Separator's Digest - GEA Westfalia Separator Group

in peru, a country with an important fish
industry, the government has introduced
new environmental legislation, including a
requirement for all companies in the fish
meal industry to employ better treatment
for effluent which is generated. since this
year, this has been practiced very successfully
by the largest fish meal manufacturer in the
world, namely Technología de alimentos
s. a. (Tasa), using a special decanter from
Gea westfalia separator systems.
Processing transport water
fishing vessels discharge their haul directly
into the factory from the vessel via large
pipelines. sea water is used as the transport
medium. when it is pumped through the
pipelines, this transport water becomes
contaminated with fish particles and fish
oils. in its 17 fish meal factories in peru with
a total capacity of around 250,000 tonnes
of fish p. a., Tasa produces between 80 and
150 tonnes fish / h. approximately three
times this quantity of water is required for
conveying the fish from the fishing vessel to
the factory. This is equivalent to a pump
water quantity of around 250 to 450 m³ / h
in the various production facilities. Until
several years ago, this pump water which
contained oils, fats and solids, was
discharged untreated into the sea. at the
end of 2007, Tasa then installed a processing
stage at its location in pisco­ica with
a capacity of 140 tonnes fish / day; the main
aim of this installation was to recover the
oils, fats as well as the solids contained in
the water so that they could be further
processed in the production process. for
this purpose, the pump water is initially
floated in a daf unit (dissolved air flotation),
and is then processed via two three­phase
decanters type Ucc 458. These machines
separate the transport water into oils and
solids, which can be further processed, as
well as effluent.
Second treatment stage
however, the water remaining from this
initial flotation process still contains excessive
levels of oils and fats (3000 to 5000 ppm)
and solids (8000 to 10,000 ppm). however,
in its new legislation, the peruvian government
has specified values of 1500 ppm oils
and fats and 2500 ppm solids specifically for
the fish meal industry. But this is not enough:
in four years, these figures will be reduced
further to 350 ppm (oils and fats) and
700 ppm (solids). further effluent treatment
using a second flotation unit was necessary
GEA Westfalia Separator Systems 33
Separator’s Digest 3 | 2008
for this purpose, with subsequent effluent
clarification using a two­phase decanter.
The focus is not on recovering the oils and
fats; instead, the overriding objective is to
ensure that the clarified phase has to be as
clean as possible before being returned to
the sea. for this purpose, Tasa employs
type Ucd 755 decanters with new
technology using polymer flocculants.
New technology
only with the introduction of the new
technology was it possible for the 2­phase
decanter to be used for this application.
with this technology, separation was
increased from between 50 and 60 percent
to between 95 and 98 percent. The solution
functions as follows: the level of liquid in
the decanter has an effect on the clarification
performance. This so­called pond depth can
be regulated by means of regulating rings
in the discharge of the clarified liquid. if
the aim is to achieve a high degree of
clarification, the pond depth has to be
changed. if an optimum pond depth is
achieved, the turbulence in the settled solids
is reduced, and there is an improvement in
the caking of the oil which is still contained
in the effluent to the solids as well as the
settling behaviour of these solids.
Legal requirements have
been more than met
with the installed decanter, Tasa is able to
recycle a very clean centrate back into the
second daf unit. in practice, the legal
requirements are more than met. This
extensive processing of the pump water in
the peruvian fish meal factory can be
transferred to the world­wide fish meal
industry, specifically in south america and
asia in order to minimise effluent discharge
values and to protect the ocean, which is
the basis for fishing and fish processing. in
the next fishing season, there are plans for
even more extensive trials with decanters in
order to improve clarification even further.
for a clean ocean.