Department Environmental Chemistry

Master thesis topics 2017

Fate in Technical Systems

Optimization of an LC-HR-MS method, with special focus on liquid chromatography with a HILIC column

keywords:   instrument set-up, lab-work, analytical chemistry, organic   micropollutants   

Contact: Christa McAdell

Contaminant fate processes

Calibration of novel passive samplers for the monitoring of organic micropollutants at the interface between surface and groundwater in rivers (hyporheic zone)

keywords:   flume uptake experiment, uptake kinetics, passive sampling   workflow, lab work, LC-HRMS measurements of organic   pollutants

Contact: Juliane Hollender

Application of a suspect screening workflow on passive sampler extracts to identify biotransformation products formed in the hyporheic zone

keywords:  analysis of LC-HRMS data, organic pollutants, suspect   screening, elucidation of hyporheic (bio)transformation   products, sediment concentration profiles

Contact: Juliane Hollender

Water quality and management

Elucidating pesticide transfer mechanisms to streams based on time-series analysis

keywords: diffuse pollution, statistical analysis, hydrology and transport

Contact: Christian Stamm

Pesticide pollution in a tropical catchment in Costa Rica

keywords: diffuse pollution, statistical analysis, hydrology and transport

Contact: Christian Stamm

Analytics

Development of sensitive method for the quantification of emerging contaminants in surface water samples using a novel coupling technique GC-DBDI-Orbitrap

Contact: Heinz Singer

Detection of drug conjugates in waste water by high resolution mass spectrometry using post-acquisition neutral scan experiments

Contact: Heinz Singer

Identification of organic contaminants in the wastewater of chemical industries using high resolution mass spectrometry

keywords:   industrial wastewater, surface water contamination, analytical   chemistry, non-target screening, time series analysis

Contact: Heinz Singer

Environmental Fate Modeling

Evaluation of micropollutants biotransformation kinetics in temperature adapted activated sludge systems

Recent years have seen an increase in production and consumption of micropollutants, such as pharmaceuticals and anti-inflammatory drugs, which has resulted in their accumulation in influent and treated waters. Yet, their removal efficiency in biological systems is highly variable, and it is still unclear how operational and environmental parameters, such as temperature shifts (diurnal and seasonal fluctuations), affect plant performance. The current practice in environmental exposure assessment is to employ an Arrhenius approach where temperature correction factors are used to estimate biotransformation rates at different temperatures.  However, this model is highly debatable, as the Arrhenius relationship holds over a limited temperature range and, for larger temperature variations, the microbial communities may be expected to change and adapt to the process conditions, likely affecting contaminants degradation in a less predictable manner.  This project investigates the validity of using Arrhenius-based temperature correction factors to estimate micropollutants biotransformation rates in temperature-adapted activated sludge, sampled from a Swiss nitrifying wastewater treatment plant.  Biotransformation assays will be conducted in larger scale systems seeded with sludge adapted at five different temperatures (in the 10-30°C range) to evaluate the long-term temperature effect on the kinetics of micropollutant removal.  While laboratory-scale batch experiments run at different temperatures (4-40°C range) will explore the short-term impact of temperature variation on micropollutant removal in temperature-adapted sludges.  The experimental kinetic parameters obtained in the laboratory studies will be compared to Arrhenius model estimations in order to evaluate the suitability of such models to effectively predict the temperature dependence of biotransformation kinetics in wastewater treatment plants. 

Keywords: temperature, biotransformation assays, activated sludge, LC-MS analysis, kinetic modelling

Contacts: paola.meynet@eawag.chkathrin.fenner@eawag.ch

Investigating the effects of cytochrome P450 inhibitors on the biotransformation of organic micropollutants in activated sludge

keywords:   biotransformation experiments, activated sludge, LC-MS   measurements of organic micropollutants

Contact: Kathrin Fenner

Stable Isotope Lab

Assessing the biotransformation of hexachlorocyclohexane isomers in contaminated soil

Abstract:

Hexachlorocyclohexanes (HCH), such as the insecticidal gamma-HCH isomer, belong to the class of largely banned persistent organic pollutants (POP). Because HCHs only degrade over time-scales of decades and more, they are still found to contaminate soils at former production sites. In our research, we develop new approaches to track biodegradation processes based on the stable isotope fractionation that can be measured in the remaining pollutant.

In this project, we aim at understanding the C and H isotope effects pertinent to the different enzymatic dechlorination mechanisms of several HCH isomers. Candidates will learn (1) how to purify and work with LinA and LinB enzymes that are capable of transforming HCH isomers into less chlorinated compounds as well as (2) how to carry out compound-specific stable isotope analysis of H and C using gas chromatographs coupled to isotope ratio mass spectrometers.

Contact: Thomas Hofstetter

Compound-specific stable isotope analysis of insensitive munitions

Abstract:

Insensitive munitions explosives such as dinitroanisole and nitrotriazolone are new formulations that are safer to handle and transport, with less risk of self-detonation, than traditional nitroaromatic and nitramine explosives (e.g., trinitrotoluene, TNT). However, these new compounds are more water soluble and more mobile in the environment and their (bio)degradation pathways are understood only poorly.

In this work, we aim to develop new analytical tools for the measurement of carbon, nitrogen, and hydrogen isotope ratios of insensitive munitions. Isotopic fingerprints and isotope fractionation of these frequent soil and groundwater contaminants will be used to identify contamination sources and degradation pathways.

Contact: Thomas Hofstetter

Bioavailability of structural iron in smectites

Abstract:

Iron-bearing clay minerals are important redox buffers in the subsurface that can affect the biogeochemical cycling of elements and the fate, transport, and toxicity of pollutants. To assess the role that structural Fe in clay minerals plays in redox reactions in pristine and contaminated environments, we have recently developed electrochemistry-based approaches to derive thermodynamic parameters of such mineral phases.

In this work, we explore whether the activity of iron-reducing bacteria (Shewanella and Geobacter species) is controlled by the thermodynamic properties of the mineral specimen. Students will have the opportunity to combine their knowledge on biogeochemistry and thermodynamics with new experience in electrochemical analyses.

Contact: Thomas Hofstetter