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Upflow anaerobic sludge blanket digestion

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Title: Upflow anaerobic sludge blanket digestion  
Author: World Heritage Encyclopedia
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Subject: Expanded granular sludge bed digestion, Anaerobic digester types, Sanitation, Imhoff tank, Produced water
Collection: Anaerobic Digester Types, Sanitation
Publisher: World Heritage Encyclopedia

Upflow anaerobic sludge blanket digestion

Schematic of an upflow anaerobic sludge blanket reactor (UASB): Wastewater enters the reactor from the bottom and flows upward.[1]

Upflow anaerobic sludge blanket (UASB) technology, normally referred to as UASB reactor, is a form of anaerobic digester that is used for wastewater treatment.

The UASB reactor is a methanogenic (methane-producing) digester that evolved from the anaerobic clarigester. A similar but variant technology to UASB is the expanded granular sludge bed (EGSB) digester.

UASB uses an [2]

Biogas with a high concentration of methane is produced as a by-product, and this may be captured and used as an energy source, to generate electricity for export and to cover its own running power. The technology needs constant monitoring when put into use to ensure that the sludge blanket is maintained, and not washed out (thereby losing the effect). The heat produced as a by-product of electricity generation can be reused to heat the digestion tanks.

The blanketing of the sludge enables a dual solid and hydraulic (liquid) retention time in the digesters. Solids requiring a high degree of digestion can remain in the reactors for periods up to 90 days.[3] Sugars dissolved in the liquid waste stream can be converted into gas quickly in the liquid phase which can exit the system in less than a day.

UASB reactors are typically suited to dilute waste water streams (3% TSS with particle size >0.75mm).


  • Advantages over conventional treatment 1
  • See also 2
  • External links 3
  • References 4

Advantages over conventional treatment

UASB reactor shown is the larger tank. Hiriya, Tel Aviv, Israel

Conventional treatment settles sludge, digests it, and then aerates the remaining liquids which use bacteria to oxidise the potential digester fuel, and uses up energy to drive the compressors. The result is that on a standard western treatment works the energy produced from settled sludge digestion is all used by the aeration process, with little power export.

With UASB, the whole process of settlement and digestion occurs in one or more large tank(s). Only the post UASB liquids, which have a much reduced BOD concentration, need to be aerated.

This leads to a halving of the aeration energy and doubling of the power generated from digestion, leading over all to a tripling of power generated.

See also

External links

  • Bal AS, Dhagat NN (April 2001). "Upflow anaerobic sludge blanket reactor—a review". Indian J Environ Health 43 (2): 1–82.  
  • Lettinga G, Rebac S, Zeeman G (September 2001). "Challenge of psychrophilic anaerobic wastewater treatment". Trends Biotechnol. 19 (9): 363–70.   review
  • Lettinga G (1995). "Anaerobic digestion and wastewater treatment systems". Antonie Van Leeuwenhoek 67 (1): 3–28.  


  1. ^ Tilley, E., Ulrich, L., Lüthi, C., Reymond, Ph., Zurbrügg, C. (2014) Compendium of Sanitation Systems and Technologies - (2nd Revised Edition). Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland. ISBN 978-3-906484-57-0.
  2. ^ What are sludge granules? UASB Homepage
  3. ^ Finstein, M.S., Zadik, Y., Marshall, A.T., Brody, D. (2004). """The ArrowBio Process for Mixed Municipal Solid Waste – Responses to "Requests for Information (PDF). In Papadimitriou, E.K., Stentiford, E.I. Biodegradable and Residual Waste Management. 1st UK Conference and Exhibition on Biodegradable and Residual Waste Management, February 18–19, 2004, Harrogate, UK. Leeds: CalRecovery Europe Ltd. pp. 407–413.  
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