The company operating the Wansdorf sewage plant, which was completed in 1998, is a co-operation between Berliner Wasserbetriebe, four municipal authorities and a special-purpose association in Brandenburg. More than half of the waste water purified in Wansdorf comes from Brandenburg, and the rest comes from Berlin. The plant was designed for a population equivalent of 200,000.
As the waste water being purified is mainly communal, plus an additional quantity of industrial waste water, the volume of water being purified has a pollution load which corresponds to a population equivalent between 300,000 and 320,000. The maximum capacity of the sewage plant is 40,000 cubic metros of waste water every day.
Until then, the oxygen for the aeration basin had been generated by three turbo compressors, supplied by a company now owned by a German concern.
Practical experience provided the proof
However, in March 2013, permanent and costly maintenance and repairs led to an exchange of the old compressor for an AERZEN Turbo. “The old units were compressors with integrated inlet and outlet guide vanes”, explains Dipl.-Ing. Uwe Klauditz, an employee of Berliner Wasserbetriebe and technical operations manager
of Wansdorf sewage plant. “This required extensive technology and very special knowledge for maintenance. Accordingly, the costs for maintenance work and overhaul were high. We absolutely wanted to end this unsatisfactory situation.” So they decided to check with the Turbo blower made available by AERZEN, the suitability of the new Generation 5 series under practical conditions. It is a decision they did not regret, and it was the test that convinced them: “We immediately used the packaged unit via the integrated demand-dependent control in continuous operation. Following some subsequent improvements at the beginning of thetest phase, the result for us was so positive that after one year we decided to purchase the test unit”, says Klauditz.
AT Turbo for the base load
Currently, the new AERZEN turbo blower operates autonomously via its own control system; in future it is planned to be integrated as base load blower into the overriding, pressure dependent control system of the complete station. Then the two remaining units with demand-dependent capacity will cover the peak demand. Nowadays there are many good arguments for turbo blowers in biologically working large-scale sewage plants: the AERZEN compressor system works very reliably, offers high energy efficiency, distinguishes itself by high conveying volumes and offers sufficient maximum pressure of up to 1.0 bar. The new Aerzen AT-turbo blowers are driven by high-speed permanent magnetic motors (PM-motors) and may be adjusted via a frequency converter without additional mechanical adjusting devices infinitely variable between 40% and 100% to fluctuating air needs.
In the absolutely oil-free working units the only medium to be compressed in these units is the air that is used for the bearing of the shaft and for cooling the system. The new AT-series “Generation 5” made by AERZEN works with a corrosionresistant and robust impeller made of stainless steel. Its high strength makes reduced wall thicknesses possible, offers better aerodynamics and considerably improved efficiency.
The especially manufactured frequency converter also contributes to this improved efficiency. Due to permanent monitoring in case of unforeseen pressure fluctuations it avoids an uncontrolled shutdown of the machine to the surge limit.
Higher safety, lower costs
According to Managing Director Axel Swoboda, the new AERZEN turbo blower in Wansdorf makes a significant contribution to the legally conformant operation of the sewage plant - thanks to a stabilization of the stipulated inflow values of the purified waste water into the open water. The energy consumption of the blower station, by far the biggest energy consumer at Wansdorf sewage plant, cannot be recorded separately. But since the commissioning of the AERZEN unit the expenditure on energy for the entire sewage plant has reduced considerably compared with previous years.
Klauditz is sure that this positive development is mainly due to the high energy-efficiency of the new Aerzen Turbo blower. “Also, as far as energy costs are concerned, with AERZEN we are obviously on the safe side”, emphasizes Klauditz.
Therefore, based on their positive experiences, in case of further investments being made into oxygen generation, they will contact AERZEN again immediately.