Main sewage treatment plant in Vienna
The main sewage treatment plant in Vienna is a sewage treatment plant and is located at the topographically lowest point of the city on the Simmeringer Haide and purifies all municipal wastewater in the federal capital. In dry weather that is around 500,000 m³ of wastewater per day. After several years of planning, it was created in 1980 for originally 2 million population equivalents. In 2005, the plant was expanded to include a second biological treatment stage. Since the expansion opened on June 18, 2005, the plant has been able to purify wastewater to the extent of 4 million PE, with the current capacity being around 3.25 million PE.
The Simmering waste disposal company was founded in 1976 specifically for the operation of the plant, and up to the year 2000 they also operated an incineration plant for the sewage sludge and hazardous waste, including the solids that were screened out. In 2000, the thermal sewage sludge and hazardous waste treatment plant of the Simmering disposal company was taken over by Fernwärme Wien , which also operates the thermal waste treatment plants in Spittelau and Flötzersteig , and has since been continued under the name "Werk Simmeringer Haide".
power
The entire area has an area of around 40 hectares . Since the expansion was opened on June 18, 2005, the plant has been able to purify wastewater to the extent of 4 million population equivalents, with the current utilization of around 3.25 million PE. In addition, a cleaning performance of over 95% of the BOD5 has been achieved since then . Previously it was around 85%. More than 70% of the nitrogen can be removed and the flow time of the wastewater is around 20 hours instead of the previous 5 hours.
18 m³ (18,000 liters ) can be picked up for cleaning per second . Since the Vienna canal system is a mixed water system , i. H. Both rainwater and building wastewater are diverted, in rainy weather excess wastewater is dammed up by a new retention system so that all wastewater can also reach the biological treatment. Before the expansion, 12 m³ each were routed to biological and mechanical cleaning in the event of an overload, which accordingly decimated the cleaning performance during rainy seasons.
Plant engineering
- Five compressors with 45,000 Nm³ / h each or 1,250 kW each .
- In the intermediate pumping station there are eight pumps with a flow rate of 2.6 m³ / s each and six pumps with 2.7 m³ / s each.
- In the distribution structure there are 15 inductive flowmeters with control dampers, DN 1200.
- 15 aeration basins each 79 meters long, around 33 meters wide and 5.5 meters deep, resulting in a total volume of around 171,000 m³.
- 15 secondary clarifiers with an inner diameter of 64 meters each, an average depth of 4.1 meters and a total volume of 200,000 m³.
functionality
Most of the undissolved impurities are removed from the wastewater collected via the main collecting channels of the Viennese sewer system in the ballast trap , the rake system , the sand trap and in the primary clarifier . This already removes 30% of the contaminants. This is followed by biological cleaning, which uses a wide variety of added microorganisms that break down the organic impurities into their chemical components such as carbon. Four so-called aeration tanks are available for this purpose. The oxygen , which is important for the microorganisms , is blown in using 32 circular fans.
Thereafter, phosphates are precipitated from the water with the addition of iron (III) chloride in the inlets to the 16 intermediate clarifiers, in which the organic sludge is separated from the wastewater . The microorganisms then settle together with the dirt that has been absorbed as activated sludge, some of which is returned as return sludge to the activation basin of the first stage in order to accelerate the enrichment with microorganisms and to keep the degradation process intact. The excess sludge, on the other hand, is pumped into the thickener.
In the distribution structure, the wastewater flow is then evenly divided between the 15 aeration basins of the second stage, where the wastewater from further contamination u. A. is freed by denitrification . This is followed by 15 secondary clarifiers, each with a diameter of 64 meters. The now remaining sewage sludge is also pumped into the thickener, where the entire sludge is thickened under the action of gravity and then burned in fluidized bed ovens. The remaining wastewater, which has now been freed of pollutants, is now discharged into the Danube Canal via the discharge channel after a throughput time of around 20 hours (before the expansion it was only 5 hours) .
Sewage sludge incineration
In the Simmeringer Haide plant of Fernwärme Wien, around 1.8 million tons of thin sludge, which accrues annually, are heated in fluidized bed ovens and mixed with flocculants (plastic in powder form). This mass is then dewatered by centrifugation and around 180,000 tons of thick sludge with a solid content of 34 to 37% remain annually. This pre-treatment process for incineration was improved between 1986 and 1990 in cooperation with the suppliers of the devices and additives. This procedure has also been adopted for the US states of New York and Connecticut .
Thanks to the burning technology, the now dewatered sewage sludge can be used in three fluidized bed ovens at 850 to 880 ° C for energy generation. The total gas output of the three furnaces is 176,000 m³ per hour.
In the future, the sludge will no longer be directly incinerated, but first subjected to a fermentation process in newly built digestion towers. The fermentation gas obtained in this way is used in block-type thermal power stations to generate electricity and heat, while the remaining sludge, which is now lower in calorific value, continues to be burned in the fluidized bed furnaces. Construction is scheduled to start in 2015.
Web links
Coordinates: 48 ° 10 ′ 16 ″ N , 16 ° 27 ′ 51 ″ E