Water technology expedition: Donau Chemie on a voyage of discovery at the Piran wastewater treatment plant

Donau Chemie Water Technology
In November 2023, our water technology expert Uroš Dežman, accompanied by entrepreneur Marko Lokas from Okolje Piran, embarked on an exciting expedition to one of our long-standing customers, the Piran wastewater treatment plant. We have maintained a successful business relationship for seven years now, offering our products for phosphate precipitation.

Piran - a jewel of the Adriatic coast in Slovenia

Piran, the picturesque town on the Slovenian Adriatic coast, is home to the municipality and administrative unit of the same name as well as the port captain and the international border crossing point for maritime traffic.
Piran exudes Mediterranean flair to perfection. From the spacious Tartini Square, you are only a few steps away from the winding old town. Also best known as a vacation destination. Here you can enjoy sun, summer, cocktails, fish and seafood, including Slovenian hospitality. A beach vacation in its purest form can be found in Portoroz. It is known for its family-friendly beaches.
With a population of around 4,000 people, this medieval town offers a charming atmosphere characterized by narrow cobblestone streets, Venetian architecture and a variety of historical sights.
Piran's roots date back to Roman times, while the town gained great importance during Venetian rule in the Middle Ages. A striking landmark is the Gothic church of St. George, which towers majestically over the town and offers a magnificent view of the turquoise Adriatic Sea.

Piran Overview
The enchanting town of Piran delights visitors with its rich history, fascinating
architecture and breathtaking views. © Uroš Dežman


The construction of the Piran wastewater treatment plant

The Piran wastewater treatment plant was built in 1999 with the financial support of the European Union and a national environmental protection program. For Slovenia, it is an essential obligation to discharge wastewater into the Adriatic Sea only after thorough treatment in order to preserve the cleanliness of the sea.


left: The entrance to the wastewater treatment plant is located to the right of the administration building, with
Piran's central garage to the left. right: Dosing system of Donau Acquabella plus. © Uroš Dežman

The Piran wastewater treatment plant in new splendor

The Piran central wastewater treatment plant plays a key role in the collection of municipal water and rainwater from various neighboring towns. These include Piran, Portoroz, Lucija, Seca, Fiesa, Strunjan and Malije within the municipality of Izola.
In 2009, the wastewater treatment plant underwent a comprehensive renovation and modernization. The measures not only included mechanical treatment, but also expanded the capacities for biological and chemical processes for wastewater treatment. The plant now has a capacity of 33,000 PE (population equivalent).

A tour of Piran's wastewater treatment plant

The plant structure of the sewage treatment plant comprises several key components that effectively contribute to the purification and treatment of wastewater:

  • These include an inlet pumping station, a fine screen and a grit chamber with grease separator, which support the initial wastewater treatment process. 
  • In addition, there are four successive basins for the biological and tertiary treatment of wastewater to ensure comprehensive purification. 
  • A central five-blower system provides the necessary aeration during the purification process. 
  • Various facilities are available to handle the sewage sludge, including a sludge thickener and storage tank as well as a mechanical sludge thickening system. 
  • An air filter is an integral part of both the mechanical and biological treatment steps to ensure optimum purification. 
  • The treated water is discharged via two underwater outlets, which are 3,600 meters and 3,450 meters long respectively and are each equipped with a diffuser at the end.

The systems ensure efficient and environmentally friendly discharge of the treated water into the surrounding waters. In addition, the plant enables the disposal of sewage sludge and sludge from septic tanks and small sewage treatment plants in a comprehensive and environmentally friendly manner. 

In winter, dolphins can often be seen in this part of Piran Bay. The proximity of the sewage treatment
plant to the central garage (right), away from the car-free old town area, gives tourists the impression
that Piran attaches great importance to compliance with European standards. © Uroš Dežman

What is a major threat today ....

This year, Slovenia has experienced the drastic effects of climate change at first hand, particularly through the floods on August 4, 2023. At the same time, the far-reaching problem of microplastics in our seas and rivers must also come into focus. 

Strong south wind leads to considerable damage (3.11.2023). © Uroš Dežman

Uroš Dežman / Marko LokasOur trip is slowly coming to an end...

With the end of our trip comes the moment when we would like to say a special thank you to Mr. Lokas. His fascinating tour of the Piran wastewater treatment plant was more than just informative - it was an eye-opening journey through Piran and its fascinating surroundings.

A big thank you for this extraordinary experience!


Entrepreneur Marko Lokas (right)
and Uroš Dežman, (left) © Uroš Dežman

Donau Chemie Water Technology
Visit our website to find out more about our state-of-the-art water treatment products and their applications.


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