By different uses, like having a shower or flushing the toilet, drinking water becomes wastewater und gets polluted with solids and dissolved solids. The dissolved solids contain organic and inorganic carbon, nitrogen and phosphorus compounds. Unpurified wastewater is a great burden for a receiving body of water. Water bodies have natural self-cleaning properties to cope with polluted water. But because this self-cleaning process takes up oxygen, especially when organic carbon is broken down, it burdens the natural balance of the ecosystem. When the ecological status of a water body is impaired, the quality of water may substantially deteriorate and fish may get sick and die. Another key factor in sustainable water resource management is the elimination of plant nutrients like nitrogen and phosphorus. Too high levels of nitrogen in the form of ammonia and nitrite poison the fish populations. Excessive amounts of nutrients may also lead to eutrophication, which is characterised by massive algal growth in the affected water bodies. In case of a lack of oxygen, the water may become anoxic. From a sanitary perspective, unpurified wastewater poses a health risk to human beings.
This explains why the purification of wastewater in a treatment plant helps to protect the natural water resources and thus also plays an essential role in the protection of the environment. ebswien meets this challenge by operating Vienna’s main wastewater treatment plant on behalf of the City of Vienna. This plant, which started operation in 1980 and was substantially upgraded in 2005, extends over an area of 420,000 square metres - one thousandth of the city area of Vienna - and lies in the city district of Simmering. It cleans all of Vienna’s wastewater, one half produced by households and the other half by commercial and industrial businesses, and copes with more than 6,000 litres a second, or 200 billion litres per year. After mechanical-biological cleaning, the purified water flows via the Danube Canal into the Danube River. ebswienhauptkläranlage and its more than 160 employees are proud of this excellent purification result, as it allows us to see the Danube’s waters off the same clean way in which they were welcomed into the city.
The plant is favourably located in one of Vienna’s topographically lowest points. Since the wastewater can flow through Vienna’s sewerage system mostly in a natural downward gradient, very little energy is needed for pumping. ebswienhauptkläranlage generally aims to minimise resource consumption, especially the consumption of energy. This is demonstrated by numerous measures to increase the plant’s energy efficiency and the use of a broad mix of renewable fuels. The sewage sludge produced is already now used for energy recovery. Thanks to a method called “energy-optimised sludge treatment” (EOS project - Energy Optimisation Sludge Treatment), ebswien hauptkläranlage is on track to produce all the electricity needed for wastewater treatment through its own system starting in 2020.