Indigenous plants for bioremediation of closed mines Shinil Corporation, the Republic of Korea, has developed a technology for the phytoremediation of soils polluted by heavy metals which involves creating mugwort (Common Wormwood or Artemisia vulgaris) cover on the polluted soil. Sulphur, which synthesizes chelate in plants, is supplied through soil improvers (pig manure and sewage sludge) to reduce toxicity and increase resistance when plants absorb heavy metals. The technology was successfully tested in an abandoned zinc mine. Contact: National Environmental Technology Information Centre, No. 613-2, Bulgwang-dong, Eunpyeong-gu, Seoul, Republic of Korea 122-706. Tel: +82 (2) 3800 553; Fax: +82 (2) 3800 545 E-mail: apecvc@kiest.re.kr Source: www.apec-vc.or.kr Solar bioreactor for groundwater remediation A pilot-scale recirculation bioreactor has been operating at the Altus Air Force Base (AFB) in Oklahoma, the United States, since late 2003 to address a hotspot of volatile organic compounds (VOCs) in groundwater residing in weathered shale and fractured clay. A solar-powered pump operating in the extraction / collection trench keeps the groundwater recirculating through the 283 m3 bioreactor and into the aquifer to generate high-carbon leachate and enhance VOC biodegradation. Since its start-up, the system has transferred about 1,300 m3/year of organic carbon-enriched leachate from the bioreactor into the aquifer. Groundwater recirculation through the bioreactor has achieved a 98 per cent reduction in trichloroethene (TCE) concentration within the bioreactor and a 90-97 per cent reduction in plume toxicity in hotspot wells between the bioreactor cell and the extraction trench. Solar pump for groundwater circulation Prior to project start-up, TCE concentrations in the hotspot were 19 mg/litre, and the plume extended nearly 1,000 m down-gradient of the landfill. The bioreactor was constructed immediately up-gradient of hotspot wells in an excavation of 9 m × 9 m extending 3.4 m below ground surface (bgs). The cell was filled with a 1:1 mixture of sand and organic mulch consisting of woody material and cotton-gin trash. At the top of the cell a ground-water distribution system was set up between two layers of geotextile fabric. The cell was capped with a soil and native grass cover. The bioreactor relies on groundwater recirculation from down-gradient of the hotspot, which is located in the shallow aquifer 3.0-5.5 m bgs. The site’s remote location and average solar radiation of 4-5 kWh/m2/day dictated the use of solar power to cut down construction and energy costs. Groundwater recirculation is carried out by a single, photovoltaic-powered, 3 inch submersible pump that maintains an average groundwater flow rate of about 3,500 litres/day. Pollutant degradation is monitored through a network of 18 wells. Evaluation of the bioreactor performance indicates dissolved organic carbon concentrations increased from <6 mg/litre prior to start-up to 120 mg/litre in shallow wells and 30 mg/litre in deeper wells. Increased concentrations of cis-1,2-dichloroethene, vinyl chloride and ethene indicate reductive dechlorination of TCE occurs in the bioreactor. For a more complete reductive dechlorination of TCE, a semi-soluble carbon substrate and a bioaugmentation culture were added to the bioreactor. Source: www.clu-in.org New process for bioremediation of contaminated soil Canon Kabushiki Kaisha of Japan has been assigned a United States patent on a new process for remedying a contaminated soil. The new process involves freezing the contaminated region, and then injecting a micro-organism and a liquid/gas agent that is required to augment the micro-organism’s ability to decompose the pollutant more rapidly and efficiently. The frozen region is then allowed to gradually thaw. A possible explanation, yet to be proved, for the process is as follows. When the soil is frozen and then thawed as a pre-treatment, freeze expansion in the pore space will widen the fine pore space of the soil into which the liquid agent will diffuse. Agitation of the soil water retained between the soil particles by this freezing and thawing will accelerate the contact between the injected liquid agent and ground-water. The process, well known in civil engineering field, causes swelling on freezing and consolidation on thawing in the soil. While a problem to be overcome in civil engineering works, it is favourable for the uniform distribution of a micro-organism. By adopting this freezing step, the present invention can promote the remediation efficiency and shorten the soil remediation period. Source: www.freepatentsonline.com Enhanced bioremediation technology Microbial Groundwater Circulation Wells (mGCW), a concept from IEG Technologie GmbH, Germany, accelerate the natural biodegradation of organic compounds under aerobic or anaerobic conditions. These systems are specifically designed and configured to provide accelerated aerobic, enhanced anaerobic or sequential anaerobic/aerobic reactions. The special design of the wells produces a groundwater convection cell in the aquifer around the remediation well. The groundwater that circulates constantly transports both contaminants and existing degrading bacteria to the well. Small biologically active carbon reactors can be used inside the well for continuous growth, acclimation and augmentation. These reactors are found to have much higher levels of biodegradation and higher specific growth rates than other attached growth systems. Contaminants are selectively retained in the reactor, facilitating the selection and enrichment of micro-organisms that are capable of degrading pollutants. If necessary, added nutrients can be supplied to the accumulated micro-organisms. Another advantage of the mGCW is the oxygen-enriched groundwater generated by the system, which enhances the population growth of the micro-organisms in the aquifer, thus accelerating the degradation process. System variations include discontinuous circulation flow, reversing the circulation direction and installing different bioreactor configurations. These variations enable the technology to be easily customized to different contamination sites. Contact: IEG Technologie GmbH, Hohlbachweg 2, Gruibingen73344, Germany. Tel: +49 (7335) 96976-0; Fax: +49 (7335) 96976-40 E-mail: eduard.alesi@ieg-technologie.com Source: www.ieg-technologie.com Bioremediation of hydrocarbon-contamination Exxon Research and Engineering Company, New Jersey, has secured a United States patent on its invention that provides an enhanced biodegradation process by applying to petroleum-contaminated water or soil microbial nutrients in controlled release. The process is capable of releasing the microbial nutrients over a sustained period of time, for example 1-6 months, which at 25ºC is a substantially linear rate. The rate of release of microbial nutrients, which is typically less than 5 per cent per day, can be increased by raising the temperature. The nutrients may include one or more nitrogen sources, such as urea and ammonium nitrate, and optionally phosphorous sources such as phosphates. Typically the nitrogen and phosphorous sources will be combined to provide an N:P ratio, preferably, of 10:1. Optionally, the nutrient cocktail may also contain micronutrients such as magnesium, iron, manganese and calcium at very low levels. The nutrients are coated with a material – like an elastomeric sulphonated polymer such as ethylene-propylene diene terpolymer or EDPM – that controls the release of nutrients to the environment. Source: www.freepatentsonline.com Vegetable oil as a bioremediation amendment At University of Waterloo, Canada, biologists have studied the feasibility of using peanut (groundnut) oil as a cost-effective, non-toxic and biodegradable extractant for the remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs). The scientists found that extraction efficiency was higher than 90 per cent when peanut oil at concentrations of 2.5-20 per cent was used to remove anthracene from garden soil. Optimal pH values for these extractions were 6 and 7. When soil spiked with a combination of 10 PAHs at 100 ìg/g was extracted with peanut oil at different temperatures, total PAH extraction efficiency increased from 51.5 per cent at 20ºC to 81.4 per cent at 60º C. A double extraction of weathered soil from a creosote-contaminated site using 5 per cent peanut oil, followed by another extraction with 5 per cent oil was better than a single 10 per cent oil extraction. Based on the results of the study, a process was conceptualized for the treatment of PAH-contaminated soil. Source: www.sciencedirect.com