Issue 2, 2021

Effects of NaClO shock on MBR performance under continuous operating conditions

Abstract

In situ chemical cleaning with sodium hypochlorite (NaClO) is frequently employed to maintain a constant permeability in membrane bioreactor (MBR) systems. In this study, the effects of NaClO shock on MBR performance under continuous operating conditions were investigated. A lab-scale MBR was operated for three runs with in situ chemical cleaning. Experimental results demonstrate an obvious increase of the membrane fouling rate (13.7, 23.5 and 23.3 kPa d−1) on day 1 of cleaning, followed by a rapid reduction (6.4, −0.2 and 3.5 kPa d−1) on day 2 of cleaning. This indicates the rapid self-recovery ability of the NaClO-shocked sludge. Furthermore, as the operating time increased, the sludge extracellular polymeric substance (EPS) content initially increased, followed by a subsequent decrease, with the gradual improvement of sludge filterability that consequently reduced membrane fouling. Thermodynamic analysis revealed that the shocked-sludge surface properties, including the surface electron donor component (γ), hydrophobicity, adhesive energy and self-cohesive ability, were gradually restored to the raw sludge level, which reduced the membrane fouling potential.

Graphical abstract: Effects of NaClO shock on MBR performance under continuous operating conditions

Article information

Article type
Paper
Submitted
15 Aug. 2020
Accepted
17 Nov. 2020
First published
17 Nov. 2020

Environ. Sci.: Water Res. Technol., 2021,7, 396-404

Effects of NaClO shock on MBR performance under continuous operating conditions

M. Sun, B. Hou, S. Wang, Q. Zhao, L. Zhang, L. Song and H. Zhang, Environ. Sci.: Water Res. Technol., 2021, 7, 396 DOI: 10.1039/D0EW00760A

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