Heijmans Blackwell Remediation Ltd services

We cemented our reputation for undertaking challenging large scale remediation projects by successfully completing a number of complex soils washing contracts in the UK. Soils washing is a water based exsitu volume reduction technology for the treatment of contaminated soils. It employs a wide ranging set of wet separation, scrubbing and cleaning steps to physically, mechanically and chemically manipulate and separate soil particles from absorbed and particulate contamination. It is thereby able to recover a bulk volume of cleaned gravel, sand and silt material for reuse.

This process can be carried out insitu using either modified continuous flight auger soil mixing equipment or power mixers, which are attached to the arm of a long reach excavator, or exsitu using traditional excavators, batching plants and ancillary equipment. HBR has leading experts within the S/S field, who have wealth of experience in numerous such projects both here in the UK and Europe.

Biological treatment techniques rely on the natural metabolic processes of living organisms, such as bacteria and fungi, to destroy organic contaminants or convert them into less toxic forms. Carbonbearing substrates are metabolised by oxidation and other processes to generate energy for growth and reproduction. Under aerobic conditions the complete mineralisation of organics results in the production of CO2, water, biomass and inorganic salts. However, intermediate metabolites can be formed that can be more toxic than the original contaminants. Therefore, a complete understanding of the respiratory pathway and associated chemistry is essential in order to design the most appropriate system for the contaminants present. Anaerobic degradation or co-metabolism can also occur, as a result of the transformation of a non-growth substrate (the contaminant) by a microorganism using an alternative carbon substrate as an energy source.

This is a well used common approach, combining the removal of dissolved phase contaminants in groundwater in the saturated zone, together with vapour in the unsaturated zone by vacuum (slurping) also known as vacuum enhanced recovery (VER) and non-aqueous phase liquid (NAPL) or free phase product, from recovery well points.  The associated drawdown of the water table towards the well by dewatering creates a cone of depression, which enhances recovery of vapours by from the originally saturated smear zone.

Oxidation processes can be used to transform organic contaminants into less toxic and less mobile forms, with complete reactions producing carbon dioxide and water. They are referred to as `redox reactions`,  as the oxidising agent gains electrons (reduced valence state-reduction) while the contaminant loses electrons (increased valence state-oxidation).  This electron exchange breaks carbon bonds creating new smaller compounds.  Oxidants can also be used for iron and chromium precipitation and the destruction of cyanides and sulphides.

HBR can design and construct an array of low permeability containment systems to mitigate contaminant migration in the subsurface. These include vertical barriers (walls), basal barriers (floors) and surface barriers (caps).