Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Potential impact of hydrodynamic shear force in aquifer thermal energy storage on dissolved organic matter releasement : A vigorous shaking batch study
Ni, Zhuobiao ; Li, Xiao ; Wang, Yafei ; Wang, Yue ; Qiu, Rongliang ; Rijnaarts, Huub ; Grotenhuis, Tim - \ 2019
Science of the Total Environment 677 (2019). - ISSN 0048-9697 - p. 263 - 271.
Aquifer thermal energy storage (ATES) - Bioremediation - COD - Dissolved organic matter (DOM) - Hydrodynamic shear force - TOC

The combination of bioremediation and aquifer thermal energy storage (ATES) has become attractive because of the possibility of solving environmental and energy problems simultaneously. While the impact of ATES on groundwater quality due to temperature change has received ample attention in literature, the effect of the greatly enhanced groundwater flow velocity on groundwater quality has not yet received sufficient scientific attention. To fill this gap in understanding, we conducted a simple yet straightforward experiment to illustrate the impact of hydrodynamic shear force due to the water flow by ATES on the release of dissolved organic matter, which can potentially be advantageous to bioremediation. Vigorous shaking conditions were applied to simulate the enhanced dynamics at the ATES well center and nearby. As the indicators of dissolved organic matter, COD and TOC concentrations were significantly impacted by shaking. COD increased from 5.4 mgO 2 /L to 36.3 mgO 2 /L during horizontal shaking. The maximum COD level was determined as 33.8 mgO 2 /L during orbital shaking, while the TOC level was growing from 6.7 to 28.7 mg C/L. Meanwhile, redox potential (with initial level -100 mV) was decreasing to -450 mV synchronously with the elevating COD and TOC level. Temperature was also revealed as a significant factor in the organic matter releasement. Microbial iron reduction was deemed to occur, yet sulfate reduction was not initiated during the whole experiment. Eventually, the structure of the soil-water matrix has been changed due to the extensive hydraulic and particle collisions, resulting in blackish appearance and thicker layer of fine particles. Overall, the findings advance our understanding of the role of the ATES-induced water flow in the subsurface biogeochemistry and give insight into the perspective of the combination of bioremediation and ATES. In general, an increase in dissolved organic matter can be expected due to the increased shear force at high flow conditions in the ATES system.

Low carbon heating and cooling by combining various technologies with Aquifer Thermal Energy Storage
Pellegrini, M. ; Bloemendal, M. ; Hoekstra, N. ; Spaak, G. ; Andreu Gallego, A. ; Rodriguez Comins, J. ; Grotenhuis, T. ; Picone, S. ; Murrell, A.J. ; Steeman, H.J. - \ 2019
Science of the Total Environment 665 (2019). - ISSN 0048-9697 - p. 1 - 10.
Aquifer Thermal Energy Storage - Geothermal energy - Heating and cooling - Photovoltaic-thermal module - Pilot plant - Remediation - Technological innovation - Water scarcity

A transition to a low carbon energy system is needed to respond to global challenge of climate change mitigation. Aquifer Thermal Energy Storage (ATES) is a technology with worldwide potential to provide sustainable space heating and cooling by (seasonal) storage and recovery of heat in the subsurface. However, adoption of ATES varies strongly across Europe, because of both technical as well as organizational barriers, e.g. differences in climatic and subsurface conditions and legislation respectively. After identification of all these barriers in a Climate-KIC research project, six ATES pilot systems have been installed in five different EU-countries aiming to show how such barriers can be overcome. This paper presents the results of the barrier analysis and of the pilot plants. The barriers are categorized in general barriers, and barriers for mature and immature markets. Two pilots show how ATES can be successfully used to re-develop contaminated sites by combining ATES with soil remediation. Two other pilots show the added value of ATES because its storage capacity enables the utilization of solar heat in combination with solar power production. Finally, two pilots are realized in countries with legal barriers where ATES systems have not previously been applied at all.

Bacteriën moeten bodem Utrechts park kuisen
Grotenhuis, Tim ; Keijzer, Lisanne - \ 2018
Subsidence of organic dredged sediments in an upland deposit in Wormer- en Jisperveld : North Holland, the Netherlands
Oliveira, Bruna R.F. ; Smit, Martijn P.J. ; Veld, Harry ; Paassen, Leon A. van; Rijnaarts, Huub H.M. ; Grotenhuis, Tim - \ 2018
Environmental Earth Sciences 77 (2018)4. - ISSN 1866-6280
Dredged sediments - Lowlands - Organic matter oxidation - Peatlands - Shrinkage - Subsidence - Upland deposit
Land subsidence in low-lying peatlands can be caused by shrinkage and organic matter oxidation. When these areas have networks of ditches and canals for drainage purposes, the sediments that accumulate in the waterways can be used to reverse the process of land subsidence. The objective of this study is to understand how dredged sediments can be used to reverse the process of land subsidence by analysing the contribution of shrinkage and organic matter mineralization to the subsidence observed in an upland deposit. A deposit of dredged sediments in the Wormer- en Jisperveld—North Holland, the Netherlands—was characterized during 17 months in terms of subsidence of the sediments, subsidence of the soil underlying the deposit, geotechnical water content, organic matter content, type of organic matter and nutrients. The deposit was filled to a height of 195 cm, and after 17 months, the subsidence of the sediments was 88 cm. In addition, a subsidence of 19.5 cm of the underlying soil was observed. Subsidence could be attributed to shrinkage since no significant changes in the organic matter content and total organic carbon were observed. The type of organic matter changed in the direction of humification until winter 2014, stabilized from winter 2014 to spring 2015 and changed in the direction of mineralization after the spring of 2015. Subsidence of dredged sediments in upland deposits is caused by shrinkage during the first 17 months. The solution of spreading thinner layers of sediments over the land to decrease the subsidence rates should be explored since the pressure of the deposit on the underlying soil caused an extra subsidence of 19.5 cm.
Combination of aquifer thermal energy storage and enhanced bioremediation : Biological and chemical clogging
Ni, Zhuobiao ; Gaans, Pauline van; Rijnaarts, Huub ; Grotenhuis, Tim - \ 2018
Science of the Total Environment 613-614 (2018). - ISSN 0048-9697 - p. 707 - 713.
Aquifer thermal energy storage (ATES) - Clogging - Enhanced bioremediation - Fe(III) precipitate - Lactate - Pressure drop

Interest in the combination concept of aquifer thermal energy storage (ATES) and enhanced bioremediation has recently risen due to the demand for both renewable energy technology and sustainable groundwater management in urban areas. However, the impact of enhanced bioremediation on ATES is not yet clear. Of main concern is the potential for biological clogging which might be enhanced and hamper the proper functioning of ATES. On the other hand, more reduced conditions in the subsurface by enhanced bioremediation might lower the chance of chemical clogging, which is normally caused by Fe(III) precipitate. To investigate the possible effects of enhanced bioremediation on clogging with ATES, we conducted two recirculating column experiments with differing flow rates (10 and 50 mL/min), where enhanced biological activity and chemically promoted Fe(III) precipitation were studied by addition of lactate and nitrate respectively. The pressure drop between the influent and effluent side of the column was used as a measure of the (change in) hydraulic conductivity, as indication of clogging in these model ATES systems. The results showed no increase in upstream pressure during the period of enhanced biological activity (after lactate addition) under both flow rates, while the addition of nitrate lead to significant buildup of the pressure drop. However, at the flow rate of 10 mL/min, high pressure buildup caused by nitrate addition could be alleviated by lactate addition. This indicates that the risk of biological clogging is relatively small in the investigated areas of the mimicked ATES system that combines enhanced bioremediation with lactate as substrate, and furthermore that lactate may counter chemical clogging.

Bagger krijgt nieuw leven dankzij middeleeuwse methode
Figueiredo Oliveira, Bruna Raquel ; Grotenhuis, Tim - \ 2017
Lift up of Lowlands : beneficial use of dredged sediments to reverse land subsidence
Figueiredo Oliveira, Bruna Raquel - \ 2017
Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis. - Wageningen : Wageningen University - ISBN 9789462578838 - 229
dredgings - dredging - sedimentation - soil - sediment - subsidence - recycling - environmental engineering - bagger - baggeren - sedimentatie - bodem - bodemdaling - milieutechniek

In this thesis, the beneficial use of dredged sediments to reverse land subsidence in lowlands and delta areas is explored. The major constraints for beneficial use of sediments are the contaminant concentrations, and the proper managing of supply and demand of sediments (Chapter 1).

When sediments are transferred from waterways to upland conditions, a series of processes take place that transform the waterlogged sediments into aerated soils, a process known as ripening. To understand the relation between the sediments and the soils formed, physical/chemical and biological processes were studied at three scales: laboratory scale, mesoscale, and field scale. The knowledge obtained with these experiments can provide guidelines to effectively use dredged sediments to reverse land subsidence.

In the laboratory experiments, the environmental conditions were controlled, leading to constant water content and optimal oxygen concentration for biological processes. In the mesoscale experiment, the environmental parameters such as wind, precipitation and temperature, were not controlled as the 1 m3 containers used for these experiments were placed outside, in open air conditions. Still, the water level could be monitored and controlled, and the subsidence of the dredged sediment could be monitored. In the field experiment, the environmental and filling conditions could not be controlled but the changes occurring in the deposit were monitored.

In the first laboratory experiment (Chapter 2) the behaviour of dredged sediments with varying particle size distribution and organic matter content was studied. The dredged sediments were dewatered using suction chambers and then submitted to biochemical ripening during 141 days. The five types of dredged sediments had similar overall behaviour. The most significant observation was that most volume lost during dewatering and biochemical ripening was due to shrinkage and not to organic matter mineralization. Furthermore, the type of organic matter changed in the direction of humification, i.e., more stable compounds were formed. The soils formed from biochemical ripening of dredged sediments had very stable aggregates and the load-bearing capacity was enough to sustain cattle and tractors.

The second laboratory experiment (Chapter 3) was designed to investigate the influence of mixing compost and the solid fraction of swine manure (low in nutrients) with dredged sediments on dewatering and biochemical ripening. When the supply of dredged sediments is too low to compensate for land subsidence, bio-wastes, such as compost and manure, can be mixed with the sediments to reverse land subsidence. The results of this experiment confirm that most volume lost during ripening was due to shrinkage and not due to organic matter mineralization. Adding compost or the solid fraction of manure to the dredged sediments enhances the changes in the type of organic matter and CO2 production, i.e., the addition results in increased rates of organic matter mineralization which is described in the literature as the priming effect. In addition, the undrained shear strength of the mixtures of sediments with compost or manure was three times higher than the measured values for the sediments alone, meaning that organic amendments will improve the characteristics of the soil formed from ripening of sediments.

The mesoscale experiment (Chapter 4) was performed during 400 days in 1m3 containers which allowed to control the water level. Two scenarios were tested: upland deposits in which the sediments are allowed to dry; and underwater deposits in which the water level is always 2 cm above the sediments. It was expected that the upland deposit conditions would lead to a higher subsidence than the underwater conditions. However, subsidence of the sediments was very similar for the two scenarios. Also in these experiments it was observed that most subsidence could be attributed to shrinkage and not organic matter mineralization, and the type of organic matter changed in the direction of humification. Furthermore, the water balance indicated that evapotranspiration results in higher loss of water than drainage. Still, in this case the undrained shear strength after 400 days of experiment was not enough to sustain cattle or tractors even though it increased with time.

The monitored field scale upland deposit of dredged sediments (Chapter 5) is located in the Wormer- en Jisperveld area – North Holland, the Netherlands. The deposit was filled in two stages reaching a maximum height of sediments of 195 cm. After 17 months of monitoring, the subsidence of the sediments was 119 cm to which an extra subsidence of 19.5 cm of the underlying soil due to the overburden pressure was added. The results observed in the upland deposit are in line with the laboratory and mesoscale results since subsidence could also be attributed to shrinkage and no significant changes in the organic matter content were observed. However, in the case of the upland deposit, the type of organic matter changed in the direction of humification during the first 8 months (March to November), then stabilized during 7 months (November to June), and changed in the direction of mineralization afterwards.

The outcomes of this research indicate that dredged sediments have the potential to reverse land subsidence. This statement is supported by the consistent results showing that the decrease in volume of dredged sediments is caused by shrinkage and not to organic matter mineralization as traditionally reported (Chapters 2, 3, 4, and 5).

In addition, in places where composted and stable bio-wastes are available, these can be added to dredged sediments to further reverse land subsidence. Still, in this case special attention should be given to the potential priming effect (Chapter 3).

Finally it is recommended to adapt the current practices of disposal of dredged sediments in upland deposits, since 19.5 cm of subsidence observed for the underlying soil in the upland deposit (Chapter 5), was caused by the overburden pressure of the dredged sediment. From the point of view of avoiding/reversing land subsidence it is recommended to spread thin layers (in the order of cm) of sediments over the land, although this might lead to an increase in the time and costs for the stakeholders involved in dredging and in managing the water boards.

Impact of compost and manure on the ripening of dredged sediments
Figueiredo Oliveira, Bruna Raquel ; Laarhoven, Bob ; Smit, Martijn P.J. ; Rijnaarts, Huub H.M. ; Grotenhuis, Tim - \ 2017
Journal of Soils and Sediments 17 (2017)2. - ISSN 1439-0108 - p. 567 - 577.
Beneficial use - Compost - Dredged sediments - Priming effect - Ripening - Rock-Eval - Swine manure - Undrained shear strength

Purpose: In low lying areas with dense networks of canals for land drainage, sediments accumulate in the waterways and have to be periodically dredged. These adjacent areas are mainly used for farming and agriculture and suffer from high rates of subsidence. The recycling of organic amendments, such as sediments, compost and manure, in agricultural soils can improve plant growth and yield, soil carbon content, and microbial biomass and activity, and have the potential to reverse the process of land subsidence. Materials and methods: The effect of mixing bio-waste compost and the solid fraction of swine manure with dredged sediments before dewatering and biochemical ripening was investigated in terms of type and quantity of organic matter, CO2 production and O2 consumption, and N, P and S content. The water released during dewatering, the aggregate stability, and the undrained shear strength after ripening were also assessed since these areas have to be assessable by trucks and cattle. Results and discussion: For the sediment with compost and manure the transformations in the type of organic matter, CO2 production and O2 consumption were larger compared to the individual fractions, indicating a positive priming effect. Most volume lost during ripening can be attributed to the loss of water and not to the loss of organic matter. In addition, the mixtures result in very stable aggregates and showed an undrained shear strength three times higher than measured for the sediments. Conclusions: Sediments, compost and manure can be used and applied as beneficial use to reverse the process of land subsidence in low lying areas.

Functional properties of soils formed from biochemical ripening of dredged sediments—subsidence mitigation in delta areas
Figueiredo Oliveira, Bruna Raquel ; Smit, Martijn P.J. ; Paassen, Leon A. van; Grotenhuis, Tim C. ; Rijnaarts, Huub H.M. - \ 2017
Journal of Soils and Sediments 17 (2017)1. - ISSN 1439-0108 - p. 286 - 298.
Beneficial use - Biochemical ripening - Dredged sediments - Land subsidence

Purpose: In delta areas, dense networks of canals have been developed through time and have to be periodically dredged. Lowering the groundwater level in delta areas deepens the aerobic zone, leading to the oxidation of organic matter and possibly to land subsidence. The use of the dredged sediments on land can be a solution to mitigate land subsidence in delta areas. Materials and methods: Five types of dredged sediments with different organic matter content and particle size distribution were dewatered for 7 days and then submitted to biochemical ripening during 141 days on a laboratorial scale with constant temperature and relative humidity. The functional properties analysed were the type and content of organic matter, pH, total C, N, P and S, dry bulk density, water retention capacity, aggregate stability and load-bearing capacity. Results and discussion: After biochemical ripening, there was no significant loss in the mass of organic matter but there was an increase in the fraction of stable organic compounds, observed by an increase in oxygen-bearing compounds and a decrease in hydrocarbons during biochemical ripening. The pH was not affected by biochemical ripening, and the total C, N, P and S concentrations are high and therefore the dredged sediments can improve the quality of the land. Most volume lost during dewatering and biochemical ripening can be attributed to the loss of water. The water retention capacity of the dredged sediments changed with biochemical ripening. The soils formed from biochemical ripening have very stable aggregates, and its load-bearing capacity is enough to sustain cattle and tractors. Conclusions: Most volume lost during dewatering and biochemical ripening can be attributed to the loss of water and not organic matter. Therefore, the studied dredged sediments have potential to mitigate land subsidence in delta areas when spread on land.

Turbulent mixing accelerates PAH desorption due to fragmentation of sediment particle aggregates
Rakowska, Magdalena I. ; Smit, Martijn P.J. ; Kupryianchyk, Darya ; Qin, Jinyi ; Koelmans, Bart ; Rijnaarts, Huub H.M. ; Grotenhuis, Tim - \ 2017
Journal of Soils and Sediments 17 (2017)1. - ISSN 1439-0108 - p. 277 - 285.
Desorption - Mixing - Particles - Polycyclic aromatic hydrocarbons - Sediment

Purpose: Stripping contaminants from sediments with granular activated carbon (GAC) is a promising remediation technique in which the effectiveness depends on the rate of contaminant extraction from the sediment by the GAC. The purpose of the present study was to investigate the effect of mixing intensity on the short-term extraction rate of polycyclic aromatic hydrocarbons (PAHs) from contaminated sediment. Materials and methods: PAH desorption from sediment at a wide range of rotational speeds (min−1; rotations per minute (rpm)) was monitored by uptake in Tenax polymeric resins using a completely mixed batch reactor. Desorption data were interpreted using a radial diffusion model. Desorption parameters obtained with the radial diffusion model were correlated with particle size measurements and interpreted mechanistically. Results and discussion: Fast desorption rate constants, De/r2, with De the effective diffusion coefficient and r the particle radius, ranged from 3.7 × 10−3 to 1.1 × 10−1 day−1 (PHE) and 6 × 10−6 to 1.9 × 10−4 day−1 (CHR), respectively, and increased with the intensity of mixing. The De/r2 values would correspond to De ranges of 1.8 × 10−14–1.2 × 10−16 m2 × day−1 and 1.8 × 10−12–3.7 × 10−15 m2 × day−1, assuming fast desorption from the measured smallest particle size (9 μm) classes at 200 and 600 rpm, respectively. Conclusions: Desorption of PAHs was significantly accelerated by a reduction of particle aggregate size caused by shear forces that were induced by mixing. The effective intra-particle diffusion coefficients, De, were larger at higher mixing rates.

Beehold : the colony of the honeybee (Apis mellifera L) as a bio-sampler for pollutants and plant pathogens
Steen, J.J.M. van der - \ 2016
Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis; Willem Jan de Kogel. - Wageningen : Wageningen University - ISBN 9789462577510 - 206 p.
apis mellifera - honey bees - honey bee colonies - biological indicators - sampling - instruments - pollution - pollutants - heavy metals - plant pathogenic bacteria - erwinia amylovora - erwinia pyrifoliae - analytical methods - honingbijen - honingbijkolonies - biologische indicatoren - bemonsteren - instrumenten (meters) - verontreiniging - verontreinigende stoffen - zware metalen - plantenziekteverwekkende bacteriën - analytische methoden

Bio-sampling is a function of bio-indication. Bio-indication with honeybee colonies (Apis mellifera L) is where the research fields of environmental technology and apiculture overlap. The honeybees are samplers of the environment by collecting unintentionally and simultaneously, along with nectar, pollen, water and honeydew from the flowers or on the leaves, other matter (in bio-indication terms: target matter) and accumulating this in the colony. Collected target matter, in this thesis heavy metals, the plant pathogens Erwinia pyrifoliae and Erwinia amylovora and the soil pollutant γ-HCH, is collected from the colony by subsampling. Subsampling the honeybee colony is done by taking and killing bees from the hive (sacrificial) or by collecting target matter from the bee’s exterior without killing the bee (non-sacrificial). In environmental technology terms the application of the honeybee colony is a Passive Sampling Method (PSM). In this thesis the possibilities and restrictions of the PSM honeybee colony are explored.

Bio-indication is a broad research field with one common factor: a living organism (bio) is applied to record an alteration of the environment (indication). The environment may be small such as a laboratory or big such as an ecosystem. Alterations in the organism may vary from detecting substances foreign to the body to mortality of the organism. In environmental technology the concept Source-Path-Receptor (SPR) is applied to map the route of a pollutant. It describes where in the environment the pollution is, how it moves through the environment and where it ends. This environment is the same environment of all living organisms, ergo also honeybees. Honeybees depend on flowers for their food. In the SPR concept, a flower can be a source, path or receptor. Along with collecting pollen, nectar, water and honeydew, target matter is collected by honeybees. Each honeybee functions as a micro-sampler of target matter in the environment, in this case the flower. Each honeybee is part of a honeybee colony and in fact the honeybee colony is the bio-sampler. The honeybee colony is a superorganism. The well-being of the colony prevails over the individual honeybee. Food collection is directed by the colony’s need. Foragers are directed to the most profitable food sources by the bee dance and food exchange (trophallaxis). The result of this feature is that mainly profitable sources are exploited and poor food sources less or not at all. During the active foraging period hundreds to thousands of flowers are visited daily. The nectar, pollen, water and honeydew plus the unintentionally collected target matter is accumulated in the honeybee colony. In order to obtain target matter the colony must be subsampled. This is done by picking bees from the hive-entrance (hive-entering bees) or inside the hive (in-hive bees) and processing them for analysis (sacrificial). This is the most commonly applied method. However, it is possible to subsample the colony without picking and processing the bees by collecting target matter from the hive-entering bee’s exterior (non-sacrificial). For non-sacrificial subsampling of the honeybee colony the Beehold device with the sampling part Beehold tube has been developed. The results of bio-indication with honeybee colonies are qualitative and indicative for follow up study (Chapter 1).

Six bio-indication studies with honeybee colonies for bio-indication of heavy metals, the plant pathogens Erwinia pyrifoliae and Erwinia amylovora and the soil pollutant γ-HCH are presented. Chapter 2 describes how the concentration of eighteen heavy metals in honeybees fluctuate throughout the period of July, August and September (temporal) at the study sites: the city of Maastricht, the urban location with an electricity power plant in Buggenum and along the Nieuwe Waterweg at Hoek van Holland (spatial). A number of the metals have not been previously analysed in honeybees. To study whether honeybees can be used for bio-indication of air pollution, the concentrations of cadmium, vanadium and lead were compared to concentrations found in honeybees. The honeybee colonies were placed next to the air samplers. Only significant differences of metal concentrations in the ambient air also show in honeybees. This was the case with vanadium in ambient air and honeybees. The spatial and temporal differences of cadmium and lead were too futile to demonstrate a correspondence (Chapter 3). In a national surveillance study in 2008 the concentration of eighteen metals in honeybees has been analysed. The results showed a distinct regional pattern. Honeybees in the East of the Netherlands have higher concentrations of heavy metals compared to the bees in the West. Besides regional differences local differences were also recorded. An approximate description of the land use around 148 apiaries (> 50% agriculture, > 50% wooded area, > 50% urban area and mixed use) indicated the impact of land use on metal concentrations in honeybees. In areas with > 50% wood significantly higher concentrations of heavy metals were detected (Chapter 4). Subsampling of the honeybee colonies in Chapter 2, 3 and 4 was done sacrificially. In the studies presented in Chapter 5, 6, and 7 the honeybee colonies were subsampled non-sacrificially or simultaneously non-sacrificially and sacrificially. The plant pathogen E. pyrifoliae causes a flower infection in the strawberry cultivation in greenhouses. In greenhouse strawberry cultivation honeybees are applied for pollination. In Chapter 5 the combination pollination / bio-indication by honeybee colonies is studied. This proved to be a match. E. pyrifoliae could be detected on in-hive bees prior to any symptom of the infection in the flowers. In the Beehold tube, the bacterium was detected at the same time as the first tiny symptoms of the infection. In Chapter 5 the principles on which the Beehold tube is based are presented and discussed. The plant pathogen E. amylovora causes fireblight in orchards. The combination pollination / bio-indication has also been applied in this study performed in Austria in 2013. It is known that E. amylovora can be detected on honeybees prior to any symptom in the flower or on the fruit tree. A fireblight outbreak depends on flowering period, humidity and temperature. In 2013 no fireblight infection emerged in the orchards where the study was performed. Therefore, the bacterium could not be detected on the honeybees. γ-HCH (Lindane) is one of the soil pollutants in the Bitterfeld region in Saxony-Anhalt in Germany. It is the result of dumping industrial waste around the production locations. Although γ-HCH is bound to soil particles there is a flux to groundwater and surface water. Consequently, the pollution may end up in the sediments of the streambed and flood plains. The study objective was to investigate the hypothetic route of γ-HCH from polluted soil (source), via soil erosion and atmospheric deposition (route) to the receptor (flowering flowers) by detecting γ-HCH in the Beehold tube. Although on average over 17000 honeybees passed through the Beehold tube daily for a maximal period of 28 days, no γ-HCH has been detected. The pollen pattern in the Beehold tube revealed where the bees collected the food (Chapter 7).

The application of the honeybee colony has pros and cons. Distinctive pros are many micro samplers, the extensive collection of matter (both food and target matter) and the accumulation in the colony. For successful bio-indication with honeybee colonies, determining factors are: the target matter, location of the target matter, distance between target matter and the honeybee colony, individual or pooled subsampling, the minimal sampling frequency and sample size, and sacrificial or non-sacrificial subsampling applied solely or in combination. Taking bees from a colony impacts upon the colony’s performance and consequently the passive sampling method. Based on a long-years’ experience and inter-collegial discussion it is stated that 3% of the forager bees (hive-entering) and 1.5% of the in-hive bees can be sampled safely without impacting upon the colony. This restriction does not apply when carrying out non-sacrificial subsampling of the honeybee colony (Chapter 8).

Performing bio-indication with honeybee colonies has more applications than have been exploited so far. Further research can make a change. In particular I mention here the combination of pollination and bio-indication and the application of non-sacrificial subsampling solely or in combination with sacrificial subsampling.

Everywhere Apiculture is practiced (all over the world except the polar areas) bio-indication with honeybee colonies can be applied in a simple, practical and low cost way.

Combination of aquifer thermal energy storage and enhanced bioremediation : resilience of reductive dechlorination to redox changes
Ni, Zhuobiao ; Gaans, Pauline van; Smit, Martijn ; Rijnaarts, Huub ; Grotenhuis, Tim - \ 2016
Applied Microbiology and Biotechnology 100 (2016)8. - ISSN 0175-7598 - p. 3767 - 3780.
Aquifer thermal energy storage (ATES) - cis-dichloroethene (cis-DCE) - Dehalococcoides - Microbial resilience - Redox potential (E) - Reductive dechlorination

To meet the demand for sustainable energy, aquifer thermal energy storage (ATES) is widely used in the subsurface in urban areas. However, contamination of groundwater, especially with chlorinated volatile organic compounds (CVOCs), is often being encountered. This is commonly seen as an impediment to ATES implementation, although more recently, combining ATES and enhanced bioremediation of CVOCs has been proposed. Issues to be addressed are the high water flow velocities and potential periodic redox fluctuation that accompany ATES. A column study was performed, at a high water flow velocity of 2 m/h, simulating possible changes in subsurface redox conditions due to ATES operation by serial additions of lactate and nitrate. The impacts of redox changes on reductive dechlorination as well as the microbial response of Dehalococcoides (DHC) were evaluated. The results showed that, upon lactate addition, reductive dechlorination proceeded well and complete dechlorination from cis-DCE to ethene was achieved. Upon subsequent nitrate addition, reductive dechlorination immediately ceased. Disruption of microorganisms’ retention was also immediate and possibly detached DHC which preferred attaching to the soil matrix under biostimulation conditions. Initially, recovery of dechlorination was possible but required bioaugmentation and nutrient amendment in addition to lactate dosing. Repeated interruption of dechlorination and DHC activity by nitrate dosing appeared to be less easily reversible requiring more efforts for regenerating dechlorination. Overall, our results indicate that the microbial resilience of DHC in biosimulated ATES conditions is sensitive to redox fluctuations. Hence, combining ATES with bioremediation requires dedicated operation and monitoring on the aquifer geochemical conditions.

Microbial community response of an organohalide respiring enrichment culture to permanganate oxidation
Sutton, N.B. ; Atashgahi, S. ; Saccenti, E. ; Grotenhuis, J.T.C. ; Smidt, H. ; Rijnaarts, H.H.M. - \ 2015
PRJEB8632 - ERP009652
While in situ chemical oxidation (ISCO) is often used to remediate tetrachloroethene (PCE) contaminated locations, very little is known about the influence of oxidation on organohalide respiration (OHR) activity and especially microbial community structure. Here, we investigate the impact of oxidation with permanganate on OHR rates, the abundance of organohalide respiring bacteria (OHRB) and reductive dehalogenase (rdh) genes using quantitative PCR, and microbial community composition and dynamics based on sequencing of partial 16S rRNA gene fragments. A PCE degrading enrichment culture was treated with multiple rounds of low (25 µmol), medium (50 µmol), or high (100 µmol) permanganate doses, or no oxidant treatment (biotic control). Results indicate that under mild permanganate treatments (25 µmol or 50 µmol), chemical oxidation stimulated biodegradation leading to higher OHR rates and enrichment of a number of OHRB and rdh genes, as compared to the biotic control. Improved degradation rates can be attributed to enrichment of (1) OHRB able to also utilize Mn oxides as a terminal electron acceptor and (2) non-dechlorinating community members of the order Clostridiales and Deltaproteobacteria who provide essential co-factors to OHRB. In contrast, 100 µmol permanganate treatment disrupted biodegradation activity beyond cis-DCE and caused at least a 2-4 orders of magnitude reduction in the abundance of all measured OHRB and rdh genes, as compared to the biotic control. High permanganate treatments yielded the development of a notably divergent microbial community, with increased abundances of organisms capable of dissimilatory Mn reduction associated with Campylobacterales and Oceanospirillales and a decrease in the abundance of known supporters of OHRB . Although OTUs classified as syntrophic members of the order Clostridiales and OHRB increased in abundance over the course of 213 days of incubation following the final 100 µmol permanganate treatment, only limited regeneration of PCE biodegradation was observed in one of three microcosms, suggesting that strong chemical oxidation treatments can irreversibly disrupt OHR. Overall, this detailed investigation into microbial community structure changes due to permanganate treatment provides insight into the mechanisms of OHR stimulation or disruption upon chemical oxidation.
Bioremediation of chlorinated ethenes in aquifer thermal energy storage
Ni, Z. - \ 2015
Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis; P.F.M. van Gaans. - Wageningen : Wageningen University - ISBN 9789462575752 - 216
watervoerende lagen - thermische energie - verzwakking - grondwater - waterzuivering - duurzame energie - biogeochemie - aquifers - thermal energy - attenuation - groundwater - water treatment - sustainable energy - biogeochemistry

Subjects: bioremediation; biodegradation; environmental biotechnology, subsurface and groundwater contamination; biological processes; geochemistry; microbiology

The combination of enhanced natural attenuation (ENA) of chlorinated volatile organic compounds (CVOCs) and aquifer thermal energy storage (ATES) appears attractive because such integration provides a promising solution for redevelopment of urban areas in terms of improving the local environmental quality as well as achieving sustainable energy supply. It will reduce the current negative interference between groundwater contaminants and ATES systems that arises from the rapid increase of ATES system numbers and generally long duration of contaminated groundwater treatments. However, currently the implementation of the combined system is at an initial stage, and still requires comprehensive study before advancing to mature application. Studies should specifically focus on understanding of the basic biogeochemical processes in aquifer systems under conditions of ATES and enhanced bioremediation and their mutual impacts when combined in ATES-ENA. To this end, the research as reported in this thesis employed laboratory experiments and modeling approaches focused on finding the essential process factors involved in the combined system, revealing possible drawbacks, and providing a better understanding to design alternative options on better operation of the combined system.

Chapter 2 assessed the limiting factor for reductive dechlorination of PCE in an Fe(III) reducing aquifer, being the typical type of subsurface in the Netherlands. A step-wise batch study was performed which consisted of redox conditioning by lactate and ascorbic acid, followed by reductive dechlorination in different scenarios. For the sediment material sampled from the Fe(III) reducing aquifer, conditioning of the redox potential could stimulate PCE dechlorination. It was concluded that 75 µmol electron equivalents per gram dry mass of aquifer material was the threshold to obtain a redox potential of -450 mV, which is theoretically suitable for PCE reductive dechlorination. However, dechlorinating bacteria required for fully reductive dechlorination are generally lacking in Fe(III) reducing aquifers. Without bioaugmentation of dechlorinating bacteria, PCE could only be reduced to TCE or cis-DCE. The step-wise approach and findings obtained from different scenarios tested in this study are relevant for improving the cost-effectiveness of the design and operation of in situ bioremediation. The redox potential of an aquifer can be used as a general indicator to evaluate the potential for CVOCs reductive dechlorination. For achieving specific goals of in situ bioremediation projects at different CVOCs contaminated sites with various environmental conditions, the balance between cost, benefit, and potential risks (e.g. bio‑chemical well clogging due to bacteria growth and precipitation of metal-oxides) should be estimated before the design and operation of the ATES-ENA systems. This chapter provides insights into the essential factors that determine the feasibility of ATES-ENA.

In Chapter 3, the two most important impacts of ATES on enhanced bioremediation of CVOCs were investigated using batch experiments. Besides, another type of underground thermal energy storage system, the borehole thermal energy storage (BTES) was also studied as a comparison to ATES. Here cis-DCE was targeted as it is commonly found to accumulate in the subsurface due to incomplete dechlorination. Compared to a natural situation (NS) with sufficient electron donor and bioaugmentation at a constant temperature of 10 ˚C, we assessed the effect of ATES by exchanging liquid between bottles kept at 25 and 5 ˚C, and the effect of BTES by alternating temperature between 25 and 5 ˚C periodically. Under ATES warm condition, cis-DCE was dechlorinated to ethene and at an increasing rate with each liquid exchange, despite no biodegradation being observed under ATES cold condition. The overall removal rate under alternating ATES conditions reached 1.83 μmol cis‑DCE/day, which was over 1.5 and 13 times faster than those in BTES and NS conditions. Most probably growth of biomass occurred under ATES warm condition, leading to an autocatalytic increase in conversion rates due to higher biomass concentration. Comparison between batches with or without Dehalococcoides inoculum revealed that their initial presence is a determining factor for the dechlorination process. Temperature then became the dominant factor when Dehalococcoides concentration was sufficient. The results also indicated that Dehalococcoides was preferentially attached to the soil matrix. This chapter highlights the importance of the dynamic temperature regimes in ATES on the bioremediation of CVOCs and recommends to implement biostimulation actions in the ATES warm well.

Further impacts of ATES related to change in redox condition on bioremediation of CVOCs, with focus on microbial responses of Dehalococcoides, were explored in Chapter 4. In this chapter, we adopted a recirculating column experiment with a flow rate of 10 mL/min (representing the flow velocity at a distance of 1.3 m from the center of a typical ATES well) to simulate the ATES system. To mimic potential periodic redox fluctuations that accompany ATES, serial additions of lactate and nitrate were performed. Firstly, also at the relatively high liquid velocity (compared to normal bioremediation conditions) complete reductive dechlorination from cis-DCE to ethene was achieved in the column system. However, dechlorination was immediately terminated by subsequent nitrate addition due to direct interruption of Dehalococcoides retention to the soil matrix. In our column system, which was much more homogeneous than subsurface in reality, repeated interruption of dechlorination via Dehalococcoides was extremely severe. Such repeated interruption by nitrate dosing eventually led to less easily reversible while requiring more efforts for recovering dechlorination. In addition, the hypothesis of the immobility of Dehalococcoides was further confirmed by the microbial analysis of microorganism in the liquid phase where only less than 0.1% of the Dehalococcoides inoculum could be found back. Although some field studies demonstrated easier regeneration of Dehalococcoides in the subsurface after suffering oxidant, results from this chapter emphasized the sensitive resilience of Dehalococcoides which needs careful consideration in biostimulated ATES condition, and a functional combined system requires dedicated ATES operation and monitoring on the aquifer geochemical conditions.

The major concern on possible negative impact of enhanced bioremediation on ATES is biological clogging attributed to biomass growth. As chemical clogging due to Fe(III) precipitates is a common problem in the functioning of ATES, the clogging issues (both biological and chemical) should be addressed before practical application. The potential clogging issues in the combined system were then researched in Chapter 5 using the same recirculating column system as in the previous chapter. For this purpose, two flow rates, 10 and 50 mL/min, were implemented. In the two columns, enhanced biological activity and chemically promoted Fe-oxide precipitation were studied by addition of lactate and nitrate respectively. Pressure drop (∆P) between the influent and effluent of the columns was monitored to indicate clogging of the system. The results showed no increase in ∆P during the period of enhanced biological activity, with large amount of lactate and active inoculum being added, even when the concentration of total bacteria in the liquid phase increased by four orders of magnitude. Nitrate addition, however, caused significant increase of ∆P. Remarkably, in the column with higher flow rate (50 mL/min), an unforeseen blow-up occurred at the end of experiment, as the buildup of pressure in the system was higher than the strength of the glass column. However, in the column with flow rate of 10 mL/min, high pressure buildup caused by nitrate addition could be alleviated by lactate addition. Such finding indicates that the risk of biological clogging related to biostimulation is relatively small, because by maintaining a low redox condition biostimulation itself may counter chemical clogging in ATES. Nevertheless, acknowledging that a column system cannot fully mimic real ATES conditions, additional tests are necessary to further investigate the clogging issues in the combined system.

In Chapter 6, we performed a simulation of ATES-ENA with a reactive transport model, using ATES as the engineering tool for lactate injection in a hypothetical TCE contaminated aquifer which is assumed to be homogeneous. Many relevant processes in the combined system were simulated, such as TCE, cis-DCE and VC dechlorination, sulphate and Fe(III) reduction, organic acid fermentation and oxidation and growth of different biomass. In total 15 scenarios are considered in the model, including variations in lactate dosage (three concentration levels: 3.8, 1.9 and 0.38 mmol/L), temperature (three pairs for the ATES cold/warm well: 5/15 ˚C, 10/10 ˚C, 5/25 ˚C), biomass mobility (purely mobile or immobile), and pH limitation on Fe(III) reduction (absence and presence of such an effect). In the five years’ simulation by the model, complete dechlorination to ethene was achieved within 1 year, in the influence zone of the ATES wells, for the reference scenario with 3.8 mmol/L lactate, 5/15 ˚C ATES well temperatures and mobile biomass. Scenarios with lower dosage of lactate gave results with less dechlorination progress. Growth of biomass, especially iron reducer and lactate fermenter, was significant also in the first year (for both mobile and immobile biomass scenarios). Biomass also spread throughout the influence volume of ATES for both warm and cold wells. However, scenarios with different well-temperature pairs did not noteworthy differ in dechlorination progress. This could probably be due to biomass concentration being the limiting factor in this model setup, while temperature was not. Such situation was quite different than that in Chapter 3, of which experiment with bioaugmentation in the beginning. Besides, the model here could not include the important autocatalytic process (Chapter 3) which generated much faster dechlorination than just could be realized by only temperature increase in this chapter. In general, the modeling in this chapter suggests that applying ATES as engineering tool for biostimulation (substrate injection and bioaugmentation) can be a cost-effective approach to support the combined system.

Eventually in Chapter 7, overall discussions upon results gained from previous chapters were integrated and the research questions as presented in the introduction are reiterated. In addition, recommendation upon future study, and wider implications with future perspective for practical application are also discussed. We concluded that redox condition is the most essential factor in the ATES-ENA system. The mutual impacts of ATES and ENA were revealed to be quite positive. Elevated temperature in the ATES warm well synergizing with groundwater transport can provide “1 + 1 > 2” effect. Besides, ENA can probably reduce risk of chemical clogging in ATES, instead of causing biological clogging. The further investigation was recommended to perform with larger scale pilot tests. Finally, a brief review of possible applications was given for two countries, the Netherlands and China, which both have dense groundwater and subsurface contaminations around urban areas. The ATES technology is much more mature in the Netherlands, whereas in China, the advantage is the more flexible usage of subsurface. For both countries, ATES-ENA can provide cost‑effective outcomes on both energy production and groundwater management.

Chemical oxidation of unsymmetrical dimethylhydrazine transformation products in water
Abilev, M. ; Kenessov, B.N. ; Batyrbekova, S. ; Grotenhuis, J.T.C. - \ 2015
Chemical bulletin of Kazakh National University 2015 (2015)1. - ISSN 1563-0331 - p. 20 - 28.
Oxidation of unsymmetrical dimethylhydrazine (UDMH) during a water treatment has several disadvantages including formation of stable toxic byproducts. Effectiveness of treatment methods in relation to UDMH transformation products is currently poorly studied. This work considers the effectiveness of chemical oxidants in respect to main metabolites of UDMH – 1-formyl-2,2-dimethylhydrazine, dimethylaminoacetontrile, N-nitrosodimethylamine and 1-methyl-1H-1,2,4-triazole. Experiments on chemical oxidation by Fenton's reagent, potassium permanganate and sodium nitrite were conducted. Quantitative determination was performed by HPLC. Oxidation products were identified by gas chromatography-mass spectrometry in combination with solid-phase microextraction. 1-Formyl-2,2-dimethylhydrazine was completely oxidized by Fenton's reagent with formation of formaldehyde N-formyl-N-methyl-hydrazone, 1,4-dihydro-1,4-dimethyl-5H-tetrazol-5-one by the action of potassium permanganate and N-methyl-N-nitro-methanamine in the presence of sodium nitrite. Oxidation of 1-formyl-2,2-dimethylhydrazine also resulted in formation of N-nitrosodimethylamine. Oxidation of dimethylaminoacetontrile proceeded with formation of hydroxyacetonitrile, dimethylformamide and 1,2,5-trimethylpyrrole. After 30 days, dimethylaminoacetontrile was not detected in the presence of Fenton’s reagent and potassium permanganate, but it’s concentration in samples with sodium nitrite was 77.3 mg/L. In the presence of Fenton’s reagent, potassium permanganate and sodium nitrite after 30 days, N-nitrosodimethylamine concentration decreased by 85, 80 and 50%, respectively. In control sample, N-nitrosodimethylamine concentration decreased by 50%, indicating that sodium nitrite has no effect of on N-nitrosodimethylamine concentration. Only Fenton's reagent allowed to reduce the concentration of 1-methyl-1H-1,2,4-triazole to 50% in 30 days. In the presence of other oxidants, 1-methyl-1H-1,2,4-triazole concentration decreased by 15-20%. As a result of the experiment, Fenton's reagent proved to be the most effective oxidant.
Biodegradation of cis-DCE in Simulated Underground Thermal Energy Storage Systems
Ni, Z. ; Gaans, P. van; Smit, M.P.J. ; Rijnaarts, H.H.M. ; Grotenhuis, J.T.C. - \ 2015
Environmental Science and Technology 49 (2015)22. - ISSN 0013-936X - p. 13519 - 13527.
Underground thermal energy storage (UTES) use has showed a sharp rise in numbers in the last decades, with aquifer thermal energy storage (ATES) and borehole thermal energy storage (BTES) most widely used. In many urban areas with contaminated aquifers, there exists a desire for sustainable heating and cooling with UTES and a need for remediation. We investigated the potential synergy between UTES and bioremediation with batch experiments to simulate the effects of changing temperature and liquid exchange that occur in ATES systems, and of only temperature change occurring in BTES systems on cis-DCE reductive dechlorination. Compared to the natural situation (NS) at a constant temperature of 10 °C, both UTES systems with 25/5 °C for warm and cold well performed significantly better in cis-DCE removal. The overall removal efficiency under mimicked ATES and BTES conditions were respectively 13 and 8.6 times higher than in NS. Inoculation with Dehalococcoides revealed that their initial presence is a determining factor for the dechlorination process. Temperature was the dominating factor when Dehalococcoides abundance was sufficient. Stimulated biodegradation was shown to be most effective in the mimicked ATES warm well, due to the combined effect of suitable temperature, sustaining biomass growth and regular cis-DCE supply.
Coupling chemical oxidation and biostimulation: Effects on the natural attenuation capacity and resilience of the native microbial community in alkylbenzene-polluted soil
Martínez-Pascual, E. ; Grotenhuis, J.T.C. ; Solanas, A.M. ; Viñas, M. - \ 2015
Journal of Hazardous Materials 300 (2015). - ISSN 0304-3894 - p. 135 - 143.
Coupling chemical oxidation with bioremediation could be a cost-effective system to cope with soil and groundwater pollution. However, the effects of chemical oxidation on autochthonous microbial communities are scarcely known. A detailed analysis that considers both the efficiency of the two technologies and the response of the microbial communities was performed on a linear alkylbenzene-polluted soil and groundwater samples. The impacts of a modified Fenton’s reaction (MFR) at various dosages and of permanganate on the microbiota over 4 weeks were assessed. The permanganate and MFR negatively affected microbial abundance and activity. However, the resilience of certain microbial populations was observed, with a final increase in potential hydrocarbon-degrading populations as determined by both the alkB gene abundance and the predominance of well-known hydrocarbon-degrading phylotypes such as Rhodococcus, Ochrobactrum, Acinetobacter and Cupriavidus genera as determined by 16S rRNA-based DGGE fingerprinting. The assessment of the chemical oxidant impact on autochthonous microbiota should be considered for the optimization of coupled field remediation technologies.
Microbial Community Response of an Organohalide Respiring Enrichment Culture to Permanganate Oxidation
Sutton, N.B. ; Atashgahi, S. ; Saccenti, E. ; Grotenhuis, J.T.C. ; Smidt, H. ; Rijnaarts, H.H.M. - \ 2015
PLoS ONE 10 (2015)8. - ISSN 1932-6203
While in situ chemical oxidation is often used to remediate tetrachloroethene (PCE) contaminated locations, very little is known about its influence on microbial composition and organohalide respiration (OHR) activity. Here, we investigate the impact of oxidation with permanganate on OHR rates, the abundance of organohalide respiring bacteria (OHRB) and reductive dehalogenase (rdh) genes using quantitative PCR, and microbial community composition through sequencing of 16S rRNA genes. A PCE degrading enrichment was repeatedly treated with low (25 µmol), medium (50 µmol), or high (100 µmol) permanganate doses, or no oxidant treatment (biotic control). Low and medium treatments led to higher OHR rates and enrichment of several OHRB and rdh genes, as compared to the biotic control. Improved degradation rates can be attributed to enrichment of (1) OHRB able to also utilize Mn oxides as a terminal electron acceptor and (2) non-dechlorinating community members of the Clostridiales and Deltaproteobacteria possibly supporting OHRB by providing essential co-factors. In contrast, high permanganate treatment disrupted dechlorination beyond cis-dichloroethene and caused at least a 2–4 orders of magnitude reduction in the abundance of all measured OHRB and rdh genes, as compared to the biotic control. High permanganate treatments resulted in a notably divergent microbial community, with increased abundances of organisms affiliated with Campylobacterales and Oceanospirillales capable of dissimilatory Mn reduction, and decreased abundance of presumed supporters of OHRB. Although OTUs classified within the OHR-supportive order Clostridiales and OHRB increased in abundance over the course of 213 days following the final 100 µmol permanganate treatment, only limited regeneration of PCE dechlorination was observed in one of three microcosms, suggesting strong chemical oxidation treatments can irreversibly disrupt OHR. Overall, this detailed investigation into dose-dependent changes of microbial composition and activity due to permanganate treatment provides insight into the mechanisms of OHR stimulation or disruption upon chemical oxidation
Modelling and monitoring of Aquifer Thermal Energy Storage : impacts of soil heterogeneity, thermal interference and bioremediation
Sommer, W.T. - \ 2015
Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis; J. Valstar. - Wageningen : Wageningen University - ISBN 9789462572942 - 204
watervoerende lagen - thermische energie - opslag - energieterugwinning - economische impact - milieueffect - bodemsanering - grondwaterverontreiniging - aquifers - thermal energy - storage - energy recovery - economic impact - environmental impact - soil remediation - groundwater pollution

Modelling and monitoring of Aquifer Thermal Energy Storage

Impacts of heterogeneity, thermal interference and bioremediation

Wijbrand Sommer
PhD thesis, Wageningen University, Wageningen, NL (2015)
ISBN 978-94-6257-294-2

Abstract

Aquifer thermal energy storage (ATES) is applied world-wide to provide heating and cooling to buildings. Application of ATES, instead of traditional heating and cooling installations, reduces primary energy consumption and related CO2 emissions. Intensified use of the subsurface for thermal applications requires more accurate methods to measure and predict the development of thermal plumes in the subsurface related to thermal interference between systems and address issues concerning subsurface urban planning and wide spread presence of contaminants in urban groundwater systems.

In this thesis, subsurface heat transport in ATES and the associated influence on storage performance for thermal energy was assessed. Detailed monitoring of subsurface temperature development around the wells of an existing system was achieved by a unique application of Distributed Temperature Sensing (DTS) using glass fibre optical cables. The measurements reveal unequal distribution of flow rate over different parts of the well screen and preferential flow due to aquifer heterogeneity. Heat transport modelling shows that heterogeneity causes preferential flow paths that can affect thermal interference between systems, mainly depending on well-to-well distance and hydrogeological conditions.

At present, design rules are applied in such way that all negative interference is avoided. However, this limits the number of ATES systems that can be realized in a specific area, especially as these systems generally use only 60% of their permitted capacity. To optimize the use of available aquifer volume, the amount of thermal interference that is acceptable from an economical and environmental perspective was studied for different zonation patterns and well-to-well distances. Selecting the hydrogeological conditions of Amsterdam, the Netherlands, as a case study, this method shows that it is cost-effective to allow a limited amount of thermal interference, such that 30–40% more energy can be provided than compared to the case in which all negative thermal interference is avoided.

Because many urbanized areas deal with contaminated soil and groundwater, ambitions to increase the number of ATES systems are confronted with the presence of groundwater contaminants. This is of concern, because groundwater movement induced by the ATES system can result in increased mobility and spreading of these contaminants. However, the combination between ATES and soil and groundwater remediation could be a promising integrated technique, both for improving groundwater quality and development of ATES. Opportunities to use ATES as a continuous biostimulation tool for enhanced reductive dechlorination (ERD) have been explored with a reactive transport model.

Assessment of the Potential of Honeybees (Apis mellifera L.) in Biomonitoring of Air Pollution by Cadmium, Lead and Vanadium
Steen, J.J.M. van der; Kraker, J. de; Grotenhuis, J.T.C. - \ 2015
Journal of Environmental Protection 6 (2015)2. - ISSN 2152-2197 - p. 96 - 102.
The aim of our study was to explore whether honeybees (Apis mellifera L.) could be used as a reliable alternative to the standard mechanical devices for monitoring of air quality, in particular with respect to the concentration of the heavy metals cadmium (Cd), lead (Pb) and vanadium (V). We therefore tested whether the concentrations of these metals in adult honeybees and in ambient air were positively correlated, and whether differences in concentration between locations were similar for bees and air. On the basis of our measurements, conducted over a two-month period at three distinct locations in the Netherlands with each three replicate honeybee colonies placed next to mechanical monitoring devices, we concluded that a significant positive relationship between the concentrations in bees and in air could only be established for V. Also, only in the case of V, the differences between the three locations in mean concentration were similar for bees and air. Both outcomes were probably due to the relatively large range over which the concentrations of V varied, both in bees and in air, as compared to Cd and Pb. However, for V, as well as for Cd and Pb, the concentrations in ambient air were about two orders of magnitude below the established air quality standards. We therefore conclude that in the Netherlands, both variation and levels of the atmospheric concentrations of these metals are too low to establish a relationship between the concentration in bees and in air that is useful to present honeybees as an alternative to mechanical devices in monitoring of air pollution. However, in countries with larger variation and higher levels of the atmospheric concentrations of these metals, further exploration of the potential of honeybees in biomonitoring of air pollution may be worthwhile
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