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BIOLOGICAL BIOREMEDIATION OF THE ZIMNA WODA LAGOON IN ŁUKÓW  2018-2021

The Zimna Woda lagoon in Łuków is a reservoir with a very weak flow. The reservoir is located in a natural depression in the terrain, it is protected from the wind on two sides by trees. The reservoir is intensively used for recreation and has a decorative function.

About the Zimna Woda Lagoon

  • The reservoir was mechanically cleaned in 2017 and 2018 - the works lasted until the turn of May and June 2018. The renovation works consisted of completely draining the water and mechanical removal of the bottom sediment - silt.

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  • During these works, all clusters of aquatic plants were mechanically removed. All these activities led not only to the complete sterilization of the reservoir (destruction of the entire biological structure and death of most living organisms), but also deprived this ecosystem of natural defense mechanisms against pollution - the so-called self-purification of surface waters.

  • Such a sterile environment is inhabited by expansive and undemanding organisms. This means that in June and July 2018, strong large-area algae blooms occurred in the reservoir, and there was a strong putrefactive odor on the shores.

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  • Aquatic plants are one of the most important elements of any aquatic ecosystem because they not only constitute food competition for algae and block their development, but also absorb nutrients, filter, purify and oxygenate water.

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  • The shores of the reservoir are natural, locally reinforced with stone thresholds and spurs. There is a swimming area and a new tourist infrastructure on its shore.

In 2018 - in September, the process of restoring biodiversity in the Zimna Woda Lagoon in Łuków was started. The reconstruction of the natural, ecological and biological functions of the reservoir was based on two blocks of actions:

1

Construction of plant ecotones

2

Bioremediation

Bioremediation treatments performed in 2018-2020 brought the expected results. The algae blooms stopped, the silting of the bottom completely disappeared and the water quality in biological terms improved.

The plants have taken root properly and are in good condition.

2018

The tank after draining the water and after mechanical work

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vs.

2020

The reservoir after the use of ACS technology

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Reservoir condition in 2020 and 2021

In accordance with the assumptions of the technology used, the effects are assessed after twelve months.

This is necessary due to the observation of the reservoir in accordance with all cycles occurring in nature.

The general condition of the reservoir, water vegetation were assessed and the measurements of the amount of organic bottom sediments and water transparency were compared.

In addition, chemical tests of the water were carried out.

Thickness measurements of bottom sediments

Measurements were made at four points marked on the attached map. These places were selected due to their greatest importance for the functioning of the entire bathing area and showing the variability of parameters in the study area.

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24 czerwca 2019

  • P1- 75cm

  • P2 - 45cm

  • P3 - 60cm

  • P4 - 75cm

24 Lipca 2020

  • P1- no silt

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    P2 - no silt

  • P3 - 5cm

  • P4 - no silt

On June 24, 2019, at point

P1 there was a layer of mud with a thickness of 75 cm, in P2 - 45 cm, in P3 - 60 cm, in P4 - 75 cm

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After 12 months, on July 24, 2020, no silt was found in the points

P1, P2 and P4, and at point P3 a layer of mud with a thickness of 5 cm. This means complete desludging of the bottom.

 

After another 12 months - in 2021, at point

P1 there was a layer of silt with a thickness of 32 cm, in P2 - 15 cm, and in P3 - 2 cm, in P4 - 0 cm (no silt).

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Compared to 2021, bottom desludging of approximately 57-100% was achieved. The appearance of bottom sediment at points P1 and P2 (level 30 - 40% of the original state - before the start of bioremediation) indicates a fairly rapid silting of the bottom in these places of the reservoir

Water transparency measurements

June 24, 2019

  • P1- 60cm

  • P2 - 90cm

  • P3 - 110cm

  • P4 - 90cm

July 24, 2020

  • P1- 38cm

  • P2 - 45cm

  • P3 - 37cm

  • P4 - 42cm

Transparency  was measured using a Secchi disc at the same points as the bottom sediment.

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In 2019, the water transparency was:

P1 - 60 cm, w P2 – 90 cm, P3 – 110 cm, w P4 – 90 cm.

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After 12 months - in 2020, the water transparency was:
P1 – 38 cm, w P2 – 45 cm, P3 – 37 cm, w P4 – 42 cm.

 

Such low transparency is due to the large amount of suspension probably created during intensive construction works carried out in the immediate vicinity of the lake. Moreover, the tests were performed after long-term, intense rains.

Additionally, there are still too few aquatic plants in the tank, which results in reduced filtration and water purification.

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After another 12 months - in 2021, the water transparency was:

P1 – 35 cm, w P2 – 50 cm, P3 – 53 cm, w P4 – 35 cm.

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The greatest increase in transparency was found in point:

P3 – aż o 43 % oraz w punkcie P2 – o 10 %.

 

At points P1 and P3, a decrease in this parameter was found by 2 - 17%. This is due to the fact that there are still too few aquatic plants in the tank, which causes reduced filtration and water purification.

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In addition, the improvement in water transparency at points P3 and P4 is the result of inoculating these places with microorganisms in 2020

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