| 1. |
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| 2. |
- Bergqvist, Claes, et al.
(författare)
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Plants influence on arsenic availability and speciation in the rhizosphere, roots and shoots of three different vegetables
- 2014
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 184, s. 540-546
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Tidskriftsartikel (refereegranskat)abstract
- The toxicity of arsenic (As) in the environment is controlled by its concentration, availability and speciation. The aims of the study were to evaluate the accumulation and speciation of As in carrot, lettuce and spinach cultivated in soils with various As concentrations and to estimate the concomitant health risks associated with the consumption of the vegetables. Arsenic concentration and speciation in plant tissues and soils was analysed by HPLC, AAS and XANES spectroscopy. To estimate the plants influence in the rhizosphere, organic acids in lettuce root exudates were analysed by ion chromatography. The results showed that the As accumulation was higher in plants cultivated in soil with higher As extractability. Arsenate predominated in the soils, rhizosphere and root exudates of lettuce. Succinic acid was the major organic acid in lettuce root exudates. Ingestion of the tested vegetables may result in an intake of elevated levels of inorganic As.
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| 3. |
- Bettoni, Laura Nina, et al.
(författare)
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Sulfate removal from mine drainage at low temperature : Effects of three reactive porous media on microbial sulfate reduction
- 2024
-
Ingår i: Proceedings of the International Mine Water Association Conference & West Virginia Mine Drainage Task Force Symposium. - : International Mine Water Association. - 9783982529325 ; , s. 50-56
-
Konferensbidrag (refereegranskat)abstract
- Sulfate removal by microbial sulfate reduction can be promoted in anaerobic treatmentsystems where there is a supply of organic carbon for bacterial growth. This studyevaluates sulfate removal using three organic carbon media (woodchips, woodchipswith biochar and woodchips with potato peels), with and without supplementalorganic carbon (lactate), and at 5 °C. The study highlights the different factors thatcould have affected sulfate reduction and how it can be implemented in a field-basedbioreactor. It concludes that organic carbon media composition and lactate dosingneed to be considered when designing a bioremediation system.
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| 4. |
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| 5. |
- Das, Pallavi, et al.
(författare)
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Understanding the Cyclicity of Chemical Weatheringand Associated CO2Consumption in the BrahmaputraRiver Basin (India) : The Role of Major Rivers in ClimateChange Mitigation Perspective
- 2016
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Ingår i: Aquatic geochemistry. - : Springer Science and Business Media LLC. - 1380-6165 .- 1573-1421. ; 22:3, s. 225-251
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Tidskriftsartikel (refereegranskat)abstract
- Weathering of rocks that regulate the water chemistry of the river has been used to evaluate the CO2 consumption rate which exerts a strong influence on the global climate. The foremost objective of the present research is to estimate the chemical weathering rate (CWR) of the continental water in the entire stretch of Brahmaputra River from upstream to downstream and their associated CO2 consumption rate. To establish the link between the rapid chemical weathering and thereby enhance CO2 drawdown from the atmosphere, the major ion composition of the Brahmaputra River that drains the Himalaya has been obtained. Major ion chemistry of the Brahmaputra River was resolved on samples collected from nine locations in pre-monsoon, monsoon and post-monsoon seasons for two cycles: cycle I (2011-2012) and cycle II (2013-2014). The physico-chemical parameters of water samples were analysed by employing standard methods. The Brahmaputra River was characterized by alkalinity, high concentration of Ca2+ and HCO3 (-) along with significant temporal variation in major ion composition. In general, it was found that water chemistry of the river was mainly controlled by rock weathering with minor contributions from atmospheric and anthropogenic sources. The effective CO2 pressure (log) for pre-monsoon, monsoon and post-monsoon has been estimated. The question of rates of chemical weathering (carbonate and silicate) was addressed by using TDS and run-off (mm year(-1)). It has been found that the extent of CWR is directly dependent on the CO2 consumption rate which may be further evaluated from the perspective of climate change mitigation The average annual CO2 consumption rate of the Brahmaputra River due to silicate and carbonate weathering was found to be 0.52 (x10(6) mol Km(-2) year(-1)) and 0.55 (x10(6) mol Km(-2) year(-1)) for cycle I and 0.49 (x10(6) mol Km(-2) year(-1)) and 0.52 (x10(6) mol Km(-2) year(-1)) for cycle II, respectively, which were significantly higher than that of other Himalayan rivers. Estimation of CWR of the Brahmaputra River indicates that carbonate weathering largely dominates the water chemistry of the Brahmaputra River.
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| 6. |
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| 7. |
- Hellman, Maria, et al.
(författare)
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Microbial succession and denitrifying woodchip bioreactor performance at low water temperatures
- 2024
-
Ingår i: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 356
-
Tidskriftsartikel (refereegranskat)abstract
- Mining activities are increasingly recognized for contributing to nitrogen (N) pollution and possibly also to emissions of the greenhouse gas nitrous oxide (N2O) due to undetonated, N-based explosives. A woodchip denitrifying bioreactor, installed to treat nitrate-rich leachate from waste rock dumps in northern Sweden, was monitored for two years to determine the spatial and temporal distribution of microbial communities, including the genetic potential for different N transformation processes, in pore water and woodchips and how this related to reactor N removal capacity. About 80 and 65 % of the nitrate was removed during the first and second operational year, respectively. There was a succession in the microbial community over time and in space along the reactor length in both pore water and woodchips, which was reflected in reactor performance. Nitrate ammonification likely had minimal impact on N removal efficiency due to the low production of ammonium and low abundance of the key gene nrfA in ammonifiers. Nitrite and N2O were formed in the bioreactor and released in the effluent water, although direct N2O emissions from the surface was low. That these unwanted reactive N species were produced at different times and locations in the reactor indicate that the denitrification pathway was temporally as well as spatially separated along the reactor length. We conclude that the succession of microbial communities in woodchip denitrifying bioreactors treating mining water develops slowly at low tem-perature, which impacts reactor performance.
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| 8. |
- Hellman, Maria, et al.
(författare)
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Nitrogen removal and spatial distribution of denitrifier and anammox communities in a bioreactor for mine drainage treatment
- 2014
-
Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 66, s. 350-360
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Tidskriftsartikel (refereegranskat)abstract
- Mine drainage water may contain high levels of nitrate (NO3-) due to undetonated nitrogen-based explosives. The removal of NO3- and nitrite (NO2-) in cold climates through the microbial process of denitrification was evaluated using a pilot-scale fixed-bed bioreactor (27 m(3)). Surface water was diverted into the above-ground bioreactor filled with sawdust, crushed rock, and sewage sludge. At hydraulic residence times of ca.15 h and with the addition of acetate, NO3- and NO2- were removed to below detection levels at a NO3- removal rate of 5-10 g N m(-3) (bioreactor material) d(-1). The functional groups contributing to nitrogen removal in the bioreactor were studied by quantifying nirS and nirK present in denitrifying bacteria, nosZI and nosZII genes from the nitrous oxide - reducing community, and a taxa-specific part of the16S rRNA gene for the anammox community. The abundances of nirS and nirK were almost 2 orders of magnitude greater than the anammox specific 16S rRNA gene, indicating that denitrification was the main process involved in nitrogen removal. The spatial distribution of the quantified genes was heterogeneous in the bioreactor, with trends observed in gene abundance as a function of depth, distance from the bioreactor inlet, and along specific flowpaths. There was a significant relationship between the abundance of nirS, nirK, and nosZI genes and depth in the bioreactor, such that the abundance of organisms containing these genes may be controlled by oxygen diffusion and substrate supply in the partially or completely water-saturated material. Among the investigated microbial functional groups, nirS and anammox bacterial 16S rRNA genes exhibited a systematic trend of decreasing and increasing abundance, respectively, with distance from the inlet, which suggested that the functional groups respond differently to changing environmental conditions. The greater abundance of nirK along central flowpaths may indicate that the bioreactor design favored preferential flow along these flowpaths, away from the sides of the bioreactor. An improved bioreactor design should consider the role of preferential flowpaths and the heterogeneous distribution of the genetic potential for denitrification, nitrous oxide reduction and anammox on bioreactor function. (C) 2014 Elsevier Ltd. All rights reserved.
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| 9. |
- Herbert, Roger B., 1966-, et al.
(författare)
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Denitrifierande bioreaktorer : Rening av kväve i lakvatten
- 2021
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Ingår i: Vatten. - 0042-2886. ; 77, s. 173-183
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Sprängmedel baserade på ammoniumnitrat är idag de vanligaste sprängmedel som används inom industriella verksamheter såsom gruvdrift, bergtäkter och tunneldrivning för vägbygge. Studier från gruvindustrin har dock visat att en del av det sprängmedel som används (upp till 28 %) inte detonerar och med tiden läcker ut till närliggande recipienter, huvudsakligen som nitrat (NO3-). En denitrifierande bioreaktor är en passiv och kostnadseffektiv metod för att minska nitrathalter i lakvatten från sprängstensmassor och bergkrosshögar, och har sedan 2015 byggts och utvärderats på flera platser i Sverige. I sin enklaste form är bioreaktorn en grop som fylls med ett reaktivt material rikt på organiskt kol, vanligtvis träflis. Vatten med höga halter av NO3- tillåts flöda horisontellt genom det reaktiva materialet, där inkommande NO3- omvandlas till N2 genom den mikrobiella processen denitrifikation. Denna artikel sammanfattar bioreaktorstekniken och diskuterar dess användning för att minska nitrathalter i lakvatten från sprängstensmassor och bergkrosshögar, med fokus på design och drift för optimal processeffektivitet. En fallstudie från en bergtäkt i Kalmar län redovisas, där en bioreaktor har varit i drift i fyra år med en genomsnittlig nitratrening på 90 %.
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| 10. |
- Herbert, Roger B., 1966-, et al.
(författare)
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Iron isotope fractionation by biogeochemical processes in mine tailings
- 2008
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:4, s. 1117-1122
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Tidskriftsartikel (refereegranskat)abstract
- Iron isotope ratios were determined for the pore water, the 1M HCl / 1M hydroxylamine hydrochloride (HAH) – extractable solid phase, and the total extractable solid phase from sulfidic mine tailings in Impoundment 1, Kristineberg mine, northern Sweden. Within the tailings, pyrite oxidation occurs in a distinct Fe – depleted oxidation zone, and the greatest number of Fe(II)-oxidizing bacteria in the profile occur close to the boundary between oxidized and unoxidized tailings. Above the oxidation front in the oxidized tailings, a large iron isotope fractionation (‑1.3‰ to ‑2.4‰) is measured between the pore water and the HAH-extractable solid phase. This isotope fractionation is explained by aqueous Fe(II) – Fe(III) equilibrium, microbial Fe(II) oxidation, and Fe(III) oxyhydroxide precipitation. The data suggests that pyrite in the tailings is enriched in 56Fe relative to Fe-rich silicates in the same material, such that pyrite oxidation results in a decrease in the mean d56Fe value for the bulk tailings in the oxidized zone: a change in isotope composition that is not attributable to isotope fractionation. Iron isotope analyses yield valuable information on iron cycling in mine wastes, and have the potential for becoming a tool for the prediction and control of acid mine drainage.
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| 11. |
- Herbert, Roger, 1966-, et al.
(författare)
-
Bakgrundshalter av metaller i Svenska inlands- och kustvatten.
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I tillämpningen av Vattendirektivet i Sverige kommer miljökvalitetsnormer att sättas både för prioriterade och andra ämnen enligt ett dotterdirektiv till Vattendirektivet. Hänsyn kommer att tas till bakgrundshalterna av de ämnen som förekommer naturligt, och det är därför av stor betydelse att fastställa sådana bakgrundshalter. Syftet med denna studie är att utifrån befintliga data ta fram bakgrundshalter för metaller i svenska sjöar, vattendrag, kustvatten och hav. Termen bakgrundshalt i denna studie syftar på en regional bakgrundshalt som är typiskt för vatten som är opåverkat av punktutsläpp eller försurning, men kan ha påverkats av depositionen av förbränningsrester från fossila och andra bränslen samt av diffusa utsläpp från jord- och skogsbruk. Regionala bakgrundshalter kan anses vara nutida bakgrundshalter, och gäller för en viss region och/eller vattentyp.Bakgrundshalter för metaller i vattendrag och sjöar fastställdes efter inventering och kvalitetssäkring av mätdata samt inventering av punktutsläppskällor. Bakgrundshalter för metaller i kustvatten och hav fastställdes efter en enklare kvalitetssäkring. I enlighet med Naturvårdsverkets indelningskriterier för limniska typer redovisas bakgrundshalter för metaller i vattendrag och sjöar för alla sju limniska ekoregioner i Sverige, med ytterligare indelningar baserade på hydromorfologiska egenskaper (humus- och kalkhalt). Bakgrundshalten av en metall i en viss limnisk ekoregion och klass beräknades som 50-percentilen (medianvärdet) av medianhalten för varje stationer inom samma klassning.Efter kvalitetsgranskning och jämförelsen med MIFO-objekt (dvs punktutsläppskällor) reducerades den ursprungliga databasen med 613 vattendragsstationer och 454 sjöstationer till 453 respektive 444 stationer. Efter ytterligare granskning användes slutligen mätdata från 430 vattendragsstationer och 438 sjöstationer för bestämning av bakgrundshalter. För beräkning av bakgrundshalter i kust- och havsvatten användes 245 mätpunkter, varav 49 i kustzonen och resten i öppet hav.Resultaten från bestämningen av bakgrundshalter i sjöar visar att humushalt och kalkhalt (och därmed pH) har generellt sett stor inverkan på metallhalterna. De högsta bakgrundshalterna av metaller sammanfaller ofta med sura sjöar. Kalkfattiga humusrika sjöar har i allmänhet högre bakgrundshalter av Fe än kalkfattiga humusfattiga sjöar, vilket tyder på ett samband mellan humus- och järnhalt. Vissa metaller såsom Co, Cr och V visar samvariation med Fe i dessa humusrika kalkfattiga sjöar. En jämförelse med de tidigare regionala bakgrundshalterna för sjöar i norra och södra Sverige visar att många av de nyräknade bakgrundshalterna ligger högre än de tidigare halterna.Analyserna visar relativt stora skillnader i metallhalter mellan vattendrag i norra och södra Sverige. Medianhalter i norra Sverige ligger mer än 50% lägre än halterna i södra Sverige, vilket kan förklaras främst med mindre luftdeposition i norra Sverige. Relativt höga regionala bakgrundshalter för Cr, Cu och Ni har beräknats för kalkrika vattendrag i sydöstra Sverige (ekoregion 4), där vissa vattendrag kan beskrivas som slättlandsåar. Beräknade bakgrundshalter av metaller i kustvatten och havsvatten visar att det finns stor variabilitet i främst Mn- och Zn-halter, där skillnaden mellan 25:e- och 75:e-percentilen uppgår till mer än en tiopotens. En jämförelse av halter mellan filtrerade och ofiltrerade prover från Egentliga Östersjön tyder på att en stor andel av de undersökta metallerna i ofiltrerat havsvatten är partikelbundna. Detta kan förklara den stora variabiliten i främst Mn- och Zn-, men också i Cd-, Co-, Fe- och Hg-halter.För att i framtiden kunna beräkna bakgrundshalter för kustområden, Västerhavet och Bottenhavet samt för att få en bättre bild av halterna i Egentliga Östersjön behövs omfattande provtagningar och analyser med enhetliga metoder.
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| 12. |
- Herbert, Roger, 1966-, et al.
(författare)
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Barrier system for the treatment of nitrogen effluents from the Malmberget iron mine
- 2009
-
Ingår i: <em>Proceedings, Securing the Future</em>. Skellefteå, Sweden.
-
Konferensbidrag (refereegranskat)abstract
- At the Malmberget iron mine in northern Sweden, nitrogen from undetonated explosives is discharged from the mine with process water. After passing through a settling pond, excess process water is discharged to the Linaälv River via a spillway. Because of the risk for eutrophication in rivers and coastal areas downstream, it is necessary to decrease the N levels in the effluent waters. This study presents the results from laboratory column experiments under water – saturated conditions, conducted at room temperature and 5oC, which will be used in the design of a pilot-scale barrier system. The columns were filled with a reactive substrate consisting of sawdust and activated sewage sludge. The results of the room temperature experiments demonstrated that nitrate removal efficiency was >95% for flow rates < 341 liters d-1 m-3 reactive mixture. However, at flow rates of ~700 liters d-1 m-3 reactive mixture, nitrate removal efficiency decreased to ~64%. Tracer experiments indicated an increasing degree of channeling in the columns as flow rate increased, thus leading to a reduction in removal efficiency. Apparent denitrification rates were estimated to 2.8 -9.3 g N d-1 m-3 and 2.2 g N d-1 m-3 at room temperature and 5oC, respectively.
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| 13. |
- Herbert, Roger, 1966-
(författare)
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Implications of non-equilibrium transport in heterogeneous reactive barrier systems : evidence from laboratory denitrification experiments
- 2011
-
Ingår i: Journal of Contaminant Hydrology. - : Elsevier BV. - 0169-7722 .- 1873-6009. ; 123:1-2, s. 30-39
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Tidskriftsartikel (refereegranskat)abstract
- Organic substrates in reactive barrier systems are often heterogeneous material mixtures with relatively large contrasts in hydraulic conductivity and porosity over short distances. These short-range variations in material properties imply that preferential flow paths and diffusion between regions of higher and lower hydraulic conductivity may be important for treatment efficiency. This paper presents the results of a laboratory column experiment where denitrification is investigated using a heterogeneous reactive substrate (sawdust mixed with sewage sludge). Displacement experiments with a non-reactive solute at three different flow rates are used to estimate transport parameters using a dual porosity non-equilibrium model. Parameter estimation from breakthrough curves produced relatively consistent values for the fraction of the porosity consisting of mobile water (β) and the mass transfer coefficient (α), with average values of 0.27 and 0.42 d-1, respectively. The column system removes > 95% of the influent nitrate at low and medium flow, but only 50 – 75% of the influent nitrate at high flow, suggesting that denitrification kinetics and diffusive mass transfer rates are limiting the degree of treatment at lower hydraulic residence times. Reactive barrier systems containing dual porosity media must therefore consider mass transfer times in their design; this is often most easily accommodated by adjusting flowpath length.
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| 14. |
- Herbert, Roger, 1966-, et al.
(författare)
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Leachate generation and nitrogen release from small-scale rock dumps at the Kiruna iron ore mine
- 2017
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Ingår i: Mine water and circular economy. ; , s. 140-146
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Konferensbidrag (refereegranskat)abstract
- Two small-scale waste rock dumps have been constructed in Kiruna, Sweden to investigatethe dynamics of leachate generation and nitrogen release over the course of several years. The rockdumps have been constructed of low sulfur rock waste which is not acid generating. The results of thestudy indicate that, for the two years of this study, water is only discharged intermittently from therock dumps during snowmelt and during more intense rainfall events. During 2016, concentrationsof nitrate and ammonium in the discharge waters ranged up to 46 and 0.14 mg N/L, respectively. Theaverage leachate composition (n = 25) was pH 7.8, alkalinity 55 mg/L HCO3- and 1011 mg/L SO42-,which is quite similar to the composition of water in the clarification pond at the mine site.
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| 15. |
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| 16. |
- Herbert, Roger, 1966-, et al.
(författare)
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Nitrate removal from waste rock drainage with denitrifying bioreactors at the Kiruna iron ore mine
- 2024
-
Ingår i: Proceedings of the International Mine Water Association Conference & West Virginia Mine Drainage Task Force Symposium. - : International Mine Water Association. - 9783982529325 ; , s. 274-280
-
Konferensbidrag (refereegranskat)abstract
- The ultimate source of most nitrogen in mine drainage is the ammonium nitrate – based explosives used in the excavation of the mine. This study reports on the performance of a full-scale woodchip denitrifying bioreactor installed for nitrate removal at LKAB’s iron ore mine in Kiruna, Sweden. In the bioreactor, nitrate removal was at a rate of 70–80% during the first year (2018–2019) but decreased to 28% by 2021. The decrease in treatment efficiency with time is believed to be controlled at least partially by the low water temperature (average 3 °C) and a decrease in available organic carbon for denitrification.
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| 17. |
- Herbert, Roger, 1966-, et al.
(författare)
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Pilot-scale barrier system for removal of nitrate in mine drainage
- 2011
-
Ingår i: Mineralogical magazine. - 0026-461X .- 1471-8022. ; 75, s. 1012-1012
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Undetonated ammonium nitrate is readily soluble in water and quickly enters into the mine water and process water at amine site. In order to investigate the application of nitrate removal by denitrification in the cold climate of northern Sweden, a pilot-scale barrier system was constructed of sheet metal in autumn 2009 at the Malmberget iron ore mine. The barrier (9m x 2m x 1.5m) appears as an open basin with three inner dividing walls, and is filled with a reactive mixture consisting of crushed rock, sawdust, and sewage sludge. Water flows through the barrier at ca. 0.45 m3/hour.The chemical analyses of water flowing into and out of thebarrier during 2010 indicate that the degree of nitrate removal generally lay in the range between 11 and 77% of influent nitrate concentrations. Stable isotope analyses of δ15N and δ18O in nitrate demonstrate an enrichment in 15N and 18O in nitrate as water flows through the barrier, supporting theconclusion that denitrification is responsible for nitrateremoval. Ammonium concentrations in the barrier effluents are initially high, but these high levels are subsequently flushed from the barrier. In order to increase the degree of nitrate removal by denitrification in the barrier, a reactive carbon source needs to be added to the influent waters; this will be tested during the 2011 field season.
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| 18. |
- Herbert, Roger, 1966-, et al.
(författare)
-
Pilot-scale barrier system for removal of nitrate in mine drainage
- 2012
-
Ingår i: Proceedings of the 22nd V.M. Goldschmidt Conference.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionUndetonated ammonium nitrate - based explosives are readily soluble in water and quickly enter into the mine water and process water at a mine site. Process water is eventually discharged to a surface water body and, without treatment, can lead to eutrophication in the recipient. In order to investigate the application of nitrate removal by denitrification in the cold climate of northern Sweden, laboratory and field experiments have been conducted. Laboratory column experiments were designed to determine denitrification rates at relevant temperatures for northern Sweden. Based on the column experiments at low temperature, a hydraulic residence time of ca. 24 hours was one of the design criteria used for dimensioning a barrier system in the field. In autumn 2009, a pilot-scale barrier system was constructed of sheet metal at the Malmberget iron ore mine. The barrier (9m x 2m x 1.5m) appears as an open basin with three inner dividing walls, and is filled with a reactive mixture consisting of crushed rock, sawdust, and sewage sludge. A small fraction of the water discharging from the Malmberget clarification pond was fed by pump to the barrier at a rate of ca. 5 m3 day-1.ResultsIn the pilot-scale barrier system, analytical results from 2010 indicated that nitrate (NO3-) removal generally lay in the range between 11 and 77% of influent nitrate concentrations. In order to achieve a higher removal rate, the barrier system needed to be supplemented with an additional carbon and energy source for denitrifying bacteria. In 2011, a sodium acetate solution as an external electron donor was continuously added to the barrier system along with the influent water. Analytical results from 2011 indicate that the barrier system in Malmberget removes >95% of the incoming nitrate during summer months (average daily temperature 14oC for 2011) with the addition of acetate. The barrier did exhibit decreases in performance toward the end of the study period in 2011, but this is likely the result of a lower hydraulic residence time in the barrier at this time.Nitrite (NO2-) concentrations in effluent waters were initially in excess of influent values, indicating the production of nitrite in the barrier. However, both nitrite and ammonium (NH4+) concentrations decreased to below detection limits after the addition of acetate (CH3COO-), suggestion the occurrence of anaerobic ammonium oxidation (anommox) in the barrier substrate. During this period, alkalinity values peaked at 500 mg HCO3- L-1 in effluent waters, indicative of organic carbon (acetate) oxidation through denitrification:5CH3COO- + 8NO3- + 3H+ → 4N2(g) + 10HCO3- + 4H2OStable isotope analyses of δ15N and δ18O in nitrate demonstrate an enrichment in 15N and 18O along the flowpath, supporting the conclusion that denitrification is responsible for nitrate removal.
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| 19. |
- Herbert, Roger, 1966-
(författare)
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Reactive barrier system for nitrate removal from mine effluents in northern Sweden: Laboratory experiments
- 2010
-
Ingår i: Geophysical Research Abstracts, Vol. 12, EGU2010-4177. ; , s. 4177-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Laboratory column experiments have been conducted to determine nitrate removal rates from mine effluents bydenitrification, with the purpose of providing initial data for the construction of a pilot scale reactive barrier systemat the Malmberget iron mine, Sweden. Experiments were conducted at several different flow rates at 5C, 10C androom temperature; annual mean temperatures at the Malmberget site lie close to 0C. Columns were filled with anorganic substrate consisting of sawdust mixed with sewage sludge, the source of denitrifying bacteria, supportedby oven-dried clay pellets. Apparent denitrification rates, calculated from inflow and outflow nitrate concentrationsand column hydraulic residence time, ranged from 5 to 13 mg N/L/d, with the lowest rates corresponding to the 5C experiments. These rates are, however, limited to a certain degree by the low flow rate and the supply of electronsacceptors (i.e. nitrate) to denitrifying bacteria.Results from the column experiment have been used to construct a barrier system in Malmberget, Sweden.Trial runs with the pilot-scale barrier will be conducted during 2010, with the purpose of determining the performanceof the barrier as mean air temperatures increase from below to above 0C and saturated flow commences inthe barrier. The barrier system is constructed as a rectangular container with steel sheet walls (9m length in flowdirection, 1.5m deep), and the flow rate will be adjusted to a hydraulic residence time of 1 day. The pilot-scalebarrier system currently lies above ground, but a permanent barrier system would be installed
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| 20. |
- Herbert, Roger, 1966-, et al.
(författare)
-
Regnvatteninsamling från hustak på södra Gotland
- 2009
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Ingår i: Vatten : tidskrift för vattenvård. - 0042-2886. ; 65:4, s. 225-230
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- The availability of drinking water from water wells on southern Gotland is highly limited on account of the fractured limestone bedrock of the region, and one possibility for supplying water in this region is to collect rainwater from roofs. For several years, rainwater was collected from a roof on southern Gotland in order to supply a basic household with water for drinking, dishwashing, bathing, etc. After collection, the rainwater percolated through a sand filter before it was used by the household. The aim with this study was to investigate if the sand filter had been effective against microorganisms in the collected water, and if the water quality, in terms of microbiological criteria, had been improved by filtration. The analytical results show that the rainwater that was collected from the roof contained between 6.4 × 105 and 1.5 × 107 living microoganisms per milliliter water and contained E. coli, which suggests that the water had been in contact with feces, most likely bird droppings on the roof. The results from the microbiological analyses indicated that rainwater treatment with a finegrained sand filter delivered water that was suitable as drinking water, or suitable with limitations according to Swedish drinking water criteria. The results suggest that a better filter function can be attained by increasing the sand thickness and thus increasing water residence time in the filter.
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| 21. |
- Herbert, Roger, 1966-, et al.
(författare)
-
Using ash in a sustainable society, Swedish R&D programme 2002 - 2008
- 2009
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Ingår i: <em>Proceedings Sardinia 2009, Twelfth International Waste Management and Landfill Symposium</em>.
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Konferensbidrag (refereegranskat)abstract
- In Sweden, producers of combustion residues have since 2002 implemented acollaborative applied R&D programme aimed at the utilisation of combustion residues (ash). Thefuels are biomass, wastes, peat – any fuel but coal. In this contribution the main lines of theprogramme are described: ash a geotechnical material e.g. in roads, landfill construction andclosure and recycling nutrients in wood ash. Technical as well as environmental questions havebeen addressed, with a slight emphasis on environment as non-technical issues are important.Selected results from some of the ca 100 projects carried out since the inception of the AshProgramme are presented.
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| 22. |
- Kumar, Manish, et al.
(författare)
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Hydrogeochemical zonation for groundwater management in the area with diversified geological and land-use setup
- 2013
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Ingår i: Chemie der Erde. - : Elsevier BV. - 0009-2819 .- 1611-5864. ; 73:3, s. 267-274
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Tidskriftsartikel (refereegranskat)abstract
- Despite its limited aerial extent, the National Capital Territory (NCT) Delhi, India, has diversified geological and topographical setup. A geochemical assessment of prevailing conditions of aquifer underlying the NCT was attempted and further classified into different hydrogeochemical zones on the basis of statistical and analyses and its correlation with land use, geological and climatic setting. Mineral phase study and isotopic analyses were used for the verification of performed clustering. Saturation indices (SI) calculated using the geochemical modelling code PHREEQC were used to distinguish the characteristics of four zones, as saturation states of the water does not change abruptly. Four different hydrogeochemical zones were statistically identified in the area: (1) intermediate (land-use-change-impacted) recharge zone, (2) discharge (agriculture-impacted) zone, (3) recharge (ridge) zone, and (4) recharge floodplain (untreated-discharge-impacted) zone. The distinctiveness of hydro-geochemical zones was further verified using stable isotopic (H-2 and O-18) signature of these waters. GIS-based flow regime in association with long-term geochemical evidences implied that these zones are being affected by different problems; thus, it necessitates separate environmental measures for their management and conservation. The study suggested that in a diversified urban setup where the complex interactions between anthropogenic activities and normal geochemical processes are functioning, hydrogeochmical zoning based on the integration of various techniques could be the first step towards sketching out the groundwater management plan.
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| 23. |
- Kumar, Manish, et al.
(författare)
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Understanding the Seasonal Dynamics of the Groundwater Hydrogeochemistry in National Capital Territory (NCT) of India Through Geochemical Modelling
- 2016
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Ingår i: Aquatic geochemistry. - : Springer Science and Business Media LLC. - 1380-6165 .- 1573-1421. ; 22:3, s. 211-224
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Tidskriftsartikel (refereegranskat)abstract
- A geochemical assessment of seasonal dynamics in the groundwater chemistry of the National Capital Territory (NCT), Delhi, was attempted through geochemical modelling, mineral precipitation sequences with rainfall and water evaporation cycle. Saturation indices calculated using PHREEQC indicated that the degree of water-rock equilibrium changes significantly from pre-monsoon to post-monsoon. The schematic model of SI change with water table fluctuation showed that during monsoon, as rainwater percolates through the soil, partial pressure of CO2 becomes higher than that of the atmospheric value and led to the formation of more carbonic acid that react with the carbonate minerals to produce , Mg2+ and Ca2+. The thermodynamic stability relationships of water chemistry in the Na, K, Ca and Mg silicate systems showed that for the samples with higher EC equilibrium between clay and primary minerals is not likely to be the main processes controlling variation in the groundwater chemistry. Chloro-alkaline indices (CAI) are positive when the groundwater level is high and become negative with the lowering of water level, i.e. when water level is high, reverse ion exchange is dominant. In case of pre-monsoon season, lower and negative value of CAI-1 and CAI-2 indicates dominance of ion exchange process and increases dissolved solid concentration in groundwater. The conceptual geochemical model depicted that water table fluctuation resulting from heavy pumping/withdrawal and recharge in association with the variation in DO, and Fe regulates the water-mineral equilibrium. The conceptual geochemical model explained the hydrogeochemical processes and their variations with water table fluctuation and, thus, highlighted the descriptive capabilities of PHREEQC. The study suggested that in the subsurface environment, complex interactions are simultaneously functioning, and hence, significant seasonal variations are likely to be very influential due to monsoonal recharge and subsequent changes in the saturation states of the water.
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| 24. |
- Mahanta, C., et al.
(författare)
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Hydrogeochemical controls on mobilization of arsenic in groundwater of a part of Brahmaputra river floodplain, India
- 2015
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818.
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Arsenic enriched groundwater regime within low-industrialized Brahmaputra floodplains in Assam, NE India. Study focus: We examined the origin, distribution and processes of As release by investigating the salient groundwater chemistry and subsurface sedimentological characteristics. Besides collection of groundwater samples from domestic and public water supply wells, sediment samples from boreholes were investigated for textural and colour linkages. New hydrological insights for the region: Arsenic concentrations above the WHO guideline value of 10. μg/L were present in 33 wells and above the previous Indian national drinking standard of 50. μg/L were present in 15 wells. The green-olive colour sediments were more likely to yield As-enriched groundwater. The supersaturation of groundwater with respect to Fe(II) minerals, such as siderite and vivianite, explained the poor correlation between dissolved As and Fe. The result reinforced the phenomenon of reductive dissolution of Fe(III) oxyhydroxides releasing As to groundwater. This study throws light on the processes and mechanisms involved with As release in groundwater. The homogenous floodplain terrain makes the hydrological As imprint unambiguous and the hydrogeological signatures untarnished. Considering the absence of anthropogenic sources in the study area, the conclusions on the nature and causes for As release to groundwater looked dependable although the final contamination at specific subsurface sites would be influenced by advection-dispersion of groundwater flow accompanied by retardation, ion exchange, surface complexation and possible biodegradation.
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| 25. |
- Mähler, Johan, et al.
(författare)
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Hydration of arsenic oxyacid species
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42, s. 1364-1377
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Tidskriftsartikel (refereegranskat)abstract
- The bond distances in hydrated arsenic oxyacid species in aqueous solution have been studied by EXAFS spectroscopy and large angle X-ray scattering, LAXS. These results have been compared to structures in the solid state, as found in an extensive survey of available crystal structures. Protonated oxygen atoms can be distinguished with a longer As-O distance for both arsenic(V) and arsenic(III) species in the crystalline state. However, the average As-O distance for the HnAsO4(3-n)- species (0≤n≤3) remains the same. These average values are slightly shorter, ca. 0.02 Å, than in aqueous solution due to the hydration as determined by EXAFS and LAXS. The K absorption edges for arsenic(V) and arsenic(III) species are separated by 4.0 eV, and the shape of the absorption edges differs as well. Small but significant differences in the absorption edge features are seen between the neutral acids and the charged oxyacid species. The most important arsenic species from an environmental point of view is arsenous acid, As(OH)3. In addition to arsenous acid, we have used orthotelluric acid, Te(OH)6, for comparison with arsenous acid and for detailed studies of the hydration of covalently bound hydroxo groups. Arsenous acid cannot be studied with the same accuracy as orthotelluric acid, due to a relatively low solubility of As2O3(s) in neutral to acidic aqueous solution. The results from the DDIR studies support the assignment of As(OH)3 as a weak structure maker analogous to Te(OH)6, both being neutral weak oxyacids.
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| 26. |
- Nordström, Albin, et al.
(författare)
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Denitrification in a low-temperature bioreactorsystem at two different hydraulic residence times : laboratory column studies
- 2017
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 38:11, s. 1362-1375
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Tidskriftsartikel (refereegranskat)abstract
- Nitrate removal rates in a mixture of pine woodchips and sewage sludge were determined in laboratory column studies at 5°C, 12°C, and 22°C, and at two different hydraulic residence times (HRTs; 58.2–64.0 hours and 18.7–20.6 hours). Baffles installed in the flow path were tested as a measure to reduce preferential flow behavior, and to increase the nitrate removal in the columns. The nitrate removal in the columns was simulated at 5°C and 12°C using a combined Arrhenius-Monod equation controlling the removal rate, and a first-order exchange model for incorporation of stagnant zones. Denitrification in the mixture of pine woodchips and sewage sludge reduced nitrate concentrations of 30 mg N L−1 at 5°C to below detection limits at a HRT of 58.2–64.0 hours. At a HRT of 18.7–20.6 hours, nitrate removal was incomplete. The Arrhenius frequency factor and activation energy retrieved from the low HRT data supported abiochemically controlled reaction rate; the same parameters, however, could not be used to simulate the nitrate removal at high HRT. The results show an inversely proportional relationship between the advection velocity and the nitrate removal rate, suggesting that bioreactor performance could be enhanced by promoting low advection velocities.
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| 27. |
- Nordström, Albin, et al.
(författare)
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Determination of major biogeochemical processes in a denitrifying woodchip bioreactor for treating mine drainage
- 2018
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 110, s. 54-66
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Tidskriftsartikel (refereegranskat)abstract
- At the Kiruna iron ore mine in northern Sweden, mine drainage and process water contain elevated concentrationsof nitrate (NO3−) from the use of ammonium nitrate fuel oil explosives. In order to investigate thetreatment capacity of a denitrifying woodchip bioreactor technique for the removal of NO3− through denitrification,a bioreactor was installed at the mine site in 2015 and operated for two consecutive years. Neutral-pHmine drainage and process water containing 22 mg NO3−-N and 1132 mg SO42− (average) was passed throughthe bioreactor which was filled with a reactive mixture of pine woodchips and sewage sludge, at treatmenttemperatures ranging between 0.8 and 17 °C. At bioreactor temperatures above ∼5 °C, NO3− removal proceededto below detection limits (0.06 mg N L−1) without substantial production of nitrite (NO2−), ammonium(NH4+), nitrous oxide (N2O), or methane (CH4). The relative production of NH4+ and N2O to the NO3− reducedincreased as bioreactor temperatures decreased below ∼5 °C. Based on the resultant changes in alkalinity andpH from the production of bicarbonate (HCO3−) and carbonic acid (H2CO3), a stoichiometric mass balancemodel indicated that denitrification, nitrate reduction to ammonium (DNRA), sulfate reduction, and fermentationwere the major biogeochemical processes controlling pH, alkalinity and nitrogen, sulfur and carbonconcentrations in the system. It is suggested that fermentation changed from being mainly butyrate producing toacetate producing with time, triggering a decline in biogeochemical process diversity and leaving denitrificationas the sole major electron accepting process.
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| 28. |
- Nordström, Albin, et al.
(författare)
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Identification of the temporal control on nitrate removal rate variability in a denitrifying woodchip bioreactor
- 2019
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 127, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- Nitrate (NO3−) removal rates in a denitrifying woodchip bioreactor (DWB) removing NO3− from mine water in a subarctic climate was modeled with the purpose of determining the processes controlling variability in NO3− removal rates over time. The Eyring equation was used to define the temperature dependency, while a rate law was used to describe the NO3− concentration dependency of the NO3− removal rates. The results show that the temperature and NO3− concentration dependency of the NO3− removal rates changes over time in the DWB due to the preferential selection of conceptualized NO3− - reducing bacteria favoring low temperatures, with the mean temperature optimum of the NO3− reducing consortium decreasing from 24.2 °C to 16.0 °C following the first year of DWB operations. It is suggested that the selection of the low temperature NO3− reducers in the DWB represented an increased dependence on cross-feeding between a fermentative community, producing the reactive organic carbon substrate, and a denitrifying community, consuming the organic carbon substrate, with the temporal variability in NO3− removal rates being controlled by the stabilization of the microbial community structure. It is also suggested that the life expectancy of DWBs is more related to the stability of the cross-feeding between the fermenting microbial community and the denitrifying microbial community, than to the total carbon content.
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| 29. |
- Nordström, Albin, et al.
(författare)
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Microbial controls on net production of nitrous oxide in a denitrifying woodchip bioreactor
- 2021
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Ingår i: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 50:1, s. 228-240
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Tidskriftsartikel (refereegranskat)abstract
- Denitrifying woodchip bioreactors (DWBs) are potential low‐cost technologies for the removal of nitrate (NO3−) in water through denitrification. However, if environmental conditions do not support microbial communities performing complete denitrification, other N transformation processes will occur resulting in the export of nitrite (NO2−), nitrous oxide (N2O), or ammonium (NH4+). In order to identify the factors controlling the relative accumulation of NO2−, N2O, and/or NH4+ in DWBs, porewater samples were collected over two operational years from a DWB designed for removing NO3− from mine water. Woodchip samples were collected at the end of the operational period. Changes in the abundances of functional genes involved in denitrification, N2O reduction, and dissimilatory nitrate reduction to ammonium were correlated with pore water chemistry and temperature. Temporal changes in the abundance of the denitrification gene nirS were significantly correlated with increases in porewater N2O concentrations, and indicated the preferential selection of incomplete denitrifying pathways ending with N2O. Temperature and the TOC/NO3− ratio were strongly correlated with NH4+ concentrations and inversely correlated with the ratio between denitrification genes and the genes indicative of ammonification (∑nir/nrfA), suggesting an environmental control on NO3− transformations. Overall, our results for a DWB operated at hydraulic residence times of 1.0 ‐ 2.6 days demonstrate the temporal development in the microbial community and indicate an increased potential for N2O emissions with time from the DWB.
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| 30. |
- Parvage, Mohammed Masud, et al.
(författare)
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Sequential removal of nitrate and sulfate in woodchip and hematite : coated biochar bioreactor
- 2023
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Ingår i: Environmental Science. - : Royal Society of Chemistry. - 2053-1400 .- 2053-1419. ; 9:2, s. 489-499
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory column experiments have been used to study the sequential removal of nitrate (NO3−) and sulfate (SO42−) from mine water, where NO3− was removed through denitrification and SO42− was removed through SO42− reduction and the subsequent precipitation of hydrogen sulfide (H2S) in a hematite-coated biochar (HCB) bioreactor. Denitrification and SO42− reduction were investigated in columns filled with pine woodchips and pine woodchips + biochar, both with and without the addition of lactate. Experimental results indicated that a >90% NO3− removal from 50 mg L−1 NO3−-N was achieved at a hydraulic residence time of 5 days without lactate addition, but that SO42− reduction was minimal after an initial startup period. Lactate was added to stimulate SO42− reduction, producing H2S with >90% SO42− removal from an initial concentration of 361 mg L−1 SO42−-S. Sulfate concentrations were reduced to a greater extent in the woodchip + biochar column, and NH4+ production was enhanced in both columns after lactate addition. After treatment in the HCB columns, H2S and NH4+ were removed to >95%. X-ray photoelectron spectroscopy (XPS) indicated that S2−, S22−, S0 and NH4+ were accumulating in the HCB columns and surface-bound iron was converted from Fe(III) to Fe(II). The XPS results suggested that the reductive dissolution of hematite preceded the precipitation of H2S as FeS, pyrite and elemental sulfur on the HCB surfaces.
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| 31. |
- Romero-Picó, Amparo, et al.
(författare)
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Hypothalamic κ-Opioid Receptor Modulates the Orexigenic Effect of Ghrelin.
- 2013
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Ingår i: Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology. - : Springer Science and Business Media LLC. - 1740-634X. ; 38:7, s. 1296-307
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Tidskriftsartikel (refereegranskat)abstract
- The opioid system is well recognized as an important regulator of appetite and energy balance. We now hypothesized that the hypothalamic opioid system might modulate the orexigenic effect of ghrelin. Using pharmacological and gene silencing approaches, we demonstrate that ghrelin utilizes a hypothalamic κ-opioid receptor (KOR) pathway to increase food intake in rats. Pharmacological blockade of KOR decreases the acute orexigenic effect of ghrelin. Inhibition of KOR expression in the hypothalamic arcuate nucleus is sufficient to blunt ghrelin-induced food intake. By contrast, the specific inhibition of KOR expression in the ventral tegmental area does not affect central ghrelin-induced feeding. This new pathway is independent of ghrelin-induced AMP-activated protein kinase activation, but modulates the levels of the transcription factors and orexigenic neuropeptides triggered by ghrelin to finally stimulate feeding. Our novel data implicate hypothalamic KOR signaling in the orexigenic action of ghrelin.
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| 32. |
- Rullander, Gabriella, et al.
(författare)
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How effective is the retention of microplastics in horizontal flow sand filters treating stormwater?
- 2023
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Ingår i: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 344
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Tidskriftsartikel (refereegranskat)abstract
- Microplastics accumulate in stormwater and can ultimately enter freshwater recipients, and pose a serious risk to aquatic life. This study investigated the effectiveness of lab-scale horizontal flow sand filters of differing lengths (25, 50 and 100 cm) in retaining four types of thermoplastic microplastics commonly occurring in stormwater runoff (polyamide, polyethylene, polypropylene, and polyethylene terephthalate). Despite the differences in particle shape, size and density, the study revealed that more than 98% of the spiked microplastics were retained in all filters, with a slightly increased removal with increased filter length. At a flow rate of 1 mL/min and after one week of operation, 62–84% of the added microplastics agglomerated in the first 2 cm of the filters. The agglomerated microplastics included 96% of high-density fibers. Larger-sized particles were retained in the sand media, while microplastics smaller than 50 μm were more often detected in the effluent. Microplastics were quantified and identified using imaging based micro Fourier Transform Infrared Spectroscopy. The efficient retention of microplastics in low-flow horizontal sand filters, demonstrated by the results, highlights their potential importance for stormwater management. This retention is facilitated by various factors, including microplastic agglomeration, particle sedimentation of heavy fibers and favorable particle-to-media size ratios.
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| 33. |
- Rullander, Gabriella, 1992-
(författare)
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Microplastic Mitigation in Urban Stormwater : Assessing Horizontal-Flow Filters of Bark, Biochar and Sand as Remediation Strategies
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Urban stormwater has been suggested as a significant vector through which microplastics (MPs) reach aquatic environments. Currently, only a small fraction of stormwater in Sweden undergoes any form of treatment. Therefore, a considerable portion of the runoff reaches and pollutes recipients with microplastics, which have demonstrated adverse effects on aquatic life. In recent years, there has been a growing interest in the decentralized treatment of stormwater, shifting the treatment of stormwater upstream and close to the runoff source through filtration-based techniques. Filtration-units can be incorporated into urban environments prone to high runoff coefficients– such as roads, parking lots, and other paved surfaces. At present, there is an opportunity to also shape decentralized treatments towards sustainable and environmentally positive approaches, by utilizing forestry by-products as filter media. Due to the promising characteristics of large specific surface areas and high porosity, the carbon-rich bark and biochar materials have been suggested as potential filter media. This thesis aims to evaluate MP pollution in urban environments, with the city of Uppsala as a case study and parking lots as sampling sites. Then, the thesis assesses the current capabilities of removing MPs in traditional sand media, followed by an evaluation of the potential of bark and biochar, as filter media for removing MPs in stormwater.Road dust and spiderwebs were sampled from parking lots in Uppsala City, to assess the ground-based and airborne MP pollution. A wide range of MP types were identified, such as polyurethane (PU), polypropylene (PP), polyester (PET), Acrylic (PMMA), polyethylene (PE), polystyrene (PS), polyamide (PA), and cellulose acetate. The PU was especially dominant in the indoor parking and PET fibers were commonly found to be airborne. Overall, the road dust and spiderwebs contained 5.78–4951 and 2500–505000 MPs/g, respectively. Horizontal-flow filters of 25, 50, and 100 cm were established to evaluate the removal efficacy of MPs using sand, bark and biochar as filtration media. The filters were introduced to a heterogeneous mix of MPs, including PET and PP fibers, spherical PA, PE and PS, and fragmented PP, representative of the polymer types identified in Uppsala city. The analysis revealed a substantial removal, >97%, of individual MPs for all filter media, achieving an overall MP retention exceeding 99%. The high removal was achieved even with filter lengths of 25 cm, with a slight increased removal with increased filter length. This thesis has proved that MPs are present in a multitude of surfaces in the urban environment, including air, and showed that sand, bark, and biochar should be considered as potential media for filtration-based remedies to improve MP mitigation in urban stormwater.
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| 34. |
- Wang, Jingjing, et al.
(författare)
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Multirate mass transfer simulation of denitrification in a woodchip bioreactor
- 2023
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Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 624
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Tidskriftsartikel (refereegranskat)abstract
- Denitrifying woodchip bioreactors (DWBs) have proven to be an efficient nature-based solution for nitrate removal. Modeling DWBs is required for improving their design and operation, but is hindered by the complexity of the modeled system where numerous chemical species and model parameters are needed. Reactions inside the woodchips are different from those at the edges, causing chemical localization (i.e., apparent simultaneous occurrence of incompatible reactions). We used the Multi Rate Mass Transfer (MRMT) approach to overcome these problems when simulating reactive transport processes in a DWB located at Kiruna, Sweden. Besides denitrification, other nitrogen-cycling processes (e.g., nitrification, dissimilatory nitrate reduction to ammonium, anammox) and alternative electron donors (e.g. oxygen, sulfate) were also considered. Biomass concentration is incorporated into the biochemical reaction rates, including growth and decay, to characterize microbial catalysis. We found that the MRMT model: 1) can account for the heterogeneity of the porous woodchips; 2) was capable of reproducing the nitrogen species evolution in the DWB with kinetic parameters from the literature; and 3) allows reproducing localized biochemical reactions (e.g., aerobic reactions on the woodchip edges, near the DWB entrance and anaerobic reactions inside); and 4) reproduces the full denitrification reactions sequence, but with the different reactions occurring in different portions of the woodchip (e.g., nitrate to nitrite near the edges and nitrite to nitrous oxide further inside). The latter observation suggests that increasing woodchip size may reduce the outflow of these undesired species.
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