Granular activated carbon promoting re-granulation of anammox-hydroxyapatite granules for stable nitrogen removal at low phosphate concentration

Lei Liang, Jinghuan Luo, Xiangmin Xiao, Jianwei Wang, Meng Hong, Chao Deng, Yu You Li, Jianyong Liu

Research output: Contribution to journalArticlepeer-review

Abstract

Anaerobic ammonium oxidation (anammox) coupled with hydroxyapatite (HAP) crystallization not only achieves simultaneous nitrogen removal and phosphorus recovery, but also cultivates excellent anammox granules. However, a floatation and wash-out of anammox-HAP granules was occurred at low phosphate concentrations. In this study, a reactor inoculated with mature anammox-HAP granules and fed with low phosphate (5 mg P/L) was added with granular activated carbon (GAC) to maintain sludge granulation and nitrogen-removing stability. At influent total nitrogen >800 mg/L and nitrogen loading rate ~ 9.8 kg/m3/d, a satisfactory nitrogen removal of around 88% was maintained during 140 days of operation. Insufficient phosphate supplement resulted in a sludge bulking, with suspended solid and sludge density decreased whereas sludge water content and expansion ratio increased due to HAP loss. Nevertheless, the sludge re-granulation was found at the later stage as the proportion of granules in 2.8– 3.35 mm went up to 37.4% after large granules disintegrated into small pieces at the initial stage. The settling velocity was finally ranging from 129.8 to 182.2 m/h. In addition, Candidatus Brocadia was increased from 2.1% to 20.1% and dominated in the microbial community. These findings suggest GAC was able to promote re-granulation of anammox-HAP granules at low phosphate concentration, which avoids sludge flotation and widens their application as an inoculum.

Original languageEnglish
Article number150359
JournalScience of the Total Environment
Volume805
DOIs
Publication statusPublished - 2022 Jan 20

Keywords

  • Anammox
  • Granular activated carbon
  • Granulation
  • Hydroxyapatite
  • Sludge disintegration

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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