Aluminum-humic colloid formation during pre-coagulation for membrane water treatment: Mechanisms and impacts

Zhengyang Wang, Benoît Teychene, Talia E. Abbott Chalew, Gaurav S. Ajmani, Tao Zhou, Haiou Huang, Xiaohui Wu

Research output: Contribution to journalArticlepeer-review

Abstract

Precoagulation has been widely used by low pressure membrane filtration (LPMF) plants to reduce membrane fouling and increase natural organic matter (NOM) removal. Formation of aluminum and aluminum-NOM moieties plays a fundamental role in this important water treatment process. This study comprehensively investigated the mechanisms of aluminum-NOM species formation during precoagulation and their impacts on LPMF performance. The results show that, at low alum doses, e.g. 0.5mg and 1.0mgAlL-1, humic substances (HS) and Al species (amorphous Al(OH)3, or Al(OH)3(am)) reacted to form small Al(OH)3(am)-HS colloids. Increases in alum dose resulted in sequential transitions of the Al-HS moieties to larger particles and, eventually, precipitates. Compared to waters containing only naturally occurring organic colloids (OC) or HS, the coexistence of OC and HS facilitated the formation of Al-HS precipitates, thereby increasing the removal of HS by 7-15%, but the removal of OC was decreased by 3-20%. Interestingly, these transitions in Al-HS moieties did not affect membrane fouling. Both short-term and long-term filtration results demonstrate that OC, rather than the Al(OH)3(am)-HS colloids, primarily caused membrane fouling. These findings highlight the dynamics of particulate Al-NOM formation during precoagulation and its relationship with membrane fouling, which can be utilized to optimize the operation of integrated precoagulation-LPMF systems on full-scale installations.

Original languageEnglish (US)
Pages (from-to)171-180
Number of pages10
JournalWater Research
Volume61
DOIs
StatePublished - Sep 15 2014

Keywords

  • Coagulation mechanism
  • Fractionated natural organic matter
  • Membrane fouling
  • Microfiltration

ASJC Scopus subject areas

  • Ecological Modeling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

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