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Teaching in Practice: Biological Treatment of Polluted Water

Carmen Bucovala is a teacher of biology from the Ovidius High School in Constanta, Romania. She came up with a nature-inspired outdoor project and resource for secondary level students of science and biology. Carmen and her pupils put in place a real life water treatment project for the Tabacarie Lake in Constanta, and learnt more about local ecology - she explains more about how she and her pupils worked outside.

Water pollution causes loss of biomass, affecting some organisms until they disappear and also blooms of phytoplankton destroying the ecosystems, due to the loss of oxygen from the water. The most important measures to remediate the area were building dams, cleaning residual water, building areas of protected water, and building special places to collect the residues, to prevent direct discharge in the surface water.


The objectives of the project we developed with the students were to:

  • Identify living organisms in Tabacarie Lake
  • Show the importance of specialized bibliographical information
  • Study the material in the mass media relating to the problem of polluted water in Tabacarie
  • Lake and the influence on people’s health
  • Demonstrate experimentally the effects of the chosen plant species on polluted water
  • Present the location of the lake and the most populated districts in Constanta
  • Evaluate different types of pollution in the Tabacarie Lake
  • Propose solutions for using the resulting biomass gained from the increasing population of aquatic plants
  • Study the knowledge of the local population about this issue
  • Disseminate information collected and propose adequate actions.

Why is the area polluted?

As every kind of pollution eventually ends up in water, the hydrosphere is the most polluted domain. Water is very important in nature, and its protection must be considered when thinking about the future of our planet. The Tabacarie Lake, located in the Mamaia-Constanţa zone has suffered a quick process of clogging and eutrophication, demonstrated by the accumulation of organic sediments accelerated by pollution and permanent algal blooms.

The lake lies in Mamaia, a tourist area, near centres of entertainment and leisure. The lake drains into the Black Sea, and so the water has to be kept within certain quality limits so that it doesn't affect the health of tourists, local people and the wider marine ecosystem.

Natural approaches

Using natural methods to clean the lake's water represents an efficient and revolutionary solution. This can be made possible by studying the support capacity of the Tabacarie Lake ecosystem and by reducing the rate of pollutant discharge under the tolerance limit, thus using the self-cleaning capacity of the lake.

Another very efficient method is to introduce exotic species with a high efficiency of bioaccumulation and bioconversion. They contribute to the remediation of the lake, together with the indigineous species found there already. Pistia stratiotes and Eichhornia crassipes are two species of tropical plants with a high efficiency of accumulation of toxic substances and conversion, which were used in the project.

Seasonal changes

From our experiments, we noticed that the lake undergoes important changes according to the seasons – we tested both water quality and physical and chemical indicators. The main cause of these variations is the pressure of people using the lake and its surroundings – due to waste from homes and industry, which are very rich in nutrients and other organic substances. These drain into the lake and make it clog up and eutrophy very quickly.

The knowledge of the clearing process and the necessity to make that efficient has conducted to the use of native, aquatic plants like Pistia stratiotes and Eichhornia crassipes. Introducing them to the lake has proved that the pollutants can be converted into biomass.


We reached the following conclusions:

  • Using “green filters” in the form of aquatic macrophytes is highly efficient, and works better than the typical methods used
  • The plants clean the areas of water with high levels of organic substances, through bioaccumulation and bioconversion
  • Highest efficiency of cleaning is found in polluted waters that have a high level of organic substances
  • The plants can be easily transported for cleaning in distant areas, with the condition that they are kept in plastic bags, which prevent the water from evaporating. As they are tropical plants, during winter they can be kept in glass-houses
  • The macrophytes can be valuable after. For instance, they are not toxic for animals, and they contain proteins, pigments etc. so could be used as food for animals, for the extraction of pigments and proteins; for alcohol, biogas or other fermented products
  • The plants can also be used to extract metals or radioactive elements from the water
    The plants have fundamentally changed the principal physical and chemical states of the lake
  • The physical and chemical qualities of the water have strong influences on plant growth - the increase of biomass is proportional to the quantity of organic substances found in the water
  • Bioremediation using these macrophytes is not polluting, does not consume energy, and imitates natural processes – plants are a great technology for the future to improve water quality.

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