In natural waters, high concentrations of ammonia are toxic to fish, and the oxidation of ammonia to nitrate (NO₃-) consumes large quantities of dissolved oxygen. The influent to municipal wastewater treatment plants in the United States typically contains approximately 40 mg/L of ammonia nitrogen (NH₃₋ N). Almost all of this ammonia must be removed in a wastewater treatment process before the effluent is discharged to the natural environment. This dramatic decrease is accomplished by the aerobic biological process of nitrification, in which ammonia is oxidized to nitrate Biological denitrification is an anoxic biological process in which nitrate (NO₃-) is reduced to nitrogen gas (N₂). Denitrification can increase the alkalinity in activated sludge aeration basins and decrease the concentration of filamentous organisms. The staff at the City of Austin Water Utility decided to implement a denitrification system at Walnut Creek Wastewater Treatment Plant to control filamentous organisms and increase the alkalinity within the aeration basins. The denitrification configuration that the staff implemented was unconventional because no structural changes were made to the aeration basins to encourage denitrification. However, the system functioned well and allowed operators to turn off one of the two air blowers, which saves the plant a significant amount of energy. The current operation has occasional problems, where the alkalinity in the aeration basin decreases or the effluent ammonia increases. When the alkalinity decreases to the point where the pH drops to near 6.0, operators are forced to add chemicals to increase the alkalinity. When the effluent ammonia increases to near the permitted concentration (2.0 mg NH₃-N/L),operators are forced to turn back on the second blower which eliminates the anoxic zone. These problems occur most often during the winter, when the wastewater is the coldest. The wastewater temperature at Walnut Creek varies from a high of 30°C during the summer to a low of 18°C during the winter. The goal of this research was the identification of ways to make the operation more robust which would prevent the need for chemical addition and minimize the use of the second blower. Laboratory-scale reactors were operated to assess possible improvements that could be made to the operation and configuration of the denitrification system at Walnut Creek. The data observed in the laboratory scale experiments showed that the population of denitrifying bacteria limits denitrification and is especially important during the winter. Increasing the solids retention time to 20 days appeared to be the best way to increase the population of denitrifying bacteria and improve denitrification. Improvements can also be made by increasing the volume of the anoxic zone. Increasing the volume of wastewater and biomass recycled will most likely not benefit denitrification until other improvements have been made. Recommendations to the City of Austin Water Utility include the following: 1) increase the solids retention time at Walnut Creek, 2) Increase the volume of the anoxic zone, 3) Separate the anoxic zone from the aerobic section of each aeration basin, 4) During the winter, operate the flow equalization basins to reduce the dissolved oxygen entering the anoxic zone, 5) Continually mix some of the effluent from the aeration basins with the primary effluent in the flow equalization basins. / text

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A novel method for determination of tetrabromobisphenol-A (TBBPA), was developed using gas chromatography-negative ion chemical ionization-mass spectrom- etry (GC-NCI-MS). Samples of municipal wastewater treatment plant (WWTP) influent were analyzed for TBBPA. Levels ranged from 1 to 41 ng/L, with an average of 20 ± 14 ng/L. Matrix effects were shown to be 30 ± 17 % in the influent and -30 ± 11 % in membrane permeate. The method limit of quantitation was 0.1 ng/L TBBPA. Sorption of TBBPA to fresh mixed-liquor suspended solids (MLSS) from a membrane bioreactor (MBR) were studied. In a kinetic study, sorption was found to be essentially complete after 12 hours of exposure to MLSS. Log Koc and log Kd were measured at 4.7 ± 0.8 and 1.9 ± 0.8 respectively (n = 22). These values were much higher than modelled estimates based on Kow (p ≥ 0.05), and higher than modelled estimates based on Kow and pKa (p ≥ 0.05). Data was successfully modelled using the Freundlich isotherm, having a Kf value of 8.5 and an n value of 1.7. TBBPA adsorbed to borosilicate glassware, with a wall-loss coefficient (Kw) of 0.15 ± 0.1 (n ≥ 3). TBBPA levels in WWTP influent varied from 13 to 29 ng/L while effluent concentrations varied from 0 to 2.2 ng/L over the same period. Three pilot-scale membrane bioreactors (MBRs) removed less TBBPA during the same time period, though MBR removal was also significant (p ≥ 0.05). Increasing MBR sludge residence time (SRT) increased removal at the 86 % confidence interval (p = 0.14). A nitrifying MABR was shown to remove TBBPA significantly when spiked with ammonia and TBBPA (p ≥ 0.05), showing that nitrifying bacteria can degrade TBBPA. An MABR hollow fibre was found to adsorb TBBPA. Various soluble microbial products (SMP) were studied from MBRs fed munici- pal influent. Using current measurement practices, SMP were shown to be sensitive to matrix effects. Use of the standard addition technique (SA) can compensate for this. Measurements using SA showed SMP degrades rapidly during storage in the fridge and due to freezing. SA was also used to compare commonly used SMP extraction techniques, and showed that extraction method influences recovery.

Nous avons étudié l’application de plusieurs mesures d’isotopes stables afin de caractériser les processus du cycle de l’azote et les sources d’azote dans les lacs tempérés à diverses échelles spatiales et temporelles. Les résultats d’une étude à travers 65 lacs sur un gradient trophique ont démontré que le ratio d’isotopes stables d’azote (δ15N) des sédiments de surface est un indicateur de l’importance relative des sources d’azote anthropique, mais que ce ratio peut être altéré par la diagenèse. La mesure du δ15N des sédiments demeure néanmoins un outil permettant de déterminer à long terme le changement des charges en azote anthropique aux écosystèmes lacustres et les causes de l’eutrophisation de ces systèmes. Nos résultats d’une étude sur la variation saisonnière de plusieurs isotopes stables dans trois lacs peu profonds situés sur un gradient trophique et ayant différents régimes de stratification ont démontré que cette approche est prometteuse dans les lacs mésotrophes et stratifiés. Dans ces systèmes, le δ15N de la matière organique particulaire (MOP) aurait le potentiel de déterminer les sources d’azote assimilées par le phytoplancton. Cependant les mesures d’isotopes stables du carbone (δ13C) et du ratio C:N indiquent que les apports de matières organiques du bassin versant peuvent altérer les relations observées. Nous avons également constaté une déviation de la relation 1:1 entre les isotopes stables d’azote et d’oxygène (δ18O) du nitrate (NO3-) indiquant son assimilation et sa nitrification simultanée. Cette application est particulièrement prometteuse puisque la nitrification est méconnue dans les lacs et peut exacerber les effets de l’eutrophisation. / We studied the application of multiple stable isotopes measures with the overall objective of improving our understanding of nitrogen cycling and sources in temperate lakes over different spatial and temporal scales. Results from our study across 65 lakes on a trophic gradient demonstrated that surface sediment nitrogen stable isotope ratio (δ15N) is an indicator of the relative importance of anthropogenic N loads, but that diagenesis can alter this ratio. Nevertheless, sediment core δ15N is a powerful proxy for the determination of longterm changing anthropogenic N loads to lake ecosystems and the causes of lake eutrophication. Results from our second study on multiple stable isotopes seasonal variation in three shallow lakes along a trophic gradient and with different stratification regimes have demonstrated that such an approach is particularly promising in mesotrophic and stratified lakes. In these systems, our results showed that the suspended particulate organic matter (SPOM) δ15N could be used to assess the nitrogen sources assimilated by phytoplankton. However, measurement of carbon stable isotopes (δ13C) and C:N ratios from the SPOM showed that the observed relationships can be altered by watershed derived organic matter. We have also found a deviation from the 1:1 relationship between nitrogen and oxygen stable isotopes (δ18O) of nitrate (NO3-) indicating a simultaneous NO3- assimilation and nitrification in our stratified system. The application of dual nitrate isotopes is promising in the study of nitrification since this process is not well understood in lakes and can increase the severity of eutrophication symptoms.

The effectiveness of partial ozonation of return activated sludge for enhancing denitrification and waste sludge minimization were examined. A pair of nitrifying sequencing batch reactors was operated in either aerobic or alternating anoxic/aerobic conditions, with one control and one ozonated reactor in each set. The amount of solids decreased with the ozone dose. Biomass in the anoxic/aerobic reactor was easier to destroy than in the aerobic one, generating approximately twice as much soluble chemical oxygen demand (COD) by cell lysis. Increased COD favoured production of extracellular polymers in ozonated reactors, enhancing flocculation and improving settling. Floc stability was also strengthened in prolonged operation in alternating treatment, resulting in declined solids destruction. Dewaterability was better in alternating reactors than in aerobic ones indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation. Ozone successively destroyed indicator estrogenic compounds, contributing to total estrogen removal from wastewater. Denitrification rate improved up to 60% due to additional carbon released by ozonation. Nitrification rates deteriorated much more in the aerobic than in the alternating reactor, possibly as a result of competition created by growth of heterotrophs receiving the additional COD. Overall, ozonation provided the expected benefits and had less negative impacts on processes in the alternating treatment, although after prolonged operation, benefits could become less significant. The alternating anoxic/aerobic reactor achieved twice the nitrification rates of its aerobic counterpart. Higher removal rates of estrogens were associated with higher nitrification rates, supporting the contention that the nitrifying biomass was responsible for their removal. The alternating treatment offered the better estrogen biodegradation. Microbial populations in both reactors were examined with fluorescent in situ hybridization. Dominance of rapid nitrifiers like Nitrosomonas and Nitrobacter (79.5%) in the alternating reactor, compared to a dominance of slower nitrifiers like Nitrosospira and Nitrospira (78.2%) in the aerobic reactor were found. The findings are important to design engineers, as reactors are typically designed based on nitrifiers’ growth rate determined in strictly aerobic conditions.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Dans un contexte de société où le développement durable est mis de l'avant, la gestion de lisiers provenant de la production d'animaux d'élevage est de plus en plus difficile. En effet, l'épandage de lisiers est soumis à des lois gouvernementales plus strictes afin de prévenir les problèmes environnementaux pouvant y être associés. Une solution envisagée est de traiter le lisier avant de l'épandre afin d'en réduire la charge polluante. L'objet de la présente étude consiste donc à optimiser l'élimination de l'azote contenu dans un lisier de porc synthétique (affluent) à l'aide d'un procédé biologique. Plus spécifiquement, l'étude comprend le démarrage, le développement et l'opération d'un biofiltre percolateur où le lixiviat (l'effluent traité) est recirculé dans le but d'éliminer la charge azotée sous forme d'ammonium (NH 4+ ) de l'affluent. Deux biofiltres percolateurs ont été opérés en étant alimentés en continu en lisier synthétique. La première étape du traitement consiste à un procédé biochimique de nitrification effectué par des bactéries autotrophes dans un environnement en aérobiose. Cette étape est combinée à un procédé de bio-oxydation de la matière organique du lisier. Durant le procédé de nitrification, le NH 4 + est oxydé en nitrite (NO2- ) puis en nitrate (NO3- ). La deuxième étape du traitement est d'associer la nitrification et la bio-oxydation de la matière organique à un procédé de dénitrification où le NO3- obtenu de la nitrification est réduit en azote atmosphérique (N2 ), acceptable pour l'environnement. Différents paramètres ont été variés afin d'optimiser le procédé. Trois méthodes de purge (sans purge, purge en discontinu et purge en continu), deux types de garnissage (sphères de polypropylène et billes de céramiques), quatre débits de recirculation (0, 0.5, 1 et 1.5 L min -1 ) et trois charges du lisier en carbone (137, 275 et 550 g C m-3 h-1 ) et en azote (60, 120 et 240 g N m-3 h -1 ) ont été testés. Principalement, les résultats indiquent que la purge en continu a un effet positif sur la production de biomasse et la production de CO 2 . L'augmentation du débit de recirculation a eu pour effet de diminuer la conversion du NH4+ pour les deux types de garnissages. L'effet a par contre été différent en ce qui concerne la production de CO2 : cette dernière a augmenté dans le biofiltre garni de sphères de polypropylène et diminué dans le biofiltre garni de billes de céramique. Lorsque les biofiltres étaient opérés sans recirculation, des taux de conversion de plus de 99% ont été obtenus. L'augmentation du débit de recirculation a également favorisé la production de NO 2- dans le lixiviat. Pour les deux types de garnissage, le fait d'augmenter la charge azotée de l'affluent a auFenté la production de CO2 pour les deux débits de recirculation testés (0 et 0.5 Lmin-1 ) et des conversions de plus de 99% ont été obtenues sans recirculation du lixiviat. Lorsque le lixiviat était recirculé (débit de 0.5 Lmin -1 testé) avec le biofiltre garni avec des billes de céramique, l'augmentation de la charge azotée a eu pour effet d'augmenter la conversion de NH4+ de 90% à 99%. Par contre, l'augmentation de la charge azotée semble n'avoir aucun effet sur la conversion du NH4+ lorsque les biofiltres sont opérés sans recirculation. [symboles non conformes]

The effectiveness of partial ozonation of return activated sludge for enhancing denitrification and waste sludge minimization were examined. A pair of nitrifying sequencing batch reactors was operated in either aerobic or alternating anoxic/aerobic conditions, with one control and one ozonated reactor in each set. The amount of solids decreased with the ozone dose. Biomass in the anoxic/aerobic reactor was easier to destroy than in the aerobic one, generating approximately twice as much soluble chemical oxygen demand (COD) by cell lysis. Increased COD favoured production of extracellular polymers in ozonated reactors, enhancing flocculation and improving settling. Floc stability was also strengthened in prolonged operation in alternating treatment, resulting in declined solids destruction. Dewaterability was better in alternating reactors than in aerobic ones indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation. Ozone successively destroyed indicator estrogenic compounds, contributing to total estrogen removal from wastewater. Denitrification rate improved up to 60% due to additional carbon released by ozonation. Nitrification rates deteriorated much more in the aerobic than in the alternating reactor, possibly as a result of competition created by growth of heterotrophs receiving the additional COD. Overall, ozonation provided the expected benefits and had less negative impacts on processes in the alternating treatment, although after prolonged operation, benefits could become less significant. The alternating anoxic/aerobic reactor achieved twice the nitrification rates of its aerobic counterpart. Higher removal rates of estrogens were associated with higher nitrification rates, supporting the contention that the nitrifying biomass was responsible for their removal. The alternating treatment offered the better estrogen biodegradation. Microbial populations in both reactors were examined with fluorescent in situ hybridization. Dominance of rapid nitrifiers like Nitrosomonas and Nitrobacter (79.5%) in the alternating reactor, compared to a dominance of slower nitrifiers like Nitrosospira and Nitrospira (78.2%) in the aerobic reactor were found. The findings are important to design engineers, as reactors are typically designed based on nitrifiers’ growth rate determined in strictly aerobic conditions.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Lignosulfonate (LS), a by-product of the pulp and paper industry, may have the potential to increase fertilizer N availability by acting as a urease and nitrification inhibitor. Four consecutive laboratory studies were conducted to evaluate the behavior of LS in agricultural soils. The effects of various types and rates of LS on soil respiration and soil N dynamics were determined. Effects of LS in combination with fertilizers on microbial activity and N dynamics were measured. Due to the high water solubility of LS a leaching column study was conducted to determine the potential leaching of LS. / Higher rates (20% w/w) of LS initially inhibited microbial activity. Generally LS was relatively resistant to degradation by soil microorganisms and small proportions of added LS-C ($<$2.1%) were leached from the soil columns, but leaching was a function of soil and moisture regime. Recovery of added mineral LS-N from soil treated with LS was low ($<$41%). Mineral N recovered from LS plus fertilizer amended soil was higher than recovery from corresponding fertilizer treatments. Lignosulfonate reduced urea hydrolysis and the proportion of added N volatilized as NH$ sb3$-N from a LS plus urea treatment. The mineral N pool from LS plus fertilizer treated soils had significantly lower NO$ sb3$-N concentrations than corresponding fertilizer treatments. Nitrification inhibition was believed to have been due to high fertilizer concentrations. At reduced urea and LS concentrations, LS decreased NO$ sb3$-N recovery in one of four soil types. However, reduced recovery may not have been from nitrification inhibition but possibly from denitrification or chemical reactions between N and phenolics from LS.