Christopher M Sales | Drexel University (original) (raw)

Papers by Christopher M Sales

ACS Publications, 2016

A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutan... more A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutant, in low and high salinity (0−10 g/L salt) solutions is presented. The first order rate constants in the presence of 0, 300, and 500 mM fructose were 0.23 ± 0.04, 0.54 ± 0.01, and 1.18 ± 0.03 min −1 , respectively. Experimental evidence has shown generation of hydrogen peroxide and singlet oxygen from the UV-C exposure of fructose, which may have accelerated PCP degradation. Although salts (sodium, potassium, and calcium chloride, 1101:6.4:1) are expected to enhance the degradation rate due to generation of reactive halide species (RHS) from exposure to UV-C light, 10 g/L salt decreased the degradation rates in both the absence and presence of fructose. An LC-ESI-MS spectrum of the reaction mixture revealed a high relative abundance at m/z of 215 that corresponds to a fructose−chlorine adduct, indicating that fructose may have scavenged these RHS and prevented their reaction with PCP.

Construction and Building Materials

International Journal of Solids and Structures

Applied and Environmental Microbiology, Nov 1, 2007

Rhodococci are common soil heterotrophs that possess diverse functional enzymatic activities with... more Rhodococci are common soil heterotrophs that possess diverse functional enzymatic activities with economic and ecological significance. In this study, the correlation between gene expression and biological removal of the water contaminant N-nitrosodimethylamine (NDMA) is explored. NDMA is a hydrophilic, potent carcinogen that has gained recent notoriety due to its environmental persistence and emergence as a widespread micropollutant in the subsurface environment. In this study, we demonstrate that Rhodococcus sp. strain RHA1 can constitutively degrade NDMA and that activity toward this compound is enhanced by approximately 500-fold after growth on propane. Transcriptomic analysis of RHA1 and reverse transcriptase quantitative PCR assays demonstrate that growth on propane elicits the upregulation of gene clusters associated with (i) the oxidation of propane and (ii) the oxidation of substituted benzenes. Deletion mutagenesis of prmA, the gene encoding the large hydroxylase component of propane monooxygenase, abolished both growth on propane and removal of NDMA. These results demonstrate that propane monooxygenase is responsible for NDMA degradation by RHA1 and explain the enhanced cometabolic degradation of NDMA in the presence of propane.

AGUFM, Dec 1, 2017

Effluent affected diversity and structure of community downstream of WWTPs. • Effluent-impacts on... more Effluent affected diversity and structure of community downstream of WWTPs. • Effluent-impacts on community composition changed with AMC. • WWTP-associated taxa significantly decreased with distance from source. • Major nutrients (N and P) did not control shifts in community structure. • Efficacy of using a microbial indicator subset was verified.

Water Research, Apr 1, 2006

A bioreactor system without a biomass-liquid separation unit is evaluated for its chemical oxygen... more A bioreactor system without a biomass-liquid separation unit is evaluated for its chemical oxygen demand (COD) removal and biomass retention capabilities under the nitrogen deficient and low F/M conditions that are known to produce bulking biomass. A fully oxygenated stream recycled from an external oxygenator delivers the oxygen to an upflow bioreactor in which a biomass zone is formed and maintained in the absence of gas effervescence. COD is removed with up to 90% efficiency by means of aerobic and anaerobic bacterial activities occurring in the biomass zone. The biomass is bulking which is brought about by the extensive filamentous growth caused by the nitrogen deficient and low F/M conditions adopted. However, the biomass zone is undisturbed at superficial upflow velocities as high as 0.66 cm/min, because it has a porous, mat-like matrix that is augmented by the entanglement of filamentous bacteria with the cell clusters. A low-VSS effluent (i.e.,o10 mg/L) is produced directly from the bioreactor.

Plasma

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine surfactants th... more Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine surfactants that are resistant to typical methods of degradation. Thermal techniques along with other novel, less energy-intensive techniques are currently being investigated for the treatment of PFAS-contaminated matrices. Non-equilibrium plasma is one technique that has shown promise for the treatment of PFAS-contaminated water. To better tailor non-equilibrium plasma systems for this application, knowledge of the energy required for mineralization, and in turn the roles that plasma reactive species and heat can play in this process, would be useful. In this study, fundamental thermodynamic equations were used to estimate the enthalpies of reaction (480 kJ/mol) and formation (−4640 kJ/mol) of perfluorooctanoic acid (PFOA, a long-chain legacy PFAS) in water. This enthalpy of reaction estimate indicates that plasma reactive species alone cannot catalyze the reaction; because the reaction is endothermi...

MATEC Web of Conferences

The goal of this research is to develop innovative damage-responsive bacterial-based self-healing... more The goal of this research is to develop innovative damage-responsive bacterial-based self-healing fibers (hereafter called BioFiber) that can be incorporated into concrete to enable two functionalities simultaneously: (1) crack bridging functionality to control crack growth and (2) crack healing functionality when a crack occurs. The BioFiber is comprised of a load-bearing core fiber, a sheath of bacteria-laden hydrogel, and an outer impermeable strain-responsive shell coating. An instant soaking manufacturing process was used with multiple reservoirs containing bacteria-laden, hydrophilic prepolymer and crosslinking reagents to develop BioFiber. Sodium-alginate was used as a prepolymer to produce calcium-alginate hydrogel via ionic crosslinking on the core fiber. The dormant bacteria (spore) of Lysinibacillus sphaericus was incorporated in hydrogel as a self-healing agent. Then, an impermeable polymeric coating was applied to the hydrogel-coated core fibers. The impermeable strain-...

Social Science Research Network, 2023

In order to identify appropriate environmental conditions and media components that are either es... more In order to identify appropriate environmental conditions and media components that are either essential or that enhance its growth and Microbial induced calcium carbonate precipitation (MICP) activity, in this study, a series of experiments were conducted to investigate the effects of media components and oxygen conditions on the growth rate and MICP activity of Lysinibacillus sphaericus strain MB 284. From these experiments, it was observed that aerobic conditions could lead to increased calcium carbonate production and up to three times faster growth rates by strain MB284 when compared to anoxic conditions. It was also determined that considering the measured growth rate, final biomass concentration, ureolysis activity, amount of calcium carbonate precipitation, and cost of media components for designing undefined culture media for industrial applications, yeast extract is the most economically appropriate option. In our attempts to grow strain MB284 in urea, sucrose, and ammoniu...

Environmental harsh conditions are one of the main challenges to the survivability of bacteria du... more Environmental harsh conditions are one of the main challenges to the survivability of bacteria during the microbially induced calcium carbonate precipitation (MICP) process. Due to the high resistivity of endospores against inhospitable conditions in comparison with vegetative cells, different sporulation methods were applied to Lysinibacillus sphaericus strain MB284 by changing the environmental conditions to investigate the growth of germinated cells. It was found that the sporulation yield was more when both carbon source starvation and the thermal shock process were applied to this bacterium. In addition, extending the sporulation time of cells into the minimal medium at 2 °C for a couple of weeks had a great impact on improving the sporulation yield. Comparing the growth rate of germinated endospores in natural conditions (pH 7 and 25 °C) and harsh conditions (pH 12, temperature of -10 to 60 °C, salinity up to 100 g/l) showed that endospores generated by thermal shock are able ...

Plasma Chemistry and Plasma Processing, 2021

Scaling up of transitional “warm” plasmas to industrial level gives possibility to develop plasma... more Scaling up of transitional “warm” plasmas to industrial level gives possibility to develop plasma systems that combine advantages of thermal and non thermal discharges such as low temperature and high process selectivity (compare to thermal plasma) at high pressure and average power density. Non-equilibrium “cold” gliding arcs (with observation of equilibrium to non equilibrium transition) has been demonstrated at power level 2–3 kW and proved to be a highly efficient plasma stimulators of several plasma chemical and plasma catalytic processes, including hydrogen/syngas generation from biomass, coal and organic wastes, exhaust gas cleaning, fuel desulfurization and water cleaning from emerging contaminants. The gliding arc evolution includes initial micro-arc phase with fast transition to transient non-equilibrium phase with elevated electric field, low gas and high electron temperatures, as well as selective generation of active species typical for cold plasmas. The paper will describe experimentally achieved scaling up of the non-equilibrium gliding arc discharges to the level of 10–15 kW, as well as theoretical scaling up limitations of this powerful non-equilibrium plasma systems.

MATEC Web of Conferences

Vegetative cells used for the concrete bio self-healing process often face threatening environmen... more Vegetative cells used for the concrete bio self-healing process often face threatening environmental conditions such as extreme temperature, pH, salinity, shear stress, and starvation during the hardening process and the service life of the concrete. These conditions can eventually lead to cell death. Since endospores are likely to remain dormant for prolonged periods and can survive, germinate, and grow under inhospitable conditions, they are a suitable bacterial phenotype to introduce into concrete for microbial-inducing calcite precipitation. This study investigated how different endosporulation methods affect the endosporulation ratio (i.e., the fraction of vegetative cells that are converted to endospores during endosporulation), as well as the germination ratio (i.e., the fraction of endospores that are converted to vegetative cells following germination) and the microbial-induced calcite precipitation (MICP) performance of germinated endospores after facing harsh conditions o...

Journal of Environmental Engineering

Plasma, Jan 30, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Environmental Science: Processes & Impacts

Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made fluorinated organic chem... more Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made fluorinated organic chemicals that can accumulate in the environment.

Scientific Reports

Due to the shortage of personal protective equipment (PPE) during the COVID-19 pandemic, the inte... more Due to the shortage of personal protective equipment (PPE) during the COVID-19 pandemic, the interest and demand for sterilization devices to reuse PPE has increased. For reuse of face masks, they must be effectively decontaminated of potential infectious agents without compromising its filtration ability during sterilization. In this study, we utilized an atmospheric pressure pulsed dielectric barrier discharge (DBD), combined with nebulized liquid microdroplets to generate plasma-activated mist (PAM). MS2 and T4 bacteriophages were used to conduct the decontamination tests on two types of N95 respirators. Results showed at least a 2-log reduction of MS2 and T4 on N95 respirators treated in one cycle with 7.8% hydrogen peroxide PAM and at least a 3-log reduction treated in 10% hydrogen peroxide PAM. In addition, it was found that there was no significant degradation in filtration efficiency of N95 respirators (3M 1860 and 1804) treated in 10% hydrogen peroxide PAM found after 20 cy...

Journal of Visualized Experiments

A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation... more A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation and study of high density microbial communities. Past studies have evaluated the performance of the reactor for the removal of COD 1 and nitrogen species 2-4 by heterotrophic and chemoautotrophic bacteria, respectively. The HDBR design eliminates the requirement for external flocculation/sedimentation processes while still yielding effluent containing low suspended solids. In this study, the HDBR is applied as a photobioreactor (PBR) in order to characterize the nitrogen removal characteristics of an algae-based photosynthetic microbial community. As previously reported for this HDBR design, a stable biomass zone was established with a clear delineation between the biologically active portion of the reactor and the recycling reactor fluid, which resulted in a low suspended solid effluent. The algal community in the HDBR was observed to remove 18.4% of total nitrogen species in the influent. Varying NH 4 + and NO 3 concentrations in the feed did not have an effect on NH 4 + removal (n=44, p=0.993 and n=44, p=0.610 respectively) while NH 4 + feed concentration was found to be negatively related with NO 3 removal (n=44, p=0.000) and NO 3 feed concentration was found to be positively correlated with NO 3 removal (n=44, p=0.000). Consistent removal of NH 4 + , combined with the accumulation of oxidized nitrogen species at high NH 4 + fluxes indicates the presence of ammonia-and nitrite-oxidizing bacteria within the microbial community.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

ACS Publications, 2016

A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutan... more A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutant, in low and high salinity (0−10 g/L salt) solutions is presented. The first order rate constants in the presence of 0, 300, and 500 mM fructose were 0.23 ± 0.04, 0.54 ± 0.01, and 1.18 ± 0.03 min −1 , respectively. Experimental evidence has shown generation of hydrogen peroxide and singlet oxygen from the UV-C exposure of fructose, which may have accelerated PCP degradation. Although salts (sodium, potassium, and calcium chloride, 1101:6.4:1) are expected to enhance the degradation rate due to generation of reactive halide species (RHS) from exposure to UV-C light, 10 g/L salt decreased the degradation rates in both the absence and presence of fructose. An LC-ESI-MS spectrum of the reaction mixture revealed a high relative abundance at m/z of 215 that corresponds to a fructose−chlorine adduct, indicating that fructose may have scavenged these RHS and prevented their reaction with PCP.

Construction and Building Materials

International Journal of Solids and Structures

Applied and Environmental Microbiology, Nov 1, 2007

Rhodococci are common soil heterotrophs that possess diverse functional enzymatic activities with... more Rhodococci are common soil heterotrophs that possess diverse functional enzymatic activities with economic and ecological significance. In this study, the correlation between gene expression and biological removal of the water contaminant N-nitrosodimethylamine (NDMA) is explored. NDMA is a hydrophilic, potent carcinogen that has gained recent notoriety due to its environmental persistence and emergence as a widespread micropollutant in the subsurface environment. In this study, we demonstrate that Rhodococcus sp. strain RHA1 can constitutively degrade NDMA and that activity toward this compound is enhanced by approximately 500-fold after growth on propane. Transcriptomic analysis of RHA1 and reverse transcriptase quantitative PCR assays demonstrate that growth on propane elicits the upregulation of gene clusters associated with (i) the oxidation of propane and (ii) the oxidation of substituted benzenes. Deletion mutagenesis of prmA, the gene encoding the large hydroxylase component of propane monooxygenase, abolished both growth on propane and removal of NDMA. These results demonstrate that propane monooxygenase is responsible for NDMA degradation by RHA1 and explain the enhanced cometabolic degradation of NDMA in the presence of propane.

AGUFM, Dec 1, 2017

Effluent affected diversity and structure of community downstream of WWTPs. • Effluent-impacts on... more Effluent affected diversity and structure of community downstream of WWTPs. • Effluent-impacts on community composition changed with AMC. • WWTP-associated taxa significantly decreased with distance from source. • Major nutrients (N and P) did not control shifts in community structure. • Efficacy of using a microbial indicator subset was verified.

Water Research, Apr 1, 2006

A bioreactor system without a biomass-liquid separation unit is evaluated for its chemical oxygen... more A bioreactor system without a biomass-liquid separation unit is evaluated for its chemical oxygen demand (COD) removal and biomass retention capabilities under the nitrogen deficient and low F/M conditions that are known to produce bulking biomass. A fully oxygenated stream recycled from an external oxygenator delivers the oxygen to an upflow bioreactor in which a biomass zone is formed and maintained in the absence of gas effervescence. COD is removed with up to 90% efficiency by means of aerobic and anaerobic bacterial activities occurring in the biomass zone. The biomass is bulking which is brought about by the extensive filamentous growth caused by the nitrogen deficient and low F/M conditions adopted. However, the biomass zone is undisturbed at superficial upflow velocities as high as 0.66 cm/min, because it has a porous, mat-like matrix that is augmented by the entanglement of filamentous bacteria with the cell clusters. A low-VSS effluent (i.e.,o10 mg/L) is produced directly from the bioreactor.

Plasma

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine surfactants th... more Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine surfactants that are resistant to typical methods of degradation. Thermal techniques along with other novel, less energy-intensive techniques are currently being investigated for the treatment of PFAS-contaminated matrices. Non-equilibrium plasma is one technique that has shown promise for the treatment of PFAS-contaminated water. To better tailor non-equilibrium plasma systems for this application, knowledge of the energy required for mineralization, and in turn the roles that plasma reactive species and heat can play in this process, would be useful. In this study, fundamental thermodynamic equations were used to estimate the enthalpies of reaction (480 kJ/mol) and formation (−4640 kJ/mol) of perfluorooctanoic acid (PFOA, a long-chain legacy PFAS) in water. This enthalpy of reaction estimate indicates that plasma reactive species alone cannot catalyze the reaction; because the reaction is endothermi...

MATEC Web of Conferences

The goal of this research is to develop innovative damage-responsive bacterial-based self-healing... more The goal of this research is to develop innovative damage-responsive bacterial-based self-healing fibers (hereafter called BioFiber) that can be incorporated into concrete to enable two functionalities simultaneously: (1) crack bridging functionality to control crack growth and (2) crack healing functionality when a crack occurs. The BioFiber is comprised of a load-bearing core fiber, a sheath of bacteria-laden hydrogel, and an outer impermeable strain-responsive shell coating. An instant soaking manufacturing process was used with multiple reservoirs containing bacteria-laden, hydrophilic prepolymer and crosslinking reagents to develop BioFiber. Sodium-alginate was used as a prepolymer to produce calcium-alginate hydrogel via ionic crosslinking on the core fiber. The dormant bacteria (spore) of Lysinibacillus sphaericus was incorporated in hydrogel as a self-healing agent. Then, an impermeable polymeric coating was applied to the hydrogel-coated core fibers. The impermeable strain-...

Social Science Research Network, 2023

In order to identify appropriate environmental conditions and media components that are either es... more In order to identify appropriate environmental conditions and media components that are either essential or that enhance its growth and Microbial induced calcium carbonate precipitation (MICP) activity, in this study, a series of experiments were conducted to investigate the effects of media components and oxygen conditions on the growth rate and MICP activity of Lysinibacillus sphaericus strain MB 284. From these experiments, it was observed that aerobic conditions could lead to increased calcium carbonate production and up to three times faster growth rates by strain MB284 when compared to anoxic conditions. It was also determined that considering the measured growth rate, final biomass concentration, ureolysis activity, amount of calcium carbonate precipitation, and cost of media components for designing undefined culture media for industrial applications, yeast extract is the most economically appropriate option. In our attempts to grow strain MB284 in urea, sucrose, and ammoniu...

Environmental harsh conditions are one of the main challenges to the survivability of bacteria du... more Environmental harsh conditions are one of the main challenges to the survivability of bacteria during the microbially induced calcium carbonate precipitation (MICP) process. Due to the high resistivity of endospores against inhospitable conditions in comparison with vegetative cells, different sporulation methods were applied to Lysinibacillus sphaericus strain MB284 by changing the environmental conditions to investigate the growth of germinated cells. It was found that the sporulation yield was more when both carbon source starvation and the thermal shock process were applied to this bacterium. In addition, extending the sporulation time of cells into the minimal medium at 2 °C for a couple of weeks had a great impact on improving the sporulation yield. Comparing the growth rate of germinated endospores in natural conditions (pH 7 and 25 °C) and harsh conditions (pH 12, temperature of -10 to 60 °C, salinity up to 100 g/l) showed that endospores generated by thermal shock are able ...

Plasma Chemistry and Plasma Processing, 2021

Scaling up of transitional “warm” plasmas to industrial level gives possibility to develop plasma... more Scaling up of transitional “warm” plasmas to industrial level gives possibility to develop plasma systems that combine advantages of thermal and non thermal discharges such as low temperature and high process selectivity (compare to thermal plasma) at high pressure and average power density. Non-equilibrium “cold” gliding arcs (with observation of equilibrium to non equilibrium transition) has been demonstrated at power level 2–3 kW and proved to be a highly efficient plasma stimulators of several plasma chemical and plasma catalytic processes, including hydrogen/syngas generation from biomass, coal and organic wastes, exhaust gas cleaning, fuel desulfurization and water cleaning from emerging contaminants. The gliding arc evolution includes initial micro-arc phase with fast transition to transient non-equilibrium phase with elevated electric field, low gas and high electron temperatures, as well as selective generation of active species typical for cold plasmas. The paper will describe experimentally achieved scaling up of the non-equilibrium gliding arc discharges to the level of 10–15 kW, as well as theoretical scaling up limitations of this powerful non-equilibrium plasma systems.

MATEC Web of Conferences

Vegetative cells used for the concrete bio self-healing process often face threatening environmen... more Vegetative cells used for the concrete bio self-healing process often face threatening environmental conditions such as extreme temperature, pH, salinity, shear stress, and starvation during the hardening process and the service life of the concrete. These conditions can eventually lead to cell death. Since endospores are likely to remain dormant for prolonged periods and can survive, germinate, and grow under inhospitable conditions, they are a suitable bacterial phenotype to introduce into concrete for microbial-inducing calcite precipitation. This study investigated how different endosporulation methods affect the endosporulation ratio (i.e., the fraction of vegetative cells that are converted to endospores during endosporulation), as well as the germination ratio (i.e., the fraction of endospores that are converted to vegetative cells following germination) and the microbial-induced calcite precipitation (MICP) performance of germinated endospores after facing harsh conditions o...

Journal of Environmental Engineering

Plasma, Jan 30, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Environmental Science: Processes & Impacts

Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made fluorinated organic chem... more Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made fluorinated organic chemicals that can accumulate in the environment.

Scientific Reports

Due to the shortage of personal protective equipment (PPE) during the COVID-19 pandemic, the inte... more Due to the shortage of personal protective equipment (PPE) during the COVID-19 pandemic, the interest and demand for sterilization devices to reuse PPE has increased. For reuse of face masks, they must be effectively decontaminated of potential infectious agents without compromising its filtration ability during sterilization. In this study, we utilized an atmospheric pressure pulsed dielectric barrier discharge (DBD), combined with nebulized liquid microdroplets to generate plasma-activated mist (PAM). MS2 and T4 bacteriophages were used to conduct the decontamination tests on two types of N95 respirators. Results showed at least a 2-log reduction of MS2 and T4 on N95 respirators treated in one cycle with 7.8% hydrogen peroxide PAM and at least a 3-log reduction treated in 10% hydrogen peroxide PAM. In addition, it was found that there was no significant degradation in filtration efficiency of N95 respirators (3M 1860 and 1804) treated in 10% hydrogen peroxide PAM found after 20 cy...

Journal of Visualized Experiments

A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation... more A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation and study of high density microbial communities. Past studies have evaluated the performance of the reactor for the removal of COD 1 and nitrogen species 2-4 by heterotrophic and chemoautotrophic bacteria, respectively. The HDBR design eliminates the requirement for external flocculation/sedimentation processes while still yielding effluent containing low suspended solids. In this study, the HDBR is applied as a photobioreactor (PBR) in order to characterize the nitrogen removal characteristics of an algae-based photosynthetic microbial community. As previously reported for this HDBR design, a stable biomass zone was established with a clear delineation between the biologically active portion of the reactor and the recycling reactor fluid, which resulted in a low suspended solid effluent. The algal community in the HDBR was observed to remove 18.4% of total nitrogen species in the influent. Varying NH 4 + and NO 3 concentrations in the feed did not have an effect on NH 4 + removal (n=44, p=0.993 and n=44, p=0.610 respectively) while NH 4 + feed concentration was found to be negatively related with NO 3 removal (n=44, p=0.000) and NO 3 feed concentration was found to be positively correlated with NO 3 removal (n=44, p=0.000). Consistent removal of NH 4 + , combined with the accumulation of oxidized nitrogen species at high NH 4 + fluxes indicates the presence of ammonia-and nitrite-oxidizing bacteria within the microbial community.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.