    (2016-06) Peterson, Kira
    New rules regarding total nitrogen levels in wastewater treatment plant (WWTP) effluents may result in widespread implementation of total nitrogen removal technologies. Conventional nitrification systems do not remove total nitrogen, instead only oxidizing ammonium to nitrate. Conventional nitrification, however, does result in estrogen degradation. One estrogen naturally secreted by humans, estrone (E1), is a major contributor to the estrogenicity of WWTP effluent. The objective of this work was to provide guidance on the impact that changes in wastewater treatment practices could have on E1 removal by comparing E1 degradation in conventional nitrification systems with that in a range of treatment technologies designed to remove total nitrogen from wastewater. E1 removal was assessed in the following lab scale systems: conventional treatment at room temperature, e.g. 21±2 °C, (96% mean E1 removal), conventional treatment at 15 °C (99% mean E1 removal), Modified Ludzack-Ettinger treatment (96% mean E1 removal), aerobic granular sludge treatment (14% mean E1 removal), a sequencing semi-batch treatment (97% mean E1 removal) and an anaerobic ammonium oxidation (ANAMMOX) treatment (99.8% mean E1 removal). This work demonstrated that the choice of nitrogen removal technology used by a treatment plant could have a significant impact on the estrogenicity of WWTP effluent. Of particular note was that granular aerobic sludge treatment was contraindicated for applications where the estrogenicity of the effluent is important to consider, whereas the energy efficient ANAMMOX technology may be a good option for total nitrogen removal in similar situations.
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    Investigating Wastewater Reuse at MnDOT Truck Stations
    (Minnesota Department of Transportation., 2019-05) Heger, Sara; Doro, Jessica; Rutter, Melissa C; Gustafson, Dave; Larson, Sondra
    The University of Minnesota (UMN) and the Minnesota Department of Transportation (MnDOT) conducted a study to determine whether implementing a wastewater reuse program would be a feasible option for MnDOT-owned truck washing stations. MnDOT has 137 truck stations in the state, where trucks are frequently washed to remove road salt build-up. MnDOT recognized an opportunity to potentially reuse the wastewater for appropriate greywater uses and recapture the salt for road use. Sampling was done to assess the wastewater contaminants in truck wash water at 11 truck-washing stations in Minnesota. Then technologies suited to removing organics and total suspended solids (TSS) but not chlorides were reviewed. The recommendation is that either a recirculating sand filter (RSF) or a membrane bioreactor (MBR) would be feasible technologies to use for this purpose. Using the MnDOT truck station in Arden Hills, Minnesota, an economic evaluation was done. Both systems could be used to effectively treat wastewater and produce brine for reuse, but the most economical solution for MnDOT would be to invest in a MBR. Compared with a RSF, an MBR is one-third less expensive over time, primarily due to low material and installation cost as well as a lower annual maintenance costs.
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    Zeolite Incorporated Materials for Targeted Biomass Retention and Pollutant Removal
    (2022-04) Chester, Anndee
    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.