Bavaria, Germany, Beratzhausen Wastewater Pressure Pipeline

Background

Nestled in the rolling hills of the Bavarian Upper Palatinate lies Markt Beratzhausen, the pearl of the Labertal valley. Under the responsibility of the local municipality, more than 27 pumping stations transport wastewater to the central sewage treatment plant in Beratzhausen, via pressure pipelines. Approximately 100,000 m³ of mixed wastewater is pumped per year, and there is also a stormwater reservoir with a volume of 300 m³ that is continuously emptied after rain events.

Challenges

High costs; high delivery head

Due to low volumes of wastewater (1,000 population equivalent), long retention times and high pump head, the wastewater treatment plant could only be operated at high pressure, generated by compressors. The pneumatic pump station features two vessels, into which sewage flows. When the vessel is full, sewage is pushed into the pipeline by the compressor. However, the silencer of the pressure vessel’s expansion was liable to freeze, even at an outside temperature of 20°C in summer, which made heating necessary. This resulted in enormous energy requirements, frequent malfunctions, high operating costs and extensive retrofitting work. These factors, together with air pockets that were inherent in the system, impeding flow and increasing the pump head, ultimately led to the need for hydraulic improvement of the pipeline.As with many assets that are situated in chambers below ground, communications for the smart system presented a challenge. Locating the antenna within the chamber would provide only an intermittent signal, so the antenna would have to be affixed to the outside of the chamber.

Solution

Venting the pressure line

As an immediate measure to solve the persistent operating issues and unacceptably high energy costs, it was agreed to manually vent the pressure line initially, to remove the diagnosed air pockets. A hole was dug in the ground at an agreed location and the pressure line was vented via a 32 mm tapping valve. This process took about 20 minutes, during which time a drop in the operating pressure at the pumping station from 7 bar to less than 4 bar was recorded. This confirmed the diagnosis of an air blockage beyond doubt.

The manual venting was then replaced by a single, A.R.I. compact shaft, type D-025- L-SB air valve which releases the air accumulations that were blocking the line. The ARISENSE smart air valve was installed with a manhole pit-level float switch sensor, enabling Wessex Water to know in real time if the manhole chamber of the air valve becomes flooded.

Result

Smooth operation; energy efficiency

Since its installation, the A.R.I. air valve has ensured automatic venting of the pressure line, maintaining the operating pressure at a value of approximately 3.6 bar – almost 50 percent less than before the valve was installed.

To avoid odor nuisance and deposits, the pressure line continues to be flushed by compressed air twice a day, again without any problems because the valve is equipped with an adjustable throttle for compressed air flushing. The result is trouble-free, energy-efficient operation of the pumping station.