Bringing Brownfield Sites Back to Use: The Evolution of Contaminated Land Remediation
This is the third instalment in a series of blog posts which will briefly present examples of some of the most innovative technologies for the clean-up of contaminated sites.
Recent Groundsure blogs on remediation of contaminated land have looked at the steps recommended by the authorities to bring formerly industrial sites back to use and how some high-profile events such as the Olympic Games have become great examples of the successful redevelopment of previously contaminated areas. In this blog, Maria presents some of the most cutting edge remediation/clean-up techniques in the market with a brief explanation of how they have been developed and study cases. If you have any questions or comments about this blog, you can contact the commercial consultancy team at firstname.lastname@example.org.
Soil clean-up has traditionally entailed either simple disposal or isolation of contaminated land, but fortunately these are no longer considered acceptable methods to deal with contaminated land by experts in the field.
Sustainable remediation, a relatively new concept in the remediation field, has drawn much attention in the last decade. The sustainable remediation concept emerged in the early 2000s when European policy-makers and industrial associations started to advocate a risk-based approach in contaminated land management. (1) There is a variety of criteria in determining whether or not a remediation alternative is sustainable and the technology chosen for investigation and clean-up processes plays a crucial role in it.
The technologies presented below are considered to be some of the most innovative and well-established in the market:
Laser Induced Fluorescence (UVOST, Ultra-Violet Optical Screening Tool)
The UVOST is a recently developed technique used in sites where leaks of gasoline, diesel, hydraulic fluids and oils are suspected to have occurred. This technology works on the principle that polycyclic aromatic hydrocarbons (PAHs), components usually contained within the aforementioned substances, are located in soil and/or groundwater fluoresce when irradiated by ultraviolet light. Different types of PAHs will fluoresce at different wave lengths leaving a characteristic fluorescent signature. Measuring the intensity and wavelength of the fluoresced PAH allows one to assess the type and relative concentration of PAH present in the CPT-UVOST (Cone Penetration Testing-Ultra-Violet Optical Screening Tool) sounding. Performing CPT-UVOST soundings at multiple locations across a site allows for an accurate determination of the site stratography and piezometric profile along with the location of the residual phase NAPL (Non-aqueous Phase Liquid) present at the site. This data can be used to select appropriate sampling and monitoring well locations which allows for a more rapid, accurate and cost effective site assessment and remediation program when compared with the traditional multi-phase drilling and sampling program. (2)
This has been one of the techniques implemented during the remediation of Knotttingly chemical works, in Leeds.
Geotubes have been used in the past years as a low-cost and high-volume de-watering solution. The process has proven to be a simple and effective way to handle sludge, hazardous contaminated soils or dredge waste materials. The process consists of the following phases:
Step 1: Filling - Sludge is pumped into the geotube's container. Environmentally safe polymers are added to the sludge, which makes the solids bind together and water separate. The geotube container's fabric confines the fine grains of the material. (3)
Step 2: De-watering - Clear effluent water simply drains from the geotube’s container through the small pores in the specially engineered textile. This results in effective de-watering and efficient volume reduction of the contained materials and this volume reduction allows for the repeated filling of the geotube’s container. Over 99% of solids are captured and clear filtrate can be collected and recirculated through the system. The decanted water is often of a quality that can be reused/returned for processing or returned to native waterways without additional treatment. (3)
Step 3: Consolidation - After the final cycle of filling and de-watering, the solids remain in the bag and continue to densify due to desiccation as residual water vapour escapes through the fabric. Volume reduction can be as high as 90 percent. When full, the geotube container and contents can be deposited at a landfill, remain on-site or the solids can be removed and land-applied when appropriate. (3)
This technology has been used during the decommissioning and remediation of LLandarcy Oil Refinery in South Wales.
Soil bioremediation is a complex process that aims to restore contaminated sites to environmentally sustainable conditions using microorganisms. (4) The process relies upon the ability of microorganisms to alter and break down organic molecules into other substances. A number of remediation technologies have been developed to clean up contaminated wastes:
Biosparging – This is an in-situ remediation technology that uses indigenous microorganisms to biodegrade organic constituents in the saturated zone. In biosparging, air (or oxygen) and nutrients (if needed) are injected into the saturated zone to increase the biological activity of the indigenous microorganisms. Biosparging can be used to reduce concentrations of petroleum constituents that are dissolved in groundwater, absorbed to soil below the water table and within the capillary fringe. Although constituents adsorbed to soils in the unsaturated zone can also be treated by biosparging, bioventing is typically more effective for this situation. (5)
Biostimulation – This technology involves the modification of the environment to stimulate existing bacteria capable of bioremediation. This can be done by the addition of various forms of limiting nutrients and electron acceptors, such as phosphorus, nitrogen, oxygen or carbon which are otherwise available in quantities low enough to constrain microbial activity (Elektorowicz, 1994; Piehler et al., 1999; Rhykerd et al., 1999). (6)
Anaerobic biotransformation – This technique is used for the degradation of organic compounds that are resistant to the aerobic bioremediation, such as chlorinated hydrocarbons, polychlorinated phenols and nitro-aromatics. Anaerobic treatment processes produce much smaller quantities of biomass. Moreover, anaerobic biotransformation of polychlorinated hydrocarbons is of particular interest on the remediation of contaminated soil and groundwater, since dechlorination rates are generally faster under these conditions. Substrate concentration, availability, temperature, pH, co-factor supply, concentration of cells, viability of cells and type of operation are some of the major factors responsible for the successful anaerobic biotransformation processes. (4)
As mentioned above, sustainability has recently become a new imperative in contaminated land remediation and brownfield redevelopment. New technologies, such as the ones presented above are the means for the implementation of sustainable development. Over the last few years, some mega projects have successfully demonstrated how sustainable construction practices can be incorporated into brownfield remediation, making the current lack of greenfield land no longer a barrier for new development projects.
Groundsure have a number of reports that allow you to understand potential contaminated land risks, including our Fire Insurance Plans report, which helps you see the past more clearly for contaminated land assessments. For more information about which Groundsure reports include contaminated land data, click here.
- Sustainable site clean-up from megaprojects: lessons from London 2012. Available at: https://www.repository.cam.ac.uk/bitstream/handle/1810/246514/Hou_et_al-2015-Proceedings_of_the_Institution_of_Civil_Engineers-Engineering_Sustainability-VoR.pdf?sequence=7&isAllowed=y [Accessed 18th August 2016]
- Laser Induced Fluoresce (UVOST). Available at: http://www.greggdrilling.com/equipment/GMHWv/laser-induced-fluorescence-uvost [Accessed 13th January 2017]
- TenCate Geotube Master Distributor. Available at: http://www.tencate.com/amer/geosynthetics/solutions/dewatering_technology/how-it-works.aspx [Accessed 13th January 2017]
- Sustainable Soil Remediation. Volume 6, Number 6. Published December 2010.
- How to evaluate alternative cleanup technologies for underground storage tank sites. https://www.epa.gov/sites/production/files/2014-03/documents/tum_ch8.pdf [Accessed 12th January 2017]
- Science and Education Publishing. From Scientific Research to Knowledge. Bioremediation, Biostimulation and Bioaugmention: A Review. Available at: http://pubs.sciepub.com/ijebb/3/1/5/ [Accessed 12th January 2017]