Sludge flotation, its causes and control in granular sludge upflow reactors

Bo Wang, Di Wu, Xiao Lei Zhang, Hamish Mackey, Guang Hao Chen

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Sludge flotation is a commonly reported and long-standing issue hindering not only the widespread implementation of upflow anaerobic sludge bed (UASB)-type bioreactors in wastewater treatment but also the development of novel anaerobic/anoxic treatment processes such as anammox, partial denitrification, and biological sulfate reduction. This review attempts to address the instability of UASB-type bioreactors due to sludge flotation. Possible causes of sludge flotation are classified into intrinsic and extrinsic ones. Extrinsic causes include substrate overloading, inappropriate carbon source, overloading of proteins or oils, insufficient reactor mixing, a low temperature, and a low pH. These unfavorable extrinsic conditions can lead to unexpected intrinsic changes in sludge granules, including high gas production, formation of hollow space inside the granules, filamentous bacterial overgrowth, inappropriate production of extracellular polymeric substances, and development of an adhesive granule surface. These intrinsic changes can increase the flotation potential of sludge through reducing the granule density and promoting gas entrapment. To control the sludge flotation problem, both preventive and corrective strategies are summarized. Preventive strategies include maintaining a temperature of 30–35 °C and a pH of 7–9, preventing substrate overloading, providing sufficient nutrients and multiple carbon sources in the influent, applying pre-acidification, and enhancing reactor mixing. If the causes of a sludge flotation incident cannot be identified quickly, corrective strategies including breaking up floating granules and dosing with chemicals such as Fe2+ and surfactants can be applied to suppress the flotation problem.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalApplied Microbiology and Biotechnology
DOIs
Publication statusAccepted/In press - 3 Jun 2018

Fingerprint

Sewage
Bioreactors
Carbon
Gases
Denitrification
Temperature
Waste Water
Surface-Active Agents
Adhesives
Sulfates
Oils
Food

Keywords

  • Anaerobic treatment
  • Sludge flotation
  • Solid-liquid separation
  • Upflow anaerobic sludge bed (UASB)

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology

Cite this

Sludge flotation, its causes and control in granular sludge upflow reactors. / Wang, Bo; Wu, Di; Zhang, Xiao Lei; Mackey, Hamish; Chen, Guang Hao.

In: Applied Microbiology and Biotechnology, 03.06.2018, p. 1-10.

Research output: Contribution to journalArticle

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