Enhancement of anaerobic digestion of waste activated sludge by alkaline solubilization

Jih-Gaw Lin, Cheng Nan Chang, Shou Chung Chang

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191 Scopus citations


The performance of an anaerobic digestion fed with waste activated sludge (WAS) pretreated with NaOH was examined. The sludge was periodically collected from a municipal wastewater-treatment plant. The laboratory work was run in four 1-l semi-continuous anaerobic digestion reactors. Reactor A was fed with untreated WAS at 1% total solids (TS). The other three reactors, B, C and D, were respectively fed with WAS (1% TS) pretreated with 20 meq/l NaOH, WAS (1% TS) pretreated with 40 meq/l NaOH, and WAS (2% TS) pretreated with 20 meq/l NaOH. The reactors were operated at 35°C at four hydraulic retention times - 20, 13, 10 and 7.5 days. The performances of reactors B, C and D, in terms of chemical oxygen demand (COD), volatile solids (VS) removal, and gas production, were superior to that of reactor A. At a retention time of 10 days, the COD removals of reactors A, B, C and D were 38, 46, 51 and 52%, respectively. The gas productions of reactors B, C and D were, respectively, increased by 33, 30 and 163% over that of reactor A. The sludge dewaterability wets examined by capillary suction time (CST). The dewaterability of digested sludge was improved in reactors B, C and D. Capillary suction of digested sludges gave times in the range 148-389 s, compared with 309-735 s for undigested sludges.

Original languageEnglish
Pages (from-to)85-90
Number of pages6
JournalBioresource Technology
Issue number3
StatePublished - 1 Dec 1997


  • Anaerobic digestion
  • Chemical pretreatment
  • Dewaterability
  • Hydrolysis
  • Waste activated sludge

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