Efficient polymer metering - Mannheim sewage plant

Five PolyRex systems from ProMinent GmbH have been operating successfully at the central sewage treatment plant in Mannheim for several years. There they reliably and precisely meter polymer solutions in the advanced treatment stage and during thickening of the sewage sludge.

Optimised waste water treatment through the addition of polymers

Every day, the central sewage treatment plant near Sandhofen treats an average of 81,000 m³ of waste water from households and industries in the city of Mannheim. To remove pollutants, the waste water passes through a multi-stage mechanical and biological treatment process within 24 hours. A new advanced treatment stage was built in 2015. Before the waste water treated with powdered activated carbon is fed into a sedimentation tank, a precipitant and a flocculation aid (polymer) are added to improve and speed up sedimentation. Initially, two PolyRex systems from ProMinent GmbH were used for this purpose. In 2020, the existing polymer preparation systems for sludge dewatering were replaced due to their age. To thicken the sewage sludge, the polymer solution is added upstream of the excess or raw sludge centrifuges. Based on its positive experience with the first two PolyRex systems, the city of Mannheim decided to install three more of the same.

Key data

  • Multi-stage cleaning of an average of 81,000 m³ of waste water per day and sludge treatment in Mannheim’s central sewage treatment plant
  • Use of five PolyRex metering systems with maximum extraction rates of between 1280 and 3200 litres/h (equivalent to 6.4-16.0 kg/h of polymer) and corresponding big bag emptying system for each one
  • Metering of dry powder and liquid flocculation aids (polymers) to optimise sedimentation and for thickening of the sewage sludge

PolyRex systems – well thought-out and efficient

These robustly designed systems for different capacity ranges can be used to process and optimally utilise liquid and dry powder polymers. They are therefore suitable for various applications, such as in the Mannheim sewage plant, and can be integrated into the customer's master PLC. The double-deck batching station consists of the feed and mixer unit and two stainless steel tanks. The upper tank is the batching/maturing tank, whilst the lower one is for storing the prepared polymer solution. The dry powder polymer is transported via a big bag emptying system or vacuum conveyor to the powder feeder which has two conveyor screws and is mixed with water in three stages in the mixer unit below. The solution is pumped into the upper tank by the water pressure of the dilution water. This allows the polymer solution to mature completely, avoiding a short-circuit effect. After maturing, the solution can be transferred to the lower supply tank via a motorised valve.

Precise and versatile metering systems

After a short installation period, the first two PolyRex systems were put into operation at the end of April 2016. As per the process described above, the required polymer solution is prepared in exactly the right concentration. ProMinent also supplies the pumps used for precise metering. This effectively supports sedimentation in the advanced treatment stage at the Mannheim sewage plant. Since early 2020, three further PolyRex systems operating according to the same principles have been ensuring extremely reliable thickening of the sewage sludge. For greater flexibility in terms of polymer availability, liquid polymer can also be used in addition to the dry powder version. Thanks to their smooth operation and precise metering, the five PolyRex systems are playing a key role in waste water treatment – to the delight of the city of Mannheim and its residents!

  • Dust-free filling of the powder storage tank by big bag emptying system or vacuum conveyor
  • Water apparatus with wetting cone and injector for producing a homogeneous polymer solution
  • Slow-running stirrer in the upper tank for gentle mixing of the polymer solution
  • High dosing precision ensures the lowest possible chemical consumption
  • Long system service life thanks to robust stainless steel design

Used Products - Efficient polymer metering - Mannheim sewage plant

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