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Chemical flocculation as pretreatment for energy efficient biological treatment.
Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
2012 (English)In: 10th IWA Symposium on Forest Industry Wastewater and 8th International Conference on the fate and effect of Pulp and Paper Mill Effluents, 2012, p. 42-Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Biological treatment of forest industry wastewaters uses large amounts of electrical energy. For many mills aeration is the single most energy intensive process in the wastewater treatment plant. The oxygen transfer from bubbles into the water volume is quite slow with low aeration efficiency as result. If the oxygen transfer can be improved, the efficiency can be improved and less compressed air will be needed for aeration with decreased energy costs as the result. It has been shown that surface-active extractives, such as fatty acids and resin acids, have a large impact on oxygen transfer in diffuser aeration systems. With chemical flocculation, extractives can be removed from the process streams. Trials have been made where pulp-mill process streams were pretreated with chemical flocculation before the oxygen transfer tests. When the chemical flocculation conditions were optimized to increase surface tension in the process stream, extractives were removed and the oxygen transfer rate increased in the following oxygen transfer tests. With the pretreatment also COD concentration decreased. The effect will be less need for oxygen for degradation in the following biological process. With decreased COD concentration and increased oxygen-transfer rate, energy can be saved in the biological treatment. Energy savings resulted in greater economic return than the cost for flocculating chemicals. If waste sludge can be used as energy source, one can even achieve a better result.

Acknowledgements. This work was supported by ÅF-forskningsstiftelse and Stora Enso Skoghall mill.

Place, publisher, year, edition, pages
2012. p. 42-
Keyword [en]
aerobic treatment, pulp-mill effluent, extractives, oxygen transfer, Chemical flocculation
National Category
Engineering and Technology
Research subject
Environmental and Energy Systems
Identifiers
URN: urn:nbn:se:kau:diva-30126OAI: oai:DiVA.org:kau-30126DiVA, id: diva2:666246
Conference
10th IWA Symposium on Forest Industry Wastewaters Concepción Chile 8-12 Januari
Available from: 2013-11-22 Created: 2013-11-22 Last updated: 2014-07-02Bibliographically approved

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Sandberg, Maria

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
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  • de-DE
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Output format
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  • asciidoc
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