Restoration of lakes and fjords with pure
oxygen
Oxygen depletion caused by eutrophication is a common
problem in many lakes and fjords. It is caused by run-off of
nutrients from farmed land and by household
and industry sewage. Major efforts are well underway to address
these causes but it will unfortunately take a
considerable amount of time for the full impact to be
seen. The internal load will continue for decades.
Restoring lakes and fjords with pure oxygen (O2)
has an immediate effect. Oxygen prevents the release of
phosphorus and toxic gases (hydrogen sulphide and
ammonia) from the sediment,
accelerates the decomposition of “past sins” and
breathes new life into the environment.
As the only company in the EU we develop, install and
service oxygenation systems for deep lakes and fjords.
We have more than 20 years of experience with injecting
pure oxygen into deep bodies of water.
The method is gentle towards the environment. Oxygen is
a 100% natural substance with no adverse
side effects.
Our unique diffuser systems are highly effective. Up to
95% of the injected oxygen dissolves and is distributed
to all parts of the hypolimnion without disturbing the
thermocline. The oxygen saturation in the hypolimnion
can precisely be managed using a land-based control
panel.
An
oxygenation
system consumes very little energy. It runs with
the evaporation of liquid oxygen. Each system is
individually developed, designed and adjusted for the particular
conditions in a given lake or fjord.
We are happy to provide rough estimates of oxygen demand
and of the cost of installing and servicing.
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Example 1
Lake area: 3 km2
Depth: 30 m
Volume: 50 mi. m3
Retention time: 2 years
Lack of oxygen: 300 t/1st year *
Installation: 150.000 Euro
Oxygen: 50.000 Euro/1st year *
Maintenance/servicing: 30.000 Euro/year ** |
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Example 2
Lake area: 10 km2
Depth: 40 m
Volume: 150 mi. m3
Retention time: 5 years
Lack of oxygen: 800 t/1st year *
Installation: 350.000 Euro
Oxygen: 120.000 Euro/1st year *
Maintenance/servicing: 60.000 Euro/year ** |
* Consumption of oxygen will diminish from year to year.
** Includes full yearly servicing,
dynamic optimization
of oxygen input and full warranty within period of
service contract.
Lake Fure and Lake Hald
Lake Fure and
Lake Hald were for many years suffering severe problems
with poisonous H2S and cyanobacterial bloom which
caused death of fish and prohibition of bathing.
In both lakes these problems rapidly vanished after only
1-2 years with oxygenation.
Since 2003 Multidyk has been restoring Lake Fure with
pure oxygen. Lake Fure is located close to Copenhagen
and has an area of 10 km2 and a depth of 38
metres - the deepest lake in Denmark. After only a few
years the results are significant and well documented:
Lake Fure is changing remarkably for the better after
decades in very poor environmental conditions.
In Lake Hald, 31
metres - the second deepest lake in Denmark - the first
attempt of injecting pure oxygen into deep water was
made in 1985. Over time the technology has been
developed and the efficiency has improved radically. In
2006 we installed our newest generation of oxygenation
systems in Lake Hald. Today Lake Hald
is one of the cleanest lakes in Denmark!
In the figures
are shown “before” and “now” situations for the average
summer concentrations of phosphorous together with the
average secchi depth.
The effect of the
oxygenation is an impressive reduction of the internal
loading of phosphorous which leads to a reduction of the
production of plankton algae causing a much larger
transparency in the lake water.
In Lake Fure the
underwater vegetation now grows down to 8.5 metres and
in Lake Hald to 6.5 metres. And animal life is widely
spread even in the deepest parts of the lakes.
The restorations of Lake Fure and Lake
Hald are considered by many experts to be the most
successful environmental projects in Denmark. Hypolimnic
oxygenation has dramatically changed the environmental
conditions in two lakes of great biological
and recreational value.
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Restoration of Lake Fure,
EU-LIFE-project:
LIFE02NAT/DK/8589.
Final Report, page 44-45:
"The oxygenation project has demonstrated that it is
possible to achieve a significant and, above all,
rapid improvement in the environmental condition in
deep lakes with lack of oxygen in the hypolimnion.
In many similar lakes in the EU there are the same
problems as in Lake Fure. For decades phosphoric
waste-water has been discharged to the lakes
resulting in accumulation of a pool of phosphorus in
the sediments. The consequent seasonal internal load
will prevail for many decades and will be one of the
reasons why the
EU Water Framework Directive objectives
cannot be met within the time frames even if the
nutrient supply is reduced significantly.
In a transitional period, brief or long, the oxygen
supply can contribute to substantial improvements in
the conditions of lakes and the survival of
threatened species." |
