Sorption of VOCs on material surfaces as the deciding factor when choosing a ventilation strategy

The interaction between different ventilation strategies, and the adsorption and desorption of volatile organic compounds on material surfaces in small test chambers, is investigated. In test chamber experiments, nylon carpet was exposed to a mixture of toluene and α-pinene at two different dosing rates. The ventilation strategies were chosen to mimic the conditions in real buildings, i.e. with an air exchange rate of 2 h⁻¹ during the working day (8–17) and a rate of 0.67 h⁻¹ during the remainder of the 24 h. The results show that the sorption behavior has to be included when estimating the concentration variations in a room based on source characteristics and ventilation rates. The software application “EnviSim” was used to model the concentrations in a model room based on the experimental conditions. As the ventilation strategy influences the resulting concentrations, it is recommended that the ventilation system be “turned on” a couple of hours before the start of the working day and “turned down” again soon after the occupants have left the building.     

Heat balance and tracer gas technique for airflow rates measurement and gaseous emissions quantification in naturally ventilated livestock buildings

Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO₂-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH₃, CH₄, CO₂ and N₂O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO₂-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO₂-balance. The AFRs, subject to TGT, were 0.12 m³ s⁻¹ m⁻², 1.15 m³ s⁻¹ cow⁻¹, 0.88 m³ s⁻¹ LU⁻¹, 56 h⁻¹, 395 m³ s⁻¹ and 470 kg s⁻¹ through summer seasons, and 0.08 m³ s⁻¹ m⁻², 0.83 m³ s⁻¹ cow⁻¹, 0.64 m³ s⁻¹ LU⁻¹ 39 h⁻¹, 275 m³ s⁻¹ and 328 kg s⁻¹ through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h⁻¹ cow⁻¹; and through winter seasons were 4.8, 19, 2332 and 2.6 g h⁻¹ cow⁻¹, for NH₃, CH₄, CO₂ and N₂O, respectively.     

Natural ventilation with traditional Korean opening in contemporary house

In this study, a natural ventilation opening was designed based on the traditional Korean opening to improve indoor environment on the contemporary house. The prototype of the opening was composed of three hanji papers and two air layers to improve airflow rate, and also to recovery heat lose. The performance of the heat recovery and airflows of the prototype was measured in laboratory, and the CFD simulation was used to verify its performance in the contemporary house. The airflow rate of the prototype is exponentially increased according to the pressure differences, and it ranges from 12.6 to 39.6 m³/m² h in 3–10 Pa, pressure difference. The total amount of heat recovery ranges from 47.8 to 67.7 W/m² in the prototype, and the heat recovery rate is about 25% at 10 Pa. In the CFD simulation, the prototypes were installed at 25% of the total window areas of the model house. The outside air was totally supplied through the prototypes at 67.2 m³/h in the model house, and it is equivalent to 0.2 h⁻¹ ventilation rate. The results show that the prototype is capable of providing natural ventilation even at low wind pressure, and also that it prevent cold draft in heating period. Further analysis of the ventilation performance including the thermal force is needed to apply the prototype to the contemporary house.     

Biodegradation of geosmin by a novel Gram-negative bacterium; isolation, phylogenetic characterisation and degradation rate determination

Biologically active sand filters within water treatment plants (WTPs) are now recognised as an effective barrier for the removal of geosmin. However, little is known regarding the actual microbiological processes occurring or the bacteria capable of degrading geosmin. This study reports the enrichment and isolation of a Gram-negative bacterium, Geo48, from the biofilm of a WTP sand filter where the isolate was shown to effectively degrade geosmin individually. Experiments revealed that Geo48 degraded geosmin in a planktonic state by a pseudo-first-order mechanism. Initial geosmin concentrations ranging from 100 to 1000 ng/l were shown to directly influence geosmin degradation in reservoir water by Geo48, with rate constants increasing from 0.010 h⁻¹ (R² = 0.93) to 0.029 h⁻¹ (R² = 0.97) respectively. Water temperature also influenced degradation of geosmin by Geo48 where temperatures of 11, 22 and 30 °C resulted in rate constants of 0.017 h⁻¹ (R² = 0.98), 0.023 h⁻¹ (R² = 0.91) and 0.019 h⁻¹ (R² = 0.85) respectively. Phylogenetic analysis using the 16S rRNA gene of Geo48 revealed it was a member of the Alphaproteobacteria and clustered with 99% bootstrap support with an isolate designated Geo24, a Sphingopyxis sp. previously described as degrading geosmin but only as a member of a bacterial consortium. Of the previously described bacteria, Geo48 was most similar to Sphingopyxis alaskensis (97.2% sequence similarity to a 1454 bp fragment of the 16S rRNA gene). To date, this is the only study to report the isolation and characterisation of a Gram-negative bacterium from a biologically active sand filter capable of the sole degradation of geosmin.     

Characterization of copper bioreduction and biosorption by a highly copper resistant bacterium isolated from copper-contaminated vineyard soil

Copper is an essential but toxic heavy metal that negatively impacts living systems at high concentration. This study presents factors affecting copper bioremoval (bioreduction and biosorption) by a highly copper resistant monoculture of Pseudomonas sp. NA and copper bioremoval from soil. Seven bacteria resistant to high concentration of Cu(II) were isolated from enrichment cultures of vineyard soils and mining wastes. Culture parameters influencing copper bioreduction and biosorption by one monoculture isolate were studied. The isolate was identified by 16S rRNA gene sequence analysis as a Pseudomonas sp. NA (98% similarity to Pseudomonas putida, Pseudomonas plecoglossicida and other Pseudomonas sp.). The optimal temperature for growth was 30 °C and bioremoval of Cu(II) was maximal at 35 °C. Considerable growth of the isolate was observed between pH 5.0 and 8.0 with the highest growth and biosorption recorded at pH 6.0. Maximal bioreduction was observed at pH 5.0. Cu(II) bioremoval was directly proportional to Cu(II) concentration in media. Pseudomonas sp. NA removed more than 110 mg L^− 1 Cu(II) in water within 24 h through bioreduction and biosorption at initial concentration of 300 mg L^− 1. In cultures amended with 100 mg L^− 1, 20.7 mg L^− 1 of Cu(II) was biologically reduced and more than 23 mg L^− 1 of Cu(II) was biologically removed in 12 h. The isolate strongly promoted copper bioleaching in soil. Results indicate that Pseudomonas sp. NA has good potential as an agent for removing copper from water and soil.     

Indoor/outdoor relationship of fine particles less than 2.5 μm (PM2.5) in residential homes locations in central Indian region

The high levels in developing countries and the apparent scale of its impact on the global burden of disease underline the importance of particulate as an environmental health risk and the consequence need for monitoring them particularly in indoor microenvironment. PM2.5 μm, 1.0 μm, 0.5 μm and 0.25 μm were measured inside and outside 14 residential homes located in different microenvironment during a six-month period (October 2007–March 2008) in Agra located in the central region of India. Particulate mass concentrations were measured using Grimm aerosol spectrometer for 24 h inside and outside the homes located in roadside, rural and urban area, along with the field survey study done in the same region. The indoor average concentrations recorded for PM_2.5, PM_1.0, PM_0.5 and PM_0.25 were maximum for the rural homes (173.03 μgm⁻³, 133.26 μgm⁻³, 96.02 μgm⁻³, 8.56 μgm⁻³) followed by roadside homes (137.93 μgm⁻³, 117.09 μgm⁻³, 68.17 μgm⁻³, 8.55 μgm⁻³) and then by urban homes (135.55 μgm⁻³, 102.92 μgm⁻³, 38.38 μgm⁻³, 6.35 μgm⁻³). The average I/O ratios for PM_2.5, PM_1.0, PM_0.5 and PM_0.25 in roadside and rural areas were close to or above 1.00 and less than 1.00 for urban areas. The I/O ratios obtained were linked to the indoor activities using occupant's diary entries. The positive values of correlation coefficient (r) also indicated the indoor concentrations of particulate matter were correlated with the corresponding outdoor concentrations.     

Contribution of the ozonation pre-treatment to the biodegradation of aqueous solutions of 2,4-dichlorophenol

The effect of ozonation on the biodegradability of 100-ppm aqueous solutions of 2,4-dichlorophenol has been investigated. BOD at 5, 10 and 21 days, BOD/COD and BOD/TOC ratios and the average oxidation state are presented. Biodegradability measured as BOD₅/COD ratio was increased from 0 of the original solution to 0.25 at the moment of removing all the initial compound (corresponding to an ozone dose of 0.12 g L⁻¹, 0.48 for BOD₂₁/COD ratio). To test the effect of this pre-treatment, the biological oxidation of these pre-ozonated solutions was performed in two semi-continuous stirred tank reactors, one with non-acclimated sludge and one with acclimated-to-phenol sludge. The study showed that the TOC content of the pre-treated solution could be removed up to 68% by an aerobic biological treatment as well as co-digested with municipal wastewater (TOC removal up to 82%), with similar operating retention times to a municipal wastewater plant (12-24 h). Kinetic studies based on Monod model have also been carried out. Pseudo-first-order kinetic constants were found to be in the range of 0.5-0.8 L g TVSS⁻¹ h⁻¹.     

Effect of COD/SO4ratio and Fe(II) under the variable hydraulic retention time (HRT) on fermentative hydrogen production

The effect of chemical oxygen demand/sulfate (COD/SO₄²⁻) ratio on fermentative hydrogen production using enriched mixed microflora has been studied. The chemostat system maintained with a substrate (glucose) concentration of 15 g COD L⁻¹ exhibited stable H₂ production at inlet sulfate concentrations of 0-20 g L⁻¹ during 282 days. The tested COD/SO₄²⁻ ratios ranged from 150 to 0.75 (with control) at pH 5.5 with hydraulic retention time (HRT) of 24, 12 and 6 h. The hydrogen production at HRT 6 h and pH 5.5 was not influenced by decreasing the COD/SO₄²⁻ ratio from 150 to 15 (with control) followed by noticeable increase at COD/SO₄²⁻ ratios of 5 and 3, but it was slightly decreased when the COD/SO₄²⁻ ratio further decreased to 1.5 and 0.75. These results indicate that high sulfate concentrations (up to 20,000 mg L⁻¹) would not interfere with hydrogen production under the investigated experimental conditions. Maximum hydrogen production was 2.95, 4.60 and 9.40 L day⁻¹ with hydrogen yields of 2.0, 1.8 and 1.6 mol H₂ mol⁻¹ glucose at HRTs of 24, 12 and 6 h, respectively. The volatile fatty acid (VFA) fraction produced during the reaction was in the order of butyrate > acetate > ethanol > propionate in all experiments. Fluorescence In Situ Hybridization (FISH) analysis indicated the presence of Clostridium spp., Clostridium butyricum, Clostridium perfringens and Ruminococcus flavefaciens as hydrogen producing bacteria (HPB) and absence of sulfate reducing bacteria (SRB) in our study.     

Simultaneous biodesulphurization and denitrification using an oil reservoir microbial culture: Effects of sulphide loading rate and sulphide to nitrate loading ratio

Biooxidation of sulphide under denitrifying conditions is a key process in control of souring in oil reservoirs and in treatment of gas and liquids contaminated with sulphide and nitrate. In this work, biooxidation of sulphide was studied using a representative culture originated from an oil reservoir. Effects of sulphide concentration, sulphide to nitrate molar ratio, and loading rates of sulphide and nitrate on their removal rates and composition of the end products were investigated. In the batch system sulphide removal rate passed through a maximum as sulphide concentration was increased from 2.1 to 16.3 mM, with the highest rate (2.06 mM h⁻¹) observed with 10.7 mM sulphide. Nitrate removal was coupled to sulphide oxidation and the highest removal rate was 1.05 mM h⁻¹. In the continuous bioreactors fed with 10 and 5, 15 and 7.5, and 20 and 10 mM sulphide and nitrate, cell wash-out occurred as dilution rate was increased above 0.15, 0.13 and 0.08 h⁻¹, respectively. Prior to cell wash-out linear increases in sulphide and nitrate removal rates were observed as loading rate was increased. The highest sulphide and nitrate removal rates of 2.0 and 0.92 mM h⁻¹ were obtained in the bioreactor fed with 15 mM sulphide and 7.5 mM nitrate at loading rates of 2.1 and 0.93 mM h⁻¹, respectively. Short residence times and high sulphide to nitrate ratios promoted the formation of sulphur, a desired end product for ex situ treatment of contaminated streams. Combination of long residence times and low sulphide to nitrate ratios, which favours formation of sulphate, is the suitable strategy for in situ removal of H₂S from oil reservoirs.     

Exposure of children to airborne particulate matter of different size fractions during indoor physical education at school

Although moderate regular aerobic exercise is recommended for good health, adverse health consequences may be incurred by people who exercise in areas with high ambient pollution, such as in the centres of large cities with dense traffic. The exposure of children during exercise is of special concern because of their higher sensitivity to air pollutants. The size-segregated mass concentration of particulate matter was measured in a naturally ventilated elementary school gym during eight campaigns, seven to ten days long, from November 2005 through August 2006 in a central part of Prague (Czech Republic). The air was sampled using a five-stage cascade impactor. The indoor concentrations of PM_2.5 recorded in the gym exceeded the WHO recommended 24-hour limit of 25 μg m⁻³ in 50% of the days measured. The average 24-h concentrations of PM_2.5 (24.03 μg m⁻³) in the studied school room did not differ much from those obtained from the nearest fixed site monitor (25.47 μg m⁻³) and the indoor and ambient concentrations were closely correlated (correlation coefficient 0.91), suggesting a high outdoor-to-indoor penetration rate. The coarse indoor fraction concentration (PM_2.5–10) was associated with the number of exercising pupils (correlation coefficient 0.77), indicating that human activity is its main source. Considering the high pulmonary ventilation rate of exercising children and high outdoor particulate matter concentrations, the levels of both coarse and fine aerosols may represent a potential health risk for sensitive individuals during their physical education performed in naturally ventilated gyms in urban areas with high traffic intensity.     

Exposure of birds to radionuclides and other contaminants in Special Protection Areas (SPAs) in North-West England

There has been a decline in the population of some bird species at Morecambe Bay and the Solway Firth Special Protected Areas in North-West England during the last fifty years. It was suggested that the declines were caused, in part, by contaminants in the food and environment, primarily from the radioactive effluent discharge from the Sellafield Ltd nuclear fuel reprocessing plant in Cumbria. This study analysed bird feathers and tissues, vegetation and sediment for radionuclides, metals and persistent organic compounds. The non-radionuclide results were all low compared to relevant action limits. The ERICA model was used with field data to estimate the radiological dose to birds from exposure to ¹³⁷Cs and ²⁴¹Am with results between 1.26 to 3.83 μGy h^− 1, below the ERICA screening level of 10 μGy h^− 1 and within the IAEA 40 μGy h^− 1 guideline value below which potential adverse impacts on biota are unlikely. The study showed no link between bird population decline and anthropogenic discharges to the SPAs.     

Nitrogen and phosphorus removal from an abattoir wastewater in a SBR with aerobic granular sludge

The formation and performance of granular sludge was studied in an 8 l sequencing batch reactor (SBR) treating an abattoir (slaughterhouse) wastewater. Influent concentrations averaged 1520 mg l⁻¹ volatile suspended solids (VSS), 7685 mg l⁻¹ Chemical oxygen demand (COD), 1057 mg l⁻¹ total kjeldahl nitrogen (TKN), 217 mg l⁻¹ total P. The COD loading was 2.6 kg m⁻³ d⁻¹. The SBR was seeded with flocculating sludge from a SBR with an 1 h settle time, but granules developed within 4 days by reducing the settle time to 2 min. The SBR cycle also had 120 min mixed (anaerobic) fill, 220 min aerated react, and 18 min draw/idle. The granules had a mean diameter of 1.7 mm, a specific gravity of 1.035, a density of 62 g VSS l⁻¹, a zone settling velocity (ZSV) of 51 m h⁻¹, and a sludge volume index (SVI) of 22 ml g⁻¹. Without optimizing process conditions, removal of COD and P were over 98%, and removal of N and VSS were over 97%. Nitrification and denitrification occurred simultaneously during react. The results indicate that conventional SBRs treating wastewaters with flocculating sludge can be converted to granular SBRs by reducing the settle time.     

Feeding characteristics of a golden alga (Poterioochromonas sp.) grazing on toxic cyanobacterium Microcystis aeruginosa

Microcystis aeruginosa has quickly risen in infamy as one of the most universal and toxic bloom-forming cyanobacteria. Here we presented a species of golden alga (Poterioochromonas sp. strain ZX1), which can feed on toxic M. aeruginosa without any adverse effects from the cyanotoxins. Using flow cytometry, the ingestion and maximal digestion rates were estimated to be 0.2∼1.2 and 0.2 M. aeruginosa cells (ZX1 cell)⁻¹ h⁻¹, respectively. M. aeruginosa in densities below 10⁷ cells mL⁻¹ could be grazed down by ZX1, but no significant decrease was observed when the initial density was 3.2 × 10⁷ cells mL⁻¹. ZX1 grazing was a little influenced by the light intensity (0.5∼2500 lx) and initial pH of the medium (pH = 5.0∼9.5). ZX1 could not survive in continuous darkness for longer than 10 days. The pH value was adjusted to 8 by ZX1 while to 10 by M. aeruginosa. This study may shed light on understanding the ecological interactions between M. aeruginosa and mixotrophic Poterioochromonas sp. in aquatic ecosystems.     

Synthesis of monodispersed CMC-stabilized Fe-Cu bimetal nanoparticles for in situ reductive dechlorination of 1,2,4-trichlorobenzene

Monodispersed carboxymethyl cellulose (CMC)-stabilized Fe-Cu bimetal nanoparticles with an average diameter of less than 20 nm were successfully synthesized by a modified water-based approach. The as-resulting particles exhibit a core-shell structure and are quite uniform in size and shape. Batch experiments demonstrated that these nanoparticles could effectively dechlorinate 1,2,4-trichlorobenzene (1,2,4-TCB). Near 90% of reduction efficiency was achieved by CMC-stabilized Fe-Cu for 24 h treatment. By monitoring the reaction products with time by GC-MS, it was found that 1,2,4-TCB transformation mainly followed the sequential hydrogenolysis to 1,2-dichlorobenzene (12DCB), then chlorobenzene (CB) and eventually benzene. The pseudo first order 1,2,4-TCB degradation rate were 0.09 h⁻¹ and 0.06 h⁻¹ as CMC-to-Fe molar ratios were 0.00248 and 0.00124, respectively. Dechlorination mechanism was also proposed in this study.     

Exposure to fine particulate matter in ten night clubs in Athens Greece: Studying the effect of ventilation, cigarette smoking and resuspension

The aim of the present work is to study the occupants' exposure to fine particulate concentrations in ten nightclubs (NCs) in Athens, Greece. Measurements of PM₁ and PM_2.5 were made in the outdoor and indoor environment of each NC. The average indoor PM₁ and PM_2.5 concentrations were found to be 181.77 μg m^− 3 and 454.08 μg m^− 3 respectively, while the corresponding outdoor values were 11.04 μg m^− 3 and 32.19 μg m^− 3. Ventilation and resuspension rates were estimated through consecutive numerical experiments with an indoor air quality model and were found to be remarkably lower than the minimum values recommended by national standards. The relative effects of the ventilation and smoking on the occupants' exposures were examined using multiple regression techniques. It was found that given the low ventilation rates, the effect of smoking as well as the occupancy is of the highest importance. Numerical evaluations showed that if the ventilation rates were at the minimum values set by national standards, then the indoor exposures would be reduced at the 70% of the present exposure values.     

Summer fluxes of atmospheric greenhouse gases N2O, CH4 and CO2 from mangrove soil in South China

The atmospheric fluxes of N₂O, CH₄ and CO₂ from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 μmol m⁻² h⁻¹, 11.9 to 5168.6 μmol m⁻² h⁻¹ and 0.69 to 20.56 mmol m⁻² h⁻¹ for N₂O, CH₄ and CO₂, respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N₂O and CH₄ fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N₂O and CO₂ fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH₄⁺-N contents, as well as the soil porosity. However, only soil NH₄⁺-N concentration had significant effects on CH₄ fluxes.     

Determination of aromatic amines in water samples by capillary electrophoresis with amperometric detection

Aromatic amines such as aniline and its derivatives are an important class of environmental water pollutants. A method based on capillary zone electrophoresis with amperometric detection (CZE-AD) at carbon disk electrode was developed for the determination of aromatic amines in water samples. The effects of working potential, pH and concentration of running buffer, separation voltage and injection time were investigated. Under the optimum conditions, 2,3-diaminonaphthalene, aniline, o-phenylenediamine and p-chloroaniline could be separated in 0.16 mol/L Na₂HPO₄-citric acid buffer (pH 4.6) within 23 min. The detection limits of them were 1.0 × 10⁻⁷, 3.3 × 10⁻⁸, 5.0 × 10⁻⁸, and 1.3 × 10⁻⁷ mol/L (S/N = 3), respectively. The method can be applied directly for the determination of aromatic amines in real water samples with satisfactory results.     

Air infiltration in Catalan dwellings and sealed rooms: An experimental study

In this study, we performed a series of trials to measure the infiltration air exchange rate (ACH) of several single-family dwellings throughout Catalonia, as well as the ACH of sealed rooms that could be used as indoor shelters. A shelter is an indoor room where people can take protection in case of a toxic gas release, while the toxic cloud passes through the dwelling. Experimental measurements were made using the tracer gas decay technique with CO₂ as the tracer gas in 2 periods—summer and winter—with the aim of characterizing air infiltration in Catalan dwellings. The geometric means obtained for the ACH of shelters and dwellings were 0.16 and 0.23 h⁻¹, respectively, that is, lower than those reported for North American (0.56 h⁻¹) and Greek (0.76 h⁻¹) dwellings. In general, the ACH was lower for shelters than for dwellings, and the average reduction obtained in shelters with respect to dwellings was 35%. The largest reductions were obtained in old dwellings with small floor areas and few stories. As for meteorological conditions, we found that the ACH of dwellings was more closely linked to wind speed than indoor–outdoor temperature difference, while the ACH of shelters was more affected by indoor–outdoor temperature and temperature differences inside the dwelling, particularly in dwellings with 3 or more stories.     

Nitrous oxide production kinetics during nitrate reduction in river sediments

A significant amount of nitrogen entering river basins is denitrified in riparian zones. The aim of this study was to evaluate the influence of nitrate and carbon concentrations on the kinetic parameters of nitrate reduction as well as nitrous oxide emissions in river sediments in a tributary of the Marne (the Seine basin, France). In order to determine these rates, we used flow-through reactors (FTRs) and slurry incubations; flow-through reactors allow determination of rates on intact sediment slices under controlled conditions compared to sediment homogenization in the often used slurry technique. Maximum nitrate reduction rates (R_m) ranged between 3.0 and 7.1 μg N g⁻¹ h⁻¹, and affinity constant (K_m) ranged from 7.4 to 30.7 mg N-NO₃⁻ L⁻¹. These values were higher in slurry incubations with an R_m of 37.9 μg N g⁻¹ h⁻¹ and a K_m of 104 mg N-NO₃⁻ L⁻¹. Nitrous oxide production rates did not follow Michaelis-Menten kinetics, and we deduced a rate constant with an average of 0.7 and 5.4 ng N g⁻¹ h⁻¹ for FTR and slurry experiments respectively. The addition of carbon (as acetate) showed that carbon was not limiting nitrate reduction rates in these sediments. Similar rates were obtained for FTR and slurries with carbon addition, confirming the hypothesis that homogenization increases rates due to release of and increasing access to carbon in slurries. Nitrous oxide production rates in FTR with carbon additions were low and represented less than 0.01% of the nitrate reduction rates and were even negligible in slurries. Maximum nitrate reduction rates revealed seasonality with high potential rates in fall and winter and low rates in late spring and summer. Under optimal conditions (anoxia, non-limiting nitrate and carbon), nitrous oxide emission rates were low, but significant (0.01% of the nitrate reduction rates).