STADTWERKE FLENSBURG - Sludge thickening plant with PolyLines from sera

1. The challenge

The process of mechanical sludge thickening at the Flensburg sewage treatment plant was to be operated more economically and stably during its new construction. The existing operation caused high flocculant consumption and limited the achievable dry matter content. At the same time, operational safety, throughput, and operability had to be improved. The goal was a solution that would integrate the polymer approach into the new plant in a reproducible, process-safe and efficient manner.

2. The sera solution

sera supplied a custom-designed 2-chamber oscillating polymer preparation station made of stainless steel, each chamber with a 2 m³ usable volume. While polymer solution is prepared and brought to optimal maturity in one chamber, the second chamber is ready for withdrawal—thus ensuring an uninterrupted supply. Two eccentric screw pumps with dry-run protection and overpressure protection convey the polymer solution to the belt thickener. The system was equipped with a custom control system (9" panel) and integrated into the wastewater treatment plant’s central process control system. Large tank lids facilitate maintenance and operation during ongoing operations.

3. Customer Benefits

• Significantly lower flocculant consumption
• Increased final dry matter content of the thick sludge to 6–8%
• Higher operational reliability and increased throughput of the plant
• Reduced energy and operating costs of the sludge line

4. Summary

The project demonstrates: A stable, precise polymer dosing system is a direct driver of cost-effectiveness and process performance in sludge thickening.