Overcrowded megacities without adequate water supplies or sewage-disposal facilities, and frequent flooding and extreme drought are problems that a new urban infrastructural concept can help solve. It has a flexible, water-saving vacuum sewerage network.
While Germans consume an average of 130 l of clean water each day, they drink only three. A third of the total amount is flushed down the toilet.
"Water is one of our most valuable resources, and it is far too precious to waste on the transportation of fecal matter,“ says Professor Walter Trosch, of the Fraunhofer Institute for Interfacial Engineering and Biotechnology, in Stuttgart, Germany.
Together with Dr Werner Sternad, of the same institute, and Dr Harald Hiessl, of the Institute for Systems and Innovation Research, in Karlsruhe, he designed and created DEUS 21, a decentralised urban infrastructure system.
The team won the Joseph von Fraunhofer Prize for 2007 for this achievement. The jury was impressed by the process engineering used to treat water and the comprehensive approach to effective materials recycling.
HOW IT WORKS
"DEUS is an integrated model that looks at water as a commodity, all the way from the faucet to the treatment plant,“ says Trosch.
A novelty in the scientists' approach is that they collect rainwater instead of channeling it away unused through the sewers. The rainwater is collected separately from wastewater and treated in a modern membrane plant. As the membrane's pores are even smaller than bacteria and viruses, pathogens can be filtered out.
The resultant germ-free water meets German drinking-water standards. This very soft water flows back into households through a separate supply network, and can be used for showering or for washing dishes or clothes. In this way, residents use less drinking water and save money.
Wastewater from the households is then collected in a vacuum sewerage system. It offers the special advantage of being able to ingest shredded kitchen scraps, obviating the need for separate biological waste collection. The wastewater is transported to a hermetically sealed high-performance reactor containing rotation filters, which consist of porous ceramic microfiltration membranes.
These filters remove everything that is bigger than 0,2 micrometers from the wastewater, including the bacteria that decompose organic waste. Any biogas that is recovered can be used to generate power and heat.
Nitrogen and phosphate are also reclaimed from the wastewater and processed to produce high-quality fertiliser. What remains is the purified wastewater which meets the quality requirements of the European directive on bathing water quality. It can be drained away or discharged into a body of water.
The pilot applications in Knittlingen and Neurott, Germany, have both economic and ecological benefits that are attractive on an international scale.
Projects are already being planned in Namibia, China and Romania.
GLAS-REINFORCED PIPES FOR TRANSPORTING DRINKING WATER
Centrifugally cast glass-reinforced plastic (CC-GRP) pipes are used in Unterroblingen, Germany, for transporting drinking water to brown-coal plant Romonta and all neighbouring municipalities. The pipes run through an old industrial area and replace a 1,5-km-long steel pipeline that was laid in the 1970s.
CC-GRP pipes were chosen for their ability to withstand highly corrosive soil and their watertight characteristics, which guarantee a clean water supply.
The manufacturer, Hobas, claims that the 6-m lengths are easy to install. The pipes are lightweight and can be quickly joined by hand with their push-to-fit sealtight couplings, premounted at one end of each pipe.
For more information, visit www.hobas.com.