Understanding the role of river restoration in maintaining good water quality

We are used to living with our back turned to the environment. In particular, related to rivers, we usually enjoy them without any interest on their quality. We don’t usually go further than to check if the water seems clean, if it  looks clear and looks good to swim on it. However, the river is more than that, it is a whole ecosystem where external factors  cause dramatic changes to water quality and that in turn affects us.

Rivers are naturally dynamic; they flood adjacent lands, erode their banks and bed, and move sediment around. However, human activities have affected them causing changes on the river and increasing risk of flooding as well as may effect on the habitat diversity. This is why, river restoration is achieving strength as an alternative way to protect ecosystem health, preserve water resources and provide flood protection.

This issue is a global problem, affecting all parts of the world. To have a better understanding of river restoration projects and their effect of water quality, , Vidhya Chittoor Viswanathan, early stage researcher in ADVOCATE Project, in tandem with Professor Mario Schirmer have published recently a paper titled “Water quality deterioration as a driver for river restoration: a review of case studies from Asia, Europe and North America“.

This review is aimed at transferring lessons learned from various restoration projects focusing on water quality improvement from different parts of the world. To achieve this, restoration projects aimed at water quality amelioration through river restoration are chosen from four countries across three continents (Europe, Asia and North America).

In general terms, the situation is as follows, the rivers from industrialized countries have been subjected to spills, overuse or the misuse of them, decreasing their quality. Several restoration projects around the world were found to focus on water quality amelioration through river restoration. However, there is a major lack of understanding of the biogeochemical processes affected by river restoration.  The Thur River in Switzerland is used as example,  to test river restoration’s influence on water quality on a river reach and catchment scale.

The river Thur in Switzerland is a tributary of the Rhine. It is a highly dynamic river in a catchment with no reservoirs to control its dynamic discharge patterns. The landuse also varies significantly in the pre-demoninantly agricultural catchment, which is 61 % agriculture, 30 % forest and only 9 % urban.   As the lower part of the Thur River was often flooded by melt water in Spring, the river restoration was considered to be an alternative flood protection measure by the Cantonal authorities. The 2km stretch river restoration project in the lower part of the river was completed in 2003. Although, it was mainly done for flood protection it is also expected to improve water quality and provide ecological improvement  by increasing habitat diversity as well.


That sounds great; on the other hand, as most restored rivers are not monitored at all, it is difficult to predict consequences of restoration projects or analyse why restoration projects  fail or are successful.Evaluating the success of this river restoration is often restricted in large catchments due to a lack of high frequency water quality data, which are needed for process understanding. Vidhya Chittoor has developed a study in the framework of ADVOCATE Project where these challenges were addressed by looking at the diurnal and seasonal changes in flow and water quality and measuring water quality parameters including dissolved oxygen (DO), temperature, pH, electrical conductivity (EC), nitrate and dissolved organic carbon (DOC) with a high temporal frequency (15 minutes – 1 hour). In addition, the stable isotopes of water (δD and δ18O-H2O) as well as those of nitrate (δ15N-NO3 and δ18O-NO3) were also measured to follow changes in water quality in response to the hydrological changes in the river.Finally, this study may be found in further detail on the paper titled “Does river restoration affect diurnal and seasonal changes to surface water quality? A study along the Thur River, Switzerland”, whose author is Vidhya Chittor Viswanathan. This paper is still in press.


Chittoor Viswanathan, V., & Schirmer, M. (2015). Water quality deterioration as a driver for river restoration: a review of case studies from Asia, Europe and North America Environmental Earth Sciences DOI: 10.1007/s12665-015-4353-3

Microbial nitrogen transformation in constructed wetlands

Oksana Coban explores within ADVOCATE Project the role of aerobic and anaerobic microbial processes for the removal of ammonium from contaminated groundwater in constructed wetlands (CWs) downstream of the chemical industrial area in Leuna, Germany. In this video she shows us an overview about how CWs works.

If you would like to learn more about this topic, please don’t miss our previous post on this blog about Oksana research topic titled “Constructed Wetlands: A promising system”



Coban, O., Kuschk, P., Kappelmeyer, U., Spott, O., Martienssen, M., Jetten, M., & Knoeller, K. (2015). Nitrogen transforming community in a horizontal subsurface-flow constructed wetland Water Research, 74, 203-212 DOI: 10.1016/j.watres.2015.02.018


Coban, O., Kuschk, P., Wells, N., Strauch, G., & Knoeller, K. (2014). Microbial nitrogen transformation in constructed wetlands treating contaminated groundwater Environmental Science and Pollution Research DOI: 10.1007/s11356-014-3575-3

Electricity generation from pollution? Yes, it is possible !

Electricity is a form of energy associated with the presence of electrically charged particles (e.g. electrons). It is typically generated at power stations by a movement of a magnet through a loop of wire; the movement is driven by heat engines fuelled by chemical combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. Electricity can be also produced by collecting the energy of the sun in photovoltaic cells or geothermal power. Scientists are currently researching new technology of electricity generation using bacteria and waste or contamination.

Bacteria are present everywhere, even in contaminated groundwater. They “eat” the organic contaminants degrading them to carbon dioxide, electrons and protons. These electrons then have to be transferred from bacteria in order to complete the degradation. It is a perfect opportunity to collect these electrons and also enhance the bacterial degradation of contaminants. We could place an electrode (anode) under the ground into contaminated groundwater and it would accept electrons released by bacteria. As the electrons are transported via the wire and resistor to the second electrode (cathode), electricity is produced.

Electricity generation

The amount of electricity produced from this process is small (one “bacterial battery” like this would not be able to power a house) but it is more beneficial to the environment when compared with the technologies currently used in clean up of contamination. Today’s techniques for pollution removal consume electricity, whereas “bacterial batteries” produce a small amount of it, making it more sustainable. Petra Hedbavna, early-stage researcher at the University of Sheffield, has been examining this technology in the lab and the first results look promising. Nevertheless, there is still a lot of work to be done by the scientists before the “bacterial batteries” are applied in the field.


Schreiberová O, Hedbávná P, Cejková A, Jirků V, & Masák J (2012). Effect of surfactants on the biofilm of Rhodococcus erythropolis, a potent degrader of aromatic pollutants. New biotechnology, 30 (1), 62-8 PMID: 22569140

On the trail of nitrogen to quantify N removal from contaminated aquifers

In the early 20th century Fritz Haber developed a process to create reactive ammonia, which the chemical company BASF scaled up to industrial level production by 1910. To fuel the agricultural revolution, BASF established a chemical industry in Leuna thanks to syngas sources needed to make the nitrogen fertilizers. The site was rapidly expanded, becoming one of the biggest chemical industrial complexes in Germany in the last century. However, there’s another side to this story. The spills, accidental discharges, etc … from the industry in Leuna have persisted over the last.


Figure 1. Leuna industrial area, photographed October 2013, Naomi S. Wells

Unfortunately, this problem is not unique to Leuna: EU states have over 100.000 groundwater sites that have been found to be too contaminated for human consumption. In order to make sure that the measures taken to prevent the spread of contamination into adjacent waterways, it’s important to understand both the biological and the hydrological factors that control its spread.

 How can we solve it?

The microorganisms living in the soil and groundwater are capable to remove nitrogen pollution (known as natural attenuation). However, it’s difficult to measure the rates that these processes are happening in groundwater. For instance, a measured concentration decrease could also be caused by rainfall (dilution) or mixing of different source plumes below ground, this means that more information is needed in order for measurements to determine whether or not these microorganisms actually did something.

In the nature, the ammonia molecule undergoes many different transformations changing from one form to another as illustrated on the figure (N-cycle).


The major transformations of nitrogen are nitrification (yellow area) and denitrification (green area), while new evidence shows that anaerobic ammonium oxidation (anammox; pink area), and dissimilatory reduction of nitrate to ammonium (DNRA), nitrifier-denitrification, co-denitrification (not shown) can play important roles under certain conditions. Environmental conditions dictate which processes are energetically favourable for microbes to perform

How to quantify N removal from contaminated aquifers?

Dr. Naomi S. Wells is an experienced researcher on ADVOCATE Project working on the quantification the importance of in situ nitrogen cycling for the remediation of contaminated groundwater megasites. She is developing “isoflux” type models to improve estimations of nitrogen loss pathways and rates within complex contaminated aquifers.

Addressing this question, to quantify N removal, there is a promising avenue: the use of multiple  N isotopes and the detection of microbial populations for developing sensitive indicators of in situ transformations. This includes measuring the isotopic composition of both oxygen and nitrogen on NO318O-NO3 and δ15N-NO3); as well as newer techniques to measure the isotopic composition of NO215N-NO2 and δ18O-NO2) and ammonium (δ15N-NH4+). Variations in all of these species are being used to identify the N removal hotspots that would be missed by measuring only NO3 isotopes and the isotopic composition of ammonium.

Naomi Wells and her colleagues from the department Catchment Hydrology at the UFZ are carrying out a study on site, where they are measuring the distribution of all N isotopes across the aquifer in Leuna, and analysing how these change in conjunction with concentrations over time (see below figure).


Figure 2. Caption: water samples collected from the Leuna site being prepared for isotopic analysis. Note the distinct colours of samples from various locations across the contaminant plume! (Photo credits: Naomi S. Wells)

Preliminary results revealed a seasonal development of N attenuation hotspots along the plume fringe. The broad correlation of these hotspots with redox transition zones and changes in key microbial populations showed that N removal in groundwater may be much more variable than has traditionally been assumed. And, while coupled nitrification and denitrification did seem to dominate the biological removal of ammonium from Leuna, at least two hotspots of anammox activity were identified within the contaminant plume.

To learn more about Naomi Wells’s expertise here are her latest papers

Wells, N., Baisden, W., & Clough, T. (2015). Ammonia volatilisation is not the dominant factor in determining the soil nitrate isotopic composition of pasture systems Agriculture, Ecosystems & Environment, 199, 290-300 DOI: 10.1016/j.agee.2014.10.001

Wells, N., Clough, T., Johnson-Beebout, S., & Buresh, R. (2014). Land management between crops affects soil inorganic nitrogen balance in a tropical rice system Nutrient Cycling in Agroecosystems, 100 (3), 315-332 DOI: 10.1007/s10705-014-9644-7

Wells, N., Clough, T., Condron, L., Baisden, W., Harding, J., Dong, Y., Lewis, G., & Lear, G. (2013). Biogeochemistry and community ecology in a spring-fed urban river following a major earthquake Environmental Pollution, 182, 190-200 DOI: 10.1016/j.envpol.2013.07.017

The importance of protecting aquifers from contaminated plumes

Do you know how many people depend directly on aquifers for drinking water? And the water used on irrigation for food production? No, right? The answer is that two billion people depend directly upon aquifers for drinking water, and 40 per cent of the world’s food is produced by irrigated agriculture that relies largely on groundwater according to The United Nations Environment Association.

Have you ever stopped a minute and thought about this? The real situation is that water stored in the ground beneath our feet is invisible and so its depletion or degradation due to contamination proceeds unnoticed for us.

So, what should we do about it? Over the years hundreds of studies have been carried out from all different angles to try and solve this problem, however, the industrial legacy and the current industrially dependent world where we live does not make it easy to get a solution. The realistic situation is that the world consumes beyond its resources generating non stop contamination and not taking enough decisions to stop them .

With this introduction, the scene is set up for the next step, what are we really doing to get a solution? Well, projects like ADVOCATE, NanoRem, SuRF-UK, CLARINET, etc. in the framework of Europe are looking for sustainable remediation practices, assessments, etc.

Technologies that range from natural attenuation to advanced oxidation processes such as wet air oxidation or supercritical CO2 extraction, etc., have been studied to date, however, this time, I would like to draw your attention to “Permeable Reactive Barriers (PRBs)” being one of the most promising remediation technologies to intercept and decontaminate plumes in the subsurface.

But, how do these barriers work? Why is it a promising technology? Johana Grajales and Franklin Obiri Nyarko, ADVOCATE’s fellows, are specialized in this topic and recently have published a detailed overview about it in the paper “An overview of permeable reactive barriers for in situ sustainable groundwater remediation”.

The PRB can be defined as a groundwater remediation technology that consists of introducing a wall of reactive material perpendicular to the groundwater flow path to intercept and treat the contaminants. The contaminants in the plume react with the media leading to either their transformation to less harmful compounds or fixation to the reactive materials. The challenge is to match the reactive material and the removal process to the contaminant.

In this paper, Johana and Franklin have carried out a detailed study of the state-of-art explaining the reactive media used so far and the mechanisms employed to transform or immobilize contaminants.

Although this is a promising low cost remediation technology there is still a lot to be done regarding the long-term performance of PRBs and improving their treatment of a broad spectrum of contaminants, and thereby expand their remit.

If you would like to know more about this paper, please click here:


Obiri-Nyarko F, Grajales-Mesa SJ, & Malina G (2014). An overview of permeable reactive barriers for in situ sustainable groundwater remediation. Chemosphere, 111, 243-59 PMID: 24997925

A sample restoration project at the Chriesbach river in Dübendorf, Switzerland to explain the features of a restored river


Prof. Dr. Mario Schimmer is involved in ADVOCATE Network. He works at EAWAG Research Institute in Switzerland. His work on numerical modelling, laboratory and field work concerning biodegradation processes of industrial and urban contaminants in the subsurface involves several research areas, such as contaminant hydrogeology, geochemistry, microbiology, engineering, social sciences and numerical methods.

He gives us through this video an introduction about a sample restoration project at the Chriesbach river in Dübendorf, Switzerland to explain the features of a restored river.

Developing in situ treatment strategies for mixed contaminants from contaminated groundwater megasites


Naomi Wells is working on developing better ways of measuring where water pollution comes from, and how long it’s going to stick around for. She uses light stable isotopes to improve the understanding of the fate and transport of key nutrients across biomes, landscapes, and scales.

Check out this video and knowing a bit more how the industrial legacy is harmful to us and our environment. Don’t miss it !