Roskilde, Denmark
Roskilde, Denmark

Time filter

Source Type

Kidmose J.,Geological Survey of Denmark | Troldborg L.,Geological Survey of Denmark | Refsgaard J.C.,Geological Survey of Denmark | Bischoff N.,Orbicon
Journal of Hydrology | Year: 2015

Only few studies have attempted to couple a storm water runoff model with a distributed hydrological model even though infiltration or exfiltration processes between pipes and canals of urban runoff systems and groundwater are widely recognised. We present a fully coupled model that allows simulation of the complete urban freshwater cycle including: runoff from paved and impervious areas, flow through the runoff network, overland flow, infiltration through the unsaturated zone, evapotranspiration (at green areas), and groundwater flow in complex, urban geology. For example, at the investigated urban area at the City of Silkeborg, Western Denmark, the coupled model show that one fourth (24%) of water input to the storm water runoff systems arrives from groundwater sources. The study furthermore quantifies groundwater feedback mechanisms of forced infiltration to surface water systems by the fully coupled hydrological and urban runoff model. Three local area recharge scenarios with forced infiltration are compared with the present situation without forced infiltration. The forced infiltration impacts the local groundwater table with an average rise of up to 69. cm resulting in significant feedback from the groundwater to the runoff system via drains, overland flow and leakage of groundwater to the pipes and canals of the urban runoff network. © 2015 Elsevier B.V.

Damgaard I.,Technical University of Denmark | Bjerg P.L.,Technical University of Denmark | Baelum J.,Geological Survey of Denmark | Baelum J.,Technical University of Denmark | And 6 more authors.
Journal of Contaminant Hydrology | Year: 2013

The degradation of chlorinated ethenes and ethanes in clay till was investigated at a contaminated site (Vadsby, Denmark) by high resolution sampling of intact cores combined with groundwater sampling. Over decades of contamination, bioactive zones with degradation of trichloroethene (TCE) and 1,1,1-trichloroethane (1,1,1-TCA) to 1,2-cis-dichloroethene (cis-DCE) and 1,1-dichloroethane, respectively, had developed in most of the clay till matrix. Dehalobacter dominated over Dehalococcoides (Dhc) in the clay till matrix corresponding with stagnation of sequential dechlorination at cis-DCE. Sporadically distributed bioactive zones with partial degradation to ethene were identified in the clay till matrix (thickness from 0.10 to 0.22 m). In one sub-section profile the presence of Dhc with the vcrA gene supported the occurrence of degradation of cis-DCE and VC, and in another enriched δ13C for TCE, cis-DCE and VC documented degradation. Highly enriched δ13C for 1,1,1-TCA (25‰) and cis-DCE (- 4‰) suggested the occurrence of abiotic degradation in a third sub-section profile. Due to fine scale heterogeneity the identification of active degradation zones in the clay till matrix depended on high resolution subsampling of the clay till cores. The study demonstrates that an integrated approach combining chemical analysis, molecular microbial tools and compound specific isotope analysis (CSIA) was required in order to document biotic and abiotic degradations in the clay till system. © 2013 Elsevier B.V.

Damgaard I.,Technical University of Denmark | Bjerg P.L.,Technical University of Denmark | Jacobsen C.S.,Geological Survey of Denmark | Tsitonaki A.,Orbicon | And 2 more authors.
Groundwater Monitoring and Remediation | Year: 2013

At a low permeability clay till site contaminated with chlorinated ethenes (Gl. Kongevej, Denmark), enhanced reductive dechlorination (ERD) was applied by direct push injection of molasses and dechlorinating bacteria. The performance was investigated by long-term groundwater monitoring, and after 4 years of remediation, the development of degradation in the clay till matrix was investigated by high-resolution subsampling of intact cores. The formation of degradation products, the presence of specific degraders Dehalococcoides spp. with the vinyl chloride (VC) reductase gene vcrA, and the isotope fractionation of trichloroethene, cis-dichloroethene (cis-DCE), and VC showed that degradation of chlorinated ethenes occurred in the clay till matrix as well as in sand lenses, sand stringers, and fractures. Bioactive sections of up to 1.8 m had developed in the clay till matrix, but sections, where degradation was restricted to narrow zones around sand lenses and stringers, were also observed. After 4 years of remediation, an average mass reduction of 24% was estimated. Comparison of the results with model simulation scenarios indicate that a mass reduction of 85% can be obtained within approximately 50 years without further increase in the narrow reaction zones if no donor limitations occur at the site. Long-term monitoring of the concentration of chlorinated ethenes in the underlying chalk aquifer revealed that the aquifer was affected by the more mobile degradation products cis-DCE and VC generated during the remediation by ERD. © 2012, National Ground Water Association.

Sivertsen A.,Soil and Groundwater | Ellehoj K.V.,Orbicon | Kornbeck T.,ALS Denmark
Remediation | Year: 2016

The Capital Region of Denmark tested the Multi Increment Sampling® (MIS) technology at 14 children's playgrounds in the region to assess whether the method provides representative test results and an improved foundation for risk assessment. The purpose of the investigation was to determine whether the previous uses of the playground areas have led to soil contamination that poses a health risk to its current users (children). The unpaved areas of the playgrounds were divided into decision units based on historical data along with the expected patterns of movement from its users. The samples from each unit consisted of 45 to 100 increments were collected from three depths within the upper one-half meter. Furthermore, triplicate samples were taken from the upper sampling depth in at least one unit for quality control purposes. The investigation results showed excellent consistency between the pollution parameters and contamination levels in different decision units for each playground. The decision units where high levels of soil contamination exist coincide well with the previous site history. The MIS method has proven to be expensive and time consuming. However, in the future it will be easier to implement as we gain more experience with use of this method. ©2016 Wiley Periodicals, Inc. ©2016 Wiley Periodicals, Inc.

Broholm M.M.,Technical University of Denmark | Hunkeler D.,University of Neuchatel | Tuxen N.,Orbicon | Jeannottat S.,University of Neuchatel | Scheutz C.,Technical University of Denmark
Chemosphere | Year: 2014

The fate and treatability of 1,1,1-TCA by natural and enhanced reductive dechlorination was studied in laboratory microcosms. The study shows that compound-specific isotope analysis (CSIA) identified an alternative 1,1,1-TCA degradation pathway that cannot be explained by assuming biotic reductive dechlorination. In all biotic microcosms 1,1,1-TCA was degraded with no apparent increase in the biotic degradation product 1,1-DCA. 1,1,1-TCA degradation was documented by a clear enrichment in 13C in all biotic microcosms, but not in the abiotic control, which suggests biotic or biotically mediated degradation. Biotic degradation by reductive dechlorination of 1,1-DCA to CA only occurred in bioaugmented microcosms and in donor stimulated microcosms with low initial 1,1,1-TCA or after significant decrease in 1,1,1-TCA concentration (after~day 200). Hence, the primary degradation pathway for 1,1,1-TCA does not appear to be reductive dechlorination via 1,1-DCA. In the biotic microcosms, the degradation of 1,1,1-TCA occurred under iron and sulfate reducing conditions. Biotic reduction of iron and sulfate likely resulted in formation of FeS, which can abiotically degrade 1,1,1-TCA. Hence, abiotic degradation of 1,1,1-TCA mediated by biotic FeS formation constitute an explanation for the observed 1,1,1-TCA degradation. This is supported by a high 1,1,1-TCA 13C enrichment factor consistent with abiotic degradation in biotic microcosms. 1,1-DCA carbon isotope field data suggest that this abiotic degradation of 1,1,1-TCA is a relevant process also at the field site. © 2014 Elsevier Ltd.

Nielsen S.,Orbicon
Water Science and Technology | Year: 2011

The dewatering of the sludge with loss on ignition between 50 and 65% will have a maximal drainage on the order of 0.008-0.020 L/s/m2. Dewatering of the sludge with loss of ignition higher than 65% of dry solids will have a maximal drainage on the order of only 0.001-0.004 L/s/m2, approximately five to 10 times lower. It can be seen that there is a tendency for the achievable dewatering result to increase with the decrease of loss on ignition or fat in the feed sludge. The correlation shows that if the loss of ignition is higher than 65% of dry solids in the feed sludge the dewatering results in approximately 10% dry solid or lower in the sludge residue, and in approximately 5% dry solid or lower in the sludge residue if the fat concentration is above 10,000 mg/kg ds in the feed sludge. In systems treating sludge with high contents of fat (15,000-30,000 mg/kg ds) and oil (2,300-7,000 mg/kg ds) and if the loss of ignition is higher than 65% (between 65-76%) the dewatering efficiencies only achieve 5-15% dry solid in the sludge residue. In systems treating sludge with low contents of fat (4,000-8,000 mg/kg ds) and oil (50-2,000 mg/kg ds) and with loss on ignition between 50-65% contents of organic solids the dewatering efficiencies achieve 20-37% dry solid in the sludge residue. © IWA Publishing 2011.

Hunkeler D.,University of Neuchatel | Abe Y.,University of Neuchatel | Broholm M.M.,Technical University of Denmark | Jeannottat S.,University of Neuchatel | And 5 more authors.
Journal of Contaminant Hydrology | Year: 2011

The fate of chlorinated ethenes in a large contaminant plume originating from a tetrachloroethene (PCE) source in a sandy aquifer in Denmark was investigated using novel methods including compound-specific carbon and chlorine isotope analysis and quantitative real-time polymerase chain reaction (qPCR) methods targeting Dehaloccocoides sp. and vcrA genes. Redox conditions were characterized as well based on concentrations of dissolved redox sensitive compounds and sulfur isotopes in SO 4 2-. In the first 400 m downgradient of the source, the plume was confined to the upper 20 m of the aquifer. Further downgradient it widened in vertical direction due to diverging groundwater flow reaching a depth of up to 50 m. As the plume dipped downward and moved away from the source, O 2 and NO 3 - decreased to below detection levels, while dissolved Fe 2+ and SO 4 2- increased above detectable concentrations, likely due to pyrite oxidation as confirmed by the depleted sulfur isotope signature of SO 4 2-. In the same zone, PCE and trichloroethene (TCE) disappeared and cis-1,2-dichloroethene (cDCE) became the dominant chlorinated ethene. PCE and TCE were likely transformed by reductive dechlorination rather than abiotic reduction by pyrite as indicated by the formation of cDCE and stable carbon isotope data. TCE and cDCE showed carbon isotope trends typical for reductive dechlorination with an initial depletion of 13C in the daughter products followed by an enrichment of 13C as degradation proceeded. At 1000 m downgradient of the source, cDCE was the dominant chlorinated ethene and had reached the source δ 13C value confirming that cDCE was not affected by abiotic or biotic degradation. Further downgradient (up to 1900 m), cDCE became enriched in 13C by up to 8‰ demonstrating its further transformation while vinylchloride (VC) concentrations remained low (< 1 μg/L) and ethene was not observed. The correlated shift of carbon and chlorine isotope ratios of cDCE by 8 and 3.9‰, respectively, the detection of Dehaloccocides sp genes, and strongly reducing conditions in this zone provide strong evidence for reductive dechlorination of cDCE. The significant enrichment of 13C in VC indicates that VC was transformed further, although the mechanism could not be determined. The transformation of cDCE was the rate limiting step as no accumulation of VC occurred. In summary, the study demonstrates that carbon-chlorine isotope analysis and qPCR combined with traditional approaches can be used to gain detailed insight into the processes that control the fate of chlorinated ethenes in large scale plumes. © 2010 Elsevier B.V. All rights reserved.

Rasmussen R.S.,Technical University of Denmark | Ostenfeld T.,Orbicon
Aquaculture International | Year: 2010

This study describes growth variation within groups of salmonids and the relation to initial fish weights and feeding levels. PIT-tagged rainbow trout (RT) and brook trout (BT) of start weight 120-170 g were reared in separate tanks for 9 weeks. Both species were fed each day either a high ration close to satiation (H) or half of this ration (L). Four experimental groups (RT-H, RT-L, BT-H, BT-L) were studied with regard to their propensity to increase weight in accord with their initial weight. The slope of the regression line between initial weights (g) and weight increases for individuals in each tank in each period was applied as indicator for this propensity (termed "slope"). All calculated slopes in the experiment were positive which indicates the general ability of weighty fish to gain more weight than smaller individuals. The average slope during all 9 weeks was 2-4 times higher for RT-L (5.91) than for all other groups (RT-H: 1.50, P < 0.01; BT-H: 1.76, P < 0.01 and BT-L: 2.88, P < 0.05), indicating the particular propensity of large RT to gain weight when feed was restricted. Overall, ration level had large impact on slopes (H: 1.63, L: 4.39, P < 0.01), while this was not the case for species (RT: 3.71, BT: 2.32, P > 0.05). The magnitude of slopes decreased over time (weeks 0-3:4.27, weeks 3-6:3.02 and weeks 6-9:1.74, P < 0.05). The observed differences in weight gains between experimental groups were reflected in differences in coefficients of variations (CVs) for body growth. RT had larger body weight (BW) CVs compared to BT (0.257 vs. 0.206, P < 0.01) indicating more uneven feed share among RT than among BT in general. RT-L had significantly higher BW CVs than all other groups (0.300 vs. 0.184-0.229, P < 0.01). The observed differences in weight gains enhance size variations in terms of higher CVs, and this may have implications for feeding tactics in aquaculture where large size variations in groups may be disadvantageous to fish farmers. © 2010 Springer Science+Business Media B.V.

Nielsen S.,ORBICON | Peruzzi E.,CNR Institute of Ecosystem Study | Macci C.,CNR Institute of Ecosystem Study | Doni S.,CNR Institute of Ecosystem Study | Masciandaro G.,CNR Institute of Ecosystem Study
Water Science and Technology | Year: 2014

Sludge stabilisation and mineralisation during periods of operation between 10 and 21 years were investigated in three different systems receiving sludge from urban wastewater treatment plants situated in Denmark. Samples were taken along the entire profiles, in order to compare the effectiveness of the sludge stabilisation process. Particular attention was given to the stabilisation process occurring within the reed beds; in fact, parameters correlated to biochemical properties of organic sludge matter were determined. Statistical procedures were used to evaluate how the biochemical processes influence the quality of sludge organic matter. The level of total organic carbon and total nitrogen had a similar trend along the profile: their concentration decreased with increasing depth, reaching very low levels at the deepest layers. The same trend was also observed for the water-soluble carbon, N-NH3, β-glucosidase and urease activities, and hydrolytic enzymes linked to C and N cycles: their values decreased dramatically with increasing depth, meaning that the level of mineralisation of the organic matter was higher in the deepest layers. The determination of extracellular enzymes bound to humic substances and humic carbon permitted evaluation of the stabilisation of organic sludge matter, and also allowed individuation of the ways in which the sludge was stabilised, in terms of mineralisation and humification of the organic matter. © IWA Publishing 2014.

PubMed | Orbicon, Copenhagen University, DHI and Technical University of Denmark
Type: Journal Article | Journal: Water science and technology : a journal of the International Association on Water Pollution Research | Year: 2015

Stormwater management using water sensitive urban design is expected to be part of future drainage systems. This paper aims to model the combination of local retention units, such as soakaways, with subsurface detention units. Soakaways are employed to reduce (by storage and infiltration) peak and volume stormwater runoff; however, large retention volumes are required for a significant peak reduction. Peak runoff can therefore be handled by combining detention units with soakaways. This paper models the impact of retrofitting retention-detention units for an existing urbanized catchment in Denmark. The impact of retrofitting a retention-detention unit of 3.3 m/100 m (volume/impervious area) was simulated for a small catchment in Copenhagen using MIKE URBAN. The retention-detention unit was shown to prevent flooding from the sewer for a 10-year rainfall event. Statistical analysis of continuous simulations covering 22 years showed that annual stormwater runoff was reduced by 68-87%, and that the retention volume was on average 53% full at the beginning of rain events. The effect of different retention-detention volume combinations was simulated, and results showed that allocating 20-40% of a soakaway volume to detention would significantly increase peak runoff reduction with a small reduction in the annual runoff.

Loading ORBICON collaborators
Loading ORBICON collaborators