Stuart Group

Tel: +44 (0) 1953 454540

Fax: +44 (0) 1953 456968

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Soil Washing


A new aqueous process developed for soil washing and hydrocarbon removal/recovery including the tank bottom and interceptor sludge´s, production residues, waste lagoons, etc. This process utilises an innovative combination of established and proven technologies: cavitation scrubbing, separator/clarifier columns and electro coagulation water treatment combined with proprietary chemistry.

The main advantages of the process are:

  • It is a low hazard, aqueous process with integrated water treatment so that water/process solutions may be recycled within the process and decontaminated prior to discharge.
  • Highly cost effective in comparison with competing processes (solvent extraction, thermal treatment).
  • Cavitation scrubbing ensures almost complete separation of hydrocarbons from particulates.
  • The solids/particulates will only have a low residual hydrocarbon content (Less than %), which should be suitable be suitable for rapid biodegradation treatment to reach required (non-hazardous) target levels, or immediate reuse dependant on specific on site requirements.
  • It enables the rapid separation, cleaning and recovery of hydrocarbons from soil, sludge´s; self-contained systems may be supplied to process 5, 10 and 20 tonnes per hour.
  • Hydrocarbons are separated and recovered and may be suitable for use as fuels in cement kilns, etc.

The waste sludges will be processed by the system as follows:

  • The first stage of the process utilises the energy released and intense pressures of cavitation bubble collapse to “scrub” the hydrocarbons from the solid particulates, combined with a small quantity of an appropriate chemical agent to reduce the viscosity of the hydrocarbons and facilitate their rapid separation.
  • Hydrocarbon contaminated soil, production sludges, etc., are loaded into the feed hopper of the cavitation scrubbing unit Depending upon the nature and viscosity of the hydrocarbons, chemical agents may either be pre-blended with the soil, sludges, etc., (if viscous/heavy, e.g. coal tar) or added simultaneously into the feed hopper. The high pressure pump is fed by the water tank, which is in turn filled both by the process solution overflow from the hydrocarbon separation unit and the returning process solution from the water treatment system.
  • The particulates and hydrocarbons are ejected by the cavitation scrubbing unit into the lower section of the process solution column in the hydrocarbon separation unit. This consists of a column, sized so that the upward velocity of the process solution is low enough to allow incoming hydrocarbons at the bottom time to coalesce into droplets as they rise towards the oil trap. The controlled upward velocity in the column also acts to classify the particulates in the sludges/scales, dense particles and any suspended particulates with a size greater than approximately 100 microns in size settle out downwards. The hydrocarbons are collected in the first oil trap and are either periodically discharged to collection barrels or alternatively may be removed with a continuous oil skimmer. Excess process solution underflows the weirs in the oil trap into a second oil separator and from there into the main process solution system tank.
  • The particulates are dropped out from the bottom of the hydrocarbon separation unit back into the hopper of the cavitation scrubbing unit, scrubbed and ejected back into the hydrocarbon separation unit. This process is repeated for a pre-set period of time, until the particulates are determined to be carrying less than the minimum required level of hydrocarbon contamination. At this point, the particulates are transferred by the sludge pump to the enclosed screw elevator/drier.
  • An amount, typically 10% or 20% of the process solution overflowing from the hydrocarbon separation unit is drawn off and treated using either one or two stages of electrocoagulation to remove any accumulating suspensions of ultrafine particulates, emulsified oils, etc.. The process solution is first pumped through a multi-cyclone to ensure that no large particulates accidentally enter the electrocoagulation cell.
  • The process solution which drains from the sludges, flocs and sediments is collected at the bottom of the enclosed screw elevator/drier and pumped back to the hopper of the cavitation scrubber for re-circulation and treatment within the process.

Other Services


We can assist you in large number of remediation services. Please follow the link to find a list of the different services we can offer.

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Contaminated Land

We can provide you with skilled, knowledgeable and effective remediation design and implementation to deal with contaminated land.

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Statutory Treatment Licenses

We can provide you with all the necessary mobile treatment and waste carriers licenses to suit your projects requirements.

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Brownfield Land

Government requirements state that 60% of all new homes should be built on brownfield land. This makes brownfield land an important part of this countries future.

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