Bilfinger Berger Magazine 2/2008

ARE WE USING OUR WATER RESOURCES WISELY? A NEW CONCEPT HELPS PROTECT THE ENVIRONMENT AND SAVE MONEY.

“So what about your water bill?” Mandy Alfeo looks puzzled. Yes, the water bill, how much is it? What does your family pay per month for its drinking water? Mrs. Alfeo claps her hand to her forehead. “Oh, that’s what you mean! It’s ages since I looked, it’s so little.” Searching through a folder, she pulls out the latest bill from the local utility company and says, “Five euros a month.”
The Alfeo family lives in the new housing development “Am Römerhof” in Knittlingen. From outside there is little to distinguish their house from any other in Germany. You would have to be a mole to discover that underground, almost nothing about this house is what you would expect. There is no big concrete sewer pipe to take the waste to the treatment plant, just a plastic pipe hidden in a manhole out front. Put your ear to the ground, and maybe now and then you might hear a low sucking sound from the manhole when the collecting tank empties under negative pressure, like an aircraft toilet.
When Mandy Alfeo cooks spätzle, a local Swabian delicacy made from egg noodles, for her Swabian-Sicilian husband Salvatore and their two children Lisa (3) and Robin (7), there is rarely any left over. “But if there is,” she says, “we just throw it in the disposal unit.” The garbage disposal unit is unlike what you would find in an ordinary kitchen: Like a little shredder beneath the sink, it chews up organic waste and swallows it greedily. It consumes anything thrown into it, transporting the mangled mass via a small plastic pipe to the waterworks. And there the noodles and the rest of the organic garbage together with the toilet waste are turned into clean energy in a biogas plant.

KNITTLINGEN’S LITTLE MARVEL
Knittlingen is the right place for a bit of magic. Not that many people know that this little southern German town between Karlsruhe and Pforzheim is the supposed birthplace of the legendary Doctor Faustus who gained immortality through the pages of Goethe’s “Faust.” It was from here in Knittlingen that the real Faust is said to have kept the entire region spellbound with his fortune-telling and magic 500 years ago. And now Knittlingen again amazes us, this time with “Deus 21,” as the Decentralized Urban Infrastructure System is called by its inventors. A system that has made the little town the stuff of legend in heavyweight publications such as “Die Zeit” and “Wirtschaftswoche.”
Knittlingen has seen the future of water. This system, a world first, is virtually independent of the local network and entirely different from conventional waste water technology. It supplies water to and takes waste from about 100 houses. Developed by the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) and implemented jointly with Bilfinger Berger Environmental Technology, the concept is based on a principle as simple as it is revolutionary: Water is a valuable resource. But instead of conserving this resource, we misuse drinking water to wash clothes, water the garden and even as a means of transport to flush sewage down the toilet. That doesn’t sound very clever.Why not use rainwater to irrigate the lawn, or in the dishwasher? Why not use organic waste and sewage to generate energy? Why lay miles of concrete pipes beneath our communities, so the local authority can spend a fortune maintaining them? “It is high time to stop and think and come up with some solutions,” says Dr. Markus Gerlach, Head of Process Engineering at Bilfinger Berger Environmental Technology. Dr. Gerlach has no doubts: “In the future, water supply and disposal will be organized along very different lines compared with today.” Conceivably along the same lines as in Knittlingen: Here the rainwater runoff from roofs and residential streets is collected in an underground cistern, filtered and treated until it is of similar quality to drinking water. This “secondary water” then flows back to the houses where it is used for everything except drinking. If there is insufficient rainwater available in times of extended drought, the system can be topped up with drinking water from the mains supply.
The really revolutionary part is what happens to the waste water: The centerpiece of the Knittlingen project is the vacuum sewage system developed by Bilfinger Berger subsidiary Roediger Vacuum.Waste water extraction requires neither a gravity fall nor big concrete pipes. Sunk in the ground in front of every house is a transfer shaft. Once it is filled to a predetermined level, a valve opens and the waste water is sucked out. Once at the water treatment plant, it is biologically purified in a hermetically sealed environment. The resulting mix of carbon dioxide and methane is then used to power a turbine that generates electric power and heat. The minimal solid residue that remains has a high concentration of ammonia and phosphate— making it an ideal fertilizer. The purified water that emerges from the plant is not suitable for drinking, but can be discharged with impunity into the nearest stream.

A CUPBOARD FULL OF PATENTS
Dr. Volker Zang, Managing Director of Roediger Vacuum, has dozens of folders in his cupboard containing descriptions of 130 patents. Pointing to the cabinet, Zang remarks: “There are solutions in there for countries the world over.” In the arid United Arab Emirates, for example, whole new developments have been equipped with vacuum technology. Dubai’s artificial Palm Island is just one of them. “But the technology can also be used in poor and remote parts of the world, because we don’t require costly sewer pipe systems,” Zang explains. And in areas where there is no electric power supply, the methane released in the local water treatment process can also drive a generator: “Our systems are entirely adaptable to meet local needs,” concludes Volker Zang. “Knittlingen is just one of many concepts.”

Text: Philipp Mausshardt, Photos: Barbara von Woellwarth
Bilfinger Berger Magazine 2/2008