Nitrous oxide (N₂O) is a powerful greenhouse gas, and its atmospheric concentration is increasing dramatically. N₂O is produced through the microbially-mediated processes of nitrification and denitrification. Since these processes have different substrates and isotopic enrichment factors, stable isotope analysis (δ¹⁵N and δ¹⁸O) of N₂O can be used to study the production of this important greenhouse gas. Although production in rivers accounts for a significant portion of the global N₂O budget, the isotopic composition of N₂O from this source is poorly characterized. Most of the previous work using stable isotopes of N₂O has been conducted in terrestrial or oceanic environments, and only one published study has measured δ¹⁵N and δ¹⁸O of N₂O produced in a riverine environment. The purpose of this research project was to use stable isotope analysis to characterize the processes responsible for N₂O production in the Grand River, Ontario, Canada, and to determine the spatial and temporal variability of the isotopic composition of the N₂O flux. To meet the study objectives, an offline “purge and trap” method was developed to collect and purify dissolved N₂O for stable isotope analysis. Using this method, δ¹⁵N and δ¹⁸O analysis of dissolved N₂O is possible for samples with concentrations as low as 6 nmol N₂O/L. Due to the isotopic effects of gas exchange and the back flux of tropospheric N₂O, there is a complex relationship between the δ¹⁵N and the δ¹⁸O of source, dissolved, and emitted N₂O in aquatic environments. A simple box model (SIDNO – Stable Isotopes of Dissolved Nitrous Oxide) was developed to properly interpret isotopic data for dissolved N₂O. Using this model, it was determined that the isotopic composition of emitted N₂O is much more representative of N₂O production in aquatic environments than the isotopic composition of dissolved N₂O. If the concentration, δ¹⁵N and δ¹⁸O of dissolved N₂O are measured, the magnitude and isotopic composition of the N₂O flux can be calculated. Sampling downstream of the major wastewater treatment plants (WWTPs) on the Grand River indicates that nitrification and denitrification in the river are strongly tied to diel changes in dissolved oxygen (DO) concentration. During the day, when DO concentrations are high, nitrification or nitrifier-denitrification is the dominant N₂O production pathway, with sediment denitrification also contributing to N₂O production. At night, when DO concentrations are low, denitrification in the sediments and at the sediment / water interface is the dominant production pathway. Using the SIDNO model, N₂O produced during the day was found to have a δ¹⁵N of -22‰ and a δ¹⁸O of 43‰. N₂O produced at night had a δ¹⁵N of -30‰ and a δ¹⁸O of 30‰. The isotopic composition of N₂O emitted from the Grand River is dominated by night-time production downstream of the Waterloo and Kitchener WWTPs during the summer. The flux and time weighted annual average isotopic composition of N₂O emitted from the Grand River is -18.5‰ and 32.7‰ for δ¹⁵N and δ¹⁸O respectively. These values are significantly more depleted than the only other published data for riverine N₂O production. If the Grand River is representative of global riverine N₂O production, these results will have significant implications for the global isotopic budget for atmospheric N₂O.

Avloppsreningsverk står inför uppgiften att rena inkommande vatten för att möta lagstiftade gränsvärden till en så låg kostnad som möjligt. Att syresätta biologiska reningsprocesser är kostsamt eftersom luftningsanordningen förbrukar mycket energi. Ungefär en femtedel av Himmerfjärdsverkets totala elenergiförbrukning går till luftning av biologiska processer. För att öka Himmerfjärdsverkets energieffektivitet startades under 2010 experiment med olika strategier för luftflödesstyrning. En av verkets nitrifikationsbassänger byggdes då om för att möjliggöra zonvis reglering av syrehalten. Syftet med denna studie var att utvärdera reglering med ammoniumåterkoppling och syrehaltsprofil för styrning av Himmerfjärdsverkets nitrifikationsprocess. Utvärderingen baserades på reningsresultat och energiförbrukning. Med nuvarande reglerstrategi varieras luftningen genom återkoppling från syrehalten i den andra av sex zoner i varje luftad bassäng. Denna reglering medför att det uppstår ett överskott av syre i slutet av bassängerna. Det finns således potential att spara energi om luftningen kan regleras så att syreöverskott undviks. Modellsimuleringar i Benchmark Simulation Model no. 1 (BSM1) användes för att jämföra snabb och långsam ammoniumåterkoppling samt olika typer av syrehaltsprofiler inför försök i full skala. Modellen byggdes om och kalibrerades för att efterlikna Himmerfjärdsverkets process. Strategierna utvärderades för två scenarier; ett utan några övre begränsningar för luftningen och ett där Himmerfjärdsverkets luftflödesbegränsningar simulerades. Resultatet från simuleringarna visade att långsam ammoniumåterkoppling var den mest energieffektiva reglerstrategin i båda scenarierna. Resultatet visade även att det var möjligt att minska syretoppar genom en stigande syrehaltsprofil längs med bassängens flödesriktning. Genom fullskaleförsök utvärderades syrehaltsprofil och ammoniumåterkoppling. Resultatet visade att ammoniumåterkoppling var den reglerstrategi som förbrukade minst luft per mängd avskiljt ammoniumkväve och jämfört med ursprunglig reglering erhölls en 16 % lägre energiförbrukning. / Wastewater treatment plants (WWTP) have the challenging task to treat incoming water in order to meet the discharge limits at the lowest possible cost. Aeration of biological treatment processes is one of the most energy consuming posts at a WWTP. At Himmerfjärden WWTP approximately one fifth of the total electric energy consumption is used for aeration of biological processes. With the purpose of making Himmerfjärden WWTP more energy efficient full-scale experiments with different aeration control strategies started in 2010. In one of the aerated tanks a new control system was installed in order to allow zonewise control of the dissolved oxygen (DO). The objective of this master thesis was to evaluate ammonium feedback control and DO-profile control at Himmerfjärden WWTP. The evaluation was made with regard to effluent quality and aeration needs. With the original control strategy aeration is varied to maintain a constant concentration of dissolved oxygen in the second of six zones in each aerated tank. With this control strategy oxygen peaks occur in the last zones of the aerated tank. Thus, there is potential to save energy if these oxygen peaks can be avoided. Simulations were carried out in the Benchmark Simulation Model no. 1 (BSM1) where fast and slow ammonium feedback control and different DO-profiles were evaluated. The model was modified and calibrated to resemble the process at Himmerfjärden WWTP. The simulations showed that the slow ammonium feedback control was the most energy-efficient strategy. The results also showed that it was possible to reduce oxygen peaks by increasing the oxygen set-point along the aerated tank, e.g. an increasing DO-profile. The full-scale experiments included ammonium feedback control and DO-profile control. The results show that ammonium feedback control needed less airflow per amount ammonium removed, compared to both the DO-profile and the original control strategy, with a 16 % lower energy consumption compared to the original control strategy.

Nitrous oxide (N₂O) is a powerful greenhouse gas, and its atmospheric concentration is increasing dramatically. N₂O is produced through the microbially-mediated processes of nitrification and denitrification. Since these processes have different substrates and isotopic enrichment factors, stable isotope analysis (δ¹⁵N and δ¹⁸O) of N₂O can be used to study the production of this important greenhouse gas. Although production in rivers accounts for a significant portion of the global N₂O budget, the isotopic composition of N₂O from this source is poorly characterized. Most of the previous work using stable isotopes of N₂O has been conducted in terrestrial or oceanic environments, and only one published study has measured δ¹⁵N and δ¹⁸O of N₂O produced in a riverine environment. The purpose of this research project was to use stable isotope analysis to characterize the processes responsible for N₂O production in the Grand River, Ontario, Canada, and to determine the spatial and temporal variability of the isotopic composition of the N₂O flux. To meet the study objectives, an offline “purge and trap” method was developed to collect and purify dissolved N₂O for stable isotope analysis. Using this method, δ¹⁵N and δ¹⁸O analysis of dissolved N₂O is possible for samples with concentrations as low as 6 nmol N₂O/L. Due to the isotopic effects of gas exchange and the back flux of tropospheric N₂O, there is a complex relationship between the δ¹⁵N and the δ¹⁸O of source, dissolved, and emitted N₂O in aquatic environments. A simple box model (SIDNO – Stable Isotopes of Dissolved Nitrous Oxide) was developed to properly interpret isotopic data for dissolved N₂O. Using this model, it was determined that the isotopic composition of emitted N₂O is much more representative of N₂O production in aquatic environments than the isotopic composition of dissolved N₂O. If the concentration, δ¹⁵N and δ¹⁸O of dissolved N₂O are measured, the magnitude and isotopic composition of the N₂O flux can be calculated. Sampling downstream of the major wastewater treatment plants (WWTPs) on the Grand River indicates that nitrification and denitrification in the river are strongly tied to diel changes in dissolved oxygen (DO) concentration. During the day, when DO concentrations are high, nitrification or nitrifier-denitrification is the dominant N₂O production pathway, with sediment denitrification also contributing to N₂O production. At night, when DO concentrations are low, denitrification in the sediments and at the sediment / water interface is the dominant production pathway. Using the SIDNO model, N₂O produced during the day was found to have a δ¹⁵N of -22‰ and a δ¹⁸O of 43‰. N₂O produced at night had a δ¹⁵N of -30‰ and a δ¹⁸O of 30‰. The isotopic composition of N₂O emitted from the Grand River is dominated by night-time production downstream of the Waterloo and Kitchener WWTPs during the summer. The flux and time weighted annual average isotopic composition of N₂O emitted from the Grand River is -18.5‰ and 32.7‰ for δ¹⁵N and δ¹⁸O respectively. These values are significantly more depleted than the only other published data for riverine N₂O production. If the Grand River is representative of global riverine N₂O production, these results will have significant implications for the global isotopic budget for atmospheric N₂O.

<p>Large amounts of human pharmaceutical products are consumed worldwide. Many drugs and their metabolites, referred to as pharmaceutically active compounds (PhACs), are not fully metabolized prior to household discharge resulting in their common occurrence in wastewater treatment plants (WWTPs). In most instances, WWTPs present the first treatment opportunity for removing PhACs and preventing significant environmental exposure. Because most municipal WWTPs rely on the microbial component of the activated sludge process, there is a need to estimate the influence of PhACs in wastewater influent on the activated sludge microbial communities and the treatment performance of WWTPs. The objective of this dissertation was to determine the impact of selected PhACs (i.e., ketoprofen, naproxen, clofibric acid, carbamazepine and gemfibrozil) on activated sludge microorganisms and key individual microbial species in domestic wastewater treatment. Analyses were performed in batch reactors initially and then in laboratory-scale sequencing batch reactors (SBR) which mimic WWTP operations. Ammonia oxidizing bacteria (AOB) were selected as indicator organisms because of their importance in wastewater treatment and demonstrated sensitiveness to toxic compounds. </p><p>The batch experiments results suggested that microbial growth inhibition was correlated to organic loadings. In the presence of 0.2% (v/v) ethanol, significant inhibition, ranging from 34 to 43%, was observed for all PhACs other than clofibric acid. </p><p>Nitrification inhibition studies using Nitrosomonas europaea, a model AOB strain showed that ketoprofen, naproxen, carbamazepine and gemfibrozil inhibited nitrite production. The corresponding maximum nitrification inhibition rates were 25, 29, 22 and 26%, respectively. Inhibition was shown to increase with PhAC concentration for concentrations greater than 0.1 µM. Results from membrane integrity tests suggest that the inhibition may be due to the disturbance of the cell membrane by PhACs and such inhibition was shown to be irreversible. </p><p>Even though PhACs were shown to inhibit the nitrification rate in pure culture studies, the performance of SBRs exposed to individual PhACs was not adversely affected neither in terms of COD nor ammonia removal. Microbial fingerprinting for both total bacteria and AOB confirmed that no significant shifts occurred when microbial communities were exposed to PhACs. However, some PhACs introduced in binary mixture were found to both inhibit the nitrification of N. europaea as well as the performance of SBRs. The mixture composed of 0.5 &#956;M ketoprofen and 0.5 &#956;M naproxen showed significant inhibition (25%) on the nitrite production of N. europaea although neither 0.5 &#956;M ketoprofen nor 0.5 &#956;M naproxen had significant effect when presented alone. Similarly, both COD and ammonia removal were significantly impacted by binary mixtures of PhACs. These results suggest that mixture effects can play an important role in an overall treatment's nitrification potential and this phenomenon should be further investigated.</p> / Dissertation

Fixed nitrogen is important as a nutrient for organic matter formation and as an electron donor (nitrification) and acceptor (denitrification) for energy generation, but it is scarcely available in aquatic systems. Nitrification oxidizes ammonium to nitrite and nitrate. Denitrification uses these fixed species to form dinitrogen gas. The classic understanding of the nitrogen cycle requires dissolved oxygen for nitrification and assumes denitrification reduces nitrate to dinitrogen through various intermediates in anaerobic conditions. The global nitrogen budget is imbalanced with more marine denitrification measrued than previously estimated in the classic nitrogen cycle, suggesting alternative anaerobic nitrification and denitrification pathways exist. One alternative denitrification pathway is anammox, which directly oxidizes ammonium to dinitrogen with nitrite as the electron acceptor. Other alternative pathways for both nitrification and denitrification involve redox metals as catalysts. Manganese-catalyzed anaerobic nitrification and denitrification are thermodynamically favorable at neutral pH. However, experimental evidence for these processes is still lacking. This investigation seeks to uncover evidence of manganese-catalyzed nitrification and denitrification in saltmarsh sediments. Batch reactors with anaerobic sediment slurries from a saltmarsh in coastal Georgia were incubated in the presence and absence of colloidal manganese oxides and isotope-labeled ammonium and nitrate to trace dinitrogen formation. Results show that denitrification is more prominent in the manganese-treated reactors and that the classic denitrification pathway may not be substantial in shallow saltmarsh sediments. These data indicate that anammox and/or manganese-coupled denitrification are major contributors to the removal of fixed nitrogen. Ammonium removal in the manganese-treated reactors is accompanied by a high nitrite production compared to the nitrogen-only treatment, indicating manganese-coupled denitrification exists and/or anammox is promoted in the presence of manganese. Primary productivity is generally high in saltmarshes, but oxygen penetrates less than a few millimeters in the sediment. These observations suggest that oxygenic nitrification does not fuel denitrification below the sediment-water interface. The data show that manganese may play a role in the formation of nitrite and nitrate in oxygen-limited sediments.

The main contents of campus sewage are BOD and inorganic nutrients. Conventional secondary treatment processes can remove BOD efficiently, whereas the inorganic nutrients remain mostly left. Therefore, the effluents may cause eutrophication to the receiving water bodies. Using constructed wetland treatment system to reduce nutrients become more and more popular recently. Vertical flow type subsurface process is particularly efficient in nitrogen transformations. In this research we studied the nitrogen transformation dynamics by using different types vertical flow constructed wetland system with various natural materials as the media to treat the secondary effluents from a campus sewage treatment plant. Six self designed experiment columns with broken concrete blocks, oyster shells, different sizes of marble granules, and river sands were used for this study as vertical flow constructed wetland systems. The methods of operation included batch type, continuous flow with filled water and trickling filter type, which were tested by controlling the influent flows into those six test columns. The efficiencies of various combinations in treatments and their mechanisms were discussed in the study. The experimental results showed that the best ammonium nitrogen removal efficiency was measured equal to 46.6% in batch type operations, while the continuous flow with filled water type operation showed the best performance by using concrete blocks as the media (42.8%). However, the best ammonium nitrogen removal rate in the trickling operation was found in the column with media of 3 mm marble granules (91.1%). The medium of river sand obtained the best phosphorous removal rate by using a batch flow operation. Vegetating presented only minor contributions in the column with medium of smaller grain size materials. The optimum C/N ratios for denitification tests are 3.5 and 3 by using the media of concrete and oyster, respectively.

The aim of this investigation was to use hybrid constructed wetlands to treat the secondary effluents from NSYSU campus sewage treatment plant, which had high phosphate and ammonium nitogen and from a textile industrial wastewater treatment plant, which had high chemical oxygen demand(COD) . The purpose of this study is to design optimum operation, conditions and to select suitable types of filter media through optimum combinations of vertical flow (VF) and horizontal flow (HF) constructed wetland systems. The flow regimes for vertical flow operation in this study include continuous flow with filled water, trickling filter type and batch type, while the flow types for horizontal flow operation include high water level and low water level effluents. The experimental of results showed that the best ammonium nitrogen removal efficiency was found in trickling filter type, which was because high oxygen was provided under this flow pattern creating a suitable condition for nitrification , especially in V3 column(39.09%), while the best denitrification effect was fonnd in low water level horizontal operation, especially in H2 bed(42.56%). The experimental results of treating the Everest effluent from the wastewater treatment plant showed that the flow regime in V3 system had best removal of COD in batch type. In trickling filter and low water level type, the optimum hybrid of V3+H3 had the COD removal efficiency eqail to(33.3%)+(49.8%) respectirely .For the experimental results of tolerance of macrophyte, Hedycbium coronarium Koenig live well, but no significant removal efficiencies of nutrient was fund.

High strength wastewater (HSWW) generated in food processing industries is characterized by high organic carbon and nitrogen content, and thus high oxygen demand. Biological nitrogen removal (BNR) is a technology widely used for the treatment of HSWW. Food processing facilities practice sanitation to keep food contact surfaces clean and pathogen-free. Benzalkonium chlorides (BACs) are cationic quaternary ammonium antimicrobial compounds (QACs) common in industrial antimicrobial formulations. BAC-bearing wastewater generated during sanitation applications in food processing facilities is combined with other wastewater streams and typically treated in BNR systems. The poor selectivity and target specificity of the antimicrobial BACs negatively impact the performance of BNR systems due to the susceptibility of BNR microbial populations to BAC. Objectives of the research were: a) assessment and quantification of the inhibitory effect of QACs on the microbial groups, which mediate BNR in HSWW treatment systems while treating QAC-bearing HSWW; b) evaluation of the degree and extent of the contribution of QAC adsorption, inhibition, and biotransformation on the fate and effect of QACs in BNR systems. A laboratory-scale, multi-stage BNR system was continuously fed with real poultry processing wastewater amended with a mixture of three benzalkonium chlorides. The nitrogen removal efficiency initially deteriorated at a BAC feed concentration of 5 mg/L due to complete inhibition of nitrification. However, the system recovered after 27 days of operation achieving high nitrogen removal efficiency, even after the feed BAC concentration was stepwise increased up to120 mg/L. Batch assays performed using the mixed liquors of the BNR system reactors, before, during, and post BAC exposure, showed that the development of BAC biotransformation capacity and the acquisition of resistance to BAC contributed to the recovery of nitrification and nitrogen removal. Kinetic analysis based on sub-models representing BNR processes showed that BAC inhibition of denitrification and nitrification is correlated with BAC liquid-phase and solid-phase concentrations, respectively. Simulations using a comprehensive mathematical BNR model developed for this research showed that BAC degradation and the level of nitrification inhibition by BAC were dynamic brought about by acclimation and enrichment of the heterotrophic and nitrifying microbial populations, respectively. The fate and effect of BACs in the BNR system were accurately described when the interactions between adsorption, inhibition, and resistance/biotransformation were considered within the conditions prevailing in each reactor. This work is the first study on the fate and effect of antimicrobial QACs in a continuous-flow, multi-stage BNR system, and the first study to quantify and report parameter values related to BAC inhibition of nitrification and denitrification. Results of this study enable the rational design and operation of BNR systems for the efficient treatment of QAC-bearing wastewater. The outcome of this research provides information presently lacking, supporting the continuous use of QACs as antimicrobial agents in food processing facilities, when and where needed, while avoiding any negative impacts on biological treatment systems and the environment.

This research estimates nitrogen removal from stormwater runoff using a denitrifying bioretention system using the USEPA Storm Water Management Model Version 5 (SWMM-5). SWMM-5 has been used to help planners make better decisions since its development in 1971. A conventional bioretention system is a type of Low Impact Development (LID) technology, which designed without a media layer specifically for achieving nitrogen removal. More recently studies have showed that high TN removal efficiencies are possible when incorporating a denitrification media layer. These systems are known as denitrifying bioretention systems, or alternative bioretention systems. LID projects are currently being designed and developed in Sarasota County, Florida. These projects include a bioretention cell retrofit project on Venice East Blvd., in Venice, FL where thirteen bioretention cells will be developed. Although implementation of LID has already begun in southwest Florida, little research exists on whether these systems are effective at reducing non-point sources of nutrients. Therefore, the overall goal of this research project was to investigate the performance of a proposed bioretention system in Venice, FL to treat non-point sources of nitrogen from stormwater runoff. An alternative bioretention cell (ABC) model was designed to conceptually address water routing through a layered bioretention cell by separating the model into treatment layers- the layers where the nitrification and denitrification reactions are expected to occur within an alternative bioretention system (i.e., nitrification is assumed to occur in the sand media layer, and denitrification in the wood chip media layer). The bioretention cell configuration was based largely on the development plans provided by Sarasota County; however, the configuration incorporated the same electron donor media for denitrification that was used in a prior study (i.e., wood chips). Site-specific input parameters needed to calibrate the ABC model were obtained from laboratory analyses, the literature, and the US Geological website (websoilsurvey.nrcs.usda.gov). Using a mass balance approach, and the hydraulic residence time (HRT) values from the results of a previous study, first-order loss rate coefficients for both nitrification and denitrification (k1 and k2, respectively) were estimated. The rate coefficients were then used to develop treatment expression for nitrification and denitrification reactions. The treatment expressions were used to estimate the annual load reductions for TKN, NO3--N, and TN at the Venice East Blvd. bioretention retrofit site. Six storm events were simulated using a range of nitrogen concentrations. The simulation results showed minimal nitrification removal rates for storm events exceeding 1 inch, due to the planned bioretention system area being only 1% of the subcatchment area. A new ABC model was created (based on EPA bioretention cell sizing guidelines), to be 6% of the subcatchment area. Both systems were used to estimate TN removal efficiencies. The larger sized ABC model results showed average TKN, NO3--N and TN reductions of 84%, 96%; and 87%, respectively; these are comparable to results from similar studies. Results indicate that adequate nitrogen attenuation is achievable in the alternative bioretention system, if it is sized according to EPA sizing guidelines (5-7%).

published_or_final_version / Civil Engineering / Master / Master of Philosophy