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.

Picture1

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.

ResearchBlogging.org

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

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.

ResearchBlogging.org

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.

Figure1

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).

Figure2

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).

Figure3

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

Constructed Wetlands: A promising system

It is easy to leave the tap running without caring about where the water is coming from. How often do we do this when brushing our teeth or washing dishes? However, the real cost of this wastage may be considerable, if we think about the loss of this valuable natural resource and the expense of water treatment. Thinking of wastewater, have you also considered what happens when you flush the toilet or dispose of laundry water containing soap or oils down the sink? Well, our urban wastewater receives treatment before it is discharged to the environment.

However, our situation is not the reality of developing countries, where water is often scarce and water treatment technologies must be reliable and sustainable. Efforts to mitigate negative environmental impacts and reduce public health risks in these countries require the development of low-cost wastewater treatment technologies that effectively eliminate wastewater contaminants; facilitating the breakdown and removal of pollutants using biological processes that avoid the hazards associated with chemical-based systems and their additional cost. A promising wastewater treatment system for this context is constructed wetlands (CW), which can provide sustained access to improved water and sanitation services.

Oksana Voloschenko, a Marie Curie fellow within the ADVOCATE project, is researching the development of this treatment concept, within the topic “microbial nitrogen transformation in horizontal subsurface flow constructed wetlands for the treatment of contaminated groundwater”. The focus is on the removal by CW of ammonium (NH4+) a major pollutant in groundwater from agricultural sources. Firstly, we need an overview of how CW serve as natural wastewater treatment systems for projects carried out in Africa, Latin America or India.

In general terms, constructed wetlands consist of beds of aquatic macrophytes (wetland plants). Their root systems provide surfaces for the attachment of microorganisms, enhancement of filtration effects and stabilization of the bed surface. Moreover, the roots contribute to the development of microorganisms by the release of oxygen and nutrients within the host material. Depending on flow conditions we can distinguish surface flow or subsurface flow CW (horizontal and vertical flow), as shown in the diagrams below.

Figure1

  • Surface flow CW consists of large, shallow lagoons that contain submerged, emergent, or floating plant species. They are most commonly used to remove nutrients to prevent eutrophication (algae growth) in the receiving water body.
  • Subsurface flow CW consist of shallow basins filled with coarse sand or gravel as filter material. Wetland plants are grown on the surface of the filter bed, and pre-treated wastewater flows through the bed horizontally below the surface. Subsurface flow CW can treat both nitrogen and phosphorus.

How do they work?

If we look at subsurface flow CW the main components are: a waterproof basin, filter material, wetland plants and inlet and outlet structures. This is shown in the diagram below.

Figure2

 

The waterproof basin is used to prevent soil and groundwater contamination through wastewater infiltration. Filter material has several functions. It retains solids from the pre-treated wastewater, provides surfaces for the adhesion and development of the microorganisms that play a crucial role in the degradation of organic pollutants and transformation of nitrogen compounds, and supports the development of root systems in the filter material for the wetland plants. Inlet and outlet structures are required for wastewater distribution and collection, respectively.

Our research efforts are focused on understanding the removal mechanism for pollutants, due to the complexity of the wetland systems, and the role that aerobic and anaerobic zones play within the root zone of the plants. This is the Oksana’s research. Obviously, as with all water treatment technologies, CW designs have limitations. These are currently are being studied by researchers such as Oksana.

ResearchBlogging.org

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

How is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures?

If we take a glance at the scientific literature, particularly those on soil treatments, the number of articles, reports and books available are uncountable. Suddenly the question comes to mind – which treatment is best for a define case? We know that all of them differ from each other and have their advantages and disadvantages, many factors come into play when deciding on the best technology. In addition, variations in boundary conditions defined between technologies, produce distorted environmental impact results. Thereupon, a balance between environmental, social, and economic costs and benefits must be required in identifying the optimal remediation solution. Key indicators need to be defined in each case.

More precisely, an indicator is a single characteristic that can be compared between the different tools to evaluate their relative weight in each technology. An important perspective about the indicators is how they are measured and how all of them are ultimately balanced in the evaluation of potential remediation strategies.

Determining the most appropriate course of action when faced with soil or groundwater contamination requires the consideration of technologies or approaches that can feasibly remove the contamination to the required target level within project-defined time and cost constraints. Consequently, the technology selection phase in the planning process consists of two steps: identify the feasible technologies and evaluate the financial, social and environmental financial costs of the different alternatives.

On the other hand, Decision Support Systems (DSSs) provide us a structured method of comparing these alternative courses. On the commercial market there are many examples of soil and groundwater remediation. Some DSSs examples are MMT (Mega-site Management Tool), DESYRE (Decision Support System for the Rehabilitation of contaminated sites), SBR (Sustainable Brownfields Redevelopment tool), CO2 calculator, SRT (Sustainable Remediation Tool), REC (Risk reduction, Environmental merit and Costs tool) or GoldSET.

Between all the above DSSs described, Alistair Beames and his colleagues from VITO established the use of four of them for its study on a specific contaminated area of Antwerp, exactly a petrochemical storage and distribution facility, providing a meta-analysis of sustainability appraisal of four technically feasible remediation alternatives proposed for the site: ex situ soil washing, ex situ thermal desorption, in situ thermal desorption and monitored natural attenuation.

The results generated after this study are compiled in a more detailed article titled Sustainability appraisal tools for soil and groundwater remediation: How is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures?

About the tools used, the CO2 calculator is an example of a standard environmental footprint calculator and considers an inventory solely focused on energy consumption and CO2 emissions. SRT and REC are tools with larger inventories across a range environmental impacts that also account for financial costs. SRT aggregates the different criterion scores according to economic valuation. REC integrates different criterion scores within a multi-criteria analysis framework. GoldSET is an example of tools used by consultants on behalf of clients and considers a broader range of impacts across the three pillars of sustainability (environmental, social and economic), many of which are measured qualitatively.

In conclusion, the results generated by these tools differ from one another when applied to the same case study, due to differing indicator sets and aggregation methods. Clearly broadening the scope of the assessment from only a few environmental indicators and financial costs to also considering social impacts and indirect economic impacts will influence the sustainability performance of the remediation alternatives.

All the information is available on the article

Beames A, Broekx S, Lookman R, Touchant K, & Seuntjens P (2014). Sustainability appraisal tools for soil and groundwater remediation: How is the choice of remediation alternative influenced by different sets of sustainability indicators and tool structures? The Science of the total environment, 470-471, 954-66 PMID: 24239816

ResearchBlogging.org

Stimulating bacterial growth to enhance natural biodegradation processes – a low cost treatment option for environmental pollutant removal

                                                           “No amount of experimentation can ever prove me right; a single experiment can prove me wrong.”

Albert Einstein

Naturally occurring bacteria found in soil, groundwater, water and sediments may be a key for environmental pollutant removal. This so-called biodegradation is a part of natural attenuation, which according to the US Environmental Protection Agency could be defined as “The effect of naturally occurring physical, chemical and biological processes, or any combination of those processes to reduce the load, concentration, flux or toxicity of polluting substances without human intervention”. The effectiveness of biodegradation depends on the type of contaminant present as well as on the complex environmental conditions that determine microbial community structure, electron donor availability (the electron donors could be defined as releasing an electron during cellular respiration, resulting in the release of energy. Microorganisms, such as bacteria, obtain energy in the electron transfer processes) and degradation reactions in the subsurface.  Under natural conditions, biodegradation of many contaminants is often a slow process and long timeframes may be required to achieve a remediation objective. Because of this, scientists lately focus more and more on stimulating the growth of that part of the site-specific microbial community that demonstrates the largest degradation potential. Here the idea is to study natural biodegradation processes occurring at a contaminated site in the lab to understand the microbial community structure, kinetics and determine the maximum degradation potential. Once these aspects are sufficiently understood and the site´s hydrogeology has been characterized, a growth-stimulating medium can be injected at certain locations to enhance biodegradation.

Although many studies have been carried over several decades, to improve our understanding of natural attenuation processes there is still a great deal to be learned regarding the mechanisms governing natural attenuation processes and their ability to address different types of contamination problems.

For example, chlorinated solvents, such as tetrachloroethene (PCE) and trichloroethene (TCE), represent a common class of contaminants used for degreasing in the dry cleaning, electronic manufacturing and machine maintenance industries. Where these contaminants had been used excessively in the past they often have leaked into the subsurface from storage tanks and machinery and have formed large plumes in the groundwater that often shows chlorinated ethene concentrations, which have been proven unhealthy.

The bacterium Dehalococcoides mccartyi is an organic halide-respiring anaerobic bacterium that uses chlorinated compounds for its dehalogenation activity. In other words, this bacterium is specialized to grow with halogenated compounds such as chlorinated aliphatic hydrocarbons as electron acceptor via a respiratory process, i.e. an electron-consuming process, and in most of the cases hydrogen is used as the final electron donor.

The removal of chlorinated ethenes by Dehalococcoides mccartyi via dehalogenation follows the sequential degradation of PCE to TCE to the dichloroethene isomers (cis-DCE, trans-DCE, 1,1-DCE), then to vinyl chloride (VC) and finally to ethene/ethane. However, a complete dechlorination always depends on the environmental conditions and other limiting factors. During the last two decades, several studies have been carried out based on the addition of electron donors for achieving a complete removal of chlorinated compounds, nevertheless, no convincing conclusions have yet been drawn.

declhoronation sequential

As a precursor to an in-situ stimulation of the natural biodegradation potential, Uwe Schneidewind and his colleagues from VITO evaluated the dechlorination reaction occurring at an aquifer contaminated with TCE and its daughter products, discharging into the Zenne River, Belgium, in their article titled “Kinetics of dechlorination by dehalococcoides mccartyi using different carbon sources”.

Sediment material was collected from three locations of the aquifer as well as from the riverbed and used in microcosm studies (measurement of microbial activity). The growth of the microbial community was stimulated by using different carbon sources (i.e. external supply of energy in the form of food) such as lactate (C3H6O3) or molasses (C6H12NNaO3S) and the dechlorination reaction in each microcosm was monitored. Afterwards, the observed reactions were modelled using first order, Michaelis-Menten and Monod kinetics.

Reductive dechlorination of TCE took place only when external carbon sources were added to microcosms, and occurred concomitant with a pronounced increase in the Dehalococcoides mccartyi cell count as determined by 16S rRNA gene-targeted qPCR (i.e. growth measurements and bioremediation monitoring method). This indicates that native dechlorinating bacteria are present in the aquifer of the Zenne site and that the oligotrophic nature of the aquifer prevents a complete degradation to ethene. The type of carbon source, the cell number of D. mccartyi or the reductive dehalogenase genes, however, did not unequivocally explain the observed differences in degradation rates or the extent of dechlorination. Results point to the role of the supporting microbial community but it remains to be verified how the complexity of the microbial (inter)actions should be represented in a model framework.

ResearchBlogging.org

Schneidewind, U., Haest, P., Atashgahi, S., Maphosa, F., Hamonts, K., Maesen, M., Calderer, M., Seuntjens, P., Smidt, H., Springael, D., & Dejonghe, W. (2014). Kinetics of dechlorination by Dehalococcoides mccartyi using different carbon sources Journal of Contaminant Hydrology, 157, 25-36 DOI: 10.1016/j.jconhyd.2013.10.006