Lendava wastewater treatment plant: a prime example of modern wastewater technology

The Lendava wastewater treatment plant is an example of modern wastewater technology and functioning cooperation between industry and the municipality. Embedded in the culturally rich town of Lendava, it has been ensuring that both municipal and industrial wastewater is treated efficiently and in an environmentally friendly manner for over two decades.

 

Lendava - A town on the border and a bridge between cultures

Lendava is located in the far east of Slovenia, nestled in the rolling hills of Prekmurje and close to the borders with Hungary and Croatia. At the foot of the Lendava Mountains and not far from the River Mura, the town reflects the rich cultural tradition of the region. Slovenians, Hungarians, Croats and people of other nationalities live together here, creating a multicultural center that shapes the identity of the town and municipality.

The municipality of Lendava is officially recognized as an ethnically mixed municipality: In addition to the Slovenian majority, an autochthonous Hungarian community is present in almost all settlements - with the exception of Benica and Hotiza. With an area of 123 km², the municipality of Lendava comprises 18 districts and 23 settlements.



Figure 1: View of the multicultural town of Lendava at the foot of the Lendava Mountains, where Slovenia, Hungary and Croatia meet. ©Ljuba brank, CC BY-SA 4.0, via Wikimedia Commons

 

Two partners, one goal: efficient wastewater treatment in Lendava

Since its commissioning in 2002, the Lendava wastewater treatment plant has been treating wastewater from the municipality and the pharmaceutical company Lek/Sandoz. The municipal wastewater from Lek/Sandoz flows into the treatment plant together with the other municipal wastewater via the sewer system.

Industrial wastewater, on the other hand, is conveyed via a separate pressure pipe, which carries around 20% of the total volume of wastewater fed into the treatment plant each year, depending on the hydraulic load of the treatment plant. With a high COD load (chemical oxygen demand), industrial wastewater can account for up to 80 % of the total COD load.

The ownership structure of the wastewater treatment plant reflects the partnership between industry and the municipality: 74.5 % of the plant is owned by Lek/Sandoz and 25.5 % by the municipality of Lendava. The daily capacity of the wastewater treatment plant is 29,000 population equivalents (PE) and it handles an average wastewater volume of 2,600 m³ per day.

Figure 2: Overview of the most important operating parameters of the Lendava wastewater treatment plant. © Donau Chemie AG

 

Multi-stage wastewater treatment

The Lendava wastewater treatment plant purifies wastewater using a combination of mechanical and biological processes and utilizes environmentally friendly, multi-stage treatment:

1. mechanical pre-treatment: coarse particles are removed to prepare the wastewater for the subsequent treatment stages.
2. aerobic biological stage: organic substances are broken down with the help of microorganisms to improve the water quality.
3. anaerobic biological stage: in the absence of oxygen, microorganisms break down organic matter, stabilizing the sludge and preparing the wastewater for subsequent treatments.
4. sludge dewatering and drying: The sludge is mechanically dewatered and thermally dried to reduce the water content and increase the energy density.
5. sludge disposal: Dried sewage sludge is disposed of in an environmentally friendly way by using it as fuel. Lek/Sandoz takes care of this part. The rest of the excess sludge that is not incinerated is disposed of by a company.

 
 

Automated process control and sustainable energy supply

Modern technology meets smart monitoring: at the Lendava wastewater treatment plant, automated systems control every process and seamlessly document the entire process history.

Under the leadership of Director Boris Nemet, the plant has been continuously modernized in recent years - with a new monitoring system in 2022 and a high-performance sludge dehydration line, which has been in operation since November 2023. In March 2024, a solar power plant was also connected to the grid to support the energy supply and ensure a sustainable future.

Figure 3: Director Boris Nemet emphasizes the importance of regular maintenance and the good condition of all technical systems. This is the only way the wastewater treatment plant can maximize the efficiency of its work processes. Donau Chemie AG

 

Monitoring water quality in our own laboratory

The wastewater treatment plant has its own laboratory, which checks all inflows, the operating parameters of the basins and the quality of the treated water discharged into the River Lendava on a daily basis. The following parameters are checked regularly:

• In the inflow: total nitrogen, total phosphorus, COD
• In the wastewater: Undissolved solids, total nitrogen, total phosphorus, COD
• Purification effect: Comparison of the inflow and purified wastewater values of total nitrogen, total phosphorus and COD.

All tests are carried out by an accredited institute, the National Laboratory for Health, Environment and Food.

 

Partnership with Donau Chemie

Donau Chemie also makes an important contribution to the smooth operation of the wastewater treatment plant. Wherever there is a need to reduce the phosphorus value in wastewater, our expertise and our own products make us the right choice.

In addition to a reliable supply of products for wastewater treatment, we also offer comprehensive support from our R&D department.

One such example is Lendava, which needed a more effective phosphorus precipitant. In the past, aluminum sulfate was used. As there were also problems with floating sludge caused by filamentous bacteria, a trial with a sample of the wastewater showed that our combination product of iron and aluminum was more suitable. This improved both the coagulation results in the wastewater and the decomposition of filamentous bacteria. This also solved the problem of floating sludge in the wastewater treatment plant.

Figure 4: On site on time: Donau Chemie tanker delivering to the Lendava wastewater treatment plant. © Donau Chemie AG
 

Finally, a big thank you to Mr. Nemet, who gave us exciting insights into the daily processes of the wastewater treatment plant. Every visit to Lendava leaves a positive impression and shows us what a strong and reliable partnership can look like.

We look forward to continuing our successful collaboration with the Lendava wastewater treatment plant in the future!

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