A review on sediment bioflocculation: Dynamics, influencing factors and modeling

Abstract

Sediment in a water column provides excellent substratum for microorganism colonization, and biological processes would alter the physical and chemical of sediment, resulting in substantial changes in sediment dynamics. The flocculation of sediment with biological processes are defined as sediment bioflocculation, which has been ubiquitously observed across aquatic ecosystems, activated sludge plants and bioflocculant applications, as a result of various processes involving particle aggregation and breakage under the complex effects of microorganisms and their metabolic products (e.g., extracellular polymeric substances EPS). EPS are complex high-molecular-weight mixtures of polymers, which are the primary components that hold microbial aggregates together by acting as a biological glue. Several mechanistic aggregation theories such as the alginate theory, adsorption bridging theory, divalent cation bridging theory, and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and a number of influencing factors (e.g., sediment properties, microbial activity, EPS quantities and components, and external environment conditions) have been proposed to elucidate the role of microorganisms and EPS in sediment aggregation, promoting the investigation of the sediment bioflocculation evolution and kinetics models. However, due to the complex interrelationships of multiple physical, chemical, and biological processes and the incomprehensive knowledge of microorganisms and EPS, considerable research should be further conducted to fully understand their precise roles in the sediment bioflocculation process. In this study, a review of dynamic characterizations, mechanism, influencing factors and models of sediment bioflocculation are given to obtain a more comprehensive understanding of sediment bioflocculation dynamics.

Critical transitions in suspended sediment dynamics in a temperate meso-tidal estuary

“…Flocs in natural waters constitute a complex matrix of microbial communities, organic and inorganic particles 38 . Thus, while SPM concentration and local turbulence are prime determinants of floc size 39,40 , also the organic matter and the microbial organisms that are associated with the flocs determine their aggregation and disaggregation rate, their strength and shape 22,41–43 . Particularly in the Scheldt, the decreasing OM and nutrient inputs, decreasing ammonium concentrations and increasing oxygenation, have been accompanied by a change in the balance between bacterial heterotrophic and chemo-autrophic metabolism (i.c.…”

“…The biophysical determinants of aggregation-disaggregation dynamics of cohesive sediments is currently a hot research topic (e.g. 22 ). In estuaries this is particularly important since the settling velocity of aggregates co-determines the location and intensity of the maximum turbidity zone.…”

Physical and biological controls on fine sediment transport and storage in rivers

“…The matrix of the biofilm microenvironment is comprised mostly of extracellular polymeric substances (EPS) (Flemming, Neu, & Wozniak, 2007;Wingender, Neu, & Flemming, 1999), which are synthesized by the biofilm microbial community. The properties of these EPS are influential on the sediments upon which they establish, altering their physicochemical characteristics and, therefore, their dynamics through bioflocculation (Lai, Fang, Huang, He, & Reible, 2018). An experimental study (Valentine, Mariotti, & Fagherazzi, 2014) found that the erodibility and resulting resuspension of settled cohesive sediments was reduced with weak biofilm EPS growth when exposed to low shear stress (<0.1 Pa).…”

Grand Challenges (and Great Opportunities) in Sedimentology, Stratigraphy, and Diagenesis Research

“…A recent advance in physical-chemical-biological interactions is the recognition that EPSs, and other cohesive fine-grained material, are major controls on sedimentary processes. Cohesive sediments and sticky substances, including EPS, impact the erodibility of substrate, and sediment transport and deposition processes (e.g., Malarkey et al, 2015;Lai et al, 2018;Lichtman et al, 2018). An associated advance is the understanding that many sedimentary processes involve mixed grain-size and grain-type flows (polydisperse), and challenge established bedform-phase diagrams that assume very narrow (monodisperse) grain-size distributions, leading to reanalysis of many sedimentary structures, and process interpretations (Baas et al, 2016).…”