Browsing by Subject "denitrification"

Now showing 1 - 5 of 5
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    Characterization of streams and rivers in the Minnesota River Basin Critical Observatory: water chemistry and biological field collections, 2013-2016
    (2017-09-06) Dolph, Christine, L.; Hansen, Amy, T.; Kemmitt, Katie, L.; Janke, Ben; Rorer, Michelle; Winikoff, Sarah; Baker, Anna; Boardman, Evelyn; Finlay, Jacques, C.; dolph008@umn.edu; Dolph, Christine, L.
    This dataset was collected to inform the Water, Sustainability and Climate Minnesota River Basin Observatory, and was supported by the National Science Foundation under Grant No. 1209402 Water, Sustainability and Climate (WSC) – Category 2, Collaborative: Climate and human dynamics as amplifiers of natural change: a framework for vulnerability assessment and mitigation planning. The dataset contains point locations, watershed areas and water quality information for 231 ditch, stream, river and wetland sites located in the Le Sueur River, Chippewa River, Cottonwood River, Cannon River, Wantonwan River and Blue Earth River basins of Minnesota. Study sites ranged in size from 1st order ditches and streams to an 8th order river. Each of these sites was sampled at least once between 2013-2016 (most sites were sampled multiple times) for one or more of the following parameters: 1) water chemistry (total dissolved nitrogen, nitrate-N, nitrite-N, ammonium-N, particulate nitrogen, soluble reactive phosphorus, total dissolved phosphorus, particulate phosphorus, total phosphorus, dissolved organic carbon, dissolved inorganic carbon, particulate carbon, chlorophyll a, total suspended solids, volatile suspended solids, delta-H-2 and delta-O-18 stable isotopes of site water, specific UV absorbance (SUVA) of site water, fluorescence index (FI) of site water); 2) stable isotopes (delta-C-13, delta-N-15, delta-H-2) of invertebrate consumers, particulate carbon and potential food sources; 3) denitrification rates and characteristics of benthic sediment in agricultural drainage ditches; and 4) stream discharge. This dataset also includes spatial data files containing study site locations and watershed areas delineated for each site.
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    Electrochemical Stimulation of Denitrification In Woodchip Bioreactors and Wetlands
    (2020-10) Ramrattan, Kevin
    Elevated concentrations of nitrate in agricultural runoff can contribute to nutrient enrichment in coastal environments and when ingested can result in methemoglobinemia, a potentially fatal condition in infants. Woodchip bioreactors are ditches constructed at the edge of fields to create anaerobic environments replete with woodchips as carbon and electron sources to promote the growth of denitrifying bacteria to reduce nitrate to inert nitrogen gas. In the Midwest snow melt coincides with fertilizer application, creating a large volume of water with a high nitrate load that limits the efficiency of woodchip bioreactors. The lower temperatures also restrict microbial nitrate-reducing metabolism. One avenue for improving denitrification is the implementation of current-carrying electrodes to supply electron donors to the bacteria. Pyrogenic carbon (Biochar) has been demonstrated to sorb the water-soluble nitrate and acts as an electron shuttle. It is unknown how these two variables in tandem affect denitrification rates, and the microbes associated with these substrates remain uncharacterized. Here, we use batch bioreactors to test the nitrate removal capabilities of woodchip reactors amended with biochar and electrochemical stimulation. Aliquots were collected to measure nitrate removal using a continuous flow analyzer and bacterial communities were characterized based on 16S rRNA gene analysis. Electrode-containing reactors were significantly (p-value < 0.05) less efficient at treating nitrate during the first 8 hours following nutrient injection, but by 24 hours all reactors performed comparably with respect to nitrate removal. Electrode biofilms also had less α-diversity and in terms of β-diversity. Microbiome samples under the influence of electrodes were different from those that were not exposed to any electrochemical stimulation. The difference is bacterial community and the performance lag during the first 8 hours of operation may be a result of increased oxygen concentration in the reactors as a result of O2 evolution during electrolysis in the electrode-containing bioreactors. Biochar had no discernable effect on nitrate removal and did not have a significantly different microbiome from woodchips and water. Electrode biofilm samples were found to enrich Cyanobacteria while the biofilm on the biochar enriched Acidobacteria. Using the results of our experiment we propose the construction of a benchtop-scale electrochemically stimulated constructed wetland reactor.
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    Identification of Microorganisms for the Bioremediation of Nitrate and Manganese in Minnesota Water
    (2018-08) Anderson, Emily
    Bioremediation is a way to safely and cost-effectively remove contaminants using living organisms. In this thesis, microorganisms capable of remediating two pollutants, nitrate and manganese, were identified using culture-dependent and –independent approaches. Nitrate in agricultural wastewater can lead to algal blooms and eutrophication. Edge-of-field woodchip bioreactors are a promising approach to prevent nitrate in wastewater from reaching surface waters by utilizing microbial denitrification to remove nitrate from the system. However, woodchip bioreactors experience low efficiency under cold temperatures, so one strategy to enhance bioreactors in the early spring involves bioaugmentation, or inoculating the bioreactors with cold-adapted denitrifying microorganisms. In order to identify a cold-adapted denitrifier for bioaugmentation, microorganisms were isolated from field woodchip bioreactors and subjected to denitrification testing under cold temperatures, measuring nitrate, nitrite, ammonium, nitrous oxide and dinitrogen gas, as well as whole genome sequencing to identify the presence of genes involved in denitrification and other important microbial processes. Based off of these results, two strains, Microvirgula sp. BE2.4 and Cellulomonas sp. WB94 were recommended for bioaugmentation. In part two, manganese was addressed. High levels of manganese in drinking water can cause health problems, and common treatment methods require cost-intensive chemicals, conditions and maintenance. In this study, a novel algae bioreactor was established to remove manganese from water. In this bioreactor, the algae provided fixed carbon for manganese-oxidizing microorganisms that oxidized the dissolved manganese, precipitating it out of solution. Using a culture-dependent approach, manganese-oxidizing bacteria and fungi were isolated from an environmental sample, including known oxidizers Bosea, Pseudomonas, Plectosphaerella and Phoma and some not previously known to oxidize manganese such as Aeromonas, Skermanella, Ensifer and Aspergillus. A culture-independent approach was also employed to determine how abundant the isolated manganese-oxidizing bacteria are in an actively oxidizing environmental sample. Using nitrate and manganese as examples, this thesis identified useful microorganisms involved in remediation and demonstrated how microorganisms can be utilized to effectively remove pollutants from the environment.
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    Relative importance of soil properties and microbial community for soil functionality: Insights from a microbial swap experiment
    (Wiley, 2016) Delgado-Baquerizo, M; Grinyer, J; Reich, Peter B
    The most accepted theories in soil ecology suggest that broad (e.g. respiration) and specialized (e.g. denitrification) functions are affected differently by resource availability and microbial communities in terrestrial ecosystems. However, there is a lack of experimental approaches quantifying and separating the role of microbial communities from the effect of soil abiotic properties on different aspects of soil ecosystem functionality. Here, we conducted a full-factorial design microcosm experiment and used random forest and structural equation modelling (SEM) analyses to evaluate the role and the relative importance of soil properties (sterile soils A, B and C differing in abiotic attributes) and microbial communities (microbial inoculums from soils A, B and C) in driving soil respiration (i.e. broad functioning), denitrification (i.e. specialized functioning) and four enzyme activities and carbon (C) and nitrogen (N) availability in soil. Soils with the higher total C (soils B and C) promoted the highest soil C and N availability, enzyme activities and broad functioning (i.e. soil respiration); however, we did not find any effect of total C on specialized functions (i.e. denitrification rates). Random forest analyses showed that both soil properties (i.e. total C and pH) and microbial abundance determined broad functioning (i.e. soil respiration), as well as the production of enzyme activities, and C and N availability in soil. However, we found that microbial communities were more important than soil properties for modulating specialized functioning (i.e. denitrification rates) in soil environments. Finally, our SEM also indicated that broad functioning, which is widely distributed across living organisms, is limited by both resource availability and microbial abundance. Furthermore, specialized functioning, which is conducted by particular groups of organisms, may be highly sensitive to changes in the microbial community. Overall, our findings provide direct experimental evidence for the relative importance of soil properties and microbial communities on broad and specialized functioning. Such evidence helps advance our understanding of different drivers of soil ecosystem functioning which will be crucial to developing an ecologically relevant theory about below-ground ecosystem functioning.
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    Using unique carbon source combinations to increase nitrate and phosphate removal in bioreactors
    (2016-06) Roser, Marta
    Nitrogen (N) and phosphorus (P) losses from croplands contribute to impairment of water bodies. This study was conducted to test candidate denitrifying bioreactor media for nitrate-N and dissolved reactive P (DRP) removal from agricultural effluent in drainage ditches. The nitrate-N and DRP removal performance of carbon materials widely available in the Midwest, wood chips (WC) and corn cobs (CC), were compared to treatments of mixed materials: wood chips and hardwood biochar (WC+BC), wood chips and sodium acetate (WC+A), corn cobs and modified coconut coir (CC+MC), and corn cobs, modified coconut coir, and modified macadamia biochar (CC+MC+MBC). Water with a nitrate-N concentration of 20 mg N L-1 and a DRP concentration of 0.3 mg P L-1 was pumped through PVC columns packed with treatment media. The flow rate was adjusted to match the rise and decay of a typical drainage hydrograph. Effluent was sampled after hydraulic residence times (HRT) of 1.5, 8, 12, and 24 h. The laboratory experiment was conducted at 15°C for 14 weeks, 5°C for 13 weeks, and 15°C again for 7 weeks in a temperature controlled chamber, designated the warm run, cold run and rewarm run, respectively. Nitrate-N load reductions ranged from 24% to 96% in the warm and rewarm runs and from 4% to 80% in the cold run. Nitrate-N load reduction performance at all temperatures was in the order of: WC+A > CC+MC > CC > CC+MC+MBC > WC > WC+BC. The nitrate removal rate (NRR) was highest at the 1.5h HRT for the WC+A treatment at all temperatures. Cumulative DRP load reductions in the warm and rewarm runs were statistically higher in the CC, CC+MC, and CC+MC+MBC treatments, with DRP load reductions of 74%, 81%, and 67%, respectively. The WC+A treatment had the highest DRP load reduction in the cold run, with a 45% reduction. The CC, CC+MC, and CC+MC+MBC treatments had both high NRR and high DRP percent concentration removal in the warm and rewarm runs, but the WC+A treatment had higher removal of both nutrients in the cold run and specifically at lower HRTs. For both nitrate-N and DRP load reductions during high flows and cold temperatures, WC+A would be the recommended treatment. Future work should focus on the addition of carbon such as sodium acetate to enhance bioreactor performance during high drainage and cold temperature conditions.