Use of PAS 100 compost as an amendment for the bioremediation of hydrocarbons

Transcription

1 Brownfield Trailblazer 2006 final report Use of PAS 100 compost as an amendment for the bioremediation of hydrocarbons Across the UK there are thousands of brownfield sites with hydrocarbon contamination resulting from previous industrial use. Project code: OBF ISBN: [Add reference] Research date: Sept 2006 March 2008 Date: March 2009

2 WRAP helps individuals, businesses and local authorities to reduce waste and recycle more, making better use of resources and helping to tackle climate change. Document reference: WRAP organics trailblazer final report Written by: T.J.Aspray Environmental Reclamation Services (ERS) Ltd, Westerhill Road, Bishopbriggs, Glasgow, G64 2QH Front cover photography: WRAP library WRAP and (Consultants Name) believe the content of this report to be correct as at the date of writing. However, factors such as prices, levels of recycled content and regulatory requirements are subject to change and users of the report should check with their suppliers to confirm the current situation. In addition, care should be taken in using any of the cost information provided as it is based upon numerous project-specific assumptions (such as scale, location, tender context, etc.). The report does not claim to be exhaustive, nor does it claim to cover all relevant products and specifications available on the market. While steps have been taken to ensure accuracy, WRAP cannot accept responsibility or be held liable to any person for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. It is the responsibility of the potential user of a material or product to consult with the supplier or manufacturer and ascertain whether a particular product will satisfy their specific requirements. The listing or featuring of a particular product or company does not constitute an endorsement by WRAP and WRAP cannot guarantee the performance of individual products or materials. This material is copyrighted. It may be reproduced free of charge subject to the material being accurate and not used in a misleading context. The source of the material must be identified and the copyright status acknowledged. This material must not be used to endorse or used to suggest WRAP s endorsement of a commercial product or service. For more detail, please refer to WRAP s Terms & Conditions on its web site:

3 Executive summary Soil historically contaminated with total petroleum hydrocarbon (TPH) was treated using ex situ bioremediation as two separate biopiles (each approx 3000 m 3 ). One biopile was amended with horse manure (biopile H) and the other with <20 mm accredited green waste compost (biopile P) both at 10 % (v/v). The biopiles were covered with composting fleeces and treatment carried out over the winter 2007/08 (a period of 20 weeks). The technical performance of both amendments for ex situ bioremediation was made by measuring soil characteristics (including ph, moisture content, macronutrient concentration), microbial numbers and activity (plate counts and soil respirometry), and total petroleum hydrocarbon (TPH) concentration from samples taken from the biopiles during treatment. Although ph and moisture content did not differ significantly between the two biopiles, macronutrient (Total C, Total N, Total P, NH 4, PO 4 ) were significantly higher in biopile P. Biopile P had greatest microbial numbers and activity during the first 6 weeks of treatment, after which these parameters were comparable for the two biopiles. A significant decrease in TPH concentration was found in both biopiles by week 12; however, no difference was seen between the two biopiles. In terms of the financial implications of using either horse manure or green waste compost as an amendment, delivered horse manure was cheaper by just short of 1 tonne for this project. However, sourcing and arranging loading/delivery of horse manure took considerably more than for the same amount of material. Therefore, is a potentially cost effective amendment for larger (> 1000 m 3 contaminated soil) remediation projects. Use of PAS 100 compost as an amendment for the bioremediation of hydrocarbons 1

4 Contents 1.0 Introduction & Objectives Materials and Methods Biopile development Biopile monitoring Soil sampling and handling Physico-chemical analysis Enumeration of culturable bacteria Basal soil respiration Total petroleum hydrocarbon (TPH) analysis Results Temperature Soil gas ph...7 Moisture content Macronutrient status Heterotrophic plate counts Soil respiration TPH composition TPH degradation Financial considerations Conclusions Acknowledgements References Appendices

5 1.0 Introduction & Objectives Across the UK there are thousands of brownfield sites with hydrocarbon contamination resulting from previous industrial use. These sites present potential significant risk to human health and/or the environment. Traditionally, disposal to landfill has been the approach for dealing with contaminated material arising from such sites, however, legislative and financial drivers now make this a less desirable option. Ex situ bioremediation of hydrocarbon contaminated soil is a well established remediation technique. The approach involves excavating the contaminated soil, arranging it into a biopile or windrows, and aerating using a passive or active system. To enhance degradation of the contaminants, the soil is amended with either inorganic nutrients (biostimulation) or microbial cultures (bioaugmentation). There are many reports on the use of biostimulation and bioaugmentation for petroleum hydrocarbon contaminated soils (Margesin and Schinner, 2001; Evans et al., 2004; Bento et al., 2005). An alternative approach to the use of inorganic nutrients is to amend contaminated soil with agricultural or horticultural organic wastes such as poultry litter, spent mushroom compost, horse manure or green waste composts (Atagana, 2004; Rodríguez-Vázquez et al., 1999; Semple et al., 2001). When significant amounts of these organic residues are added, porosity, ph, and oxygen diffusion increase (Semple et al., 2001). The wastes are generally rich in nutrients such as phosphorus, nitrogen, and carbohydrates which are potentially important for the growth of organic pollutant degraders (Roldán-Martín et al., 2007) and, as slow-release nutrient sources the possibility of external ecosystem contamination from nutrient leaching (as in the case of inorganic nutrient (fertilizer) application) is minimal (Sarkar et al., 2005). Composts have enormous potential for bioremediation, as they are capable of sustaining diverse populations of microorganisms, all with the potential to degrade a variety of organic contaminants (Scelza et al., 2007). Composts have been successfully applied in bioremediation of soils contaminated with organic contaminants (Semple et al., 2001). Despite previous successful application of compost bioremediation, problems associated with the use of composts or manures to date include heterogeneity of material obtained from different sources, commercial issues relating to availability of volumes, potential health risk from human and animal pathogens, and generation of unpleasant odours. The use of an accredited compost material such as for bioremediation may enable better prediction of bioremediation timescales/treatment targets compared to heterogeneous composts and manures. The requirement for human and animal pathogen indicator testing of material will help to ensure a high level of health and safety in bioremediation projects. In addition, this material produces no unpleasant odours unlike several of the products commonly used in bioremediation helping to make activities less disturbing to local communities. Project objectives: 1. Compare the technical performance of accredited green waste compost with an alternative organic amendment 2. Compare financial implications of using accredited green waste compost to an alternative organic amendment 2.0 Materials and Methods 2.1 Biopile development Hydrocarbon contaminated soil from a site in Ayrshire, Scotland was excavated, grid-screened and placed as two separate biopiles (each containing ~ 3000m 3 of soil) on a treatment area. The treatment area consisted of a graded surface overlain with an impermeable liner (HDPE) which allowed water run off to collect in a lined sump for subsequent treatment and disposal. One biopile was amended with compost (biopile P) and the second with horse manure (biopile H). The horse manure was sourced locally from two different stables (22.7 and 16.3 miles from site, respectively) and consisted of fouled bedding, composed of a mixture of straw and sawdust material. The compost (20 mm grade) was sourced from WM Tracey Ltd (Middleton Composting Facility, Beith, Ayrshire). The typical chemical composition of this material can be found in appendix 1. The amendments were added at a ratio of 1:10 (v/v) (compost/manure:soil), mixed using an ALLU bucket and each biopile was then covered with a compost fleece to help maintain elevated temperatures and minimise the formation of contaminated leachate. In addition, the fleece was used to minimise soil erosion. 3

6 2.2 Biopile monitoring Temperature was monitored in each biopile using a thermocouple probe (9.5 (d) x 1400mm (l)) attached to a thermometer (Therma 2; Electronic Temperature Instruments Ltd, West Sussex). Carbon dioxide and oxygen (%) were measured in the two biopiles using an LMSxi Multigas analyser (GAS DATA Ltd, Coventry, UK) fitted to an in-house penetration probe. Readings were taken at time 0, 2, 4, 6, 12, 16 and 20 weeks from 30 different points at depths between m for both temperature and soil gas. 2.3 Soil sampling and handling Composite and spot soil samples were obtained in a grid pattern from both biopiles at depths ranging from 0.5 to 1.5 meters. Composite samples taken on time 0, 12 and 20 weeks and spot samples taken on 2, 4, 6 and 16 weeks. Composite samples consisted of 9 spot samples. Soil samples were incubated prior to analysis, which was carried out within 7 days of sampling. For basal respiration analysis, samples were incubated at 22 o C for h prior to analysis. For all other analysis parameters, samples were held at 4 o C 2.4 Physico-chemical analysis Soil ph was determined using 5 g of field moist soil in deionised water using a glass electrode. Analysis for soil content of NH 4, total N, total C, PO 4, total P and total K were performed by an independent analytical laboratory. Briefly, NH 4 and total N were analysed by titration, total C by loss on ignition and, PO 4, total P and total K by inductively coupled plasma - optical emission spectrometer (ICP-OES). 2.5 Enumeration of culturable bacteria Total numbers of culturable heterotrophic bacteria were determined as colony forming units per gram of soil (CFU g -1 ). Briefly, 1 g of soil (dry weight) was mixed with 9 ml phosphate buffered saline solution (8 gl -1 NaCl, 1.21 gl - 1 K 2 HPO 4 and 0.34 gl -1 KH 2 PO 4 ) and vortexed for 60 s. The suspensions were diluted in decimal steps using a solution of 0.85 % NaCl, plated in triplicate on nutrient agar (NA; Oxoid Ltd, Basingstoke, UK) and incubated for 48 h at 25 o C. 2.6 Basal soil respiration Soil microcosms were prepared using 50 g of soil (dry weight) into 250 ml Duran flasks. The samples were incubated at 30 C and soil respiration measured continuously for 24 h (± 1 h) using an ER10 Oxymax respirometer (Columbus Instruments, Ohio, USA) connected to a PC. The system s CO 2 analyser was calibrated prior to analysis and parameters for individual chambers were as per settings previously reported (Aspray et al., 2007) 2.7 Total petroleum hydrocarbon (TPH) analysis Total petroleum hydrocarbon (TPH) extraction and analysis of soil samples were carried out by two independent analytical laboratories using solvent extraction followed by gas chromatograph flame ionisation detection (GC- FID) analysis. TPH total (used to monitor degradation) was carried out at the Contaminated Land Assessment & Remediation Research Centre (CLARRC) using a solvent extraction previously described (Aspray et al., 2008) with the exception of a pre-sieving (< 8 mm) step. TPH fractionated (aliphatic and aromatic) analysis was carried out by an accredited analytical laboratory. 4

7 3.0 Results 3.1 Temperature Temperature was measured in the two biopiles at regular intervals over the treatment period. Temperature was highest in both biopiles at 2 weeks following amendment with horse manure or green waste compost. A gradual decrease in temperature was observed between week 2 and 12. Both biopiles increased in temperature by week 20. Biopile P was consistently warmer than biopile H, the difference being greatest at week 2 (2.8 C). Figure 1 Average temperature probe measurements in the two biopiles. No measurements were taken at time 0 due to a fault with the temperature probe. Standard error values smaller than the data points are not visible Temperature ( C) Time (weeks) 3.2 Soil gas Soil gas (CO 2 and O 2 ) were measured directly in the field using an in-house developed penetration probe. Carbon dioxide was analysed in order to provide a rapid indication of biological activity within the biopiles. Oxygen was analysed in order to monitor depletion of this gas, vital for aerobic biodegradation. Carbon dioxide concentration (%) increased in both biopiles during the first 4 weeks of treatment showing increased efflux of this gas during that period. In biopile P, CO 2 concentration had declined to a level similar to the initial by week 6, before peaking again at week 16. In biopile H, elevated CO 2 declined throughout the course of the experiment. For oxygen (%), there was high variability between sample timepoints. Despite this, there appears to be a slight trend towards increasing oxygen concentration (%) during the course of the experiment. 5

8 Figure 2. Average (n=30) carbon dioxide (a) and oxygen (b) concentration (%) in the two biopiles measured using a penetration probe. Standard error values smaller than the data points are not visible Carbon dioxide (%) a) PA S Time (weeks) Oxygen (%) b) Time (weeks) 6

9 3.3 ph Soil ph showed a dramatic increase in both biopiles during weeks 0-4. From weeks 4 to 20 ph remained relatively stable at 8.1 ± Figure 3. Average (n=7) ph in the two biopiles. Standard error values smaller than the data points are not visible ph value Time (weeks) 3.4 Moisture content Measured in soil samples taken from the biopiles, moisture content is an important parameter for aerobic biodegradation in soils. Too low or two high and aerobic microbial biodegradation will be impeded or sub-optimal. Both biopiles showed a gradual increase in moisture content over the course of the 20 week experiment. Initially, biopile H had higher moisture content but by week 20 both biopiles were comparable. Figure 4 Average (n= 7) moisture content in samples taken from the two biopiles. Standard error values smaller than the data points are not visible. Moisture content (%) Time (weeks) 7

10 3.5 Macronutrient status Biopile P had a higher level of all major macronutrients at the start of the experiment. Most significant was in the case of total nitrogen; this was more than twice that of biopile H. Available nitrogen (NH 4 ) was below the limits of detection for both biopiles. Table 1. Macronutrient concentrations in the two biopiles at time 0 and 6 months. Biopile Horse manure Time Macronutrients (weeks ) TOC a Total N a b NH 4 Total P b b PO 4 Total K b ± ± ± 1914 ± ± < ± ± 630 ± ± < 85 < ± ± ± 2000 ± ± < ± ± 590 ± ± < 85 < a % b mg/kg 3.6 Heterotrophic plate counts The numbers of culturable bacteria in the two biopiles was determined using heterotrophic plate counts. Counts were consistently higher in biopile P than H for the first 6 weeks of treatment (Figure 5). The difference was greatest at week two with approximately five times as many bacteria in biopile P to H (1.0 x 10 7 and 2.5 x 10 6 cfu/g soil dry weight, respectively) corresponding to the highest level of culturable bacteria in both biopiles. By week 12 counts were similar in both biopiles. The counts then proceeded to decrease to comparable lowest levels by week 20 (5.4 x 10 5 and 4.8 x 10 5 cfu/g soildry weight for biopiles P and H, respectively). Figure 5. Average (n = 7) heterotrophic plate counts in samples taken from the two biopiles. Standard error values smaller than the data points are not visible. 1.21E+07 Microbial counts (cfu/g soil dry weight) 1.01E E E E E E Time (weeks) 8

11 3.7 Soil respiration Soil respiration (measured as CO 2 production) was analysed in order to determine microbial activity in the biopiles over the treatment period. Biopile P was consistently more active than biopile H at all sampling points throughout the 20 week project (figure 6). In biopile P, there was an increase in activity at week 4; however, by week 6 the activity was back to that at the start of the experiment. Biopile H also showed an increase in CO 2 production at week 4, remaining virtually constant to week 20. Figure 6. Average (n= 7) soil respiration (as accumulative CO 2 ) over 24 h period in samples taken from the two biopiles. Standard error values smaller than the data points are not visible Acumulative CO 2 (µl) Time (weeks) 3.8 TPH composition Hydrocarbon contamination in soil was composed predominantly of heavy end (C21-40) aromatic fractions (Figure 7). Figure 7 Average (n = 7) concentrations of aliphatic and aromatic petroleum hydrocarbon fractions in samples taken from the two biopiles at time zero. TPH concentration (mg/kg) C6-C8 Aliphatic C8-C10 Aliphatic C10-C12 Aliphatic C12-C16 Aliphatic C16-C21 Aliphatic C21-C40 Aliphatic Total Aliphatic C5-C7 Aromatic C7-C8 Aromatic C8-C10 Aromatic C10-C12 Aromatic C12-C16 Aromatic C16-C21 Aromatic C21-C40 Aromatic Total Aromatic TPH fractions 9

12 3.9 TPH degradation Total petroleum hydrocarbon (TPH) concentrations during the course of the experiment are reported (Figure 8). A significant decrease in TPH concentration was observed in both biopiles by week 12. No significant difference in TPH concentration was observed between the two biopiles. Figure 8. Average (n = 7) of total petroleum hydrocarbon (TPH) in samples taken from the two biopiles during the course of the experiment TPH concentration (mg/kg) Time (weeks) 4.0 Financial considerations Although differences in microbial numbers/activity and physicochemical properties could be seen between the two amended biopiles, no difference in TPH biodegradation was observed during the project. Therefore, financial considerations of using the two amendments are made based on the assumption that both were effective. The cost of delivered <20 mm green waste compost was 7.06 per tonne (inc. VAT) compared to 6.10 tonne (inc VAT) for delivered horse manure. However, both these costs should be seen as specific to this project. In particular, the cost of delivered horse manure is highly dependant on loading capabilities which can affect haulage costs and options. Although it appears that horse manure was more cost effective on a delivered weight basis, the time involved in organizing transport of this material has not been factored into the cost. In particular, for larger soil remediation projects (> 1000 m 3 contaminated soil), where several sources are required to gain sufficient horse manure, the more simplified logistics of may provide financial cost savings. 5.0 Conclusions In terms of a significant reduction in TPH concentration, the use of green waste compost was found to be comparable with horse manure as an amendment. As such, green waste compost is a potentially useful amendment for bioremediation of hydrocarbon contaminated soil, although studies are required to further assess its performance. Despite no difference in TPH degradation, several significant differences in technical performance were observed between the two amended biopiles which may have consequences for bioremediation under different circumstances and for different soils. For example, the amended biopile was warmer than the horse manure amended biopile to a large extent initially following amendment (difference 2.8 C). This increased temperature may have attributed to the increased activity observed in biopile P. However, the increase in activity is more likely the result of introducing nutrients (such as carbon and nitrogen) which would stimulate the indigenous microbial community, together with the introduction of a larger microbial community within the material itself. The increase in microbial numbers in biopile P supports the latter. Several other parameters were recorded showing no difference between the two amendments. For example, results on the effectiveness of the two amendments to improve oxygen diffusion within the biopiles were highly variable and as such inconclusive. Likewise, no difference in water retention was observed between the two 10

13 biopiles. Moisture content increased in both biopiles during the course of the experiment, most likely from rainwater influx due to treatment occurring over winter months. Otherwise, the ph level increased in the first four weeks of treatment in both biopiles. The increase is likely to result from ammonium content of the organic amendments (Atagana, 2004). The financial costs of using green waste compost as an organic amendment for bioremediation of hydrocarbon contaminated soil are comparable with horse manure. As mentioned previously, time savings could be made through using compost on larger bioremediation projects, as opposed to sourcing horse manure from various locations. Although not an issue for this project, seasonality may have financial implications on other projects. For example, in the summer months horse manure is typically spread on agricultural land reducing availability for alternative use. Conversely, the availability of green waste compost is dependant on facility throughput which in turn may be strongly influenced by council collections of green waste which typically do not run during winter months. 6.0 Acknowledgements I would like to acknowledge David Carvalho (ERS) for collecting samples and carrying out microbial analysis at the ERS treatability laboratory. Acknowledgement is also made to Peter Anderson and Tanya Peshkur of the Contaminated Land Assessment & Remediation Research Centre (CLARRC) for TPH analysis. 7.0 References Aspray, T.J., Carvalho, D. Philp, J.C., Use of soil slurry respirometry to monitor and optimise ex situ bioremediation. International Biodeterioration and Biodegradation 60, Aspray, T.J., Gluszek, A., Carvalho, D., Effect of nitrogen amendment on respiration and respiratory quotient (RQ) in three hydrocarbon contaminated soils of different type. Chemosphere 72, Atagana, H.I., Co-composting of PAH-contaminated soil with poultry manure. Letters in Applied Microbiology 39, Bento, F.M., Camargo, F.A.O., Okeke, B.C., Frankenberger, W.T., Comparative bioremediation of soils contaminated with diesel oil by natural attenuation, biostimulation and bioaugmentation. Bioresource Technology 96, Evans, F.F., Rosado, A.S., Sebastian, G.V., Casella, R., Machado, P.L.O.A., Holmstrom, C., Kjelleberg, S., van Elsas, J.D., Seldin, L., Impact of oil contamination and biostimulation on the diversity of indigenous bacterial communities in soil microcosms. FEMS Microbiology Ecology 49, Margesin, R., Schinner, F., Bioremediation (natural attenuation and biostimulation) of diesel-oilcontaminated soil in an Alpine glacier skiing area. Applied and Environmental Microbiology 67, Roldán-Martín, A., Calva-Calva, G., Rojas-Avelizapa, N., Diaz-Cervantes, M., Rodríguez-Vázquez, R., Solid culture amended with small amounts of raw coffee beans for the removal of petroleum hydrocarbon from weather contaminated soil. International Biodeterioration and Biodegradation 60, Sarkar, D., Ferguson, M., Datta, R., Birnbaum, S., Bioremediation of petroleum hydrocarbons in contaminated soils: comparison of biosolids addition, carbon supplementation, and monitored natural attenuation. Environmental Pollution 136, Scelza, R., Rao, M.A., Gianfreda, L., Effects of compost and of bacterial cells on the decontamination and the chemical and biological properties of an agricultural soil artificially contaminated with phenanthrene. Soil Biology and Biochemistry 39, Semple, K.T., Reid, B.J., Fermor, T.R., Impact of composting strategies on the treatment of soils contaminated with organic pollutants. Environmental Pollution 112,

14 Appendices Appendix 1 - product information 12

15 13

16 14

17 Printed on xx% recycled content paper