Anaerobic stabilisation and conversion of biopolymers in primary sludge-effect of temperature and sludge retention time

N. Mahmoud, G. Zeeman, H.J. Gijzen, G. Lettinga

Research output: Contribution to journalArticleAcademicpeer-review

83 Citations (Scopus)

Abstract

The effect of sludge retention time (SRT) and process temperature on the hydrolysis, acidification and methanogenesis of primary sludge was investigated in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain SRTs of 10, 15, 20 and 30 days at process temperatures of 25°C and 35°C. The rates of hydrolysis and the biodegradability of primary sludge were assessed in batch reactors incubated at 15°C, 25°C and 35°C
The effect of sludge retention time (SRT) and process temperature on the hydrolysis, acidification and methanogenesis of primary sludge was investigated in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain SRTs of 10, 15, 20 and 30 days at process temperatures of 25degreesC and 35degreesC. The rates of hydrolysis and the biodegradability of primary sludge were assessed in batch reactors incubated at 15degreesC, 25degreesC and 35degreesC. The results revealed that the major amount of sludge stabilisation occurred between 0 and 10 days at 35degreesC and 10 and 15 days at 25degreesC. Hydrolysis was found to be the rate limiting-step of the overall digestion process, for the reactors operated at 35degreesC and 25degreesC, except for the reactor operated at 10 days and 25degreesC. At the latter conditions, methanogenesis was the rate-limiting step of the overall digestion process. Proteins hydrolysis was limited to a maximum value of 39% at 30 days and 35degreesC due to proteins availability in the form of biomass. The biodegradability of primary sludge was around 60%, and showed no temperature dependency. The hydrolysis of the main biopolymers and overall particulate COD of the primary sludge digested in CSTRs were well described by first-order kinetics, in case hydrolysis was the rate-limiting step. Similarly, the hydrolysis of the overall particulate COD of the primary sludge digested in batch reactors were described by first-order kinetics and revealed strong temperature dependency, which follows Arrhenius equation. (C) 2003 Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)983-991
JournalWater Research
Volume38
Issue number4
DOIs
Publication statusPublished - 2004

Keywords

  • anaerobic treatment
  • sewage sludge
  • waste water treatment
  • anaerobic digestion
  • biodegradation
  • domestic sewage
  • digestion
  • hydrolysis
  • lipids
  • water
  • acid

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