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High-loaded Activated Sludge: Effects of Different Aeration Strategies at Sjölunda WWTP

Persson, Gabriel LU (2015) VVA820 20151
Chemical Engineering
Abstract
The activated sludge process has existed for over a century and despite its age the development of new theories, methods and technologies is ongoing. Despite huge technological breakthroughs in the last decades the activated sludge process is still a very energy demanding process however, and it is possible to make significant energy savings by optimizing the aeration strategy of an activated sludge plant. Sjölunda WWTP, one of the largest wastewater treatment plants in Sweden, have gradually lowered the oxygen concentrations in its highloaded activated sludge process to try to find an optimal aeration solution through full-scale tests.

The treatment plant is facing challenges in the form of increasing load and a need to expand or... (More)
The activated sludge process has existed for over a century and despite its age the development of new theories, methods and technologies is ongoing. Despite huge technological breakthroughs in the last decades the activated sludge process is still a very energy demanding process however, and it is possible to make significant energy savings by optimizing the aeration strategy of an activated sludge plant. Sjölunda WWTP, one of the largest wastewater treatment plants in Sweden, have gradually lowered the oxygen concentrations in its highloaded activated sludge process to try to find an optimal aeration solution through full-scale tests.

The treatment plant is facing challenges in the form of increasing load and a need to expand or change the current nitrogen removal process. A pilot study is investigating the possibility of implementing total autotrophic nitrogen removal, i.e. the nitritation-anammox process, as an alternative for the next nitrogen removal upgrade. The nitritation-anammox process is sensitive however, and required a low organic matter to nitrogen ratio to function optimally, a ratio that is difficult to accomplish with the aeration strategy in use at the plant today.

An ASM2d model was created in the wastewater modelling software MIKE WEST with the aim to investigate if it was possible to find an optimized aeration strategy that could increase the treatment efficiency of the activated sludge process and reduce the COD/N ratio without causing significant increases in energy demand. As the treatment plant is producing biogas it was also of interest to investigate whether the methane production potential of the activated sludge would benefit from low oxygen concentrations in the process.

It was discovered that the settling model most commonly in use in activated sludge modelling today was not able to sufficiently estimate what happens with the treatment efficiency of at different oxygen concentrations in the activated sludge process and focus was therefore spent on full-scale tests of different aeration strategies. The full-scale tests showed that it was not possible to see a clear trend that the oxygen concentration were affecting the methane potential of the sludge, but it was possible to lower the energy demand of the process while maintaining the same treatment efficiency by evening out the oxygen concentrations between the aerated basins. (Less)
Popular Abstract (Swedish)
Sjölunda avloppsreningsverk är ett av de största reningsverken i Sverige och tar hand om avloppsvatten från stora delar av det snabbt växande Malmö. Befolkningsökningen sätter press på verket, där vattenreningen måste förbättras för att reningsverket ska kunna ta hand om ökande volymer avloppsvatten. För att nå detta mål drivs flera förbättringsprojekt på Sjölundaverket, däribland projekt som fokuserar på aktivtslamprocessen, en av de viktigaste och mest energikrävande reningsmetoderna.
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author
Persson, Gabriel LU
supervisor
organization
course
VVA820 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
methane potential, High-loaded activated sludge, activated sludge modelling, aeration strategies, ASM2d, vattenförsörjningsteknik, avloppsteknik, water engineering, environmental engineering
language
English
id
8410392
date added to LUP
2015-12-21 11:08:30
date last changed
2015-12-21 11:08:30
@misc{8410392,
  abstract     = {The activated sludge process has existed for over a century and despite its age the development of new theories, methods and technologies is ongoing. Despite huge technological breakthroughs in the last decades the activated sludge process is still a very energy demanding process however, and it is possible to make significant energy savings by optimizing the aeration strategy of an activated sludge plant. Sjölunda WWTP, one of the largest wastewater treatment plants in Sweden, have gradually lowered the oxygen concentrations in its highloaded activated sludge process to try to find an optimal aeration solution through full-scale tests.

The treatment plant is facing challenges in the form of increasing load and a need to expand or change the current nitrogen removal process. A pilot study is investigating the possibility of implementing total autotrophic nitrogen removal, i.e. the nitritation-anammox process, as an alternative for the next nitrogen removal upgrade. The nitritation-anammox process is sensitive however, and required a low organic matter to nitrogen ratio to function optimally, a ratio that is difficult to accomplish with the aeration strategy in use at the plant today.

An ASM2d model was created in the wastewater modelling software MIKE WEST with the aim to investigate if it was possible to find an optimized aeration strategy that could increase the treatment efficiency of the activated sludge process and reduce the COD/N ratio without causing significant increases in energy demand. As the treatment plant is producing biogas it was also of interest to investigate whether the methane production potential of the activated sludge would benefit from low oxygen concentrations in the process.

It was discovered that the settling model most commonly in use in activated sludge modelling today was not able to sufficiently estimate what happens with the treatment efficiency of at different oxygen concentrations in the activated sludge process and focus was therefore spent on full-scale tests of different aeration strategies. The full-scale tests showed that it was not possible to see a clear trend that the oxygen concentration were affecting the methane potential of the sludge, but it was possible to lower the energy demand of the process while maintaining the same treatment efficiency by evening out the oxygen concentrations between the aerated basins.},
  author       = {Persson, Gabriel},
  keyword      = {methane potential,High-loaded activated sludge,activated sludge modelling,aeration strategies,ASM2d,vattenförsörjningsteknik,avloppsteknik,water engineering,environmental engineering},
  language     = {eng},
  note         = {Student Paper},
  title        = {High-loaded Activated Sludge: Effects of Different Aeration Strategies at Sjölunda WWTP},
  year         = {2015},
}