Since the wastewater treatment plant was built in 1993, steel augers had been in use for the return sludge, and these had been subjected to heavy wear and tear over the decades. Corrosion, material fatigue, and increasing maintenance requirements made it increasingly clear that a sustainable solution was needed.

The ongoing operation of the wastewater treatment plant could not be interrupted at any time. Consequently, the time window for replacing the screws was extremely tight. Therefore, a solution was needed that was a perfect fit, quick to install, and permanently reliable.

After taking precise on-site measurements, the decision was made to install the RobaScrew compact lifting screw in a trough-in-trough configuration. This design allows the old screws to be replaced without having to laboriously dismantle the existing reinforced concrete trough—a decisive advantage for an efficient retrofit. Installation was carried out by the Röchling service team and was completed within 1.5 days.

Along with the new RobaScrew compact screw conveyors, a modern drive system with variable-frequency drive control was installed. The result: energy savings of 48,000 kWh per year, a reduction of 18.3 tons of CO2, significantly lower maintenance requirements, and high corrosion resistance thanks to Robalon®.

In Olbernhau, the existing lifting screws in the feed section had become worn after many years of operation and were to be replaced as part of a modernization project. At the same time, the trough required refurbishment. The system consisted of two screws with a diameter of 500 mm and a flighted length of 7,000 mm.

The planned Robalon® trough lining reduced the available diameter for the screws. Nevertheless, the required conveying capacity of 25 l/s still had to be reliably achieved.

Precisely manufactured RobaScrew lifting screws were used, which were optimally matched to the new trough lining. The custom-designed construction enabled quick and smooth installation within a tight timeframe.

Since commissioning, the system has impressed with its quiet, smooth, and efficient operation. The combination of RobaScrew lift screws and trough liner ensures reliable conveying and a robust, long-term solution.