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Fuchslin H.P.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Fuchslin H.P.,Bachema AG | Schneider C.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Schneider C.,ETH Zurich | And 3 more authors.
ISME Journal | Year: 2012

The competition for glucose between Escherichia coli ML30, a typical copiotrophic enterobacterium and Chelatobacter heintzii ATCC29600, an environmentally successful strain, was studied in a carbon-limited culture at low dilution rates. First, as a base for modelling, the kinetic parameters max and K s were determined for growth with glucose. For both strains, max was determined in batch culture after different precultivation conditions. In the case of C. heintzii, max was virtually independent of precultivation conditions. When inoculated into a glucose-excess batch culture medium from a glucose-limited chemostat run at a dilution rate of 0.075 h 1 C. heintzii grew immediately with a max of 0.170.03 h 1. After five transfers in batch culture, max had increased only slightly to 0.180.03 h 1. A different pattern was observed in the case of E. coli. Inoculated from a glucose-limited chemostat at D0.075 h 1 into glucose-excess batch medium E. coli grew only after an acceleration phase of 3.5 h with a max of 0.52 h 1. After 120 generations and several transfers into fresh medium, max had increased to 0.800.03 h 1. For long-term adapted chemostat-cultivated cells, a K s for glucose of 15 g l 1 for C. heintzii, and of 35 g l 1 for E. coli, respectively, was determined in 14 C-labelled glucose uptake experiments. In competition experiments, the population dynamics of the mixed culture was determined using specific surface antibodies against C. heintzii and a specific 16S rRNA probe for E. coli. C. heintzii outcompeted E. coli in glucose-limited continuous culture at the low dilution rates of 0.05 and 0.075 h 1. Using the determined pure culture parameter values for K s and max, it was only possible to simulate the population dynamics during competition with an extended form of the Monod model, which includes a finite substrate concentration at zero growth rate (s min). The values estimated for s min were dependent on growth rate; at D0.05 h 1, it was 12.6 and 0 g l 1 for E. coli and C. heintzii, respectively. To fit the data at D0.075 h 1, s min for E. coli had to be raised to 34.9 g l 1 whereas s min for C. heintzii remained zero. The results of the mathematical simulation suggest that it is not so much the higher K s value, which is responsible for the unsuccessful competition of E. coli at low residual glucose concentration, but rather the existence of a significant s min. © 2012 International Society for Microbial Ecology All rights reserved. Source


Michen B.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Michen B.,TU Bergakademie Freiberg | Meder F.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Rust A.,Bachema AG | And 4 more authors.
Environmental Science and Technology | Year: 2012

Ceramic filter candles, based on the natural material diatomaceous earth, are widely used to purify water at the point-of-use. Although such depth filters are known to improve drinking water quality by removing human pathogenic protozoa and bacteria, their removal regarding viruses has rarely been investigated. These filters have relatively large pore diameters compared to the physical dimension of viruses. However, viruses may be retained by adsorption mechanisms due to intermolecular and surface forces. Here, we use three types of bacteriophages to investigate their removal during filtration and batch experiments conducted at different pH values and ionic strengths. Theoretical models based on DLVO-theory are applied in order to verify experimental results and assess surface forces involved in the adsorptive process. This was done by calculation of interaction energies between the filter surface and the viruses. For two small spherically shaped viruses (MS2 and PhiX174), these filters showed no significant removal. In the case of phage PhiX174, where attractive interactions were expected, due to electrostatic attraction of oppositely charged surfaces, only little adsorption was reported in the presence of divalent ions. Thus, we postulate the existence of an additional repulsive force between PhiX174 and the filter surface. It is hypothesized that such an additional energy barrier originates from either the phage's specific knobs that protrude from the viral capsid, enabling steric interactions, or hydration forces between the two hydrophilic interfaces of virus and filter. However, a larger-sized, tailed bacteriophage of the family Siphoviridae was removed by log 2 to 3, which is explained by postulating hydrophobic interactions. © 2011 American Chemical Society. Source


Keserue H.-A.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Keserue H.-A.,Federal office of Public Health of Fribourg | Keserue H.-A.,ETH Zurich | Fuchslin H.P.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | And 11 more authors.
Environmental Science and Technology | Year: 2012

Reliable, sensitive, quantitative, and mobile rapid screening methods for pathogenic organisms are not yet readily available, but would provide a great benefit to humanitarian intervention units in disaster situations. We compared three different methods (immunofluorescent microscopy, IFM; flow cytometry, FCM; polymerase chain reaction, PCR) for the rapid and quantitative detection of Giardia lamblia and Cryptosporidium parvum (oo)cysts in a field campaign. For this we deployed our mobile instrumentation and sampled canal water and vegetables during a 2 week field study in Thailand. For purification and concentrations of (oo)cysts, we used filtration and immunomagnetic separation. We were able to detect considerably high oo(cysts) concentrations (ranges: 15-855 and 0-240 oo(cysts)/liter for Giardia and Cryptosporidium, respectively) in 85 to 300 min, with FCM being fastest, followed by PCR, and IFM being slowest due to the long analysis time per sample. FCM and IFM performed consistently well, whereas PCR reactions often failed. The recovery, established by FCM, was around 30% for Giardia and 13% for Cryptosporidium (oo)cysts. It was possible to track (oo)cysts from the wastewater further downstream to irrigation waters and confirm contamination of salads and water vegetables. We believe that rapid detection, in particular FCM-based methods, can substantially help in disaster management and outbreak prevention. © 2012 American Chemical Society. Source


Wager P.A.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Schluep M.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Muller E.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Gloor R.,Bachema AG
Environmental Science and Technology | Year: 2012

The disposal and recovery of plastics from waste electrical and electronic equipment (WEEE) are of considerable importance, both from an environmental and an economic perspective. This paper presents the results of a study investigating current concentrations of hazardous substances in mixed plastics from WEEE and their implications for an environmentally sound recovery. The study included 53 sampling campaigns for mixed plastics from WEEE. The samples were analyzed with regard to heavy metals (cadmium, chromium, mercury, and lead) and flame retardants (PentaBDE, OctaBDE, DecaBDE, DecaBB) regulated in the RoHS Directive. Besides these substances, other brominated flame retardants known to occur in electronics (HBCD, TBBPA) as well as the total bromine and phosphorus contents were considered. Results show that no mixed plastics fraction from WEEE is completely free from substances regulated in the RoHS Directive. The lowest number and average concentrations were found in flat screen monitors. The highest concentrations were found in mixed plastics from CRT monitors and TVs. Mixed plastics fractions with high average concentrations of heavy metals originate from the treatment of small household appliances (cadmium), ICT equipment (lead), and consumer equipment (lead). Mixed plastics fractions with high average concentrations of brominated flame retardants mainly originate from the treatment of small household appliances for high temperature applications (DecaBDE), CRT monitors (OctaBDE and DecaBDE) and consumer equipment (DecaBDE), in particular CRT TVs (DecaBDE). To avoid a dissipation of hazardous substances into plastics and the environment, it is recommended that mixed plastics from WEEE are subject to a strict quality management. © 2011 American Chemical Society. Source


Widmer R.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Du X.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Haag O.,Bachema AG | Restrepo E.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Wager P.A.,Empa - Swiss Federal Laboratories for Materials Science and Technology
Environmental Science and Technology | Year: 2015

Concurrent with the demand for cleaner, lighter, and more efficient vehicles, many scarce metals (SMs) are used in passenger vehicles because of their unique physical and chemical properties. To explore the recycling potential of these metals, it is important to understand their distribution in the vehicles as well as their fate at the vehicles end-of-life. However, this information remains very scattered and sparse. In this paper, we present a study investigating the distribution of 31 SMs in selected electrical and electronic (EE) components of conventional passenger vehicles and in the end-of-life vehicle shredder fractions from a shredder plant in Switzerland. The results of the chemical analyses show that the mass fractions of Co, Sn, Sr, Ta, Y, and Zr were dominant with >20 000 g/t in the selected EE components and Ag, Ga, Mo, Sb, Sn, Sr, and Zr with >50 g/t in the analyzed shredder fractions. The largest masses of 17 SMs were found in the shredder light fraction, which is incinerated in municipal waste treatment plants mainly in Switzerland; thus, these SMs are currently not recovered. The SM mass fractions in both the EE components and the shredder fractions were projected to their total masses in 100 hypothetical midrange passenger vehicles. The resulting mass balance showed a mismatch of >50% for 23 metals, which indicates other important SM sources such as alloys. © 2015 American Chemical Society. Source

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