Upgrading of anaerobic digestion of waste activated sludge by a hyper-thermophilic-mesophilic temperature-phased process with a recycle system

L. J. Wu, Yu Qin, Toshimasa Hojo, Gyokuyu Ri

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

In order to upgrade the conventional mesophilic anaerobic digestion (MD) of waste activated sludge (WAS), a hyper-thermophilic (70 °C, stage I)-mesophilic (35 °C, stage II) temperature-phased anaerobic digestion system with a recycle system (TPAD-R) was constructed, with MD as a control. The accumulation of solids increased with shorter hydraulic retention time (HRT). Compared with MD, TPAD-R improved the reduction of solids by over 10%, and the removal rate of protein in TPAD-R increased by more than 20%. In stage I of TPAD-R an amount of organic matter was solubilized, in a range between 10 g L-1 and 20 g L-1, as soluble chemical oxygen demand (COD), and played an important role in enhancing hydrolysis and acidification. The specific hydrolysis and acidification rates of stage I reached their maximum values after a HRT of 10 days, 2.367 g COD per g VS per day and 1.120 g COD per g VS per day, respectively. Consequently, the methane yield in TPAD-R, primarily produced in stage II, was also improved, 29% higher than that in MD for a HRT of 10 days. Besides compensating for energy loss, TPAD-R obtained a higher net energy than MD, achieving a net energy which was 3.3 kJ g-1 VS more than that in MD for a HRT of 10 days. The TPAD-R proved to be efficient in upgrading the MD of WAS.

Original languageEnglish
Pages (from-to)68531-68541
Number of pages11
JournalRSC Advances
Volume5
Issue number84
DOIs
Publication statusPublished - 2015 Jul 30

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

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