Microbial Flocculants as an Alternative to Synthetic Polymers for Wastewater Treatment: A Review

Abstract

Microorganisms such as bacteria, fungi, and microalgae have been used to produce bioflocculants with various structures. These polymers are active substances that are biodegradable, environmentally harmless, and have flocculation characteristics. Most of the developed microbial bioflocculants displayed significant flocculating activity (FA > 70–90%) depending on the strain used and on the operating parameters. These biopolymers have been investigated and successfully used for wastewater depollution in the laboratory. In various cases, selected efficient microbial flocculants could reduce significantly suspended solids (SS), turbidity, chemical oxygen demand (COD), total nitrogen (Nt), dye, and heavy metals, with removal percentages exceeding 90% depending on the bioflocculating materials and on the wastewater characteristics. Moreover, bioflocculants showed acceptable results for sludge conditioning (accepted levels of dry solids, specific resistance to filtration, moisture, etc.) compared to chemicals. This paper explores various bioflocculants produced by numerous microbial strains. Their production procedures and flocculating performance will be included. Furthermore, their efficiency in the depollution of wastewater will be discussed.

Iron Oxide/Chitosan Magnetic Nanocomposite Immobilized Manganese Peroxidase for Decolorization of Textile Wastewater

“…Electrochemical processes, exchanging ions, flotation, coagulation-flocculation, biotic processing, adsorption, reverse osmosis, as well as separation membranes, were widely used for the elimination of organic and inorganic pollutants [10][11][12][13][14][15][16]. However, the adsorption technique is the most widely used technique among all methods due to its cheapness, simplicity, and effectiveness [17].…”

Peptides Fixing Industrial Textile Dyes: A New Biochemical Method in Wastewater Treatment

“…Traditional physicochemical treatments (adsorption, coagulation/flocculation, etc.) as well as biological methods commonly used for the depollution of these effluents generally are proved to be inefficient, nonspecific, and very expensive [34]. It seems interesting to develop new alternative treatments free from these drawbacks.…”

Agro-industrial waste materials and wastewater as growth media for microbial bioflocculants production: a review

“…Despite of these variations, the produced polymer seems very attractive for various fields such as the wastewater treatment. Hence, it could replace chemical agents (Fe 2 (SO 4 ) 3 , AlCl 3 , etc) for wastewater treatment and sludge conditioning (Ferretti et al 2003, Ben Rebah et al 2018). Generally, the preparation of waste-based medium should be done taken into consideration the waste material composition and the balance between the various nutrients required for the growth.…”

“…The second step of the bioprocess, is the strain culture and in order to determine the time of the highest polymer production, the adequate growth medium composition and operating parameters (pH, temperature, aeration, inoculation rate, etc) should be optimized. Finally, actions of separation and extraction are needed to produce the polymer (Ben Rebah et al 2018). Depending on various factors (strain, medium composition, operating parameters, etc), the produced microbial flocculants varied in composition (polysaccharides, proteins, nucleic acid, etc) and in the flocculating activity (FA) (Ben Rebah et al 2018).…”

“…Finally, actions of separation and extraction are needed to produce the polymer (Ben Rebah et al 2018). Depending on various factors (strain, medium composition, operating parameters, etc), the produced microbial flocculants varied in composition (polysaccharides, proteins, nucleic acid, etc) and in the flocculating activity (FA) (Ben Rebah et al 2018). The bioflocculant production can be enhanced through process optimization of various control parameters such culture medium composition (carbon and nitrogen sources, the ratio carbon/nitrogen (C/N), growth factors, mineral salts, etc) and growth conditions (food/microorganism (F/M), pH, temperature, aeration, inoculum rate, etc) (Fang et al 2020, Arias et al 2020, Lv et al 2019, Zhou and Xu (2019, Hu et al 2019.…”