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Paudyn Et Al Cold Regions 53(1) 102-114

Remediation of hydrocarbon contaminated soils
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  Remediation of hydrocarbon contaminated soils in theCanadian Arctic by landfarming Krysta Paudyn  a  , Allison Rutter   b, ⁎ , R. Kerry Rowe  a  , John S. Poland  b a  GeoEngineering Centre at Queen's-RMC, Department of Civil Engineering, Queen's University, Kingston, Ontario, Canada K7L 3N6   b School of Environmental Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6  Received 8 December 2006; accepted 24 July 2007 Abstract One of the preferred methods for the remediation of fuel contaminated soil today is landfarming. This is particularly true for remote sites because the method requires minimal equipment and is therefore by far the lowest cost option. The term landfarminggenerally refers to the process whereby hydrocarbon contaminated soils are spread out in a layer about half a meter thick, nutrientsare added, and periodically the soils may be mixed. During landfarming, hydrocarbons can be lost through volatilization or  bioremediation and thus landfarming refers to the combination of the two processes.In the challenging Arctic climate, the performance of landfarming studies has been variable and the relative contribution of thetwo processes has not been studied. This paper describes the successful remediation of diesel-contaminated soils at the former military base at Resolution Island, Nunavut. The site is 130 km from the nearest community and this isolation together with veryinclement weather and average summer temperatures of 3 °C presents significant challenges for remediation. Trial landfarm plotswere established in 2003 to compare four sets of conditions; daily aeration, aeration every 4 days, addition of fertilizer with aerationevery 4 days and a control plot. The field trial has clearly demonstrated enhanced bioremediation when fertilizer was added andalso significant hydrocarbon losses due to aeration by rototilling. The rate of bioremediation was similar to the rate of volatilizationin the field trial. In addition to the landfarms established on site, extensive complementary laboratory experiments have beencarried out. Bioremediation was demonstrated at 5 °C in the laboratory reactors and isoprenoid markers indicated increased bioremediation with increased temperatures. In the reactor experiments, rate constants for volatilization and bioremediationincreased with temperature.© 2007 Elsevier B.V. All rights reserved.  Keywords:  Landfarming; Hydrocarbon; Remediation; Arctic; Bioremediation; Volatilization 1. Introduction The term landfarming refers to the process wherehydrocarbon contaminated soils are spread out in a layer of 0.3 – 1.0 m thick, nutrients are added and the soils aremixed periodically. During the process of landfarming,the total petroleum hydrocarbons, (TPH), may be lost through volatilization or biodegradation. Landfarmingreferstothecombinationofthetwoprocesses.Treatment regimes for landfarms vary with climate, location, tem- perature and soil type. Enhanced bioremediation of con-taminatedsoiltypicallyinvolvestheadditionofnutrientsand water, and periodic tilling to mix and aerate the soil(McCarthy et al., 2004). Additional amendments ( e.g. ,  Available online at Cold Regions Science and Technology 53 (2008) 102 – ⁎ Corresponding author. Tel.: +1 613 533 2642; fax: +1 613 5332897.  E-mail address: (A. Rutter).0165-232X/$ - see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.coldregions.2007.07.006   bulkingagents toincreaseaeration(Straubeet al.,2003),co-substrates to stimulate microbial metabolism(Mphekgo and Cloete, 2004) or bacterial inoculations(Straube et al., 2003) are sometimes added to speed theremediation process. Landfarming has proven consis-tently successful in warmer southern climates, (Mc-Carthy et al., 2004). For instance, in the 12-monthoperational period of an Australian landfarm TPH levelswere remediated from 4644 ppm to less than 100 ppm(Line et al., 1996).In colder Antarctic and Arctic climates, trials involv-ing landfarming or bioremediation have been conductedwith mixed results (Delille, 2000; Seklemova et al.,2001; Aisablie et al., 2004; McCarthy et al., 2004).Research has shown the presence of organisms adaptedto cold conditions at sites where hydrocarbon contam-ination is present in these cold climate soils (Mohn andStewart, 2000). Hydrocarbon degrading extremophilesare thus ideal candidates for the biological treatment of  polluted extreme habitats such as the Canadian Arctic,(Rike et al., 2003; Mohn and Stewart, 2000). A widevariety of microorganisms have been detected in theactive layer in Arctic soils in northern Canada andAlaska (Deming, 2002). These cold habitats possesssufficient indigenous microorganisms for   in situ  biore-mediation, (Whyte et al., 1999; Ferguson et al., 2003).They adapt rapidly to hydrocarbon contamination in thesoil, as demonstrated by significantly increased numbersof oil degraders shortly after a pollution event (Atlas,1995). An increased number of the hydrocarbon degrad-ing bacteria in response to oil spills has been reported by both Whyte et al. (1999) and Rike et al. (2001) illustrat-ing that growth and proliferation of hydrocarbondegrading bacteria have taken place under site-specificconditions. Over the past several years, a number of studies in both Arctic and Antarctic regions have shownthat microorganisms naturally occurring in harsh envi-ronments are capable of degrading petroleum hydro-carbons (McCarthy et al., 2004; Mphekgo and Cloete,2004; Ferguson et al., 2003; Kerry, 1993).Landfarming has been used in cooler locations suchas alpine environments (Margesin and Schinner, 2001)and Alaska (Reynolds et al., 1998) where summer tem- peratures are much higher than those of the central andeastern Canadian Arctic. Rates of biodegradation andvolatilization have been shown to be slower at lowtemperatures (Snape et al., 2005), however the relativerates and therefore their contributions to landfarming inArctic climates are still relatively unknown. The per-centage of remediation attributable to aeration in variousfield studies varies (Reimer et al., 2003; Chatham, 2003;Ausma et al., 2002). In order to study the bioremediationof hydrocarbons ratios of   n -alkanes to pristine and phytane can be used for good effect (Atlas, 1995;Ferguson et al., 2003). There are many landfarms estab-lished in cold climates, however, there is a paucity of well documented field trials. This work describes a fieldstudy specifically designed to assess the relative con-tributions of bioremediation and volatilization usingaerated and fertilized regimes. The trial landfarm ex- periment was established at Resolution Island in thesummer of 2003 in order to determine the viability of thelandfarming technology for remediation of TPH con-taminated soils at the site. Resolution Island is located at the southeastern tip of Baffin Island approximately310 km southeast of Iqaluit, Nunavut. The site isaccessible for fieldwork for approximately 3 months ayear and during that time often suffers from inclement weather; including heavy fog and rainstorms. The aver-age temperature during the summer months is 3 °C.Resolution Island was the site of one of the military bases that formed the Polevault Line. The site has beenthe site of a major cleanup operation as it was highlycontaminated with polychlorinated biphenyls, (PCBs),metals and petroleum hydrocarbons (Poland et al.,2001).  Ex situ  studies of landfarming have focused on nut-rients (Ferguson et al., 2003; Braddock et al., 1997), bioaugmentation (Mohn and Stewart, 2000; Van Veenet al., 1997), cold adapted organisms (Kunihiro et al.,2005; Mikan et al., 2002), oxygen depletion (Zytner et al., 2001) and water content (Ferguson et al., 2003). Many studies attempt to assess the viability of biore-mediation using radiolabelled linear hydrocarbons(Mohn and Stewart, 2000; Braddock et al., 1997) but the extrapolation to field studies is often difficult (Zytner et al., 2001). In this study, laboratory reactorswere designed to model the trial landfarm established at Resolution Island and to investigate the effect of temperature on volatilization and bioremediation.There are many hydrocarbon contaminated sites whichrequire remediation in the Arctic and there is currentlyno criterion available to determine if landfarming will beviable at a given site. This study outlines theexperimental design and initial laboratory experimentsthat are intended to establish these criteria and field protocols. 2. Methodology 2.1. Trial landfarm Three truckloads (30 m 3 ) of TPH contaminated soilwere excavated from two diesel-contaminated areas on 103  K. Paudyn et al. / Cold Regions Science and Technology 53 (2008) 102  –  114  site. The soil was displaced to an area that had been previously leveled to a slope less than 5%. Heavyequipment was used to homogenize the soil cache andevenly distribute the material to each of the four plots.Each plot measured 5 m by 5 m with a depth of 0.3 m. Maintenance and operation of the triallandfarm included subjecting each plot to a different regime (Fig. 1). One plot was established as thecontrol plot and had no action other than sampling.Aeration was achieved by rototilling. Two plots wererototilled only; one every day and the other everyfourth day. The final plot was rototilled every 4 daysand, in addition, fertilizer was added to this plot. Thusthe four plots were maintained as follows: control plot; daily aeration; aeration every 4 days; fertilizer added with aeration every 4 days. As a result of operational experiences during the first season, in thesecond season, the regime of aeration frequencyconsidered only fair days; fair days were defined asdays when it was not raining, snowing or excessivelyfoggy.The fertilizer was added on day 16. Nitrogen and phosphorus were added to the landfarm plots in the formof granular agricultural fertilizers. Urea, containing 46%nitrogen was the primary source for nitrogen while phos- phorus was added as diammonium phosphate, (DAP),which contained 20.1% phosphorus and 18.0% nitrogen by weight. Nutrient additions were based on applying aC:N:P ratio of 100:7.5:0.5. No additional fertilizer wasadded to any of the trial landfarm plots after the initialapplication on day 16.The soil at Resolution Island can be characterized asfollows. It is largely composed of sand and gravel par-ticles with only 10% of particles finer than 75  μ M. Thesoil has no plasticity, the soil pH is 5.8 and the organiccontent is 1.1%. 2.2. Laboratory reactor design The reactor design is presented in Fig. 2. The body of the individual reactors was constructed with polyvinylchloride (PVC) sewer pipe cut into 0.36 m lengths. Thelength of the tube was chosen to accommodate approxi-mately 1.2 kg of soil such that the soil level was belowthe mid-point air inlet of the reactor. The landfarmaeration process was simulated by inverting the reactor  Fig. 1. The trial landfarm at Resolution Island Nunavut. Maintenance regime as indicated in photograph.104  K. Paudyn et al. / Cold Regions Science and Technology 53 (2008) 102  –  114  tube. At the reactor base a cap was glued in place whileat the top of the reactor tube a removable cap was pressfitted and sealed with electrical tape. Air was passedthrough the reactors at mid-height through a 0.016-m brass fitting which was screwed into the tapped sewer  pipe and sealed with Teflon tape. For the air outtake, a0.016-m brass fitting, was 0.08 m higher than the inlet and at an angle of 120° to it. A ball valve was glued into position beside the outtake tube of each reactor to allowwater to be added to the system. This arrangement allowed the inversion of the tube without soil enteringthe air passages. A 2.5-m long, 0.102-m diameter highdensity polyethylene (HDPE) tube was used as an air  pressure containment vessel between the air source andthe individual reactors. This tube was affixed to thelaboratory compressed air line. Holes were drilled andtapped into the tubing to support 24 pressure regulator valves that were then each attached to a reactor allowingregulation of air flow through each reactor. The air entering the manifold from the line was controlled to thetemperature of the room by passing source air through10 m of coiled copper pressure tubing. In addition,source air was passed through a 0.15-m long charcoalfilter (0.03 m diameter), which ensured that hydrocar- bon contamination from the source line was eliminated.Volatilized hydrocarbon was captured at the air outlet of each reactor with a granulated activated coconut char-coal (GAC) trap. Each trap was 0.20 m long with aninternal diameter of 0.015 m and filled with approxi-mately 20 g of 12×40 mesh granulated activated coco-nut charcoal. 2.3. Reactor system The individual reactors were designed to reflect the physical conditions that contaminated soil was subject to in a field landfarm. Depth, tillage (inversion of theindividual reactors), temperature, windspeed, moisturecontent were each considered in the reactor design and protocol. By monitoring both volatilized and residualhydrocarbon, it was possible to attribute loss of TPH toeither bioremediation or aeration using a mass balanceapproach.Each reactor was filled with 1.2 kg of diesel-con-taminated soil from Resolution Island. Air was passedthrough each of the closed vessels and volatilized TPHfrom the soil was collected on charcoal tubes at thereactor air outlet. The charcoal filters were replaced andanalyzed for TPH periodically and the soil in eachreactor was also analyzed periodically. Moisture content was carefully monitored and maintained in the rangeof 10 – 15% by the periodic addition of water. Flowratethrougheachreactorwasmonitoreddailyandkeptat 1 L/min. Reactor systems, each comprising 24 reactors,were set up in three temperature controlled roomsmaintained at 5 °C, 8 °C and 18 °C.Two sets of reactor experiments are reported on here.Inthefirstexperimentalset,ateachtemperature,reactors Fig. 2. Design of the laboratory reactors used for the  ex situ  work.105  K. Paudyn et al. / Cold Regions Science and Technology 53 (2008) 102  –  114
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