Enhanced Microcystis Aeruginosa removal and novel flocculation mechanisms using a novel continuous co-coagulation flotation (CCF)

Haiyang Zhang, Lili Li, Shaozhe Cheng, Cheng Li, Fangzhou Liu, Peizhong Wang, Lianjun Sun, Junbo Huang, Wen Zhang, Xuezhi Zhang

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Co-coagulation flotation (CCF) is a novel flotation technology that renders more efficient algal removal compared to traditional mechanical coagulation flotation (MCF) due to a short residence time (< 30 s) and fast rising behavior of algal flocs (> 250 m·h−1). This study compared the algal removal performance using continuous CCF and MCF using water samples taken from Lake Dianchi with severe Microcystis aeruginosa blooms. Removal efficiency, dosage of coagulant/flocculant, rising velocity and structural characteristics of the resulting flocs in the two processes were systematically compared. The results show that CCF could save >50 % polyaluminum chloride (PAC) and polyacrylamide (PAM) compared with MCF when the removal efficiency was both over 95 %. The average rising velocity of flocs in CCF could reach 254.3 m·h−1, much higher than that in MCF (154.5 m·h−1). In the respective optimal coagulation conditions, the flocs formed in CCF (G = 164.8 s−1) were larger (1843 ± 128 μm) and more spherical with a higher fractal dimension (Df = 1.85 ± 0.01) than those generated in MCF (G = 34.1 s−1). The Stokes's Law was found to correctly predict the rising velocity of spherical flocs with large fractal dimensions (Df > 1.7). In contrast, the Haarhoff and Edzwald's extended equation was more suitable for calculating the rising velocity of irregular flocs with small fractal dimension. This study provides new insights into the mechanisms of the enhanced algal removal by CCF and lays foundation for developing cost-efficient algal mitigation processes.

Original languageEnglish (US)
Article number159532
JournalScience of the Total Environment
Volume857
DOIs
StatePublished - Jan 20 2023

All Science Journal Classification (ASJC) codes

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

Keywords

  • Co-coagulation flotation
  • Floc structure
  • Fractal dimension
  • Microcysts aeruginosa
  • Rising velocity

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