Mechanical recovery using specialised machinery
In
an attempt to mitigate the limitations and drawbacks of
earthmoving machinery (in particular the ecological impact)
and manual recovery (low output), pollution response specialists
naturally turned to specialised machinery, for improved
selectivity and output, in particular for small and medium-sized
scattered pollution. On sandy beaches, four recovery principles
have been tested:
-
Scraping and suction
- Sand screening
- Rollers
Scraping
and suction
On rocks, mechanical clean-up solutions are few and far
between, and generally involve suction using small industrial
vacuum units. Manual scraping can also be mechanised using
a tool made up of a brush fitted with a suction device put
forward by a Finnish company.
(datasheets: scraping using earthmoving equipment, scraping/pumping using specialised machinery, scraping using specialised machinery)
Sand
screening (datasheet)
These machines were developed a few decades ago to respond
to a need different from that of oil spills: clearing large
solid waste from beaches. Various models exist, ranging
from large screeners (either towed, mounted or self-propelled)
to small self-propelled screeners. Most of them function
via the same principle: the surface layer of sand is removed
by an adjustable blade, then lifted by a continuous conveyor
belt, on which the screening takes place, and the refuse
is collected at the end of the belt’s stroke.
This equipment was first tested for oil spill response during
the Tanio pollution (1980), where it proved to be effective
on dry to slightly damp sand for recovering clusters of
viscous pollutant in the form of tar balls, patties and
patches, with certain adjustments.
Although the performance of different models of sand screeners may vary, the quality of screening does not only depend on the machine: the tractor, which must have certain particular characteristics, and the operator responsible for making the appropriate adjustments both play an equally important role.
Rollers (datasheet)
One of the first rollers was designed by Cedre in the early
1980s, although it never progressed beyond the prototype
stage. During the Erika, a private company put forward another
prototype, which could not however really be used as it
was only finalised when the arrivals began to peter out.
This principle of oil adhering to a special covering was
a particular point of interest during the Prestige spill,
when different type of rollers were developed to recover
the fragmented pollutant freshly deposited on the beaches,
their performance, advantages and limitations varying from
one model to another.
Table comparing specialised machinery
