Wen Zhang, Ph.D., P.E., BCEE
Principal Investigator
Professor
Phone: (973) 596-5520
Fax: (973) 596-5790
Email: wen.zhang@njit.edu
Office Location: Colton Hall 211
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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 traditional mechanical coagulation flotation (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 relationship between the rising velocity and the structural characteristics of flocs was analyzed using the Stokes's Law that corrected predicted the rising velocity of spherical flocs with large fractal dimensions. The rising velocity of irregular flocs with small fractal dimensions was successfully estimated by the Haarhoff and Edzwald's extended equation. Additionally, the model prediction also indicates that the rising velocity for flocs with high fractal dimension and moderate size can achieve the highest rising velocity. 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.
This research was financially supported by the National Natural Science Foundation of China (51909258), National Program on Basic Research Project for Governmental International Scientific and Technological Innovation Cooperation of China (2018YFE0110600).
Source of this paper:
Enhanced Microcystis Aeruginosa removal and novel flocculation mechanisms using a novel continuous co-coagulation flotation (CCF)
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