Avoidance Instead of Disposal Also Applies to Wastewater
The Municipal Department 30 – Vienna Wastewater Management – takes decisive action to promote the quality of life and ecology in the Austrian capital by integrating hydro-ecological strategies.
The public sewer network of Vienna presently measures about 2,300 km and drains sewage from 98 percent of households – a top rate in the international comparison. Connected to the sewer network of the metropolis are also a number of suburban communities, which makes the Municipal Department 30 – Vienna Wastewater Management – responsible for the collection and disposal of wastewater from 3.25 million inhabitants (population equivalents). Vienna produces about 200 million cubic metres of communal wastewaters annually, which are discharged to the Vienna Main Sewage Treatment Plant by five collecting mains. About € 36 million are annually invested in maintenance and upgrading of the Vienna sewer network.
2,000 years wastewater in Vienna
This was not always so! A sewer network did exist in Roman times in the former legionary town Vindobona, but succeeding cultures took less stock in sanitary facilities. It was only in 1830, when Vienna was – again – stricken by a cholera epidemic after a severe flood that opinions were revised. A genuine sewer construction boom set in, which had progressed by 1848 to such an extent that Vienna could boast one the most advanced sewerage networks of the time.
Confusions of the two World Wars almost stopped the further development of the sewer network. In 1950, repair of the severe bomb damage in the sewer network started in the course of reconstruction. After many further development stages, a further milestone was finally reached in 1980: The start-up of the Main Sewage Treatment Plant in the South of Vienna (Simmering), which since then treats the majority of wastewaters in an orderly way before they are discharged into the Danube.
Today, wastewater treatment does not only include state-of-the-art sewers and treatment plants, but also hydro-ecological considerations. Thus, the project “Wastewater Disposal and Water Protection for Vienna” ongoing for several years, will further improve the good water quality of Vienna’s waters in two phases until 2015. The safe drainage of all wastewaters to the largest and most advanced sewage treatment plant of Europe (Vienna Main Sewage Treatment Plant (as of mid-2005) is only one, albeit important aspect.
Technological innovations are closely related to the following strategic elements:
“Avoidance instead of Disposal” in relation to wastewater means the dropping of “end of pipe” solutions and the promotion of “at source” measures. Increasing infiltration of unpolluted stormwater can reduce the volume of wastewater. A prerequisite is a substantial reduction of soil sealing in the city area. Moreover, natural waters have to be disconnected from the sewer network (see Wien River Valley Sewer).
Sewer network management/Real Time Control/RTC Precipitation increases flow volumes in sewers by a multiple; at the same time, treatment plants are not able to treat these huge water masses immediately. For this reason, a certain share of stormwater has to be retained in the sewers. In Vienna, an online real time control network provides data on precipitation and sewer flow, which are processed by a high efficiency computer to determine the optimal use of regulators. The advantages are obvious: less pollution of rivers, optimal management of retention basins. Moreover, the sewage treatment plant capacity can be kept comparably low.
Immission and emission Austrian and EU laws are based on the emission principle. However, for an ecological functioning of regional waters, the consideration of immission is important. Thus, the Vienna Main Sewage Treatment Plant (ratio between low-water flow and treatment plant discharge of 100 : 1) pollutes the Danube only to a small extent. In the treatment plant Blumental (300.000 population equivalents) with the Liesing Brook as receiving water, the load ratio is the other way round (1 : 100)! Consequently, wastewater treatment at the plant Blumental is soon to be stopped; all Vienna wastewaters will then be treated in the expanded Main Sewage Treatment Plant.
Solution of odour problems caused by wastewater The sewer network of the federal capital was largely designed as a naturally ventilated combined system, which principally prevents noxious gas concentrations. Problem spots of odour nuisance were analysed, classified, and evaluated. Meanwhile, all grave odour problems could be solved.
The base for the combination of technology, strategic elements, and customer expectations is in Vienna the geographic information system “KANIS”, whose digital sewer register allows an efficient, rapid, and convenient planning of all work in the sewer network.
Unique like KANIS is its accessibility for our friends and associates at home and abroad: Since 2002, the digital data of the sewer network are available online as download! KANIS has thus become a forerunner for the desire of the City of Vienna to exchange know-how and experience with other, mainly Central and Eastern European metropolises – a concern that now finds a further expression in the Congress “VEDUNIA”! (Source: aqua press Int. 3A/2004, SR DI Helmut Kadrnoska, Head of the MD 30 – Vienna Wastewater Management)
