Flocculation kinetics and mechanisms of microalgae- and clay-containing suspensions in different microalgal growth phases

Que Nguyen Ho; Michael Fettweis; Jin Hur; Xavier Desmit; Jae In Kim; Dae Won Jung; Sang Deuk Lee; Sungyun Lee; Yun Young Choi; Byung Joon Lee

doi:10.1016/j.watres.2022.119300

Flocculation kinetics and mechanisms of microalgae- and clay-containing suspensions in different microalgal growth phases

Water Res. 2022 Nov 1:226:119300. doi: 10.1016/j.watres.2022.119300. Epub 2022 Oct 26.

Authors

Que Nguyen Ho¹, Michael Fettweis², Jin Hur³, Xavier Desmit², Jae In Kim⁴, Dae Won Jung⁵, Sang Deuk Lee⁵, Sungyun Lee⁶, Yun Young Choi⁴, Byung Joon Lee⁷

Affiliations

¹ Energy Environment Institute, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 37224, South Korea; Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Viet Nam.
² Operational Directorate Natural Environment, Royal Belgian Institute of Natural Sciences, Rue Vautier 29, Bruxelles B-1000, Belgium.
³ Department of Environment & Energy, Sejong University, Seoul 05006, South Korea.
⁴ Energy Environment Institute, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 37224, South Korea.
⁵ Nakdonggang National Institute of Biological Resources (NNIBR), Sangju, Gyeongsangbuk-do 37242, South Korea.
⁶ Energy Environment Institute, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 37224, South Korea; Department of Advanced Science and Technology Convergence, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 37224, South Korea.
⁷ Energy Environment Institute, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 37224, South Korea; Department of Advanced Science and Technology Convergence, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 37224, South Korea. Electronic address: bjlee@knu.ac.kr.

PMID: 36323221
DOI: 10.1016/j.watres.2022.119300

Abstract

Interplays between microalgae and clay minerals enhance biologically mediated flocculation, thereby affecting the sedimentation and transportation of suspended particulate matter (SPM) in water and benthic environments. This interaction forms larger flocs with a higher settling velocity and enhances SPM sinking. The aim of this study was to investigate the flocculation kinetics of microalgae and clay in suspension and to elucidate the mechanisms associated with such interactions. Standard jar test experiments were conducted using various mixtures of kaolinite and microalgal samples from batch cultures (Chlorella vulgaris) to estimate biologically mediated flocculation kinetics. The organic matter (OM) composition secreted by the microalgae was characterized using a liquid chromatography - organic carbon detection system, and quantitative analysis of transparent exopolymer particles was conducted separately. A two-class flocculation kinetic model, based on the interaction between flocculi and flocs, was also adopted to quantitatively analyze the experimental data from flocculation. Results from the flocculation kinetic tests and OM analyses, in association with other data analyses (i.e., floc size distribution and flocculation kinetic model), showed that flocculation increased with OM concentration during the growth phase (10-20 d). However, on day 23 during the early stationary phase, flocculation kinetics started decreasing and substantially declined on day 30, even though the amount of OM (mainly biopolymers) continued to increase. Our results indicate that an adequate quantity of biopolymers produced by the microalgal cells in the growth phase enhanced floc-to-floc attachment and hence flocculation kinetics. In contrast, an excessive quantity of biopolymers and humic substances in the stationary phase enhanced the formation of polymeric backbone structures and flocculation via scavenging particles but simultaneously increased steric stabilization with the production of a large number of fragmented particles.

Keywords: Bayesian calibration; Clay; Floc size distribution; Flocculation; Microalgae.

MeSH terms

Chlorella vulgaris*
Clay
Flocculation
Kinetics
Microalgae*
Suspensions

Substances

Clay
Suspensions