If you’ve ever used an airplane bathroom, then you will have experienced the loud sucking sound of a vacuum toilet. This water saving device is the cornerstone of Hamburg’s innovative HAMBURG WATER Cycle® (HWC), which will be incorporated into a new neighbourhood now under construction, Jenfelder Au.
The port city attracts 8,000 – 10,000 people annually to reside long term. In order for Hamburg to remain a livable and lovable city on the water, new residential areas need to be created which enable people to live alongside nature, but still in the city. Approximately 2,000 people will reside in the Jenfelder Au neighbourhood, which is built on 35 acres of land formerly occupied by the Lettow-Vorbeck Barracks.
In Hamburg, conventional wastewater is passed through a 5,000 kilometre long sewerage system connected to the final destination of the Köhlbrandhöft/Dradenau wastewater treatment plant. Domestic sewage from bathrooms and kitchens in Hamburg is mixed together with rainwater during its transport. The combination of rainwater with the sewage has a diluting effect which makes the elimination of micropollutants and the recovery of nitrogen and phosphorus more difficult. The diluted wastewater can only be cleaned by incurring high energy costs.
In addition, demographic changes have brought about an increase of pharmaceutical residues in wastewater. These pharmaceutical residues are difficult to eliminate.
Hamburg Wasser, Hamburg’s drinking water and waste water company, has set a goal to close the material and energy cycles with energy-saving technologies for Jenfelder Au with their design, the HAMBURG WATER Cycle®. Funding for the project has been received from the German federal government and the European Union.
The success of the project could determine the future for water and wastewater treatment technology.
HAMBURG WATER Cycle®
In a conventional system all domestic wastewater streams are combined and discharged together into the sewer system, the HWC decouples the wastewater flows. Thus, the blackwater, which is generated from toilet use, is separated from the greywater (kitchen, bathroom and washing machine wastewater) and the rain water is collected and separately treated.
All toilets in the Jenfelder Au project will be on a vacuum system, so only about one litre of water is used per flush. This is expected to save about 7300 litres of fresh water per year per person. The vacuum system will convey the waste to an anaerobic digester. The digester will produce biogas that will generate both heat and electricity for the housing complex.
Because the wastewater treatment system is decentralized, the proponents expect to develop systems that would recover nitrogen and phosphorus from the digested sludge, as well as preventing the release of micropollutants (such as pharmaceuticals) to the environment.
The biogas system for Jenfelder Au (with combined heat and power) is expected to produce 100 kW of electrical power and 135 kW of thermal power, enough to supply 30 per cent of the heating needs and 50 per cent of the electricity. The rest of the energy will come from a combination of solar panels and a geo-exchange heat pump system.
The system is expected to reduce by 500 tonnes per year the amount of carbon dioxide that would have been emitted in a conventional residential development of that size.
Susan MacVittie is Managing Editor of the Watershed Sentinel