2000 years of wastewater management in Vienna

Today’s state-of-the-art wastewater treatment technology at ebswien hauptkläranlage marks the (preliminary) end of a 2000-year-long history of wastewater disposal in Vienna. The first sewer system on Viennese ground dates back to the legionary town of Vindobona. Around 100 AD, Roman soldiers built a complex system of sewers akin to modern standards in the military camp at Vindobona. The sewer bottom was made of roof tiles, the top layer consisted of stone plates. For smaller sewers, terra cotta pipes were already used. With the Fall of the Roman Empire, this first sewer construction phase ended, and the high standard fell into oblivion.

During the Middle Ages, Vienna had a sanitation system typical of European towns at the time. Not only household garbage, also waste from medieval craft production was simply cast into the streets or into the nearest brooklet. There they remained until the flood waters swept the foul-smelling debris into the nearby Danube River. As a result, the city was regularly invaded by epidemic diseases. The first rudimentary sewer system evidenced dates from the late Middle Ages. One of these “moorings”, stone conduits leading from a building to a watercourse, was discovered during the construction works for the city’s underground system in front of the “Haas House“ in the inner city.

By the end of the 15th century, the area of today’s 1st Vienna city district was already serviced by numerous sewers. In the wake of a building boom following the second Turkish Siege in 1683, Vienna‘s sewer system was also expanded. In the first third of the 18th century, the densely populated areas surrounded by the bastions were almost entirely serviced by sewers. This gave Vienna a pioneering role in Europe.

Along the city limits and in the suburbs, however, sewage was still discharged into the brooks on the banks of which they were produced. As the settlements expanded, the water flow could no longer carry off the growing amounts of faecal matter. A number of disastrous flood events brought the foul debris, including dead animals, to the fore. Because of the poor sanitary conditions, epidemics were quite common at the time and caused many casualties. At the same time, plans for an expansion of the city’s sewer system emerged.

But these were locked away in a drawer until the city was shaken by a real disaster. In 1830 a gigantic ice jam on the Danube caused the filthy brooks in the Vienna city area to overflow their banks, bringing a cholera epidemic in their wake that reportedly killed more than 2,000 people. Now everything happened very quickly, and one of the largest river training projects in the city’s history was initiated. Over a construction period that eventually spanned more than 70 years, open watercourses in the city area were enclosed by vaults and two large sewage collectors, infamously known as the “cholera sewers”, were built along either bank of the Vienna river. By the year 1848, Vienna could already boast one of the most advanced sewer systems of the time.

Another milestone for the city’s sewer system was the incorporation of 33 suburban communities on 1 January 1892. To raise the sanitary standards, activities to expand the drainage facilities started already one year earlier. The open, filthy sewers were transformed into sewer mains, which still form part of the backbone of Vienna’s sewer system today.

From wastewater disposal to wastewater purification

The First and Second World War dealt a severe blow to the further expansion of the sewer system. It took until 1950 to repair the massive damage caused by the bombing raids and to bring the city back to sanitary conditions. But the wastewater was still discharged into the Viennese brooks without prior cleaning. After the Second World War, plans were made to clean the masses of sewage of up to 500 million litres a day. The city council initially erect two smaller sewage plants in the south of the city belonging to the watershed of Liesingbach. After a four-year construction period, Vienna‘s first sewage treatment plant (Inzersdorf/Gelbe Heide) destined for the communities of Hetzendorf and Altmannsdorf was inaugurated in 1951. This plant was replaced by the fully biological wastewater treatment plant of Blumental in 1969 (which was eventually closed down in 2005).

The water quality of the Danube soon also became an issue as the smell of Vienna’s wastewater spread to the settlements downstream of the city. In the 1960s, the city council made its first plans to build a central wastewater treatment plant for Vienna and chose the area of Simmering as its location. Simmering is one of Vienna’s topographically lowest points, and the hydraulic gradient allows the wastewater to drain naturally through the sewer pipes to the plant, thus saving energy for pumping. The city planners initially had the idea to build a separate wastewater treatment plant for the city districts of Floridsdorf and Donaustadt on the opposite river bank. This idea was finally abandoned and plans were made for a 567-metre-long culvert underneath the river, the so-called “Donaudüker”, through which also “transdanubian” wastewater was to be transported to the new main wastewater treatment plant in Simmering.

On 4 June 1970, Mayor Bruno Marek laid the founding stone for Vienna’s main wastewater treatment plant, which was to become one of the largest of its kind in Europe. “May this plant return purified wastewater to the cycle of nature and thereby help to make our ecosystem cleaner,“ Marek wrote into the founding deed on behalf of the Viennese population.

The inauguration of Vienna’s main wastewater treatment plant in 1980 marks the start of a new era in the city’s wastewater history. Now all of Vienna’s wastewater is purified before it is discharged into the Danube. Continuous improvements, new sewers and pumping facilities, ongoing restoration works and a major water resource protection project for Vienna, in which the upgrade of the main wastewater treatment plant forms a central component, assure that Vienna’s water resources are comprehensively protected. Since the plant’s second biological treatment stage started operation in 2005, all of the city’s wastewater has been cleaned by state-of-the-art technology without compromising the water quality of the Danube.

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