No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Low dissolved oxygen (DO) biological nutrient removal (BNR) is becoming a viable option to improve the energy efficiency of BNR. To properly model and design BNR processes for low DO operation, it is critical to fully understand how nitrifier, denitrifier, and polyphosphate accumulating organism (PAO) oxygen kinetics adapt in a shift from traditional DO operation (2 mg O2/L or more) to low DO operation. Research characterizing how oxygen kinetics shift over time in activated sludge biomass adapting to low DO is limited. Therefore, a method to characterize oxygen kinetics for nitrifiers, denitrifiers, and PAOs simultaneously is lacking. Here a method was developed to simultaneously measure the oxygen kinetics of nitrifiers, denitrifiers, and PAOs. This method, termed the SND and P-Uptake Oxygen Kinetics test, was able to estimate the ammonia oxidizing bacteria (AOB) oxygen half-saturation coefficient, ammonia maximum removal rate, denitrifier oxygen inhibition coefficient, total inorganic nitrogen (TIN) maximum removal rate, PAO oxygen half-saturation coefficient, phosphorus maximum uptake rate, and a simultaneous nitrification and denitrification (SND) optimum operation point. Three tests were conducted on the Virginia Initiative Plant (VIP) BNR Activated Sludge Pilot while it was operating at a process DO of 2 mg O2/L, and one test while it was operating at 1.5 mg O2/L. The measurements among the three initial tests showed high similarity in their parameter estimates. Estimated oxygen half-saturation and oxygen inhibition coefficients were compared to current suggested ranges and were within the expected magnitudes. At 2 mg O2/L, denitrifier oxygen inhibition coefficients and PAO oxygen half-saturation coefficients were estimated to be remarkably low here, under 0.4 and 0.1 mg O2/L, respectively. AOB oxygen half-saturation coefficients were variable here in the range of 0.62 to 2.57 mg O2/L, seeming to vary with available ammonia concentrations. Upon comparison with a previously developed respirometric test for nitrifier oxygen kinetics, termed the Declining DO test, the AOB oxygen half-saturation coefficient from the SND and P-Uptake Oxygen Kinetics test and the Declining DO test, when both were conducted on the VIP BNR Pilot, showed a similar trend. This provided validation for the AOB oxygen kinetics here and the usefulness of the test developed here. Additionally, measuring and plotting AOB and denitrifier oxygen kinetics together produced an intersection point where ammonia removal rates were equal to TIN removal rates. This intersection point was an optimum point for SND during the conditions of the test. This method can be used to characterize and track oxygen kinetic changes in a BNR system adapting from high to low DO. / Master of Science / Aerating biological processes in wastewater treatment plants is necessary to facilitate nitrogen and phosphorus removal but is extremely costly. Traditional dissolved oxygen concentrations in these processes are 2 mg O2/L or higher. Operating processes with low dissolved oxygen (DO) concentrations, less than 1 mg O2/L, can cut costs significantly. However, designing processes at low DO concentrations requires knowledge of how microorganisms utilize substrate with lower oxygen availability and how substrate utilization develops when gradually decreasing the DO concentration in a process. Here, a method was developed to measure the parameters describing the relationship between substrate utilization and DO concentration for the microorganisms responsible for nitrogen removal (nitrifiers and denitrifiers) and phosphorous removal (polyphosphate accumulating organisms). Additionally, the method provides an optimum DO setpoint for simultaneous nitrification and denitrification (SND) during testing conditions. This method, termed the SND and P-Uptake Oxygen Kinetics test, was able to estimate the following parameters simultaneously: ammonia oxidizing bacteria (AOB) oxygen half-saturation coefficient, ammonia maximum removal rate, denitrifier oxygen inhibition coefficient, total inorganic nitrogen (TIN) maximum removal rate, PAO oxygen half-saturation coefficient, and phosphorus maximum removal rate. Three tests were conducted on the Virginia Initiative Plant (VIP) BNR Activated Sludge Pilot while it was operating at a process DO of 2 mg O2/L, and one test while it was operating at 1.5 mg O2/L. The measurements among the three initial tests showed high similarity in their parameter estimates. Estimated oxygen half-saturation and oxygen inhibitions coefficients were compared to current suggested ranges and were within the expected magnitudes. Upon comparison with a previously developed test for nitrifier oxygen kinetics, termed the Declining DO test, the AOB oxygen half-saturation coefficient from the SND and P-Uptake Oxygen Kinetics test and the Declining DO test when both were conducted on the VIP BNR Pilot showed a similar trend, providing validation for the usefulness of the test developed here.

Moving bed biofilm reactors (MBBRs) have been used effectively to reach low nutrient levels in northern Europe for nearly 20 years at cold temperatures. A relatively new technology to the US, the MBBR has most typically been used in a post-denitrification configuration with methanol for additional nitrate removal. Methanol has clearly been the most commonly used external carbon source for post-denitrification processes due to low cost and effectiveness. However, with the requirement for more US wastewater treatment plants to reach effluent total nitrogen levels approaching 3 mg/L, alternative electron donors could promote more rapid MBBR startup/acclimation times and increased cold weather denitrification rates. Bench-scale MBBRs evaluating four different electron donor sources, specifically methanol, ethanol, glycerol, and sulfide (added as Na2S), were operated continuously at 12 °C, and performance was monitored by weekly sampling and insitu batch substrate limiting profile testing. Ethanol and glycerol, though visually exhibited much higher biofilm carrier biomass content, performed better than methanol in terms of removal rate (0.9 and 1.0 versus 0.6 g N/m²/day.) Maximum denitrification rate measurements from profile testing suggested that ethanol and glycerol (2.2 and 1.9 g N/m²/day, respectively) exhibited rates that were four times that of methanol (0.49 g N/m²/day.) Sulfide also performed much better than any of the other three electron donors with maximum rates at 3.6 g N/m²/day and with yield (COD/NO₃-N) that was similar to or slightly less than that of methanol. Overall, the yield and carbon utilization rates were much lower than expected for all four electron donors and much lower than previously reported; indicating that there could be advantages for attached growth versus suspended growth processes in terms of carbon utilization rates. The batch limiting NO₃-N and COD profiles were also used to find effective K_s values. These kinetic parameters describe NO₃-N and COD limitations into the biofilm, which affect the overall denitrification rates. Compared to the other electron donors, the maximum rate for methanol was quite low, but the estimated K_s value was also low (0.4 mg/L N). This suggests high NO₃-N affinity and low mass transfer resistance. The other three electron donors estimated higher K_s values, indicating that these biofilms have high diffusion resistance. Biofilm process modeling is more complex than for mechanistic suspended growth, since mass transfer affects substrate to and into the biofilm. Simulating the bench-scale MBBR performance using BioWin 3.0, verified that μ_max and boundary layer thickness play key roles in determining rates of substrate utilization. Adjustments in these parameters made it possible to mimic the MBBRs, but it is difficult to determine whether the differences are due to the MBBR process or the model. / Master of Science

Nitrogen (N) fertilizer is a required mineral nutrient in containerized crop production that is necessary for crop growth and development. Due to production aspects, the N added to crops far exceeds the amount that the plant uses and such inefficiency results in adverse environmental impacts related to N gaseous and aqueous emissions from containers on the production site. Growers are responsible for optimizing nutrient usage in crop production. Three studies were conducted to investigate and better understand the fate of applied N fertilizers, the transformations associated with individual N sources, and the influence of substrate texture on losses of aqueous and gaseous N species. The first study conducted a mass balance looking at the four major avenues of N fate in an open-air container production setting (plant uptake, immobilized or bound N in a pine bark substrate, leached aqueous N, and gaseous emissions of N), the mass balance was speciated to measure applied and intermediary forms of N fertilizer species to provide insight into the overall fate of applied N. Show Off® Forsythia ×intermedia' Mindor' were grown using two control-release fertilizer (CRF) treatments [AN (ammonium-nitrate based) or UAN (urea ammonium-nitrate)] products. This study determined that 97% of the released N from the CRF treatments was lost via aqueous or gaseous pathways. The aqueous losses were inferred to be predominately composed of NO3-N, while the gaseous emissions were inferred to be predominately lost as inert nitrogen gas (N2). During a second experiment, individual N sources treatments [urea (CH4N2O), ammonium (NH4+), and nitrate (NO3-)] were applied to established containers of At LastⓇ Rosa x 'HORCOGJIL' grown in a pine bark substrate in either open wall high tunnel or a glass greenhouse to determine subsequent reaction sequence and fate based on applied N source. By applying an individual form of N it was determined that based on the N source applied, a sequential set of reactions occurs based on the N source. This study determined that the reactive N gaseous species occurred from the hydrolysis of CH4N2O-N to NH4+ and the nitrification of NH4+ to NO3- and then the denitrification of NO3- to N2. Hibiscus moscheutos' Vintage wine' was grown in either a coarse or fine texture substrate utilizing either a water-soluble fertilizer or a CRF to compare the influence of pine bark texture on N leachate losses and RN gaseous emissions. There were few differences between the two substrate texture treatments related to aqueous or gaseous N losses. In both experiments, the Hibiscus grown in the fine texture substrate resulted in higher above and below-ground biomass at experimental termination. Working with growers to develop best management practices will help to improve the use of N fertilizers and impact growers economically, while simultaneously reducing losses leading to less environmental impact on the areas surrounding production sites. / Doctor of Philosophy / Nitrogen (N) fertilizer is a crucial mineral nutrient input to produce container crops, however excessive application can have detrimental effects on the environment including gaseous N emissions and N leaching leading to water pollution. Therefore, three studies were conducted to investigate N losses during production and potential mitigation strategies using common management practices in the production of container crops. During the first study investigating how N fertilizer is lost from production, results showed that a significant portion of the N added to the containers is either emitted from the containers into the atmosphere or leached from the container. Only a small fraction of the applied N was utilized by the plants for growth and development. The second study investigated the reactions and transformations of different N fertilizers sources. When applying single N sources urea (CH4N2O), ammonium (NH4+), or nitrate (NO3-) result in a set of sequential reactions that occur based on the applied N source. Urea is hydrolyzed via CH4N2O hydrolysis leading to the formation of NH4+ which is nitrified via nitrification to NO3- which is denitrified via denitrification leading to the production of N2 gas. In the final study two pine bark substrate classes were compared when using either a water-soluble fertilizer (WSF) or a controlled-release fertilizer (CRF). Surprisingly there were only a few differences between the two substrate treatments in either the WSF or CRF studies. This body of work show the importance of investigating N fertilizer usage in container crop production. Collaboration between researchers and growers is crucial to develop management practices that maximize the associated economic input of N fertilizers and minimize losses of N that are detrimental to the environment.