Domestic waste water is coming from the city of Samokov and the villages along Black Iskar river. Despite the long road of the river and its natural purification function the water reaches polluted to some extent the Iskar dam. Because of that it is important to find an effective way to purify the water around the reservoir.

Artificial wetlands are used in a lot of countries to treat the polluted water. Wetland plants (commonly reeds) transfer atmospheric oxygen down through their roots. The process involves bacteria that are located around the plant's roots. These bacteria use organic pollutants as food source, degrading a wide range of organic chemical products and turning them into harmless components. Thus, each reed is actually a small natural water treatment plant.

Several studies show that reed bed treatment is far more effective and cheap in comparison with traditional water treatment plants. And water treatment can be done not only in the summer but also in the winter when the deed beds look dry.