Biogas // CHLOROFILTER // Ocean methane paradox // Release of arsenic into drinking water // AsFreeH2O // The problem of arsenic contamination in Bangladesh // FAARM // Methane in oxic lake water // Contribution to sustainable mining // Methane in groundwater of Bangladesh


Optimization of anaerobic degradation processes in biogas plants by use of on-line novel optical measurement techniques 

Contact person: Daniela Polag

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In cooperation with the Chair of Urban Water Systems Engineering of Technical University München (Dr. Konrad Koch) and the Bavarian State Research Center for Agriculture in Freising (Dr. Michael Lebuhn).


In recent years, the demand for renewable energy and the reduction of greenhouse gases such as CO2 has become increasingly important within the framework of energy transition. Besides possible energy savings and increased energy recovery, the CO2 footprint of wastewater treatment is still an issue that needs to be addressed. In case of wastewater treatment plants, every year about 3 million tons of CO2 are being emitted in Germany. Thus, coupling CO2 utilization with energy recovery for better overall utilization would be a great benefit.

Recent studies involving conventional digester processes reported increased CH4 production when CO2 was provided as flush gas for the digester headspace. Bioconversion from CO2 into CH4 has the advantage of (i) reducing CO2 emissions and (ii) transformation of CO2 into energetically usable CH4. Although describing the process in dependence of various parameters (i.e., substrate composition, temperature, microbial composition), none of the few recently published studies was able to elucidate the basic effects leading to the bioconversion of CO2 to CH4.

Thus, the major goal of this project is the identification of the mechanisms leading to increased CH4 formation by the addition of CO2 during anaerobic digestion of sewage sludge.

To achieve the mentioned goal an interdisciplinary approach is required including the use of stable isotope methods as the key parameter for process identification (RKU), know-how of process engineering including the supply of a fully-equipped laboratory with expertise in the performance of continuous flow-through experiments (TUM), and accompanying microbial analyses (LfL).

To identify the basic mechanisms of the observed bioconversion from CO2 into CH4 we aim to establish two continuous anaerobic digestion test systems at TUM. One system is enriched with CO2 while the other serves as the control. The reactors will be fed with sewage sludge from a municipal wastewater treatment plant in Garching. Tests will be carried out at various loading rates indicating different stress regimes which might have a significant influence on the mechanism of CH4-formation. During the tests, standard process parameters (TS, VS, COD, VFA, Alkalinity, pH value, gas quantity and quality) will be monitored. Additionally, the biocenosis in the digestate will be characterized by state-of-the-art molecular biological methods such as guild-specific quantitative real-time PCR on DNA and mRNA levels, and community sequencing approaches.

As a special focus of the project, in order to retrace CO2 conversion to CH4, isotope techniques including isotope labeling experiments will be applied during the digestion tests (RKU). With this powerful technique it is possible to reconstruct precursors and specific pathways during CO2 addition. 




Set-up of continuous anaerobic digestions tests

Impact of microorganisms as sinks of atmospheric chloromethane

Contact person: Frank KepplerNicole Jaeger

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The project CHLOROFILTER is an interdisciplinary consortium of two French and two German partners who combine expertizes and knowledge to address the impact of microorganisms on the global budget of chloromethane (CH3Cl). Anthropogenic emissions of ozone-depleting compounds have been strongly reduced since the Montreal Protocol came into force in 1989. As a consequence, compounds released from natural sources, have become increasingly relevant in stratospheric ozone depletion. CH3Cl is the most abundant halogenated compound in the atmosphere, and originates primarily from terrestrial ecosystems. Future warmer climates will likely lead to increased CH3Cl emissions. Current estimates of its global budget are uncertain but suggest that microorganisms play a more important role in degradation of atmospheric CH3Cl than previously thought. Methylotrophic microbes, some with the capability to degrade CH3Cl, occur in soils, the phyllosphere of many plants, and have recently been reported to be active in water droplets of clouds. The main objective of CHLOROFILTER is to provide quantitative information on process-level and in depth genetic insights into these microbes.

The investigations focus on kinetic and isotope effects upon CH3Cl degradation by methylotrophs associated with soils, plants, and clouds to resolve the quantitative relevance of microbial sinks for the global CH3Cl budget. The microbial community will be characterized in selected various environmental samples using a taxonomical (16S RNA genes) and a functional gene marker for CH3Cl degradation (cmuA). Furthermore, selected samples of soil, plants, and cloud water will be subjected to 13CH3Cl in order to label the biomass of CH3Cl degrading microbes and to retrieve 13C-labeled metagenomes via DNA stable isotope probing to assess the diversity of microbial pathways for CH3Cl-degradation.

An improved quantitative understanding of the sources and sinks of atmospheric CH3Cl will be invaluable for our understanding the stratospheric chlorine chemistry and predict ozone layer stability.

Methane formation from algae in oxic seawater

Contact person: Thomas Klintzsch

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The oceans are considered to be a source of CH4 to the atmosphere although the magnitude of total net emissions is highly uncertain and sources are not well described. To explain the source of CH4 in surface waters, it has been suggested that methanogenesis takes place in anoxic microenvironments of organic aggregates. Other sources such as in-situ formation of CH4 by algae have also been suggested, however, a direct evidence of algae-derived CH4 formation from lab experiments with (axenic) algae cultures is still missing, and thus so far the accumulation of CH4 in the upper water layer has not yet been related to a direct production by algae.

The overall aim of this research project is the verification (proof of principle) and quantification of CH4 production by several species of marine algae such as haptophytes (e.g. Emiliania huxleyi). Potential precursors such as (e.g. methyl sulfides and sulfoxides) of algae-derived CH4 will be identified by using stable isotope techniques. Several environmental factors will be investigated with respect to their effect of algae-derived CH4 production. Furthermore, we will apply various microbiological tests to screen for methanogenic Archaea or bacteria potentially involved in CH4 formation. We will also focus on factors sensitive to climate change such as temperature, oxygen concentration and nutrient availability. An interdisciplinary approach requiring the interaction of several disciplines is envisaged to realize the aims of the project. The results are expected to improve our understanding of biogeochemical cycling of CH4 formation in the oceans and to better explain the CH4-enrichment of oxygenated surface waters compared to atmospheric concentration, so-called “Oceanic methane paradox”.

Influence of human waste on arsenic release into drinking water in Bangladesh - geochemical and statistical investigations

Contact person: Martin Maier

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The United Nations consider clean water as a human right and define the access to clean water as one of the sustainable development goals (Agenda 2030). The implementation of this right remains a challenge for mankind, as in many parts of the world the drinking water is polluted.

One of the most serious contaminants is arsenic. It is known to cause long term health problems as cancer of the skin, lung, bladder, kidney, and liver and to have adverse effects on the nervous, cardiovascular and immune systems. It might also cause adverse pregnancy outcomes (Naujokas et al., 2013). The most common route of exposure to arsenic is from drinking water. Arsenic contamination of groundwater and has been a massive and neglected public health problem in several countries including Argentina, China, Taiwan, India, Nepal, and Bangladesh. Particularly in Bangladesh, arsenic contamination of groundwater is a large-scale problem and has been called the "largest mass poisoning of a population in history" (Smith et al., 2000). An estimated 25% of people in Bangladesh (~40 million) are chronically exposed to groundwater arsenic concentrations exceeding the WHO drinking water recommendation (BBS & UNICEF 2015). For more information click here or visit the homepage of the HCE.



AsFreeH2O: Applicability and social acceptance of water treatment technologies with respect to future sea-level rises

Contact person: Martin Maier

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In many areas of the world, sea-level changes have a negative impact on water quality and availability of freshwater resources. Groundwater containing arsenic and increasing amounts of salt is particularly challenging – in contrast to microbially contaminated surface water – as social aspects need to be considered as well. Treatment of visibly polluted surface water is technologically and energetically more effective than treatment of the less obviously polluted groundwater, which contains arsenic. So far, few efforts have been made to give the population an understanding of this alternative and arsenic-safe water resource. The realization of this project in Bangladesh will set an example of how to overcome the challenge of arsenic contamination by collectively gaining an understanding. This way an overall approach will be developed which might be adaptable to similar cases of groundwater pollution. For more information click here or visit the homepage of HEIKA.

Geochemical investigations and scientific-technical support regarding the problem of arsenic contamination in Pabna, Bangladesh

Contact Person: Martin Maier

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The Federal Foreign Office states, that globally 663 million people do not have access to clean drinking water (as of 2015). Different factors can endanger drinking water quality. In some countries, drinking water with high arsenic content poses a major threat to public health. Continuous intake has several adverse health effects like increased risk of cancer. Particularly affected by this problem are countries in Asia like Bangladesh, India (West Bengal) and North China (Smedley et al., 2002).

The highly polluted ground water of Bangladesh and West Bengal is internationally recognized a major threat to the affected population (Smedley et al., 2002). To supply germ-free drinking water, groundwater was increasingly exploited as a drinking water resource by the government of Bangladesh and supporting NGOs (Harvey et al., 2002). But utilization of groundwater as drinking water led to the appearance of diseases, which eventually could be attributed to arsenic intake (Smedley et al., 2002). For more information click here or visit the homepage of AGAPE e.V..

FAARM Marking Tubewells and taking tubewell water samples: Geochemical investigations of drinking water quality in Sylhet, Bangladesh

Contact Person: Martin Maier

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Within the framework of a representative field study in Sylhet, Bangladesh, the University Hospital Heidelberg (PD. Dr. med. Sabine Gabrysch) is evaluating the influence of malnutrition on child stunting. Therefore, the iron content of the drinking water will be examined. For this purpose approx. 2.000 wells used for drinking water are registered, labeled and sampled. Through the collaboration with the Institute of Earth Sciences (GEOW) additional parameters like arsenic and the complete water composition can be measured in order to derive important information about redox potential and influencing factors.

Thus, analysis costs will be shared between the University Hospital Heidelberg and the GEOW. Furthermore, the “Heidelberg Center for the Environment” (HCE) awarded a start-up funding to the project for a follow-up proposal. Recent research progress is presented in the project „Influence of human waste on arsenic release into drinking water in Bangladesh – geochemical and statistical investigations“.

The outcome of this project will contribute to the findings of the AsFreeH2O project. Additionally the location in Sylhet will be considered for the implementation of newly developed arsenic removal technologies and their social acceptance. Sylhet poses a challenging research environment due to high arsenic and high poverty. For more information visit the homepage of the University Hospital Heidelberg.



 Revising the methane cycling in lakes: sources and sinks in two German lakes with specific consideration of methane accumulation in oxic waters

Contact Person: Moritz Schroll

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This project is a collaboration of two german research groups tackling the understanding of the formation and degradation processes/mechanisms of methane (CH4) in the environment and ecological aspects of lake waters to better understand the role of lakes in regional and global CH4 cycling.

Methane, an important greenhouse gas that affects radiation balance and consequently the earth’s climate, still has large uncertainties in its sinks and sources. The world’s oceans and particularly lakes are recently considered to be substantial sources of CH4 to the atmosphere (IPCC 2013), although the biogeochemical processes involved in its formation are not fully understood.Several recent studies provided strong evidence of CH4 production in oxic marine and freshwaters challenging the long-standing paradigm that microbial CH4 production occurs only under anoxic conditions and forces us to rethink the ecology and environmental dynamics of this powerful greenhouse gas.

There is emerging evidence that some marine microalgae (Lenhart et al. 2016) and freshwater algae may directly produce CH4, e.g. via photosynthesis, completely bypassing the involvement of heterotrophic microbes.Organosulfur compounds such as methanethiol, methionine, dimethyl sulfoxide (DMSO), and dimethylsulphoniopropionate (DMSP) are commonly produced by algae (Reisch et al. 2011). Furthermore, it has been reported that, under ambient atmospheric conditions, several organosulfur compounds can be chemically converted to CH4 (Althoff et al. 2014, Comba et al. 2017).

Collectively, these findings show that methanogenesis extends beyond the traditionally perceived anoxic boundaries. While the biochemical mechanisms behind this novel CH4 production remain largely unclear, the mere ability of organisms to do so forces us to re-examine the environmental dynamics of CH4 in aquatic ecosystems. Considering the new findings of CH4 formation in oxic environments on land, a revision to our fundamental understanding of CH4 dynamics in aquatic systems is urgently needed.

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Conceptual scheme of potential CH4 sources and sinks in lakes (Figure taken from Tang et al. 2016).

 Contribution to sustainable mining

Contact Person: Marcus Schneider

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For more than 100 years, the saline deposits of the Werra-Fulda-Potassium district are mined. These salts are mainly used for mineral fertilizers and the chemical industry. During volcanic phases in the Paleogene and Neogene (Rhön and Vogelsberg volcanism) mafic rocks intruded into the salt rocks (Zechstein) of the Werra Formation. Diagenesis and the mafic intrusions are accompanied by a fluid- and gasflux. For safety reasons, potential occurrences of CO2 and other gases within the salt-rocks must be explored and monitored in the mining process. At lithostatic pressure the gases may be in a liquid or in an overcritical state. If the pressure decreads due to mining and drilling activities, the gases can be released causing safety risks.

To better predict potential gas occurrences and their hazardous potential, a cooperation between the Institute of Geosciences (research groups “Thermochronology und Archäometry”, (Prof. Dr. U. A. Glasmacher) and “Biogeochemistry” (Prof. Dr. F. Keppler)) and the K+S Aktiengesellschaft was formed.

The Biogeochemistry group analyzes the gas content of mafic and salinar rocks. We analyze atmospheric gases as well as hydrocarbons (GC-BID; GC-FID). Additionally, we analyze the ratio of the stable carbon isotopes of CO2 and CH4 (GC-IRMS), hoping to find the origin of these gases and their area of distribution to ensure safe and sustainable mining. Another focus of interest is the ratio of O2 to N2 within the rocks’ fluid inclusions. With the O2 to N2 ratio of fluid inclusions in unaltered salts we hope to analyze and reconstruct the original gaseous composition of the permic atmosphere, which would be one of the oldest atmospheric archives so far.

Methane in the groundwater of Bangladesh - a driving process for aresenic release?

Contact Person: Martin Maier


The contamination of drinking water with arsenic has been an unsolved problem in Bangladesh for many decades. Arsenic compounds are toxic and arsenic mobilisation is a complex mechanism caused by several processes.

In March 2019 we took water and gas samples of groundwater from three sites in the Sylhet district (NE Bangladesh). Our aim was to identify which processes are taking place to mobilize arsenic from the sediment into groundwater with special focus on dissolved gases. So far, dissolved gases such as methane and stable carbon isotope values (δ13C values) have been rarely studied in the context of arsenic mobility. Therefore, we analysed the collected water and the gas samples for their chemical composition and determined carbon δ13C values of methane (CH4) and carbon dioxide (CO2).

The results indicate that the processes of arsenic mobilization are different at each of the three study sites and are strongly depth dependent. As described by other authors, arsenic correlates well with phosphate, TOC, bicarbonate, ammonium and methane. Organic-rich clay layers are usually assumed as a common source of these constituents (Dowling et al., 2002). For more information click here



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Latest Revision: 2020-03-26
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