Wolfgang Uhl - Academia.edu (original) (raw)

Papers by Wolfgang Uhl

Journal of Hazardous Materials, 2024

Untreated stormwater is a major source of microplastics, organic pollutants, metals, and nutrient... more Untreated stormwater is a major source of microplastics, organic pollutants, metals, and nutrients in urban water
courses. The aim of this study was to improve the knowledge about the start-up periods of bioretention filters. A
rain garden pilot facility with 13 bioretention filters was constructed and stormwater from a highway and
adjacent impervious surfaces was used for irrigation for ~12 weeks. Selected plants (Armeria maritima, Hippophae
rhamnoides, Juncus effusus, and Festuca rubra) was planted in ten filters. Stormwater percolated through the filters
containing waste-to-energy bottom ash, biochar, or Sphagnum peat, mixed with sandy loam. Influent and effluent
samples were taken to evaluate removal of the above-mentioned pollutants. All filters efficiently removed
microplastics >10 μm, organic pollutants, and most metals. Copper leached from all filters initially but was
significantly reduced in the biochar filters at the end of the period, while the other filters showed a declining
trend. All filters leached nutrients initially, but concentrations decreased over time, and the biochar filters had
efficiently reduced nitrogen after a few weeks. To conclude, all the filters effectively removed pollutants during the start-up period. Before being recommended for full-scale applications, the functionality of the filters after a
longer period of operation should be evaluated

Water Practice & Technology, 2024

The addition of powdered activated carbon (PAC) in advanced wastewater treatment is increasingly ... more The addition of powdered activated carbon (PAC) in advanced wastewater treatment is increasingly recognized for its effectiveness
in removing micropollutants from secondary effluents. This study investigates the implications of PAC dosing on treatment
performance, particularly in terms of natural and effluent organic matter (OM) removal, turbidity reduction, and sludge characteristics.
Results indicate that while PAC incorporation significantly enhances the adsorption of OM, it necessitates higher
coagulant dosages to achieve comparable or improved turbidity levels. The study also reveals that lower pH levels facilitate
the removal of OM, thereby increasing the availability of adsorption sites on PAC for micropollutants. Moreover, PAC addition
results in the formation of larger, denser flocs that settle faster, leading to a reduction in sludge volume by approximately 20%.
However, the increased coagulant demand and the subsequent rise in sludge volume highlight the need for the optimized process
design to balance treatment efficiency with operational costs. This research provides valuable insights for the design and
operation of wastewater treatment plants, emphasizing the importance of tailored coagulant dosing and process adjustments
when integrating PAC into existing treatment frameworks.

Journal of Hazardous Materials, 2024

Tunnel wash water (TWW) contains high levels of trace elements and organic micropollutants, espec... more Tunnel wash water (TWW) contains high levels of trace elements and organic micropollutants, especially in the
dissolved fraction. Discharge poses significant environmental risks. This field study aimed at improving con-
ventional sedimentation treatment by addition of novel secondary treatments: bag filtration, ceramic micro-
filtration, or granular activated carbon (GAC) filtration. Removal of nine trace elements, 16 polycyclic aromatic
hydrocarbons (PAHs), 38 per- and polyfluoroalkyl substances (PFASs), seven benzothiazoles (BTHs), seven
benzotriazoles (BTRs), five bisphenols (BPs), and five benzophenones was investigated. Primary sedimentation
significantly reduced particles and associated contaminants, achieving over 73 % average removal for trace
elements, 65 % for PAHs, and 71 % for PFASs. Subsequent GAC removed over 70 % of dissolved Cr, Cu, Pb, and
Zn and over 92 % of dissolved PFASs, BTHs, BTRs, and BPs, including several persistent, mobile and toxic
compounds. Following GAC filtration, Cr, Ni, Pb, anthracene, fluoranthene, perfluorooctanesulfonic acid, and
bisphenol-A were below environmental quality standards (EQS). GAC consistently reduced responses in in vitro
bioassays with endpoints activation of the aryl hydrocarbon receptor, oxidative stress response, and neurotoxicity below effect-based trigger values for surface water. GAC filtration is thus recommended for future
TWW treatment. Assessing water quality remains a challenging task due to lack of EQSs for many chemicals.

Environmental Science and Technology Letters, Jan 29, 2015

Biofouling is a ubiquitous problem in many places in society and technology, especially in revers... more Biofouling is a ubiquitous problem in many places in society and technology, especially in reverse osmosis or nanofiltration (NF) processes. Initial stages in the development of the biofilm include attachment of bacteria to the surface, where bacterial outer membrane components such as biopolymers, lipids, and proteins play important roles. Here we show that the glycosphingolipid (GSL) unique to Sphingomonas species is a key player in the initial attachment of bacteria to NF membranes whereas lipopolysaccharide (LPS), the major glycolipid in many Gram-negative species, is less significant. GSL and LPS were deposited on an NF membrane with subsequent bacterial culture injection in a three-dimensionally printed microfluidic flow cell. Flux, rejection, and pressure changes showed that GSL caused permanent membrane fouling. This study underlines the significance of Sphingomonas for the initial attachment of bacteria to membranes. A deeper understanding and identification of key components in the biofouling process may help define strategies for biofilm prevention.

MDPI eBooks, Aug 27, 2019

Sciences. She is an expert in transmission electron microscopy and develops hybrid nanomaterials ... more Sciences. She is an expert in transmission electron microscopy and develops hybrid nanomaterials for photovoltaic applications. She also applies nanomaterials to water remediation. She has 80 publications, 2 patents, 4 book chapters, 1 book, and an H-index of 22. She is also CEO of PRO-1 NANOSolutions, a startup company that applies nanotechnology to water remediation and nanomedicine.

Boxall, J. and Maksimovic, C. 2009. Integrating Water Systems. Proceedings of conference “Computation and Control in the Water Industry”, Sheffield (UK), September 1-3, 2009. CRC Press, Taylor&Francis Group., 2010

Based on monitoring of particle related water quality in an experimental pipe loop, the fouling o... more Based on monitoring of particle related water quality in an experimental pipe loop, the fouling of pipes under common hydraulic conditions found in distribution systems is modelled. The processes transport, deposition and re-suspension are investigated experimentally, modelled and then programmed in Matlab as a software module. As required structure and hydraulics of existent drinking water distribution systems are usually available by pipe modelling software, the interaction between modelling software and quality module becomes defined.

Journal of Environmental Management, Jun 1, 2021

Concentrations of genetic markers for antibiotic resistance genes (ARGs) were measured in the eff... more Concentrations of genetic markers for antibiotic resistance genes (ARGs) were measured in the effluents of three Norwegian wastewater treatment plants (WWTPs) and in a receiving river upstream and downstream of the discharge point of one WWTP. Calculations based on mass balances were carried out to evaluate the impact of river flow rates and treatment effectivity on the WWTP's contribution to the load of genetic markers in the river. At average river flow rates, the WWTP effluent contributes 5-15% to the genetic marker load of the respective river. However, at minimum river flow rates, the WWTP effluent contributes 22-55% to the loads of different genetic markers. Scenarios of an improved or worsened removal of genetic markers in the WWTP showed that a further 1-log removal using additional treatment would be sufficient to improve considerably the river water quality with respect to genetic markers. Then, at an average flow rate, the contribution of the WWTP effluent to the load of the river would be less than 2%. However, in the case of low treatment effectivity or malfunction of the WWTP, the marker load of the river would increase dramatically. Even at average flow rate, 75-92% of the marker load would then originate from the WWTP. The results demonstrate the importance of considering the flow rates and hydrologic characteristics of the recipient water body when deciding on priorities regarding the upgrade of WWTPs for further removal of ARGs.

Water Research, Apr 1, 2018

Overall apparent reaction rates for the removal of monochloramine (MCA) in granular activated car... more Overall apparent reaction rates for the removal of monochloramine (MCA) in granular activated carbon (GAC) beds were determined using a fixed-bed reactor system and under conditions typical for swimming pool water treatment. Reaction rates dropped and quasi-stationary conditions were reached quickly. Diffusional mass transport in the pores was shown to be limiting the overall reaction rate. This was reflected consistently in the Thiele modulus, in the effect of temperature, pore size distribution and of grain size on the reaction rates. Pores <2.5 times the diameter of the monochloramine molecule were shown to be barely accessible for the monochloramine conversion reaction. GACs with a significant proportion of large mesopores were found to have the highest overall reactivity for monochloramine removal.

Water Research, Nov 1, 2016

The extent and mechanisms by which organic matter in a solution can be retained and foul a membra... more The extent and mechanisms by which organic matter in a solution can be retained and foul a membrane largely depends on the molecular weight of the material being filtered and the molecular weight cut-off (MWCO) of the membrane. The present study investigated the effect of the MWCO of a membrane and the molecular weight distribution of natural organic matter (NOM) in a source water on the increase in resistance to the permeate flux over time. Of particular interest was the effect of oxidation, applied prior to membrane filtration, on the predominant fouling mechanism. Oxidation can change the molecular weight distribution of organic matter in raw water, and therefore the ability of a membrane to retain this organic matter. Oxidation, using both ozonation and UV/H2O2, could effectively reduce the extent of fouling for higher MWCO membranes. However, neither oxidation approaches could effectively reduce the extent of fouling for lower MWCO membranes, likely because oxidation could not effectively oxidize lower molecular weight organic matter. Althoug the data indicated that the extent of fouling is increasing with the amount of DOC retained by the membrane, no statistically significant correlation was observed between these parameters. The results suggest that oxidation did not affect the predominant fouling mechanism. However, it did affect the molecular weight distribution of the organic matter retained by the membranes, and as a result, the resistance offered by the foulant cake layer.

International Journal of Food Microbiology, May 1, 2004

Drinking water distributed without disinfection and without regrowth problems for many years may ... more Drinking water distributed without disinfection and without regrowth problems for many years may show bacterial regrowth when the residence time and/or temperature in the distribution system increases or when substrate and/or bacterial concentration in the treated water increases. An example of a regrowth event in a major German city is discussed. Regrowth of HPC bacteria occurred unexpectedly at the end of a very hot summer. No pathogenic or potentially pathogenic bacteria were identified. Increased residence times in the distribution system and temperatures up to 25 jC were identified as most probable causes and the regrowth event was successfully overcome by changing flow regimes and decreasing residence times. Standard plate counts of HPC bacteria using the spread plate technique on nutrient rich agar according to German Drinking Water Regulations (GDWR) had proven to be a very good indicator of hygienically safe drinking water and to demonstrate the effectiveness of water treatment. However, the method proved insensitive for early regrowth detection. Regrowth experiments in the lab and sampling of the distribution system during two summers showed that spread plate counts on nutrient-poor R2A agar after 7-day incubation yielded 100 to 200 times higher counts. Counts on R2A after 3-day incubation were three times less than after 7 days. As the precision of plate count methods is very poor for counts less than 10 cfu/plate, a method yielding higher counts is better suited to detect upcoming regrowth than a method yielding low counts. It is shown that for the identification of regrowth events HPC(R2A) gives a further margin of about 2 weeks for reaction before HPC(GDWR).

DESALINATION AND WATER TREATMENT, 2017

A long-channel membrane test cell (LCMTC) with the same length as full-scale elements was develop... more A long-channel membrane test cell (LCMTC) with the same length as full-scale elements was developed to simulate performance and fouling in nanofiltration and reverse osmosis spiral-wound membrane modules (SWMs). The transparent LCMTC enabled simultaneous monitoring of SWM performance indicators: feed channel pressure drop, permeate flux and salt passage. Both permeate flux and salt passage were monitored over five sections of the test cell and were related to the amount and composition of the accumulated foulant in these five sections, illustrating the unique features of the test cell. Validation experiments at various feed pressures showed the same flow profile and the same hydraulic behaviour as SWMs used in practice, confirming the representativeness and suitability of the test cell to study SWM operation and fouling. The importance to apply feed spacers matching the flow channel height in test cell systems was demonstrated. Biofouling studies showed that the dosage of a biodegradable substrate to the feed of the LCMTC accelerated the gradual decrease of membrane performance and the accumulation of biomass on the spacer and membrane sheets. The strongest permeate flux decline and the largest amount of accumulated biomass was found in the first 18 cm of the test cell. The LCMTC showed to be suitable to study the impact of biofilm development and biofouling control strategies under representative conditions for full-scale membrane elements.

Wiley-VCH Verlag GmbH eBooks, Mar 20, 2008

Aqua, May 1, 2009

The treatment of raw water by hybrid coagulation-ultrafiltration was investigated. Coagulationult... more The treatment of raw water by hybrid coagulation-ultrafiltration was investigated. Coagulationultrafiltration removed high molecular weight organics, preferentially humics. Adsorption of the trace compound cis-1,2-dichloroethene, present in raw water, on granular activated carbon was improved considerably as compounds competing for adsorption space had been removed. This was shown in isotherms and breakthrough curves. Aeration during filtration did not affect membrane performance as expressed in permeability. However, aeration in the submerged membrane container resulted in a release of organic matter from the flocs, which resulted in higher concentrations of dissolved organic carbon in the filtrate.

Chemie Ingenieur Technik, Sep 1, 1997

Nanomaterials, Jun 14, 2019

Water Science and Technology, Oct 1, 2005

For swimming pools, it is generally agreed that free chlorine levels have to be maintained to gua... more For swimming pools, it is generally agreed that free chlorine levels have to be maintained to guarantee adequate disinfection. Recommended free chlorine levels can vary between 0.3 and 0.6 mg/L in Germany and up to 3 mg/L in other countries. Bathers introduce considerable amounts of organic matter, mainly in the form of such as urine and sweat, into the pool water. As a consequence, disinfection byproducts (DBPs) are formed. Regulations in Germany recommend levels of combined chlorine of less than 0.2 mg/L and levels of trihalomethanes (THMs) of less than 20 mg/L. Haloacetic acids (HAAs), haloacetonitriles (HANs), chloropicrin and chloral hydrate are also detected in considerable amounts. However, these compounds are not regulated yet. Swimming pool staff and swimmers, especially athletes, are primarily exposed to these byproducts by inhalation and/or dermal uptake. In Germany, new regulations for swimming pool water treatment generally require the use of activated carbon. In this project, three different types of granular activated carbon (GAC) (one standard GAC, two catalytic GACs) are compared for their long time behaviour in pool water treatment. In a pilot plant operated with real swimming pool water, production and removal of disinfection byproducts (THMs, HAAs, AOXs), of biodegradable substances (AOC), of bacteria (Pseudomonas aeruginosa, Legionella, coliforms, HPC) as well as the removal of chlorine and chloramines are monitored as function of GAC bed depth. Combined chlorine penetrates deeper in the filter bed than free chlorine does. However, both, free and combined chlorine removal efficiencies decrease over the time of filter operation. The decreases of removal efficiencies are also observed for parameters such as dissolved organic carbon, spectral absorption coefficient, adsorbable organic carbon and most of the disinfection byproducts. However, THMs, especially chloroform are produced in the filter bed. The GAC beds were contaminated microbially, especially with P. aeruginosa. The contamination was not removable by backwashing with chlorine concentrations up to 2 mg/l free chlorine.

World Environmental and Water Resources Congress 2009, May 12, 2009

VANN, 2018

Effektiviteten av de ulike behandlingstrinnene for fjerning av antibiotikaresistente E. coli i av... more Effektiviteten av de ulike behandlingstrinnene for fjerning av antibiotikaresistente E. coli i avløpsvann fra to store avløpsrenseanlegg i Oslo ble undersøkt. Renseanleggene reduserer den totale mengden kultiverbare E. coli fra avløpsvannet effektivt, men fjerningen av disse bakteriene var ufullstendig i begge anleggene. Bakteriene var delvis resistente mot ampicillin og cotrimoxazole, og i mindre grad tetracyclin og ciprofloxacin. Med hensyn til fjerning av resistente E. coli viste anleggene forskjellige mønstre utover i behandlingsprosessen. Analysen av et utvalg markørgener i utslippsvannet viser forekomst av resistens mot antibiotika som brukes hyppig i Norge, men også svært sjelden brukte og kritisk viktige antibiotika, inkludert karbapenemer, colistin og cefalosporiner. Gjennom ultra- og nanofiltrering på laboratorieskala av utslippsvannet fra avløpsrenseanleggene, ble alle kultiverbare E. coli, inkludert resistente E. coli, fullstendig fjernet

Summary
Abundance of antibiotic resistance genes and
removal of antibiotic resistant E. coli in to Norwegian
wastewater treatment plants. The effectivity
of different treatment stages at two wastewater
treatment plants (WWTPs) to remove cultivable
antibiotic resistant E. coli from municipal
wastewater from Oslo City was investigated.
The WWTPs were effective in reducing total
cultivable E. coli, however, full hygienization
was not achieved. The E. coli in WWTP samples
were partly resistant to ampicillin and co-trimoxazole,
and to a lesser extent, tetracycline and
ciprofloxacin. The plants showed different patterns
with respect to the removal of resistant E.
coli. Analysis of selected antibiotics maker genes
in samples from WWTP effluent revealed the
presence of resistance against commonly used
groups of antibiotics, but also to such that are
rarely used and belong to critically important
antibiotics, including carbapenemes, colistin and
cefalosporines. By membrane filtration of WWTP
effluents, using lab-scale ultra- and nanofiltration,
all cultivable E. coli, including antibiotic
resistant ones, were removed completely.

Journal of Hazardous Materials, 2024

Untreated stormwater is a major source of microplastics, organic pollutants, metals, and nutrient... more Untreated stormwater is a major source of microplastics, organic pollutants, metals, and nutrients in urban water
courses. The aim of this study was to improve the knowledge about the start-up periods of bioretention filters. A
rain garden pilot facility with 13 bioretention filters was constructed and stormwater from a highway and
adjacent impervious surfaces was used for irrigation for ~12 weeks. Selected plants (Armeria maritima, Hippophae
rhamnoides, Juncus effusus, and Festuca rubra) was planted in ten filters. Stormwater percolated through the filters
containing waste-to-energy bottom ash, biochar, or Sphagnum peat, mixed with sandy loam. Influent and effluent
samples were taken to evaluate removal of the above-mentioned pollutants. All filters efficiently removed
microplastics >10 μm, organic pollutants, and most metals. Copper leached from all filters initially but was
significantly reduced in the biochar filters at the end of the period, while the other filters showed a declining
trend. All filters leached nutrients initially, but concentrations decreased over time, and the biochar filters had
efficiently reduced nitrogen after a few weeks. To conclude, all the filters effectively removed pollutants during the start-up period. Before being recommended for full-scale applications, the functionality of the filters after a
longer period of operation should be evaluated

Water Practice & Technology, 2024

The addition of powdered activated carbon (PAC) in advanced wastewater treatment is increasingly ... more The addition of powdered activated carbon (PAC) in advanced wastewater treatment is increasingly recognized for its effectiveness
in removing micropollutants from secondary effluents. This study investigates the implications of PAC dosing on treatment
performance, particularly in terms of natural and effluent organic matter (OM) removal, turbidity reduction, and sludge characteristics.
Results indicate that while PAC incorporation significantly enhances the adsorption of OM, it necessitates higher
coagulant dosages to achieve comparable or improved turbidity levels. The study also reveals that lower pH levels facilitate
the removal of OM, thereby increasing the availability of adsorption sites on PAC for micropollutants. Moreover, PAC addition
results in the formation of larger, denser flocs that settle faster, leading to a reduction in sludge volume by approximately 20%.
However, the increased coagulant demand and the subsequent rise in sludge volume highlight the need for the optimized process
design to balance treatment efficiency with operational costs. This research provides valuable insights for the design and
operation of wastewater treatment plants, emphasizing the importance of tailored coagulant dosing and process adjustments
when integrating PAC into existing treatment frameworks.

Journal of Hazardous Materials, 2024

Tunnel wash water (TWW) contains high levels of trace elements and organic micropollutants, espec... more Tunnel wash water (TWW) contains high levels of trace elements and organic micropollutants, especially in the
dissolved fraction. Discharge poses significant environmental risks. This field study aimed at improving con-
ventional sedimentation treatment by addition of novel secondary treatments: bag filtration, ceramic micro-
filtration, or granular activated carbon (GAC) filtration. Removal of nine trace elements, 16 polycyclic aromatic
hydrocarbons (PAHs), 38 per- and polyfluoroalkyl substances (PFASs), seven benzothiazoles (BTHs), seven
benzotriazoles (BTRs), five bisphenols (BPs), and five benzophenones was investigated. Primary sedimentation
significantly reduced particles and associated contaminants, achieving over 73 % average removal for trace
elements, 65 % for PAHs, and 71 % for PFASs. Subsequent GAC removed over 70 % of dissolved Cr, Cu, Pb, and
Zn and over 92 % of dissolved PFASs, BTHs, BTRs, and BPs, including several persistent, mobile and toxic
compounds. Following GAC filtration, Cr, Ni, Pb, anthracene, fluoranthene, perfluorooctanesulfonic acid, and
bisphenol-A were below environmental quality standards (EQS). GAC consistently reduced responses in in vitro
bioassays with endpoints activation of the aryl hydrocarbon receptor, oxidative stress response, and neurotoxicity below effect-based trigger values for surface water. GAC filtration is thus recommended for future
TWW treatment. Assessing water quality remains a challenging task due to lack of EQSs for many chemicals.

Environmental Science and Technology Letters, Jan 29, 2015

Biofouling is a ubiquitous problem in many places in society and technology, especially in revers... more Biofouling is a ubiquitous problem in many places in society and technology, especially in reverse osmosis or nanofiltration (NF) processes. Initial stages in the development of the biofilm include attachment of bacteria to the surface, where bacterial outer membrane components such as biopolymers, lipids, and proteins play important roles. Here we show that the glycosphingolipid (GSL) unique to Sphingomonas species is a key player in the initial attachment of bacteria to NF membranes whereas lipopolysaccharide (LPS), the major glycolipid in many Gram-negative species, is less significant. GSL and LPS were deposited on an NF membrane with subsequent bacterial culture injection in a three-dimensionally printed microfluidic flow cell. Flux, rejection, and pressure changes showed that GSL caused permanent membrane fouling. This study underlines the significance of Sphingomonas for the initial attachment of bacteria to membranes. A deeper understanding and identification of key components in the biofouling process may help define strategies for biofilm prevention.

MDPI eBooks, Aug 27, 2019

Sciences. She is an expert in transmission electron microscopy and develops hybrid nanomaterials ... more Sciences. She is an expert in transmission electron microscopy and develops hybrid nanomaterials for photovoltaic applications. She also applies nanomaterials to water remediation. She has 80 publications, 2 patents, 4 book chapters, 1 book, and an H-index of 22. She is also CEO of PRO-1 NANOSolutions, a startup company that applies nanotechnology to water remediation and nanomedicine.

Boxall, J. and Maksimovic, C. 2009. Integrating Water Systems. Proceedings of conference “Computation and Control in the Water Industry”, Sheffield (UK), September 1-3, 2009. CRC Press, Taylor&Francis Group., 2010

Based on monitoring of particle related water quality in an experimental pipe loop, the fouling o... more Based on monitoring of particle related water quality in an experimental pipe loop, the fouling of pipes under common hydraulic conditions found in distribution systems is modelled. The processes transport, deposition and re-suspension are investigated experimentally, modelled and then programmed in Matlab as a software module. As required structure and hydraulics of existent drinking water distribution systems are usually available by pipe modelling software, the interaction between modelling software and quality module becomes defined.

Journal of Environmental Management, Jun 1, 2021

Concentrations of genetic markers for antibiotic resistance genes (ARGs) were measured in the eff... more Concentrations of genetic markers for antibiotic resistance genes (ARGs) were measured in the effluents of three Norwegian wastewater treatment plants (WWTPs) and in a receiving river upstream and downstream of the discharge point of one WWTP. Calculations based on mass balances were carried out to evaluate the impact of river flow rates and treatment effectivity on the WWTP's contribution to the load of genetic markers in the river. At average river flow rates, the WWTP effluent contributes 5-15% to the genetic marker load of the respective river. However, at minimum river flow rates, the WWTP effluent contributes 22-55% to the loads of different genetic markers. Scenarios of an improved or worsened removal of genetic markers in the WWTP showed that a further 1-log removal using additional treatment would be sufficient to improve considerably the river water quality with respect to genetic markers. Then, at an average flow rate, the contribution of the WWTP effluent to the load of the river would be less than 2%. However, in the case of low treatment effectivity or malfunction of the WWTP, the marker load of the river would increase dramatically. Even at average flow rate, 75-92% of the marker load would then originate from the WWTP. The results demonstrate the importance of considering the flow rates and hydrologic characteristics of the recipient water body when deciding on priorities regarding the upgrade of WWTPs for further removal of ARGs.

Water Research, Apr 1, 2018

Overall apparent reaction rates for the removal of monochloramine (MCA) in granular activated car... more Overall apparent reaction rates for the removal of monochloramine (MCA) in granular activated carbon (GAC) beds were determined using a fixed-bed reactor system and under conditions typical for swimming pool water treatment. Reaction rates dropped and quasi-stationary conditions were reached quickly. Diffusional mass transport in the pores was shown to be limiting the overall reaction rate. This was reflected consistently in the Thiele modulus, in the effect of temperature, pore size distribution and of grain size on the reaction rates. Pores <2.5 times the diameter of the monochloramine molecule were shown to be barely accessible for the monochloramine conversion reaction. GACs with a significant proportion of large mesopores were found to have the highest overall reactivity for monochloramine removal.

Water Research, Nov 1, 2016

The extent and mechanisms by which organic matter in a solution can be retained and foul a membra... more The extent and mechanisms by which organic matter in a solution can be retained and foul a membrane largely depends on the molecular weight of the material being filtered and the molecular weight cut-off (MWCO) of the membrane. The present study investigated the effect of the MWCO of a membrane and the molecular weight distribution of natural organic matter (NOM) in a source water on the increase in resistance to the permeate flux over time. Of particular interest was the effect of oxidation, applied prior to membrane filtration, on the predominant fouling mechanism. Oxidation can change the molecular weight distribution of organic matter in raw water, and therefore the ability of a membrane to retain this organic matter. Oxidation, using both ozonation and UV/H2O2, could effectively reduce the extent of fouling for higher MWCO membranes. However, neither oxidation approaches could effectively reduce the extent of fouling for lower MWCO membranes, likely because oxidation could not effectively oxidize lower molecular weight organic matter. Althoug the data indicated that the extent of fouling is increasing with the amount of DOC retained by the membrane, no statistically significant correlation was observed between these parameters. The results suggest that oxidation did not affect the predominant fouling mechanism. However, it did affect the molecular weight distribution of the organic matter retained by the membranes, and as a result, the resistance offered by the foulant cake layer.

International Journal of Food Microbiology, May 1, 2004

Drinking water distributed without disinfection and without regrowth problems for many years may ... more Drinking water distributed without disinfection and without regrowth problems for many years may show bacterial regrowth when the residence time and/or temperature in the distribution system increases or when substrate and/or bacterial concentration in the treated water increases. An example of a regrowth event in a major German city is discussed. Regrowth of HPC bacteria occurred unexpectedly at the end of a very hot summer. No pathogenic or potentially pathogenic bacteria were identified. Increased residence times in the distribution system and temperatures up to 25 jC were identified as most probable causes and the regrowth event was successfully overcome by changing flow regimes and decreasing residence times. Standard plate counts of HPC bacteria using the spread plate technique on nutrient rich agar according to German Drinking Water Regulations (GDWR) had proven to be a very good indicator of hygienically safe drinking water and to demonstrate the effectiveness of water treatment. However, the method proved insensitive for early regrowth detection. Regrowth experiments in the lab and sampling of the distribution system during two summers showed that spread plate counts on nutrient-poor R2A agar after 7-day incubation yielded 100 to 200 times higher counts. Counts on R2A after 3-day incubation were three times less than after 7 days. As the precision of plate count methods is very poor for counts less than 10 cfu/plate, a method yielding higher counts is better suited to detect upcoming regrowth than a method yielding low counts. It is shown that for the identification of regrowth events HPC(R2A) gives a further margin of about 2 weeks for reaction before HPC(GDWR).

DESALINATION AND WATER TREATMENT, 2017

A long-channel membrane test cell (LCMTC) with the same length as full-scale elements was develop... more A long-channel membrane test cell (LCMTC) with the same length as full-scale elements was developed to simulate performance and fouling in nanofiltration and reverse osmosis spiral-wound membrane modules (SWMs). The transparent LCMTC enabled simultaneous monitoring of SWM performance indicators: feed channel pressure drop, permeate flux and salt passage. Both permeate flux and salt passage were monitored over five sections of the test cell and were related to the amount and composition of the accumulated foulant in these five sections, illustrating the unique features of the test cell. Validation experiments at various feed pressures showed the same flow profile and the same hydraulic behaviour as SWMs used in practice, confirming the representativeness and suitability of the test cell to study SWM operation and fouling. The importance to apply feed spacers matching the flow channel height in test cell systems was demonstrated. Biofouling studies showed that the dosage of a biodegradable substrate to the feed of the LCMTC accelerated the gradual decrease of membrane performance and the accumulation of biomass on the spacer and membrane sheets. The strongest permeate flux decline and the largest amount of accumulated biomass was found in the first 18 cm of the test cell. The LCMTC showed to be suitable to study the impact of biofilm development and biofouling control strategies under representative conditions for full-scale membrane elements.

Wiley-VCH Verlag GmbH eBooks, Mar 20, 2008

Aqua, May 1, 2009

The treatment of raw water by hybrid coagulation-ultrafiltration was investigated. Coagulationult... more The treatment of raw water by hybrid coagulation-ultrafiltration was investigated. Coagulationultrafiltration removed high molecular weight organics, preferentially humics. Adsorption of the trace compound cis-1,2-dichloroethene, present in raw water, on granular activated carbon was improved considerably as compounds competing for adsorption space had been removed. This was shown in isotherms and breakthrough curves. Aeration during filtration did not affect membrane performance as expressed in permeability. However, aeration in the submerged membrane container resulted in a release of organic matter from the flocs, which resulted in higher concentrations of dissolved organic carbon in the filtrate.

Chemie Ingenieur Technik, Sep 1, 1997

Nanomaterials, Jun 14, 2019

Water Science and Technology, Oct 1, 2005

For swimming pools, it is generally agreed that free chlorine levels have to be maintained to gua... more For swimming pools, it is generally agreed that free chlorine levels have to be maintained to guarantee adequate disinfection. Recommended free chlorine levels can vary between 0.3 and 0.6 mg/L in Germany and up to 3 mg/L in other countries. Bathers introduce considerable amounts of organic matter, mainly in the form of such as urine and sweat, into the pool water. As a consequence, disinfection byproducts (DBPs) are formed. Regulations in Germany recommend levels of combined chlorine of less than 0.2 mg/L and levels of trihalomethanes (THMs) of less than 20 mg/L. Haloacetic acids (HAAs), haloacetonitriles (HANs), chloropicrin and chloral hydrate are also detected in considerable amounts. However, these compounds are not regulated yet. Swimming pool staff and swimmers, especially athletes, are primarily exposed to these byproducts by inhalation and/or dermal uptake. In Germany, new regulations for swimming pool water treatment generally require the use of activated carbon. In this project, three different types of granular activated carbon (GAC) (one standard GAC, two catalytic GACs) are compared for their long time behaviour in pool water treatment. In a pilot plant operated with real swimming pool water, production and removal of disinfection byproducts (THMs, HAAs, AOXs), of biodegradable substances (AOC), of bacteria (Pseudomonas aeruginosa, Legionella, coliforms, HPC) as well as the removal of chlorine and chloramines are monitored as function of GAC bed depth. Combined chlorine penetrates deeper in the filter bed than free chlorine does. However, both, free and combined chlorine removal efficiencies decrease over the time of filter operation. The decreases of removal efficiencies are also observed for parameters such as dissolved organic carbon, spectral absorption coefficient, adsorbable organic carbon and most of the disinfection byproducts. However, THMs, especially chloroform are produced in the filter bed. The GAC beds were contaminated microbially, especially with P. aeruginosa. The contamination was not removable by backwashing with chlorine concentrations up to 2 mg/l free chlorine.

World Environmental and Water Resources Congress 2009, May 12, 2009

VANN, 2018

Effektiviteten av de ulike behandlingstrinnene for fjerning av antibiotikaresistente E. coli i av... more Effektiviteten av de ulike behandlingstrinnene for fjerning av antibiotikaresistente E. coli i avløpsvann fra to store avløpsrenseanlegg i Oslo ble undersøkt. Renseanleggene reduserer den totale mengden kultiverbare E. coli fra avløpsvannet effektivt, men fjerningen av disse bakteriene var ufullstendig i begge anleggene. Bakteriene var delvis resistente mot ampicillin og cotrimoxazole, og i mindre grad tetracyclin og ciprofloxacin. Med hensyn til fjerning av resistente E. coli viste anleggene forskjellige mønstre utover i behandlingsprosessen. Analysen av et utvalg markørgener i utslippsvannet viser forekomst av resistens mot antibiotika som brukes hyppig i Norge, men også svært sjelden brukte og kritisk viktige antibiotika, inkludert karbapenemer, colistin og cefalosporiner. Gjennom ultra- og nanofiltrering på laboratorieskala av utslippsvannet fra avløpsrenseanleggene, ble alle kultiverbare E. coli, inkludert resistente E. coli, fullstendig fjernet

Summary
Abundance of antibiotic resistance genes and
removal of antibiotic resistant E. coli in to Norwegian
wastewater treatment plants. The effectivity
of different treatment stages at two wastewater
treatment plants (WWTPs) to remove cultivable
antibiotic resistant E. coli from municipal
wastewater from Oslo City was investigated.
The WWTPs were effective in reducing total
cultivable E. coli, however, full hygienization
was not achieved. The E. coli in WWTP samples
were partly resistant to ampicillin and co-trimoxazole,
and to a lesser extent, tetracycline and
ciprofloxacin. The plants showed different patterns
with respect to the removal of resistant E.
coli. Analysis of selected antibiotics maker genes
in samples from WWTP effluent revealed the
presence of resistance against commonly used
groups of antibiotics, but also to such that are
rarely used and belong to critically important
antibiotics, including carbapenemes, colistin and
cefalosporines. By membrane filtration of WWTP
effluents, using lab-scale ultra- and nanofiltration,
all cultivable E. coli, including antibiotic
resistant ones, were removed completely.