Free nitrous acid pre-treatment enhances anaerobic digestion of waste activated sludge and rheological properties of digested sludge : A pilot-scale study

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Jia Meng
  • Haoran Duan
  • Huijuan Li
  • Shane Watts
  • Peng Liu
  • Sohan Shrestha
  • Min Zheng
  • Wenbo Yu
  • Zhongwei Chen
  • Yarong Song
  • Jason Dwyer
  • Shihu Hu

Detail(s)

Original languageEnglish
Article number115515
Journal / PublicationWater Research
Volume172
Online published20 Jan 2020
Publication statusPublished - 1 Apr 2020
Externally publishedYes

Abstract

In this study, the effects of free nitrous acid (FNA) pre-treatment on the rheological properties of digested sludge were investigated at a pilot-scale, along with the improvement in volatile solids (VS) destruction and biogas production. Two pilot-scale anaerobic sludge digesters were operated for one year, one receiving thickened waste activated sludge (TWAS) without pre-treatment (control) and one receiving TWAS pre-treated for 24 h at an FNA concentration of 4.9–6.1 mgN/L (nitrite = 250 mgN/L, pH = 5.0, T = 22–30 °C). The results confirmed the enhancing effect of FNA pre-treatment on methane production (37 ± 1%), consistent with previous laboratory studies. Equally importantly, FNA pre-treatment substantially reduced the shear viscosity of TWAS by 51 ± 8% at 100 s−1 and 49 ± 7% at 250 s−1, likely due to the solubilization of the TWAS (11.1 ± 0.8%). Similarly, FNA pre-treatment also reduced these viscosity parameters of the digested sludge by 80 ± 4% and 78 ± 4%, respectively, caused by both enhanced VS destruction and disintegration of the digested sludge. The dewaterability of digested sludge, assessed by dewatered solids content, capillary suction time and specific resistance to filtration, was not improved by FNA pre-treatment. The polymer requirement for dewatering was reduced by 24 ± 0.6% due to the lower solids concentration in the digested sludge achieved with FNA pre-treatment. The changes to sludge rheological properties revealed in this study further enhances the business case for the FNA pre-treatment technology. © 2020 Elsevier Ltd.

Research Area(s)

  • Anaerobic digestion, Free nitrous acid, Pilot-scale, Rheological properties, Viscosity

Citation Format(s)

Free nitrous acid pre-treatment enhances anaerobic digestion of waste activated sludge and rheological properties of digested sludge: A pilot-scale study. / Meng, Jia; Duan, Haoran; Li, Huijuan et al.
In: Water Research, Vol. 172, 115515, 01.04.2020.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review