A new Flottweg decanter with a simple rotor exchange – Turku waste water treatment plant opts for modernization measures and ensures cost efficiency

Turun seudun puhdistamo Oy is a wastewater treatment service provider serving around 14 municipalities. The sewage treatment plant in Turku (Kakolanmäki Wastewater Treatment Plant, or WWTP for short) is also part of this association. It processes the wastewater of almost 300,000 inhabitants of the Turku region as well as the industrial wastewater produced in the area. The special feature of the sewage treatment plant is that it was built completely underground for spacial reasons and thus functions as a separate small town beneath the city. 

Significant cost savings after initial modernization measures

Until 2018, the sewage sludge dewatering of the entire plant was carried out using two older decanter centrifuges. Due to poor separation results, Kakolanmäki WWTP decided to take action by modernizing its wastewater treatment: After a detailed examination and consideration of several key factors, such as price and performance, the sewage treatment plant decided to buy two C7E decanter centrifuges from Flottweg in 2018. After only a short period of operation, very positive developments emerged: "In the first two years of operation, we have already saved sludge costs of €150,000 per year, as the dry solids content has increased by about five percent. At the same time, we have saved polymer costs of around €15,000 per year and energy costs of around €3,000 per year," explains Jouko Tuomi, process engineer at the sewage treatment plant. As a result of the savings, the operators of the sewage treatment plant have been able to recoup the acquisition costs of the machines after a single year.

Further modernization measures through the switch to the Flottweg Xelletor

Despite very good dewatering results and associated savings, the sewage treatment plant decided to carry out further modernization measures in its sludge dewatering. In 2022, Tuomi learned about Flottweg's Xelletor machines at the IFAT trade fair in Munich, which achieve even better dewatering results and produce further savings in terms of energy and polymer costs. "Sludge dewatering is an important process for us, as sludge disposal is a major cost factor. That’s why it is important for our machines run reliably," explains Tuomi. For this reason, the sewage treatment plant decided to carry out further tests with the Xelletor. The aim was to further optimize the cost efficiency with regard to the TS value as well as energy and polymer consumption within the sewage treatment plant. 

The special feature of the Xelletor machines lies in the innovative design of the scroll body. The grid construction saves energy and reduces polymer consumption, while the Xelletor also enables better dewatering performance. Customers who already own a Flottweg decanter and want to achieve more efficient results can choose to modernize the centrifuge through a rotor exchange. In this case, the old rotor is replaced by a new rotor with a Xelletor scroll. The conversion only takes a few hours and only briefly interrupts ongoing operations. This means that it is not necessary to purchase a completely new machine, but only the rotor with the scroll. With the Xelletor Exchange Program, Flottweg offers its customers a simple and cost-effective way to modernize their processes. 

In 2023, the sewage treatment plant in Turku finally decided to replace one of the two rotors to increase efficiency. Previously, a number of tests had been carried out with a test rotor in the sewage treatment plant, which underlined the potential savings. And with amazing results: "We learned that by using the Xelletor machines and adjusting some parameters, we can dewater even more sludge" explains the project engineer. “Because we dispose of the sludge externally - which accounts for most of our costs - increasing sludge dewatering by 1% is very important to us.” In addition, the Turku sewage treatment plant has achieved 15% energy and polymer savings with the Xelletor rotor. This is directly reflected in the costs: "We save tens of thousands of euros annually, which means the Xelletor rotors have already paid for themselves after just a few years," says the process engineer. Based on these convincing results, the sewage treatment plant decided in 2024 to also replace the second rotor, which will commence operation in 2025. To cover maintenance requirements or in the event of unplanned incidents, the Turku sewage treatment plant decided to keep the replaced C7E rotor as a spare. 

All-round service: maintenance contract and training at the Flottweg Academy

To ensure the machines run smoothly and do not endanger daily operations, the sewage treatment plant has a maintenance contract with Flottweg. "When we call Flottweg, they come to us and check that everything is working properly. This gives us the security that the machines will continue to work without issue throughout the following year."

In addition, some of the process engineers completed a training course at the in-house Flottweg Academy. There they received a full insight into the machine and its functioning, and also got to know Flottweg as a company. "My personal highlight in the training course was the factory visit and the technical training. We had the opportunity to dismantle and reassemble the machine, which gives you a better feel for its inner workings," reports Tuomi. 

Three reasons to choose Flottweg

Due to the smooth cooperation over the last few years, the Turku sewage treatment plant is very happy with its Flottweg machines. Both the cost savings achieved by purchasing the two C7E Decanter centrifuges and the further modernization measures with the Xelletor rotor exchange presented the sewage treatment plant with convincing arguments. Flottweg’s comprehensive service rounds off their experience with the industrial centrifuge manufacturer. Process engineer Tuomi is completely convinced: "There are three reasons why we would definitely choose Flottweg again: the price, the quality of the machines, and the team behind Flottweg have left us nothing but impressed."

 

Author: Julia Deliano, PR and Content Manager, Flottweg SE