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Soil and Groundwater Remediation

Overview | Individual Project Summaries | Objectives and Outcomes | Key Research Staff | Clients and Collaborative Links

2. Demonstration and Evaluation of Remediation Technologies (DERT)

Listed under this DERT Program are Laboratory and field-scale projects carried out to demonstrate the effectiveness and efficiency of existing and innovative remediation options for cleanup of contaminated groundwater and soils include:

General References

Rao, P.S.C., Davis, G.B. and Johnston, C.D. 1996. Technologies for enhanced remediation of contaminated soils and aquifers: overview, analysis and case studies. Contaminants and the Soil Environment in the Australasia-Pacific Region (Naidu, R., et al. - Eds), Kluwer Academic Publ., Dordrecht, Chapt 12, 361-410.

Davis, G.B. 1997 Site clean-up - the pros and cons of disposal and in situ and ex situ remediation. J. Land Contamination & Reclamation 5(4), 287-290.

Davis, G.B., Naidu, R. and Anderson, B. 1998. Demonstration and evaluation of remediation technologies (DERT): Is there a place for it in Australia? Groundwater: Sustainable Solutions (T.R. Weaver and C.R. Lawrence). IAH International Groundwater Conference 1998, Melbourne, 8-13 February 1998, 375-384.

Davis, G.B and Johnston, C.D. 2004. Australian and international research and its implications for the risk-based assessment and remediation of groundwater contamination. Enviro04, Managing Contaminated Land, 28 March –1 April 2004, Sydney.

Air sparging and soil vapour extraction of petroleum hydrocarbons

A series of trials combining air sparging (air injection below the groundwater table) and soil vapour extraction has been carried out for removing dissolved gasoline constituents from groundwater and for removing residual non-aqueous phase liquid (NAPL) gasoline from a contaminated sandy aquifer. Initial trials indicated that dissolved benzene and other gasoline contaminants could be removed from groundwater within hours to days, but that the zone of effectiveness was typically within a 2 to 4 m radius of the air injection (sparging) well. Most cleanup was found to be due to volatilisation or physical stripping, rather than due to enhanced bioremediation from stimulation of aerobic bacteria by oxygen in the injected air. Further evidence of the dominance of physically stripping of BTEX (benzene, toluene, ethylbenzene, xylene) and naphthalene compounds was demonstrated in laboratory column studies. For the NAPL sparging trial, soil vapour extraction alone was found to remove only a small percentage of the total mass removed, compared to air sparging combined with soil vapour extraction. Compositional changes in the NAPL and groundwater were observed, and mass transfer limitations were apparent after sparging for a longer period. Another outcome of the work was that no significant reduction in the aquifer hydraulic conductivity was observed even though residual air was found to be still at significant levels in groundwater some nine months after air sparging had ceased.

Figure

Key contact: Colin Johnston

Key references:

Johnston, C.D., Rayner J.L., Patterson, B.M. and Davis, G.B., 1998. Volatilisation and biodegradation during air sparging of a petroleum hydrocarbon contaminated sand aquifer. Groundwater Quality: Remediation and Protection. (Proceedings of the GQ’98 Conference held at Tübingen, Germany, September 1998). IAHS Publ. No. 250, 1998, 125-131.

Johnston, C.D., Rayner, J.L., Patterson, B.M. and Davis, G.B. 1998. The contribution of volatilisation and biodegradation during air sparging of dissolved BTEX-contaminated groundwater. J. Contaminant Hydrology, 33, 377-404.

Johnston, C.D. 2001. Use of air flushing technologies for the removal of petroleum hydrocarbons from contaminated aquifers. In: Environmental Geotechnics. Proceedings of the 2nd Australia and NewZealand Conference on Environmental Geotechnics - GeoEnvironment 2001. Newcastle, New South Wales, Australia, 28-30 November 2001, 273-286.

Johnston, C.D., Rayner, J.L. and Briegel, D. 2002. Effectiveness of in situ air sparging for removing NAPL gasoline from a sandy aquifer near Perth, Western Australia. J. Contaminant Hydrology, 59, 87-111.

Johnston, C.D. and Desvignes, A. 2003. Evidence for biodegradation of dissolved petroleum hydrocarbons during in situ air sparging in large laboratory columns. Water, Air, and Soil Pollution: Focus 3: 25-33.

Multiphase extraction of petroleum fuels

Field trials were carried out to quantify and enhance light non-aqueous phase liquid (LNAPL) recovery from wells using a range of multiphase extraction techniques (dual-phase recovery, vacuum-enhanced recovery and slurping) in comparison to passive skimming. These trials involved separately and simultaneously pumping the groundwater to induce drainage of non-aqueous phase liquid (NAPL) to the recovery borehole, skimming/pumping of the LNAPL product itself, and applying a vacuum to the well to recover vapours and avoid excess lowering of the water table. Two separate trials were conducted in a sand aquifer under seasonally high and low water table conditions corresponding to small-to-negligible and relatively large (0.6 m) thicknesses in screened wells. The relative performance of the different multi-phase extraction strategies was similar for the two water table conditions. Greater recovery of the LNAPL was documented for the low water table conditions. Notably, NAPL recovery was possible using multiphase extraction (including vacuum-enhanced recovery) even where NAPL was present at negligible thicknesses in the recovery well. Vacuum-enhanced recovery using modest suctions gave greater NAPL recovery rates than water table draw down on its own. Recovery rates were up to 10 times greater than passive skimming. When combined with water table draw down, vacuum-enhanced recovery gave NAPL recovery rates as much as 16 times that of skimming. However, this may not be sustainable in the longer term. The air extraction element of the vacuum-enhanced recovery added important removal mechanisms through volatilisation and aerobic biodegradation. Under some conditions, these removal mechanisms may dominate over liquid NAPL extraction. Detailed studies of NAPL saturation and pressure distributions showed that water table manipulation had multiple effects on NAPL transmissivity (and recovery rates) in the presence of fine-scale layering in the profile. Associated NAPL baildown testing showed increased transmissivity due to the spreading of NAPL into coarse-textured layers.

Key contact: Colin Johnston

Key references:

Johnston, C.D., Fisher, S. and Rayner, J.L., 2002. Removal of petroleum hydrocarbons from the vadose zone during multi-phase extraction at a contaminated industrial site. Natural and Enhanced Restoration of Groundwater Pollution (Proc. Groundwater Quality 2001. Conference held at Sheffield, June 2001) IAHS Publ. No. 275, 287-293.Johnston, C.D., Fisher, S.J., Innes, N. and Rayner, J.L., 2004. Biodegradation and volatilisation during a field trial of multi-phase extraction of weathered petroleum hydrocarbons. In Prep.

Hydraulic fracturing for the recovery of non-aqueous phase liquid (NAPL) and contaminated groundwater

Hydraulic fracturing in a fractured rock aquifer was investigated in a pilot-scale field trial to improve the remediation of spilled hydrocarbons. The objective was to increase the permeability of selected vertical intervals in the aquifer thereby improving the rates and efficiency of non-aqueous phase liquid (NAPL) petroleum hydrocarbon and contaminated groundwater recovery. It was aimed to increase permeability of the aquifer and radius of influence of pumping wells by increasing the number, horizontal extent and conductivity of fractures. The test involved hydraulic fracturing at a number of different intervals in the same hole and measuring the vertical displacement, ground surface tilt and pressures in the aquifer to elucidate the fracturing process. Permeability of the aquifer to both water and NAPL was compared before and after the fracture treatment including down-hole testing of the intervals fractured. Overall, the fracturing treatments were observed to increase the bulk water transmissivity of the aquifer to a distance of 11.5 m from the fracture hole. The fracture treatments also improved the lateral connectivity across the site. Individual treated intervals had permeability increased by as much an order of magnitude. However, there was also evidence that the proppant used decreased permeability of an interval of naturally high transmissivity.

Key contact: Colin Johnston


Bioventing: In situ bioremediation of diesel fuel

Bioventing was evaluated as a cleanup technique for diesel fuel contamination. Air and nutrients (ammonia and phosphate) were periodically injected into a diesel-contaminated zone 3.7 to 4.5 m below ground, to stimulate aerobic biodegradation. Over a 14-month period, biodegradation rates increased by a factor of 5-10 from background rates, i.e. up to 90 mg-diesel/kg-soil/day. Phospholipid analysis of soil materials showed that microbial biomass increased dramatically where nutrients and air (oxygen) were present. Ammonia was transformed to nitrite and nitrate, and was utilised variably in the contaminated zone. Most locations showed reductions of diesel concentrations in soil cores, with preferential biodegradation of some of the diesel constituents. At some locations, diesel concentrations were reduced to below 1,000 mg/kg from starting concentrations 100-fold higher.

Figure

Key contact: Greg Davis

References:

Davis, G.B., Johnston, C.D., Patterson, B.M., Barber, C., Bennett, M., Sheehy, A. and Dunbavan, M. (1995). Monitoring bioremediation of weathered diesel NAPL using oxygen depletion profiles. In Monitoring and Verification of Bioremediation (R.E. Hinchee, G.S. Douglas and S.K. Ong - Eds). Bioremediation 3(5), 193-201.

Davis, G.B., Johnston, C.D., Patterson, B.M., Barber, C., and Bennett, M. (1998). Estimation of biodegradation rates using respiration tests during in situ bioremediation of weathered diesel NAPL. Ground Water Monitoring & Remediation 18(2), 123-132.

Rao, P.S.C., Davis, G.B. and Johnston, C.D. (1996). Technologies for enhanced remediation of contaminated soils and aquifers: overview, analysis and case studies. Contaminants and the Soil Environment in the Australasia-Pacific Region (Naidu, R., et al. - Eds), Kluwer Academic Publ., Dordrecht, Chapt 12, 361-410.

Davis, G.B., Johnston, C.D. and Patterson, B.M. (1999). Remediation of petroleum hydrocarbon-contaminated groundwater and soil – three case studies. International Workshop on Water Resources, Soil Environmental Protection and Treatment Technology. Lanzhou Railway University, Lanzhou, China, 14-15 October 1999, 137-144.

Johnston, C.D. 2001. Use of air flushing technologies for the removal of petroleum hydrocarbons from contaminated aquifers. In: Environmental Geotechnics. Proceedings of the 2nd Australia and NewZealand Conference on Environmental Geotechnics - GeoEnvironment 2001. Newcastle, New South Wales, Australia, 28-30 November 2001, 273-286.

Phytoremediation to hydraulically isolate and remediate soil and groundwater

Plants are being increasingly trialled to remediate metals and hydrocarbon contaminated soils and groundwater. Two studies have been carried out to remediate petroleum hydrocarbon impacted soil and groundwater. An initial glasshouse study aimed to evaluate the potential of three plant groups to effect enhanced biodegradation within the root zone mass, for hydrocarbon contaminated soil material. Data from the study showed that all plant varieties thrived in hydrocarbon-impacted soil at concentrations up to 100,000 mg/kg.

A five-year project currently underway, is a field trial using eucalyptus trees (River Red Gums) to hydraulically isolate and remediate petroleum impacted soil and groundwater. The study has a dual aim: (i) to determine if the trees can reduce leaching of contaminants to groundwater and perhaps reverse hydraulic gradients in groundwater to contain impact and off-site migration of a hydrocarbon plume, and (ii) to determine the enhanced biodegradation potential in plots with trees compared to an unplanted control area. The trees are 3 years old and thriving in heavily impacted soils. Long-term monitoring and investigation is being carried out to determine hydraulic changes due to the trees and changes in groundwater contaminant concentrations.

Key contact: Greg Davis

Biopile and composting treatment of hydrocarbon impacted soils

The efficiency of biotreatment pile (biopile) and composting techniques to clean up petroleum contaminated soil was tested. The biopiles consisted of engineered soil piles where oxygen in air was pulled through the soil piles to stimulate naturally occurring micro-organisms. Dissolved nutrients (nitrogen and phosphorus) were added at the top of the piles daily. Increases in microbial biomass were measured in soil material from the biopiles, temperature increases were noted in active regions of the biopiles, and nutrient concentration changes occurred within the biopile. Respiration tests (halting of aeration to observe oxygen concentration decreases, indicative of oxygen consumption by microbes and biodegradation rates) indicated that rates of microbial degradation were as high as 100 mg total petroleum hydrocarbon (TPH) per kg soil per day initially, with an average for one of the biopiles of about 70 mg TPH per kg of soil per day. At this rate, time scales for significant reduction of the TPH content of the biopiles were less than 1 year, compared to natural rates of breakdown which would take greater than 10 years. Measurement of TPH concentration changes within core material showed good agreement with these rates, with significant reductions in TPH being measured over short time periods of biopile operation. In one soil pile, the average biodegradation rates decreased steadily from 33±15 to less than 0.6±0.3 mg/kg/day over the first ~180 days, and ~90% of the hydrocarbons were removed within the first 200 days of aeration. Beyond this initial period, natural aeration of the biopiles by diffusion seemed capable of delivering the oxygen needed, without continued enhanced aeration. Composting was also tested in laboratory radiometric experiments, using a mixed compost spiked with 14C-octadecane to differentiate biodegradation from adsorption onto compost organic matter. Biodegradation of the 14C-octadecane was shown to be most rapid where the soil to compost ratio was highest at 4:1.

Key contact: Greg Davis and Bradley Patterson

Key references:

Franzmann, P. D., Zappia, L. R. and Trefry, M. G. (1999). Effect of composting on the mineralisation of hydrocarbons in hydrocarbon-contaminated soils: studies with 14C-octadecane. Contaminated Site Remediation: Challenges Posed by Urban and Industrial Contaminants (Ed. C.D. Johnston). Proc. 1999 Contaminated Site Remediation Conference, Fremantle, Western Australia, 21-25 March 1999, 577-584.

Patterson, B.M., Davis, G.B. and Briegel, D. (1999). Use of respirometry tests to monitor bioventing remediation of hydrocarbon contaminated soils. Contaminated Site Remediation: Challenges Posed by Urban and Industrial Contaminants (Ed. C.D. Johnston). Proc. 1999 Contaminated Site Remediation Conference, Fremantle, Western Australia, 21-25 March 1999, 219-226.

Bioclogging for containment and remediation of contaminated groundwater

The objective of this work was to produce a biologically active, low permeability zone or barrier in situ by stimulating micro-organisms to produce slimes which clog the pore spaces in aquifers and reduce their hydraulic conductivity. It was hoped that such a barrier would provide temporary containment of both dissolved organics and organic non-aqueous phase liquids. Laboratory work (incubated aquifer slurries) determined the extent to which indigenous bacteria from a site contaminated by BTEX (benzene, toluene, ethylbenzene, xylene) compounds produced slimes (extracellular polysaccharides) as well as the most favourable energy and nutrient conditions for this to occur. Column experiments were used to quantify reductions in hydraulic conductivity. As a final step, a pilot-scale demonstration of bioclogging was carried out at the contaminated site in Adelaide, South Australia, by stimulating the indigenous bacteria to produce polysaccharides in situ. A key element of the field demonstration was modelling the pumping and extraction of a relatively dense amendment into the groundwater to engineer a barrier with a specified configuration. Modelling was also used to design pumping tests that were used to identify changes in hydraulic conductivity of the amended parts of the aquifer.

Key contact: Colin Johnston

Key references:

Johnston, C.D., Rayner, J.L., De Zoysa, S., Ragusa, S., Trefry, M. and Davis, G.B. (1997). Studies of bioclogging for containment and remediation of organic contaminants. In Situ and On-Site Bioremediation: Volume 4 (Proc. 4th International In Situ and On-Site Bioremediation Symposium), Battelle, New Orleans, April-May 1997), 241-246.

Johnston, C. D., Trefry, M. G., Rayner, J. L., Ragusa, S. R., De Zoysa, D. S. and Davis, G. B. (1999). In situ bioclogging for the confinement and remediation of groundwater hydrocarbon plumes. Contaminated Site Remediation: Challenges Posed by Urban and Industrial Contaminants (Ed. C.D. Johnston). Proc. 1999 Contaminated Site Remediation Conference, Fremantle, Western Australia, 21-25 March 1999, 649-656.

Permeable reactive barriers for nutrient, pesticide, volatile contaminant and metal remediation

Permeable reactive barriers (PRBs) offer the potential to treat groundwater in situ, with the potential for lower long-term maintenance costs. PRBs are placed across the direction of contaminated groundwater flow to treat the contaminants of concern within the barrier and allow cleaned groundwater to flow downgradient beyond the PRB. Several projects have been carried out to determine the effectiveness of a PRB for treating ammonium, atrazine, volatile and semi-volatile contaminant plumes, and metals in groundwater. A dual barrier approach has been devised for the ammonium PRB concept. In this dual approach, oxygen is delivered in the first PRB to convert ammonium to nitrite/nitrate and a reductant (ethanol) is delivered in the second PRB to convert the nitrite/nitrate to nitrogen gas. This was successfully tested in laboratory-scale soil columns, and a field site has been instrumented with a small PRB to test the concept. Oxygen was successfully delivered through polymer mat PRBs in soil columns to biodegrade atrazine in groundwater. Carbon amendments have been trailed for solvents and metals in groundwater.

Figure

Key contact: Bradley Patterson

Key references:

Patterson, B.M., Franzmann, P.D., Davis, G.B., Elbers, J. and Zappia, L. 2002. Using polymer mats to biodegrade atrazine in groundwater: laboratory column experiments. Journal of Contaminant Hydrology 54, 195-213.

Patterson, B.M., Davis, G.B. and McKinley, A.J. 2002. Laboratory column experiments using polymer mats to remove selected VOCs, PAHs, and pesticides from ground water. Ground Water Monitoring and Remediation 22(2), 99-106.

Patterson, B.M., Grassi, M.E., Davis, G.B., Robertson, B. and McKinley, A.J. 2002. The use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation. Env. Sci. Technol. 36(15), 3439-3445.

Grassi, M.E., Patterson, B.M., McKinley, A.J. and Davis, G.B. 2003. Remediation of metal-contaminated groundwater using an innovative carbon source delivery system. Proceedings of Ozwater 2003, Perth, Western Australia, April 2003; Oz029, pp. 11.

Davis G.B. and Patterson B.M. 2003. Developments in permeable reactive barrier technology. In: Bioremediation: A Critical Review. (I.M. Head, I. Singleton and M.G. Milner - Eds). Horizon Scientific Press, UK, Chapter 8, pp. 205-226.