The raft of new EU remediation legislation means that Spain, like many other European countries, is having to readdress its clean-up projects.
A site in Cßdiz in the south of the country is a case in point. The former petrochemical storage facility for a nearby power station is being decontaminated by power company Endesa before it can be handed back to owner the Cßdiz Harbour Authority.
Leachate problems over the years have polluted the ground with hydrocarbons down to 3m, and this has been compounded by groundwater at 2.5m depth. Extraction wells and pneumatic pumps had to be installed to dewater the area before the soil cleaning could begin. An oilwater separator is cleaning the water table.
A substantial volume of material is being processed - 8,500m 3of soil over a 10,500m 2area, weighing in at 16,000t. The ground at the site comprises a 100mm thick layer of concrete overlaying sand with some clay at 2.5m.
Key to the project has been Spanish company Geocisa's imported Enviro-Klean KM-4 thermal desorption unit, the first time the Canadian units have been used in Europe.
The process can remove all hydrocarbons from naptha to lube oil and crude oil as well as most pesticides, although it cannot clean soil contaminated with inorganic material such as arsenic.
The machine works by heating soil quickly to volatise the hydrocarbons. Material passes from the top to the bottom of the processor through a series of screw conveyors. As it drops between chambers the particles are exposed to a crossflow of hot air. A thermal oxidiser eliminates the hydrocarbons that have been released to the airstream.
The cleaned soil is discharged into a pugmill where it is cooled with water that also controls dust. From here, the soil travels on a discharge conveyor and is stacked for immediate use as backfill.
Post-combustion, released gases are scrubbed with a lime and water mix before being vented.This deals with any sulfur content, some of which may have come from the diesel fuel used to power the setup. The lime also absorbs any acids that may be present.
'Essentially, what's released into the atmosphere is carbon dioxide and water, ' explains Enviro-Klean commercial manager Simon Sherry.'The unit can handle 300t to 350t a day on a 16 hour shift, depending on the level of contamination, ' he adds.
Contamination levels at the site are generally between 1,700ppm and 33,000ppm, but in the areas of highest concentration, the soil may have to be mixed to bring it within the range that the KM-4 can process.
Geocisa contracts manager Fernando GarcÝa RodrÝguez says: 'You have to know the heaviest hydrocarbon so that you can set the temperature.' The 15% soil water content at the site is acceptable, he says, although less water means a more efficient heating process and a lower diesel fuel requirement. Current fuel use is 25 to 30 litres per tonne processed depending on the kind of material. This, it is claimed, is a 50% reduction to that used by a rotary kiln.
Sherry says that because the unit comes on single trailer, it offers further benefits over conventional systems.'A rotary kiln will use maybe seven trailers and take a week to set up - this machine takes half a day, ' he says.
Equipment manager Larry Howard adds:'One skilled operator can run this machine compared to the three or four for a rotary kiln.
Once it's working properly we can switch it to automatic. If an auger stops, the screws in front of it continue, the ones behind stop and the stuck auger tries to free itself while alerting the control house.' Sherry says the equipment will be available in the UK in early 2005 and will be operated as a joint venture between Pennine Vibropiling and Geocisa.
The E1.3M (£0.9M) Cßdiz remediation contract is due to finish in March.