In-situ microscopy investigation of floc development during coagulation-flocculation with chemical and natural coagulants

ABSTRACT

This study aimed to include in-situ microscopy in the analysis of floc development during coagulation-flocculation for drinking water treatment. To this end, jartest series were carried out for natural and synthetic waters using aluminum sulfate, sulfate chloride, ferric chloride, and Opuntia sp. as coagulants. Coagulation under optimized conditions was monitored by an in-situ microscope in conjunction with image analysis. Obtained results enabled some insights on the coagulation process. Images captured different stages of initial floc development, including flocs exhibiting heterogeneous, branched, and irregular surface structures. From image analysis, wide distributions of flocculated particle sizes were found for both natural (19–15834 μm) and synthetic water (19–21607 μm), suggesting the occurrence collisions by adhesion and transport between particles, thus influencing floc formation rates depending on the medium. Average size and number of flocs, as determined by the image analysis algorithm as a function of the time, showed inverse correlation of floc growth with water clarification. The microscopic images also illustrated how different coagulants in different water sources undergo breaking through fragmentation or erosion. Our findings also highlight the importance of investigating additional aspects that involve conditions of mixing, development, breaking, regrouping, and resistance of flocs.

Graphical abstract

KEYWORDS:

• Opuntia cochenillifera
• image analysis
• aggregates
• floc development
• floc rupture
• treatability assays

Acknowledgements

This work was supported by the Global Challenges Research Fund (GCRF) UK Research and Innovation (SAFEWATER; EPSRC Grant Reference EP/P032427/1), and The National Council for Scientific and Technological Development (CNPq - Brazil) for the MSc scholarship awarded to Gustavo Santos Nunes.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Statement

Authors declare previous originality check, no conflict of interest and open access to the repository of data used in this research.

Supplementary material

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Additional information

Funding

This work was supported by the The National Council for Scientific and Technological Development (CNPq - Brazil) [unnumbered]; Global Challenges Research Fund (GCRF) UK Research and Innovation [EP/P032427/1].