Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 773, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2021.145110
Keywords
Microcystis aeruginosa, Raphidiopsis raciborskii, and Dolichospermum circinale; Drinking water treatment; Flash mixing; Shear stress; Cell integrity
Categories
Funding
- Engineering and Physical Sciences Research Council (EPSRC) [EP/P029280/1]
- Coordination for the Improvement of Higher Education Personnel -CAPES [PROEX 20/2016, PrInt 88887.311806/2018-00]
- Brazilian National Research Council -CNPq [403116/2016-3, 304164/2017-8]
- Ceara Research Support Foundation -FUNCAP [PNE-0112-00042.01.00/16]
- Brazilian National Research Council -CNPq
- EPSRC [EP/P029280/1] Funding Source: UKRI
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This study evaluated the impact of velocity gradients, mixing times, and powdered activated carbon (PAC) addition on the integrity of cyanobacteria. Results showed varying levels of sensitivity to shear stress among different cyanobacterial species, with some showing high resilience and others being more sensitive to shear stress.
Although some studies have investigated the impact caused by chemicals used on water treatment (coagulants and oxidants) on cyanobacteria integrity, the isolated effect of shear stress during coagulation is still not fully understood. This study evaluated the impact of different velocity gradients, mixing times, and the addition of powdered activated carbon (PAC) on the integrity of Microcystis aeruginosa, Raphidiopsis raciborskii, and Dolichospermum circinale, known producers of toxin and taste and odor (T&O) compounds. No association was found between R. raciborskii cell lysis and velocity gradient, with or without PAC, demonstrating the high resilience of this taxon to shear stress. In contrast, an association was found for M. aeruginosa at the highest velocity gradient evaluated (1000 s(-1)) and for D. circinale above the lowest velocity gradient studied (600 s(-1)). After PAC addition, there was a reduction in the chances of finding M. aeruginosa intact cells above velocity gradient 800 s(-1) at 45 s, while D. circinale show cell lysis in all the scenarios expect at 600 s(-1) and 10 s of agitation. The additional impact of PAC on cell lysis may lead to more release of metabolites and shows the need to adjust the hydraulic conditions in the rapid mixing stage, especially when more fragile cyanobacteria are present. Neither cyanobacterial cell size nor morphology was shown to be relevant to shear stress sensitivity, indicating that cell wall composition might have been an important factor in controlling cell lysis. (C) 2021 Published by Elsevier B.V.
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