Creosote contamination of groundwater in the vicinity of old gasworks and woodtreatment facilitie... more Creosote contamination of groundwater in the vicinity of old gasworks and woodtreatment facilities is a well-known problem. Risk assessments typically include measurements of mono-and poly-aromatic compounds and phenols. The content of nitrogen-, sulphur-and oxygen-containing heteroaromatic compounds (NSO) and their degradation products is seldom determined, although they often are strong smelling, toxic, and have high solubilities and hence constitute a potential for ground-water contamination. This paper reviews state of the knowledge regarding the analysis of NSO and their degradation products, and their occurrence and fate in groundwater under various redox conditions to assess their potential as groundwater contaminants at creosote-contaminated sites.
The transport in macroporous clayey till of bromide and 25 organic compounds typical of creosote ... more The transport in macroporous clayey till of bromide and 25 organic compounds typical of creosote was studied using a large intact soil column. The organic compounds represented the following groups: polycyclic aromatic hydrocarbons (PAHs), phenolic compounds, monoaromatic hydrocarbons (BTEXs), and heterocyclic compounds containing oxygen, nitrogen or sulphur in the aromatic ring structure (NSO-compounds). The clayey till column (0.5 m in
An experiment was conducted using a large, intact column of fractured clayey till to study the Ž ... more An experiment was conducted using a large, intact column of fractured clayey till to study the Ž transport and biodegradation of 25 organic compounds typical of creosote. The column 0.5 m in . height and 0.5 m in diameter was collected from a depth of 2.5-3 m at an experimental site on the island of Funen, Denmark. For the first 82 days of the experiment, the column was infiltrated with water containing nitrate, but no organic compounds. During this period, significant nitrate removal and nitrite production were observed indicating that denitrification occurred in the clayey till. After 82 days, a mixture of 25 organic compounds with a total concentration of approximately y1 ) Corresponding author. VKI, 0169-7722r99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved.
The Danish water sector needs competence development as a response to changing water management s... more The Danish water sector needs competence development as a response to changing water management structures and implementation of European legislation, and the number of international students enrolled in at DTU Environment is increasing. Based on their different backgrounds there is a clear need for adaptation and development of the existing courses. To accommodate this, DTU Environment has created an e-learning platform called Water Education, based on the software platform Moodle. It is scheduled to ...
Geological Society, London, Engineering Geology Special Publications, 1998
Abstract. The Rexco coal carbonization plant near Mansfield in the UK East Midlands produced coke... more Abstract. The Rexco coal carbonization plant near Mansfield in the UK East Midlands produced coke by the process known as 'Rexco' in the 1950s to early 1960s. In the process gas and coal-tar were also produced. The gas was cooled with water whereby ammonia and ...
Contamination by the herbicide mecoprop (MCPP) was detected in groundwater abstraction wells at K... more Contamination by the herbicide mecoprop (MCPP) was detected in groundwater abstraction wells at Kerteminde Waterworks in concentrations up to 0.08 µg/L. MCPP was removed to below detection limit in a simple treatment line where anaerobic groundwater was aerated and subsequently filtrated by primary and secondary rapid sand filters. Water quality parameters were measured throughout the waterworks, and they behaved as designed for. MCPP was removed in secondary rapid sand filters -removal was greatest in the sand filters in the filter line with the highest contact time (63 minutes). In these secondary sand filters, MCPP concentration decreased from 0.037 µg/L to below the detection limit of 0.01 µg/L. MCPP was removed continuously at different filter depths (0.80 m).
Hydrogen peroxide (HP) is used in aquaculture systems where preventive or curative water treatmen... more Hydrogen peroxide (HP) is used in aquaculture systems where preventive or curative water treatments occasionally are required. Use of chemical agents can be challenging in recirculating aquaculture systems (RAS) due to extended water retention time and because the agents must not damage the fish reared or the nitrifying bacteria in the biofilters at concentrations required to eliminating pathogens. This calls for quantitative insight into the fate of the disinfectant residuals during water treatment. This paper presents a kinetic model that describes the HP decomposition in aquaculture water facilitated by microbial enzyme activity. The model describes how the hydrogen peroxide removal declines and eventually stops at relatively low chemical oxygen demand (COD) concentrations. It is hypothesized that this is due to an enzyme deficit because it is destructed due to the reactive radicals created during the HP decomposition. The model assumes that the enzyme decay is controlled by an inactivation stoichiometry related to the HP decomposition. In order to make the model easily applicable, it is furthermore assumed that the COD is a proxy of the active biomass concentration of the water and thereby the enzyme activity. This was, however, not measured. The model developed successfully described the removal of HP in aquaculture water from three types of RAS and model parameters are estimated. The model and the model parameters provide new information and are valuable tools to improve HP application in RAS by addressing disinfection demand and identify efficient and safe water treatment routines.
Sorption and desorption of pentachlorophenol (PCP) to microbial biomass was studied in a series o... more Sorption and desorption of pentachlorophenol (PCP) to microbial biomass was studied in a series of laboratory experiments. Equilibrium conditions for sorption and desorption were established within 5 min after a step change in concentrations. Linear sorption isotherms were observed at up to 80 μg/l of dissolved PCP at pH 6, and up to 160 μg/l at pH 8. Linear sorption
ABSTRACT Ammonia liquor with very high concentrations of phenol and alkylated phenols is known to... more ABSTRACT Ammonia liquor with very high concentrations of phenol and alkylated phenols is known to have leaked into the subsurface at a former coal carbonization plant in the UK, giving high concentrations of ammonium in the groundwater. In spite of this, no significant concentrations of phenols were found in the groundwater. The potential for biodegradation of the phenols in the sandstone aquifer at the site has been investigated in laboratory microcosms under aerobic (oxygen amended) and mixed nitrate and iron reducing (nitrate enriched and unamended) anaerobic conditions, at a range of concentrations (low: ∼5 mg l−1, high: ∼60 mg l−1, and very high: ∼600 mg l−1) and in the presence of other organic coal–tar compounds (mono- and polyaromatic hydrocarbons (BTEXs and PAHs) and heterocyclic compounds (NSOs)) and ammonia liquor. Sandstone cores and groundwater for the microcosms were collected from within the anaerobic ammonium plume at the field site.Fast and complete degradation of phenol, o- and p-cresol, 2,5- and 3,4-xylenol with no or very short initial lag-phases was observed under aerobic conditions at low concentrations. 2,6- and 3,5-Xylenol were degraded more slowly and 3,5-xylenol degradation was only just complete after about 1 year. The maximum rates of total phenols degradation in duplicate aerobic microcosms were 1.06 and 1.76 mg l−1 day−1.The degradation of phenols in nitrate enriched and unamended anaerobic microcosms was similar. Fast and complete biodegradation of phenol, cresols, 3,4-xylenol and 3,5-xylenol was observed after short lag-phases in the anaerobic microcosms. 2,5-xylenol was partially degraded after a longer lag-phase and 2,6-xylenol persisted throughout the 3 month long experiments. The maximum rates of total phenols degradation in duplicate nitrate enriched and unamended anaerobic microcosms were 0.30–0.38 and 0.29–0.31 mg l−1 day−1, respectively. The highest phenols concentrations in the anaerobic microcosms apparently required very long adaptation periods or inhibited biodegradation of the phenols. For the intermediate concentration level, degradation occurred after comparable lag-phases and at comparable rates to those observed at low concentration. However, after a while degradation of phenols suddenly decreased drastically and then stopped. Dilution by addition of anaerobic groundwater resulted in continued but slow degradation of phenols in unamended microcosms.The effect of other organic coal–tar compounds (BTEXs, PAHs, NSOs) on the degradation of the phenols under unamended conditions was limited to slightly longer lag-phases for some of the phenols. Other constituents of the ammonia liquor did not appear to significantly affect the degradation of the phenols. Fast and complete degradation of 2,3- and 2,4-xylenol was indicated. These experiments were continued for a longer period of time and revealed complete degradation of 2,5-xylenol and, after an approximately 6-month-long lag-phase partial degradation of 2,6-xylenol.The potential for natural attenuation of phenols from process effluents from coal carbonization under aerobic conditions and mixed nitrate and iron reducing conditions appears promising.
The removal of toluene from waste gas was studied in a trickling biofitter. A high level of water... more The removal of toluene from waste gas was studied in a trickling biofitter. A high level of water recirculation (4.7 m h -t ) was maintained in order to keep the liquid phase concentration constant and to achieve a high degree of wetting. For loads in the range from 6 to 150 g m -3 h-1 the maximum volumetric removal rate (elimination capacity) was 35:5 10 g m -3 h -1, corresponding to a zero order removal rate of 0.11 4-0.03 g m -2 h -1 per unit of nominal surface area. The surface removal was zero order above the liquid phase concentrations of approximately 1.0 g m -3, corresponding to inlet gas concentrations above 0.7-0.8 g m -3. Below this concentration the surface removal was roughly of first order. The magnitude of the first order surface removal rate constant, klA, was estimated to be 0.08-0.27 m h -t (klaa = 24-86 h-l). Near-equilibrium conditions existed in the gas effluent, so mass transfer from gas to liquid was obviously relatively fast compared to the biological degradation. An analytical model based on a constant liquid phase concentration through the trickling filter column predicts the effluent gas concentration and the liquid phase concentration for a first and a zero order surface removal. The experimental results were in reasonable agreement with a very simple model valid for conditions with an overall removal governed by the biological degradation and independent of the gas/liquid mass transfer. The overall liquid mass transfer coefficient, KLa, was found to be a factor 6 higher in the system with biofilm compared to the system without. The difference may be explained by: 1. Difference in the wetting of the packing material, 2. Mass transfer occurring directly from the gas phase to the biofilm, and 3. Enlarged contact area between the gas phase and the biofilm due to a rough biofilm surface.
Water science and technology : a journal of the International Association on Water Pollution Research, 2003
In this study, the construction a model distribution system suitable for studies of attached and ... more In this study, the construction a model distribution system suitable for studies of attached and suspended microbial consisted of two loops connected in series with a total of 140 biofilm sampling points. The biofilm from the system was studied using 11 different microbial methods and the results were compared and discussed. The methods were used for biomass quantification (AODC, HPC and ATP determination), visualisation of structure (CLSM), activity measurement (leucine incorporation, AOC removal rate, respiration of benzoic acid, CTC and live/dead stains), and microbial diversity profiling (clone libraries and DGGE).
Water science and technology : a journal of the International Association on Water Pollution Research, 2002
Mathematical modeling of wastewater treatment processes has become increasingly popular in recent... more Mathematical modeling of wastewater treatment processes has become increasingly popular in recent years. To prepare students for their future careers, environmental engineering education should provide students with sufficient background and experiences to understand and apply mathematical models efficiently and responsibly. Approaches for introducing mathematical modeling into courses on wastewater treatment engineering are discussed depending on the learning objectives, level of the course and the time available.
Experimental data indicate that certain microbiological degradation experiments have a limited re... more Experimental data indicate that certain microbiological degradation experiments have a limited reproducibility. Nine identical batch experiments were carried out on 3 different days to examine reproducibility. A pure culture, isolated from soil, grew with toluene as the only carbon and energy source. Toluene was degraded under aerobic conditions at a constant temperature of 28 degrees C. The experiments were modelled by a Monod model--extended to meet the air/liquid system, and the parameter values were estimated using a statistical nonlinear estimation procedure. Model reduction analysis resulted in a simpler model without the biomass decay term. In order to test for model reduction and reproducibility of parameter estimates, a likelihood ratio test was employed. The limited reproducibility for these experiments implied that all 9 batch experiments could not be described by the same set of parameter values. However, experiments carried out the same day (within the same run) were mo...
As a representative member of the toluene-degrading population in a biofilter for waste gas treat... more As a representative member of the toluene-degrading population in a biofilter for waste gas treatment, Pseudomonas putida was investigated with a 16S rRNA targeting probe. The three-dimensional distribution of P. putida was visualized in the biofilm matrix by scanning confocal laser microscopy, demonstrating that P. putida was present throughout the biofilm. Acridine orange staining revealed a very heterogeneous structure of the fully hydrated biofilm, with cell-free channels extending from the surface into the biofilm. This indicated that toluene may penetrate to deeper layers of the biofilm, and consequently P. putida may be actively degrading toluene in all regions of the biofilm. Furthermore, measurements of growth rate-related parameters for P. putida showed reduced rRNA content and cell size (relative to that in a batch culture), indicating that the P. putida population was not degrading toluene at a maximal rate in the biofilm environment. Assuming that the rRNA content refle...
Anaerobic ammonium oxidation (anammox) is a cost-effective process to treat high-strength nitroge... more Anaerobic ammonium oxidation (anammox) is a cost-effective process to treat high-strength nitrogenous wastewater. Even without organic carbon input, the effluent contains bioproducts from autotrophic and heterotrophic bacteria. In this work, excitation-emission matrix (EEM) fluorescence spectroscopy was used to characterize the effluent dissolved organic matter (EfOM) from an anammox reactor treating synthetic wastewater. Two dominant EEM components were identified as humic acid-like (component 1) and protein-like (component 2) substances with excitation/emission peaks at <240, 355, 420/464 nm and <240, 280, 330/346 nm, respectively. The presence of both compounds in the effluent was tracked during an activity recovery period (nitrogen load increased from 0.2 to 1.3 kg Nm(-3)d(-1)). The effluent concentration of both components increased during this period, indicating correlation between production and bacterial activity. The dynamics of these bioproducts during both substrate consumption and starvation phases was analyzed in batch experiments. Component 1 was only formed during substrate consumption in a rate proportional to ammonium removal and was considered an up-take associated product characteristic of anammox activity. The results show that the composition of the EfOM was qualitatively and quantitatively influenced by process performance. Monitoring the EfOM could, therefore, offer a useful approach to assess anammox process performance and must be further explored.
As water supplies increasingly turn to use desalination technologies it becomes relevant to consi... more As water supplies increasingly turn to use desalination technologies it becomes relevant to consider the options for remineralization and blending with mineral rich water resources. We present a method for analyzing economic consequences due to changes in drinking water mineral content. Included impacts are cardiovascular diseases, dental caries, atopic eczema, lifetime of dish and clothes washing machines, heat exchangers, distribution systems, bottled water consumption and soap usage. The method includes an uncertainty assessment that ranks the impacts having the highest influence on the result and associated uncertainty. Effects are calculated for a scenario where 50% of Copenhagen's water supply is substituted by desalinated water. Without remineralization the total impact is expected to be negative (euro -0.44+/-0.2/m(3)) and individual impacts expected in the range of euro 0.01-0.51/m(3) delivered water. Health impacts have the highest contribution to impact size and uncertainty. With remineralization it is possible to reduce several negative impacts and the total impact is expected to be positive (euro 0.14+/-0.08/m(3)).
It is possible to optimize drinking water composition based on a valuation of the impacts of chan... more It is possible to optimize drinking water composition based on a valuation of the impacts of changed water quality. This paper introduces a method for assessing the potential for designing an optimum drinking water composition by the use of membrane desalination and remineralization. The method includes modeling of possible water quality blends and an evaluation of corrosion indices. Based on concentration-response relationships a range of impacts on public health, material lifetimes and consumption of soap have been valued for Perth, Western Australia and Copenhagen, Denmark. In addition to water quality aspects, costs of water production, fresh water abstraction and CO(2)-emissions are integrated into a holistic economic assessment of the optimum share of desalinated water in water supplies. Results show that carefully designed desalination post-treatment can have net benefits up to €0.3 ± 0.2 per delivered m(3) for Perth and €0.4(±0.2) for Copenhagen. Costs of remineralization and green house gas emission mitigation are minor when compared to the potential benefits of an optimum water composition. Finally, a set of optimum water quality criteria is proposed for the guidance of water supply planning and management.
Creosote contamination of groundwater in the vicinity of old gasworks and woodtreatment facilitie... more Creosote contamination of groundwater in the vicinity of old gasworks and woodtreatment facilities is a well-known problem. Risk assessments typically include measurements of mono-and poly-aromatic compounds and phenols. The content of nitrogen-, sulphur-and oxygen-containing heteroaromatic compounds (NSO) and their degradation products is seldom determined, although they often are strong smelling, toxic, and have high solubilities and hence constitute a potential for ground-water contamination. This paper reviews state of the knowledge regarding the analysis of NSO and their degradation products, and their occurrence and fate in groundwater under various redox conditions to assess their potential as groundwater contaminants at creosote-contaminated sites.
The transport in macroporous clayey till of bromide and 25 organic compounds typical of creosote ... more The transport in macroporous clayey till of bromide and 25 organic compounds typical of creosote was studied using a large intact soil column. The organic compounds represented the following groups: polycyclic aromatic hydrocarbons (PAHs), phenolic compounds, monoaromatic hydrocarbons (BTEXs), and heterocyclic compounds containing oxygen, nitrogen or sulphur in the aromatic ring structure (NSO-compounds). The clayey till column (0.5 m in
An experiment was conducted using a large, intact column of fractured clayey till to study the Ž ... more An experiment was conducted using a large, intact column of fractured clayey till to study the Ž transport and biodegradation of 25 organic compounds typical of creosote. The column 0.5 m in . height and 0.5 m in diameter was collected from a depth of 2.5-3 m at an experimental site on the island of Funen, Denmark. For the first 82 days of the experiment, the column was infiltrated with water containing nitrate, but no organic compounds. During this period, significant nitrate removal and nitrite production were observed indicating that denitrification occurred in the clayey till. After 82 days, a mixture of 25 organic compounds with a total concentration of approximately y1 ) Corresponding author. VKI, 0169-7722r99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved.
The Danish water sector needs competence development as a response to changing water management s... more The Danish water sector needs competence development as a response to changing water management structures and implementation of European legislation, and the number of international students enrolled in at DTU Environment is increasing. Based on their different backgrounds there is a clear need for adaptation and development of the existing courses. To accommodate this, DTU Environment has created an e-learning platform called Water Education, based on the software platform Moodle. It is scheduled to ...
Geological Society, London, Engineering Geology Special Publications, 1998
Abstract. The Rexco coal carbonization plant near Mansfield in the UK East Midlands produced coke... more Abstract. The Rexco coal carbonization plant near Mansfield in the UK East Midlands produced coke by the process known as 'Rexco' in the 1950s to early 1960s. In the process gas and coal-tar were also produced. The gas was cooled with water whereby ammonia and ...
Contamination by the herbicide mecoprop (MCPP) was detected in groundwater abstraction wells at K... more Contamination by the herbicide mecoprop (MCPP) was detected in groundwater abstraction wells at Kerteminde Waterworks in concentrations up to 0.08 µg/L. MCPP was removed to below detection limit in a simple treatment line where anaerobic groundwater was aerated and subsequently filtrated by primary and secondary rapid sand filters. Water quality parameters were measured throughout the waterworks, and they behaved as designed for. MCPP was removed in secondary rapid sand filters -removal was greatest in the sand filters in the filter line with the highest contact time (63 minutes). In these secondary sand filters, MCPP concentration decreased from 0.037 µg/L to below the detection limit of 0.01 µg/L. MCPP was removed continuously at different filter depths (0.80 m).
Hydrogen peroxide (HP) is used in aquaculture systems where preventive or curative water treatmen... more Hydrogen peroxide (HP) is used in aquaculture systems where preventive or curative water treatments occasionally are required. Use of chemical agents can be challenging in recirculating aquaculture systems (RAS) due to extended water retention time and because the agents must not damage the fish reared or the nitrifying bacteria in the biofilters at concentrations required to eliminating pathogens. This calls for quantitative insight into the fate of the disinfectant residuals during water treatment. This paper presents a kinetic model that describes the HP decomposition in aquaculture water facilitated by microbial enzyme activity. The model describes how the hydrogen peroxide removal declines and eventually stops at relatively low chemical oxygen demand (COD) concentrations. It is hypothesized that this is due to an enzyme deficit because it is destructed due to the reactive radicals created during the HP decomposition. The model assumes that the enzyme decay is controlled by an inactivation stoichiometry related to the HP decomposition. In order to make the model easily applicable, it is furthermore assumed that the COD is a proxy of the active biomass concentration of the water and thereby the enzyme activity. This was, however, not measured. The model developed successfully described the removal of HP in aquaculture water from three types of RAS and model parameters are estimated. The model and the model parameters provide new information and are valuable tools to improve HP application in RAS by addressing disinfection demand and identify efficient and safe water treatment routines.
Sorption and desorption of pentachlorophenol (PCP) to microbial biomass was studied in a series o... more Sorption and desorption of pentachlorophenol (PCP) to microbial biomass was studied in a series of laboratory experiments. Equilibrium conditions for sorption and desorption were established within 5 min after a step change in concentrations. Linear sorption isotherms were observed at up to 80 μg/l of dissolved PCP at pH 6, and up to 160 μg/l at pH 8. Linear sorption
ABSTRACT Ammonia liquor with very high concentrations of phenol and alkylated phenols is known to... more ABSTRACT Ammonia liquor with very high concentrations of phenol and alkylated phenols is known to have leaked into the subsurface at a former coal carbonization plant in the UK, giving high concentrations of ammonium in the groundwater. In spite of this, no significant concentrations of phenols were found in the groundwater. The potential for biodegradation of the phenols in the sandstone aquifer at the site has been investigated in laboratory microcosms under aerobic (oxygen amended) and mixed nitrate and iron reducing (nitrate enriched and unamended) anaerobic conditions, at a range of concentrations (low: ∼5 mg l−1, high: ∼60 mg l−1, and very high: ∼600 mg l−1) and in the presence of other organic coal–tar compounds (mono- and polyaromatic hydrocarbons (BTEXs and PAHs) and heterocyclic compounds (NSOs)) and ammonia liquor. Sandstone cores and groundwater for the microcosms were collected from within the anaerobic ammonium plume at the field site.Fast and complete degradation of phenol, o- and p-cresol, 2,5- and 3,4-xylenol with no or very short initial lag-phases was observed under aerobic conditions at low concentrations. 2,6- and 3,5-Xylenol were degraded more slowly and 3,5-xylenol degradation was only just complete after about 1 year. The maximum rates of total phenols degradation in duplicate aerobic microcosms were 1.06 and 1.76 mg l−1 day−1.The degradation of phenols in nitrate enriched and unamended anaerobic microcosms was similar. Fast and complete biodegradation of phenol, cresols, 3,4-xylenol and 3,5-xylenol was observed after short lag-phases in the anaerobic microcosms. 2,5-xylenol was partially degraded after a longer lag-phase and 2,6-xylenol persisted throughout the 3 month long experiments. The maximum rates of total phenols degradation in duplicate nitrate enriched and unamended anaerobic microcosms were 0.30–0.38 and 0.29–0.31 mg l−1 day−1, respectively. The highest phenols concentrations in the anaerobic microcosms apparently required very long adaptation periods or inhibited biodegradation of the phenols. For the intermediate concentration level, degradation occurred after comparable lag-phases and at comparable rates to those observed at low concentration. However, after a while degradation of phenols suddenly decreased drastically and then stopped. Dilution by addition of anaerobic groundwater resulted in continued but slow degradation of phenols in unamended microcosms.The effect of other organic coal–tar compounds (BTEXs, PAHs, NSOs) on the degradation of the phenols under unamended conditions was limited to slightly longer lag-phases for some of the phenols. Other constituents of the ammonia liquor did not appear to significantly affect the degradation of the phenols. Fast and complete degradation of 2,3- and 2,4-xylenol was indicated. These experiments were continued for a longer period of time and revealed complete degradation of 2,5-xylenol and, after an approximately 6-month-long lag-phase partial degradation of 2,6-xylenol.The potential for natural attenuation of phenols from process effluents from coal carbonization under aerobic conditions and mixed nitrate and iron reducing conditions appears promising.
The removal of toluene from waste gas was studied in a trickling biofitter. A high level of water... more The removal of toluene from waste gas was studied in a trickling biofitter. A high level of water recirculation (4.7 m h -t ) was maintained in order to keep the liquid phase concentration constant and to achieve a high degree of wetting. For loads in the range from 6 to 150 g m -3 h-1 the maximum volumetric removal rate (elimination capacity) was 35:5 10 g m -3 h -1, corresponding to a zero order removal rate of 0.11 4-0.03 g m -2 h -1 per unit of nominal surface area. The surface removal was zero order above the liquid phase concentrations of approximately 1.0 g m -3, corresponding to inlet gas concentrations above 0.7-0.8 g m -3. Below this concentration the surface removal was roughly of first order. The magnitude of the first order surface removal rate constant, klA, was estimated to be 0.08-0.27 m h -t (klaa = 24-86 h-l). Near-equilibrium conditions existed in the gas effluent, so mass transfer from gas to liquid was obviously relatively fast compared to the biological degradation. An analytical model based on a constant liquid phase concentration through the trickling filter column predicts the effluent gas concentration and the liquid phase concentration for a first and a zero order surface removal. The experimental results were in reasonable agreement with a very simple model valid for conditions with an overall removal governed by the biological degradation and independent of the gas/liquid mass transfer. The overall liquid mass transfer coefficient, KLa, was found to be a factor 6 higher in the system with biofilm compared to the system without. The difference may be explained by: 1. Difference in the wetting of the packing material, 2. Mass transfer occurring directly from the gas phase to the biofilm, and 3. Enlarged contact area between the gas phase and the biofilm due to a rough biofilm surface.
Water science and technology : a journal of the International Association on Water Pollution Research, 2003
In this study, the construction a model distribution system suitable for studies of attached and ... more In this study, the construction a model distribution system suitable for studies of attached and suspended microbial consisted of two loops connected in series with a total of 140 biofilm sampling points. The biofilm from the system was studied using 11 different microbial methods and the results were compared and discussed. The methods were used for biomass quantification (AODC, HPC and ATP determination), visualisation of structure (CLSM), activity measurement (leucine incorporation, AOC removal rate, respiration of benzoic acid, CTC and live/dead stains), and microbial diversity profiling (clone libraries and DGGE).
Water science and technology : a journal of the International Association on Water Pollution Research, 2002
Mathematical modeling of wastewater treatment processes has become increasingly popular in recent... more Mathematical modeling of wastewater treatment processes has become increasingly popular in recent years. To prepare students for their future careers, environmental engineering education should provide students with sufficient background and experiences to understand and apply mathematical models efficiently and responsibly. Approaches for introducing mathematical modeling into courses on wastewater treatment engineering are discussed depending on the learning objectives, level of the course and the time available.
Experimental data indicate that certain microbiological degradation experiments have a limited re... more Experimental data indicate that certain microbiological degradation experiments have a limited reproducibility. Nine identical batch experiments were carried out on 3 different days to examine reproducibility. A pure culture, isolated from soil, grew with toluene as the only carbon and energy source. Toluene was degraded under aerobic conditions at a constant temperature of 28 degrees C. The experiments were modelled by a Monod model--extended to meet the air/liquid system, and the parameter values were estimated using a statistical nonlinear estimation procedure. Model reduction analysis resulted in a simpler model without the biomass decay term. In order to test for model reduction and reproducibility of parameter estimates, a likelihood ratio test was employed. The limited reproducibility for these experiments implied that all 9 batch experiments could not be described by the same set of parameter values. However, experiments carried out the same day (within the same run) were mo...
As a representative member of the toluene-degrading population in a biofilter for waste gas treat... more As a representative member of the toluene-degrading population in a biofilter for waste gas treatment, Pseudomonas putida was investigated with a 16S rRNA targeting probe. The three-dimensional distribution of P. putida was visualized in the biofilm matrix by scanning confocal laser microscopy, demonstrating that P. putida was present throughout the biofilm. Acridine orange staining revealed a very heterogeneous structure of the fully hydrated biofilm, with cell-free channels extending from the surface into the biofilm. This indicated that toluene may penetrate to deeper layers of the biofilm, and consequently P. putida may be actively degrading toluene in all regions of the biofilm. Furthermore, measurements of growth rate-related parameters for P. putida showed reduced rRNA content and cell size (relative to that in a batch culture), indicating that the P. putida population was not degrading toluene at a maximal rate in the biofilm environment. Assuming that the rRNA content refle...
Anaerobic ammonium oxidation (anammox) is a cost-effective process to treat high-strength nitroge... more Anaerobic ammonium oxidation (anammox) is a cost-effective process to treat high-strength nitrogenous wastewater. Even without organic carbon input, the effluent contains bioproducts from autotrophic and heterotrophic bacteria. In this work, excitation-emission matrix (EEM) fluorescence spectroscopy was used to characterize the effluent dissolved organic matter (EfOM) from an anammox reactor treating synthetic wastewater. Two dominant EEM components were identified as humic acid-like (component 1) and protein-like (component 2) substances with excitation/emission peaks at <240, 355, 420/464 nm and <240, 280, 330/346 nm, respectively. The presence of both compounds in the effluent was tracked during an activity recovery period (nitrogen load increased from 0.2 to 1.3 kg Nm(-3)d(-1)). The effluent concentration of both components increased during this period, indicating correlation between production and bacterial activity. The dynamics of these bioproducts during both substrate consumption and starvation phases was analyzed in batch experiments. Component 1 was only formed during substrate consumption in a rate proportional to ammonium removal and was considered an up-take associated product characteristic of anammox activity. The results show that the composition of the EfOM was qualitatively and quantitatively influenced by process performance. Monitoring the EfOM could, therefore, offer a useful approach to assess anammox process performance and must be further explored.
As water supplies increasingly turn to use desalination technologies it becomes relevant to consi... more As water supplies increasingly turn to use desalination technologies it becomes relevant to consider the options for remineralization and blending with mineral rich water resources. We present a method for analyzing economic consequences due to changes in drinking water mineral content. Included impacts are cardiovascular diseases, dental caries, atopic eczema, lifetime of dish and clothes washing machines, heat exchangers, distribution systems, bottled water consumption and soap usage. The method includes an uncertainty assessment that ranks the impacts having the highest influence on the result and associated uncertainty. Effects are calculated for a scenario where 50% of Copenhagen's water supply is substituted by desalinated water. Without remineralization the total impact is expected to be negative (euro -0.44+/-0.2/m(3)) and individual impacts expected in the range of euro 0.01-0.51/m(3) delivered water. Health impacts have the highest contribution to impact size and uncertainty. With remineralization it is possible to reduce several negative impacts and the total impact is expected to be positive (euro 0.14+/-0.08/m(3)).
It is possible to optimize drinking water composition based on a valuation of the impacts of chan... more It is possible to optimize drinking water composition based on a valuation of the impacts of changed water quality. This paper introduces a method for assessing the potential for designing an optimum drinking water composition by the use of membrane desalination and remineralization. The method includes modeling of possible water quality blends and an evaluation of corrosion indices. Based on concentration-response relationships a range of impacts on public health, material lifetimes and consumption of soap have been valued for Perth, Western Australia and Copenhagen, Denmark. In addition to water quality aspects, costs of water production, fresh water abstraction and CO(2)-emissions are integrated into a holistic economic assessment of the optimum share of desalinated water in water supplies. Results show that carefully designed desalination post-treatment can have net benefits up to €0.3 ± 0.2 per delivered m(3) for Perth and €0.4(±0.2) for Copenhagen. Costs of remineralization and green house gas emission mitigation are minor when compared to the potential benefits of an optimum water composition. Finally, a set of optimum water quality criteria is proposed for the guidance of water supply planning and management.
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Papers by Erik Arvin