Remediation services

RemedX has over 15 years' experience of providing cutting edge, design-led remediation contracting solutions. From small projects through to the management of multimillion pound programmes, we have done it all. Click on the links below for more information about the remediation techniques we currently offer. For more detailed descriptions of how these are applied or how they could benefit you, please do not hesitate to get in touch!

Air- and biosparging

Air sparging entails injecting air into an aquifer. The process physically strips contaminants from dissolved and adsorbed phase. Contaminated vapours are removed from the subsurface via an extraction system. The vapours are typically treated ex situ before being discharged to the atmosphere. This technique can also be used to introduce oxygen and promote bioremediation (biosparging).

Applications
This technique is ideally suited to treat hydrocarbon-impacted saturated soils, and groundwater.

RemedX examples

Bioremediation

RemedX's bioremediation expertise includes the following:

Biopiles

Biopiles rely on the principles of bioremediation to remove contaminants from the adsorbed phase, and from pore spaces. Treatment cells are constructed and the soil placed. Depending upon the type of contaminants, the treatment will be passive or active. For the latter, a series of extraction pipes are installed through the soil. A vacuum is applied to these pipes to induce airflow, introducing oxygen that is then utilised by the soil's native microbial population to promote bioremediation.

Applications
Biopiles are well suited to treating soil contaminated with light to medium chain hydrocarbons and volatile organic compounds.

Windrowing

Contaminated soil is excavated and placed into windrows, which are covered with water-repellent fleeces when not in use. Periodically, the windrows are turned using our specialist windrow turning machine to introduce oxygen into the soil pores. The oxygen is utilised by the native microbial population to biodegrade the contaminants. Where necessary, nutrients can be added to the soil to enhance the conditions for bioremediation.

Applications
In situ

RemedX examples

Chemical oxidation

In situ chemical oxidation (ISCO) involves adding chemicals to soil and groundwater to destroy contaminants through oxidation. It is a very fast and effective technique.

Applications
ISCO is a technique suitable for treating hydrocarbons and chlorinated solvents. It can also be used to treat pesticides.

Contaminated Groundwater Management

In order to achieve temporary reductions in groundwater levels, dewatering systems are routinely used for structures or excavations which extend to below groundwater level. Contaminated groundwater management is essentially any pumping or recharge system which is used to manipulate groundwater levels.

Applications
The simplest form of contaminated groundwater management is sump pumping which comprises of a pump which is used to remove water that has accumulated in a water-collecting sump basin. RemedX specialise in proving groundwater management on sites where excavations are required to reach contamination below or near the water table. RemedX will apply and obtain the necessary environmental permits to complete the work as well as mobilising in house equipment to the site to manage groundwater. The systems can be used to remove water from excavations and to remove any free product which may be present on the water surface. These are then both treated in the same water treatment system before being discharge in line with environmental controls. This method leads to considerable cost savings on projects with high water tables or long-term excavation management.

Dual-phase extraction (DPE) and multiphase extraction (MPE)

Dual-phase extraction (DPE)

Dual-phase extraction (DPE) is a technique used to remove dissolved phase contaminants and non-aqueous phase liquids (NAPL). In a typical clean up, a series of groundwater extraction wells are constructed and pumps installed. These pumps are capable of removing both NAPL and groundwater simultaneously. Pumping results in a cone of depression being formed, encouraging NAPL to flow towards the well along the hydraulic gradient. DPE is used to gain hydraulic control over the aquifer and can prevent off-site migration of contaminants. It also effectively exposes the unsaturated zone, so that a vacuum can be applied to strip residual contaminants from the adsorbed phase.

Applications
Dual-phase extraction is used to treat groundwater contaminated with dissolved phase and separate phase compounds. It is used to gain hydraulic control. Dual-phase extraction can be used in conjunction with soil vapour extraction.

 

Multiphase extraction (MPE)

Multiphase extraction is a technique by which a vacuum is applied to the subsurface via a recovery lance. It can recover NAPL, contaminated groundwater and contaminated vapours. The aquifer is dewatered, exposing the unsaturated zone, allowing airflow to be induced and encouraging contaminants to be stripped from the adsorbed phase. Extracted liquids are treated in a water treatment plant before discharge to a foul sewer under licence. (In some instances, it is possible to gain authorisation to re-inject treated water back into the aquifer.) Extracted vapour streams are treated with activated carbon.

Applications
Soil and groundwater contamination in low permeability aquifers.  

RemedX example(s)

Light non-aqueous phase liquid (LNAPL) skimming

Light non-aqueous phase liquid (LNAPL) skimming is a technique that can be used in situ to remove LNAPL from the groundwater surface. Wells are installed so that skimming pumps can also be installed, often into existing wells. LNAPL skimming is a good, short-term emergency response to help prevent off-site migration of free phase contaminants. The LNAPL is transferred to a holding tank before disposal at a suitably licensed facility.

Applications
LNAPL contaminated groundwater, especially recent spills.

Monitored natural attenuation (MNA)

Monitored natural attenuation (MNA) is not a remediation technology per se. However, it is a viable and cost-effective option for managing the risks posed by contaminated groundwater subsequent to an active remediation scheme where naturally occurring processes in the subsurface can reduce the mass, toxicity, mobility, volume and concentration of contaminants to acceptable levels.

There are many physical, chemical, biological and geochemical parameters that may be used to demonstrate the presence of natural attenuation mechanisms. The process of selecting appropriate determinants for monitoring these mechanisms will depend upon the nature of the contaminant, the site's biochemical environment and the dominant processes under consideration.

Adoption of the MNA approach requires demonstration that natural processes are occurring at a rate that protects the wider environment and achieves remedial objectives within a reasonable time frame. Therefore, a consistent groundwater monitoring network and sampling plan is required. This should include monitoring for the contaminants of concern and its daughter products, and monitoring natural attenuation indicators such as dissolved manganese, dissolved iron, nitrate, sulphate, redox potential, carbon dioxide, dissolved methane, dissolved oxygen and pH.

In recent years, Environment Agency guidance coupled with a greater understanding of natural attenuation processes has led to a wider acceptance of the technique in isolation or conjuction with other remedial techniques.

Applications
MNA can provide a remedial solution to sites that have recently been remediated, or as a method in its own right.

Permeable reactive barrier

Permeable reactive barriers (PRBs) combine a passive chemical or biological treatment zone with subsurface fluid flow management. Treatment media may include zero-valent iron, chelators, sorbents or a zone prepared to stimulate biodegradation processes. The contaminants are either degraded or retained in the barrier material, which may need to be replaced periodically.

PRBs can be installed as permanent or semi-permanent units. The most commonly used PRB configuration is that of a continuous trench in which the treatment material is backfilled. The trench is perpendicular to and intersects the ground-water plume. It can also be installed as a reactive treatment zone created by direct injection of reactive media into the aquifer (often using direct push rigs).

Applications
PRBs can be used to treat contaminated groundwater. The technique is most successfully applied to control migration of contaminants on or off a site.

Pilot testing

A pilot test is considered a crucial step in understanding how a site will respond to remediation, especially when the remedial strategy is complex or there are high levels of uncertainty in the input data. Pilot tests give site-specific information on the performance, applicability, and feasibility of a remediation system in order to determine whether any active remediation system can effectively accomplish the desired objectives. Generally, the time spent at the front end of a project will result in time and money saved during full-scale remediation.

Applications
Before a pilot test is installed, it is crucial to review existing site information that was either collected by ourselves or was collected prior to our involvement with a project. With this information, our team will be able to evaluate a broad spectrum of potential options and will select the most appropriate remedial technologies to pilot test. A pilot test would then be designed and performed in order to gain information on how the likely remedial technologies would perform at full-scale. This data will be analysed by our team who will then determine if the selected remediation strategy is feasible based on the pilot test. The data can also be used to refine the conceptual site model and provide accurate information for improved risk assessment.

Pump and treat

This is a common method for remediating groundwater contaminated with dissolved chemicals, including industrial solvents, metals and hydrocarbons. This method is a cost-effective way to treat contaminated groundwater either as a standalone technology or in combination with hotspot excavation.

Applications
For this method, one or more extraction wells are used to pump groundwater into a treatment system, located above ground, which will remove the contaminates to allow safe discharge of the treated water. The contaminated groundwater can also be removed from excavations during hotspot removal using an in-excavation pump and similar above-ground treatment system.

Soil stabilisation

This technique is used to chemically alter potentially-toxic metals in soil, which would be allowing the soil to be handled as non-hazardous waste. This would result in substantial cost saving disposal since prior to this technique, the primary option to dispose of soil that exhibited concentrations of metal wat to ship soil to expensive, hazardous waste accepting facilities for treatment and/or disposal.

This technique is used to chemically alter potentially-toxic metals in soil and encapsulate them in a cementitious material to ensure they do not leach out of the soil. This allows for previously hazardous soils to remain on site as an aggregate resulting in substantial cost saving when compared to disposal costs. RemedX can help design the mix concentration and determine the optimal binder as well as delivering in-situ or ex-situ soil stabilisation remediation.

Applications
Soil stabilisation can be utilised on roadways, parking areas, site development projects, airports and many other situations where sub-soils are not suitable for construction. There are a wide range of sub-grade materials which stabilisation can be used to treat, varying from expansive clays to granular materials. A variety of additives are used to accomplish this process, including lime, pulverised fuel ash, and cement.

Soil vapour extraction (SVE)

Soil vapour extraction (SVE), also known as ‘soil venting’, is a technique used to remove contaminants from the unsaturated zone. Extraction wells are installed in the target zone and a vacuum is applied to the wellhead. Airflow is induced in the subsurface to encourage contaminants to move from the absorbed phase to vapour. The contaminated vapour is treated ex situ by passing through activated carbon or a catalytic oxidiser. SVE can be used alone or in conjunction with other techniques such as air sparging or dual-phase extraction.

Applications
SVE can be an effective technique to unsaturated soil contaminated with volatile organic compounds. It can be used in conjunction with other remedial techniques such as air sparging and dual-phase extraction.

RemedX example(s)

Steam injection

Steam injection can significantly enhance the volatilisation and mobilisation of volatile organic compounds and semi-volatile organic compounds. The increase in temperature can also decrease the viscosity of dense non-aqueous phase liquids (DNAPL) to encourage flow towards extraction wells where it can be recovered. Steam flooding is always combined with another technology, usually SVE and total fluids pumping. This ensures that the steam-fuelled migration of contaminants is controlled and all are captured. Steam injection is a thorough and fast solution for sites with contaminated soil and groundwater. 

Applications
Steam-enhanced recovery is suitable for treatment of soil and groundwater contaminated with volatile organic compounds and semi-volatile organic compounds. It is also effective in mobilising dense non-aqueous phase liquids.