Azo dye decolourisation by anaerobic granular sludge

Frank P. Van der Zee, Gatze Lettinga, Jim A. Field

Research output: Contribution to journalArticlepeer-review

303 Scopus citations


The decolourisation of 20 selected azo dyes by granular sludge from an upward-flow anaerobic sludge bed (UASB) reactor was assayed. Complete reduction was found for all azo dyes tested, generally yielding colourless products. The reactions followed first-order kinetics and reaction rates varied greatly between dyes: half-life times ranged from 1 to about 100 h. The slowest reaction rates were found for reactive dyes with a triazine reactive group. There was no correlation between a dye's half-life time and its molecular weight, indicating that cell penetration was probably not an important factor. Since granular sludge contains sulphide, eight dyes were also monitored for direct chemical decolourisation by sulphide. All these dyes were reduced chemically albeit at slower rates than in the presence of sludge at comparable sulphide levels. Increasing sulphide concentrations, even when present in huge excess, stimulated the azo reduction rate. The results indicate that granular sludge can decolourise a broad spectrum of azo dye structures due to non-specific extracellular reactions. Reducing agents (e.g., sulphide) in sludge play an important role. The presence of anaerobic biomass is probably beneficial for maintaining the pools of these reduced compounds.

Original languageEnglish (US)
Pages (from-to)1169-1176
Number of pages8
Issue number5
StatePublished - 2001


  • Autoxidation
  • Biological reduction
  • Chemical reduction
  • Reduction rates
  • Sulphide

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • General Chemistry
  • Pollution
  • Health, Toxicology and Mutagenesis


Dive into the research topics of 'Azo dye decolourisation by anaerobic granular sludge'. Together they form a unique fingerprint.

Cite this