Rotary lobe pump IQ112-81: Easy to use in the most limited of spaces

Case Study - Freiberg sewage treatment plant


Little space for installing, servicing and maintaining an additional pump


Vogelsang rotary lobe pump IQ112-81

The customer

The sewage treatment plant of the city of Freiberg / Neckar was put into operation in 1964. Over the years, the plant has been modernized and expanded many times. It is now designed for up to 25,000 population equivalents. In addition to the mechanical, biological and chemical treatment stages, the treatment plant includes a sludge digestion system. The digestion tower was also built in 1964, it has a capacity of 1,100m³ and is fed with about 30m³ of thickened surplus sludge and 30m³ of primary sludge each day. Added to this each week is about 2m³ of a mixture of grease and water from the longitudinal sand trap. The fermentation gas is utilized in a combined heat and power plant with 50 kWel and 100 kWth. At 100% capacity utilization, it was possible to generate in-house 61% of the electricity required by the plant. The heat is used to heat the plant's own building, the neighboring municipal building yard, three homes, a sports hall with a stadium, restaurant and apartment.

The problem

In 2012, further improvements for the sludge digestion were planned. To reduce the production of sewage sludge, there was a plan to increase the DM content in the digestion tower by drawing off about 75m³ sludge each day into a bypass, dehydrating it to about 20m³ using the existing belt thickener and then returning it to the digestion tower. As multiple progressive cavity pumps were already in use, the plans also included installing another pump of this kind.

The solution

"We then found out about the new IQ series from Vogelsang at IFAT," says wastewater manager Sternkiker. "The compact type of construction is very handy for us, given the lack of space in our pump room. The flexible connector parts made it easy to connect the pump to the pipe system. Despite our well-functioning screen, we're constantly finding foreign matter in the sludge, so we liked the higher resistance to foreign matter provided by the integrated InjectionSystem. And even if a clump does clog the pump, the quick and easy access to the pump chamber and pumping elements means that we can fix the malfunction very quickly – unlike with our progressive cavity pumps," says Sternkiker, explaining why he decided to buy the IQ pump.

Since the construction work was completed, the DM content has increased on average from 2% to 4.5%. The plan is for a DM content of 5-6%. However, the sewage sludge has already been reduced by about 50%. Meanwhile, the IQ rotary lobe pump runs trouble-free and pumps about 10 m³/h sludge at a pressure of 1.5 – 2 bar during normal operation at 25 Hz, but can also pump up to 25 m³/h at 2.5 – 3 bar when running at 50 Hz. The IQ pump has made a significant contribution to improving digestion.

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