Recent advances in polysaccharide bio-based flocculants

Deciphering the Dual Roles of an Alginate-Based Biodegradable Flocculant in Anaerobic Fermentation of Waste Activated Sludge: Dewaterability and Degradability

Biodegradable flocculants are rarely used in waste activated sludge (WAS) fermentation. This study introduces an alginate-based biodegradable flocculant (ABF) to enhance both the dewatering and degradation of WAS during its fermentation. Alginate was identified in structural extracellular polymeric substances (St-EPS) of WAS, with alginate-producing bacteria comprising ∼4.2% of the total bacterial population in WAS. Owing to its larger floc size, higher contact angle, and lower free energy resulting from the Lewis acid-base interaction, the addition of the prepared ABF with a network structure significantly improved the dewaterability of WAS and reduced capillary suction time (CST) by 72%. The utilization of ABF by an enriched alginate-degrading consortium (ADC) resulted in a 35.5% increase in the WAS methane yield owing to its higher hydrolytic activity on both ABF and St-EPS. Additionally, after a 30 day fermentation, CST decreased by 62% owing to the enhanced degradation of St-EPS (74.4%) and lower viscosity in the WAS + ABF + ADC group. The genus Bacteroides, comprising 12% of ADC, used alginate lyase (EC 4.2.2.3) and pectate lyase (EC 4.2.2.2 and EC 4.2.2.9) to degrade alginate and polygalacturonate in St-EPS, respectively. Therefore, this study introduces a new flocculant and elucidates its dual roles in enhancing both the dewaterability and degradability of WAS. These advancements improve WAS fermentation, resulting in higher methane production and lower CSTs.

Recent progress and perspectives of typical renewable bio-based flocculants: characteristics and application in wastewater treatment

The research on bio-based flocculants for waste resource utilization and environmental protection has garnered significant attention. Bio-based flocculants encompass plant-based, animal-based, and microbial variants that are prepared and modified through biological, chemical, and physical methods. These flocculants possess abundant functional groups, unique structures, and distinctive characteristics. This review comprehensively discussed the removal rates of conventional pollutants and emerging pollutants by bio-based flocculants, the interaction between these flocculants and pollutants, their impact on flocculation performance in wastewater treatment, as well as their application cost. Furthermore, it described the common challenges faced by bio-based flocculants in practical applications along with various improvement strategies to address them. With their safety profile, environmental friendliness, efficiency, renewability, and wide availability from diverse sources, bio-based flocculants hold great potential for widespread use in wastewater treatment.

Inherited Structure Properties of Larch Arabinogalactan Affected via the TEMPO/NaBr/NaOCl Oxidative System

Arabinogalactan (AG), extracted from larch wood, is a β-1,3-galactan backbone and β-1,6-galactan side chains with attached α-1-arabinofuranosyl and β-1-arabinopyranosyl residues. Although the structural characteristics of arabinogalactan II type have already been studied, its functionalization using 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation remains a promising avenue. In this study, the oxidation of AG, a neutral polysaccharide, was carried out using the TEMPO/NaBr/NaOCl system, resulting in polyuronides with improved functional properties. The oxidation of AG was controlled by analyzing portions of the reaction mixture using spectrophotometric and titration methods. To determine the effect of the TEMPO/NaBr/NaOCl system, air-dried samples of native and oxidized AG were studied by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy, as well as by gel permeation chromatography. Compounds that model free (1,1-diphenyl-2-picrylhydrazyl (DPPH)) and hydroxyl radicals (iron(II) sulfate, hydrogen peroxide, and salicylic acid) were used to study the antioxidant properties. It was found that, in oxidized forms of AG, the content of carboxyl groups increases by 0.61 mmol compared to native AG. The transformation of oxidized AG into the H+ form using a strong acid cation exchanger leads to an increase in the number of active carboxyl groups to 0.76 mmol. Using FTIR spectroscopy, characteristic absorption bands (1742, 1639, and 1403 cm-1) were established, indicating the occurrence of oxidative processes with a subsequent reduction in the carboxyl group. The functionality of AG was also confirmed by gel permeation chromatography (GPC), which is reflected in an increase in molecular weights (up to 15,700 g/mol). A study of the antioxidant properties of the oxidized and protonated forms of AG show that the obtained antioxidant activity (AOA) values are generally characteristic of polyuronic acids. Therefore, the TEMPO oxidation of AG and other neutral polysaccharides can be considered a promising approach for obtaining compounds with the necessary controlled characteristics.

Snapshot Sampling May Not Be Enough to Obtain Robust Estimates for Riverine Microplastic Loads

Wastewater treatment plants (WWTPs) have been described as key contributors of microplastics (MPs) to aquatic systems, yet temporal fluctuations in MP concentrations and loads downstream are underexplored. This study investigated how different sampling frequencies (hourly, weekly, and monthly) affect MP estimates in a stream linked to a single WWTP. Utilizing fluorescence microscopy and Raman spectroscopy, considerable hourly variations in MP concentrations were discovered, while the polymer composition remained consistent. This temporal variability in MP loads was influenced by MP concentration, discharge rates, or a mix of both. These results show a high uncertainty, as relying on sparse snapshot samples combined with annual discharge data led to significant uncertainties in MP load estimates (over- and/or underestimation of emissions by 3.8 billion MPs annually at this site). Our findings stress the necessity of higher-frequency sampling for better comprehending the hydrodynamic factors influencing MP transport. This improved understanding enables a more accurate quantification of MP dynamics, crucial for downstream impact assessments. Therefore, preliminary reconnaissance campaigns are essential for designing extended, representative site-monitoring programs and ensuring more precise trend predictions on a larger scale.

Harnessing Renewable Lignocellulosic Potential for Sustainable Wastewater Purification

Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development. However, the resulting by-products and the synthetic process characterized by complexity, high cost, and environmental pollution limit the further development of lignocellulose-based materials. Here, we developed a sustainable strategy that involved a new functional deep eutectic solvent (DES) to deconstruct industrial xylose residue into cellulose-rich residue with carboxyl groups, lignin with carboxyl and quaternary ammonium salt groups, and DES effluent rich in lignin fragments. Subsequently, these fractions equipped with customized functionality were used to produce efficient wastewater remediation materials in cost-effective and environmentally sound manners, namely, photocatalyst prepared by carboxyl-modified cellulose residue, biochar-based adsorbent originated from modified lignin, and flocculant synthesized by self-catalytic in situ copolymerization of residual DES effluent at room temperature. Under the no-waste principle, this strategy upgraded the whole components of waste lignocellulose into high-value-added wastewater remediation materials with excellent universality. These materials in coordination with each other can stepwise purify high-hazardous mineral processing wastewater into drinkable water, including the removal of 99.81% of suspended solids, almost all various heavy metal ions, and 97.09% chemical oxygen demand, respectively. This work provided promising solutions and blueprints for lignocellulosic resources to alleviate water shortages while also advancing the global goal of carbon neutrality.

Alteromonas arenosi sp. nov., a novel bioflocculant-producing bacterium, isolated from intertidal sand

A novel Gram-stain-negative, strictly aerobic and bioflocculant-producing bacterium, designated as ASW11-36T, was isolated from an intertidal sand collected from coastal areas of Qingdao, PR China. Growth occurred at 15-40 °C (optimum, 30 °C), pH 7.0-9.0 (optimum, pH 7.5) and with 1.5-7.0% (w/v) NaCl (optimum, 2.5-3.0%). In the whole-cell fatty acid pattern prevailed C16:0 and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). The major isoprenoid quinone was determined to be Q-8 and the major polar lipids were phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), one unidentified aminolipid (AL), one unidentified glycolipid (GL), and two lipids (L1, L2). Based on the phylogenetic analyses of 16S rRNA gene sequences and 618 single-copy orthologous clusters, strain ASW11-36T could represent a novel member of the genus Alteromonas and was closely related to Alteromonas flava P0211T (98.4%) and Alteromonas facilis P0213T (98.3%). The pairwise average nucleotide identity and digital DNA-DNA hybridization values of the ASW11-36T genome assembly against the closely related species genomes were 71.8% and 21.7%, respectively, that clearly lower than the proposed thresholds for species. Based on phenotypic, phylogenetic, and chemotaxonomic analyses, strain ASW11-36T is considered to represent a novel species of the genus Alteromonas, for which the name Alteromonas arenosi sp. nov. is proposed. The type strain is ASW11-36T (= KCTC 82496T = MCCC 1K05585T). In addition, the strain yielded 65% of flocculating efficiency in kaolin suspension with CaCl2 addition. The draft genome of ASW11-36T shared abundant putative CAZy family related genes, especially involved in the biosynthesis of exopolysaccharides, implying its potential environmental and biological applications.

Mechanism analysis of a novel natural cationic modified dextran flocculant and its application in the treatment of blue algal blooms

Blue algae, a type of harmful microalgae, are responsible for causing harmful algal blooms that result in severe environmental issues. To address this problem, a biopolysaccharide-based flocculant was developed for treating blue algae blooms. This flocculant was created by modifying high molecular weight dextran using the natural cationic monomer betaine (Dex-Bet), making it environmentally friendly. Various techniques were used to characterize the prepared Dex-Bet flocculant, including infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The effectiveness of the Dex-Bet flocculant was evaluated using kaolin-simulated wastewater. The results showed that the treated supernatant had a transmittance of up to 98.25 %. Zeta potential analysis revealed that the main mechanisms of flocculation were charge neutralization, charge patching, and adsorption bridging. The application of Dex-Bet in treating blue-green algae resulted in a maximum removal rate of 98.2 %. This study provides a potential flocculant for blue algae bloom treatment.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Full biomass-based multifunctional flocculant from lignin and cationic starch

Flocculation is a common process for wastewater treatment. However, the most commonly used organic synthetic flocculants such as polyacrylamide are petroleum-based. In this work, biomass lignin was grafted with cationic starch to synthesize low-cost, green and fully biomass-based multifunctional flocculants. The cationic polyacrylamide was replaced by cheap industrial cationic starch. Hyperbranched multifunctional lignin-grafted cationic starch flocculant (CS-L) was successfully prepared via ring-opening reaction with epichlorohydrin. The mass content of lignin in the grafted product was between 16.6 % and 70.1 %. With the dosage of CS-L between 4.0 and 7.5 mg/l, the turbidity removal rate for 500 mg/l kaolin suspension reached more than 97 %. When the dosage of CS-L was 24 mg/l, the removal rate of 50 mg/l Cu2+ reached 85.7 %. Importantly, when the mixed solution of kaolin particles and Cu2+ was treated, the synchronous removal rates of kaolin and Cu2+ reached 90 % and 72 % respectively in the range of 8.0-12.0 mg/l flocculant addition. The synthesized lignin-grafted cationic starch flocculant showed an excellent multifunctional flocculation function.

Advanced strategies for metabolic engineering of Bacillus to produce extracellular polymeric substances

Extracellular polymeric substances are mainly synthesized via a variety of biosynthetic pathways in bacteria. Bacilli-sourced extracellular polymeric substances, such as exopolysaccharides (EPS) and poly-γ-glutamic acid (γ-PGA), can serve as active ingredients and hydrogels, and have other important industrial applications. However, the functional diversity and widespread applications of these extracellular polymeric substances, are hampered by their low yields and high costs. Biosynthesis of extracellular polymeric substances is very complex in Bacillus, and there is no detailed elucidation of the reactions and regulations among various metabolic pathways. Therefore, a better understanding of the metabolic mechanisms is required to broaden the functions and increase the yield of extracellular polymeric substances. This review systematically summarizes the biosynthesis and metabolic mechanisms of extracellular polymeric substances in Bacillus, providing an in-depth understanding of the relationships between EPS and γ-PGA synthesis. This review provides a better clarification of Bacillus metabolic mechanisms during extracellular polymeric substance secretion and thus benefits their application and commercialization.

Bioflocculation characteristics of bound extracellular polymers substances from Pseudomonas sp. XD-3 and behavior of polysaccharides

This study aimed to investigate the bioflocculation characteristics of bound extracellular polymers substances (B-EPS), which were extracted from Pseudomonas sp. XD-3. The flocculation efficiency of B-EPS achieved about 80%- 95% with an initial pH of 4-7, kaolin concentrations of 3-7 g L-1, temperature of 25-100 ℃ and B-EPS dosage of 9-105 mg L-1. The bioflocculation process of B-EPS conformed to pseudo-second-order kinetic mode, suggesting that the bioflocculation belonged to chemical adsorption process. Enzymatic hydrolysis experiments demonstrated that both polysaccharides and proteins were active components for bioflocculation. The polysaccharides were irregular aggregates with rough and porous surfaces and contained hydroxyl and carboxyl groups, which helped to promote bridging effect. Ribose, glucose and galactose were the main monosaccharides of polysaccharides. The molecular weight of the polysaccharides was relatively small, but the relatively loose configuration exposed more ion bridging sites, thus promoting the bioflocculation. Optimizing the ingredients of culture medium and culture time for B-EPS were effective strategies to increase the yield of flocculation active components. When the conditions were 10% of 2 g L-1 KH2PO4 + 5 g L-1 K2HPO4, 0.05% of Tween-80, citrate as carbon source and 32-48 h of culture time, both proteins and polysaccharides in B-EPS were significantly improved. This study gives an in-deep understanding on the flocculation characteristics of a novel bioflocculant from Pseudomonas sp. XD-3, which is conducive to the widespread application of bioflocculation.

New chitosan-biochar composite derived from agricultural waste for removing sulfamethoxazole antibiotics in water

This study aims to develop a new chitosan-biochar composite derived from agricultural waste for removing sulfamethoxazole (SMX) antibiotics in water. Biochar was prepared from orange peel (OB) and spent coffee grounds (SCB). To fabricate chitosan-biochar composites, chitosan and biochar were crosslinked with glutaraldehyde. Results showed that pH, adsorbent dosage, time, temperature, and initial concentrations have a significant impact on the SMX adsorption. The adsorption data was better described by Langmuir (with good regression) than Freundlich model. The highest adsorption capacity (Q_max) of SMX on OB, SCB, CTS-OB, and CTS-SCB were 3.49, 7.65, 7.24, and 14.73 mg/g, respectively. The Freundlich constant (K_F) values for adsorption capacity were 1.66, 1.91, 2.57, and 5.57 (mg^1-nLⁿ/g), respectively, for OB, SCB, CTS-OB, and CTS-SCB. Ion exchange, π bonding, hydrogen bonding and pore filling, were proposed as dominant mechanisms of SMX removal process.

Effects of fluidised carriers on the community composition, settleability and energy production of indigenous microalgal consortia cultivated in treated wastewater

Fluidised-bed systems are a promising approach to microalgal cultivation, but few studies have considered their application to indigenous microalgal consortia (IMCs), which have high adaptability to wastewater. In this study, IMCs were cultivated in treated wastewater with and without fluidised carriers, and the effects of operating parameters were considered. Microalgae in the culture were confirmed to originate from the carriers, and the IMC presence on the carriers was promoted by decreasing the carrier replacement number and increasing the culture replacement volume. The presence of carriers enabled greater nutrient removal from the treated wastewater by the cultivated IMCs. Without carriers, IMCs in the culture were scattered and showed poor settleability. With carriers, IMCs in the culture exhibited good settleability owing to floc formation. The improved settleability with carriers also increased the energy production from sedimented IMCs.

Parametric and kinetic studies of activated sludge dewatering by cationic chitosan-like bioflocculant BF01314 produced from Citrobacter youngae

Bacterial strains belonging to Citrobacter spp. were reported to produce polysaccharides consisting of N-acetylglucosamine and glucosamine like chitosan, with high flocculation activity. In this work, the flocculation dewatering performance of activated sludge conditioned by a novel cationic chitosan-like bioflocculant (BF) named BF01314, produced from Citrobacter youngae GTC 01314, was evaluated under the influences of flocculant dosage, pH, and temperature. At BF dosage as low as 0.5 kg/t DS, the sludge dewaterability was significantly enhanced in comparison to the raw (untreated) sludge, featuring well-flocculated characteristic (reduction in CST from 22.0 s to 9.4 s) and good sludge filterability with reduced resistance (reduction in SRF by one order from 7.42 × 1011 to 9.59 × 10¹⁰ m/kg) and increased compactness of sludge (increase in CSC from 15.2 to 23.2%). Besides, the BF demonstrated comparable high sludge dewatering performance within the pH range between 2 and 8, and temperature range between 25 °C and 80 °C. Comparison between the BF, the pristine chitosan and the commercial cationic copolymer MF 7861 demonstrated equivalent performance with enhanced dewaterability at the dosage between 2.0 and 3.0 kg/t DS. Besides, the BF demonstrated strong flocculation activity (>99%) when added to the sludge suspension using moderate to high flocculation speeds (100-200 rpm) with at least 3-min mixing time. The BF's reaction in sludge flocculation was best fitted with a pseudo first-order kinetic model. Electrostatic charge patching and polymer bridging mechanisms are believed to be the dominant mechanistic phenomena during the BF's sludge conditioning process (coagulation-flocculation).

Synthesis of Natural-Inspired Materials by Irradiation: Data Mining from the Perspective of Their Functional Properties in Wastewater Treatment

The present study is focused on assessing the interrelation of variables involved in the synthesis of natural-inspired copolymers by electron beam grafting while taking the functionality of the resulting materials into account. In this respect, copolymers of starch-graft-polyacrylamide (St-g-PAM) were synthesized by irradiation, and their flocculation efficiency regarding the total suspended solids (TSS), chemical oxygen demand (COD), and fatty matters (FM) was tested in coagulation-flocculation experiments at laboratory scale on wastewater from the oil industry. Data mining involved approaches related to the association (correlation and dimensionality reduction with principal component analysis (PCA)), clustering by agglomerative hierarchical clustering (AHC), classifying by classification and regression tree (CART), and prediction (decision tree prediction, multiple linear regression (MLR), and principal component regression (PCR)) of treatments applied with the variation of the monomer concentration, irradiation dose, and dose rate. The relationship mining proved that the level of COD was significantly affected by the irradiation dose and monomer concentration, and FM was mainly affected by the dose rate (significance level = 0.05). TSS showed the highest negative correlation with the tested variables. Moreover, the consequences of MLR demonstrated an acceptable accuracy (mean absolute percentage error < 5%) for COD and FM; meanwhile, linear modeling together with the consequences of PCA in the structure of PCR could help to simplify and improve the prediction accuracy of equations.

High performance, cost-effective and ecofriendly flocculant synthesized by grafting carboxymethyl cellulose and alginate with itaconic acid

Natural polymer flocculant possesses an exciting prospect in water treatment due to its non-toxicity, wide source, low cost and biodegradability. In this work, we have successfully synthesized the anionic terpolymer of carboxymethyl cellulose-itaconic acid‑sodium alginate (CIS) by microwave-assisted copolymerization. By studying the flocculation properties towards cationic dye of crystal violet (CV), the optimum synthesis conditions were determined. The maximum removal rate of 100 mg/L CV simulated wastewater was 92.2 % with CIS concentration of 30 mg/L. The flocculation kinetic results showed the rapid dye removal rate and the dye decolorization ratio of 89.8 % could be obtained at 75 s. Moreover, the CIS flocculant showed excellent flocculation effects in ambient pH of 4-10, flocculation temperature of 10-40 °C, and various inorganic salts. In general, the anionic CIS flocculant shows excellent cost effectiveness, where the predicted operation cost of as-prepared CIS is about 60 % of conventional polyacrylamide flocculant. It also has the advantages of excellent ecofriendliness and rich raw material source, indicative its potential applications of wastewater treatment.

Generation of Sulfonated Lignin-Starch Polymer and Its Use As a Flocculant

This paper reports the polymerization of tall oil lignin (TOL), starch, and 2-methyl-2-propene-1-sulfonic acid sodium salt (MPSA), a sulfonate-containing monomer, in a three-component system to generate flocculants for colloidal systems. By utilizing the advanced 1H, COSY, HSQC, HSQC-TOCSY, and HMBC NMR techniques, it was confirmed that the phenolic substructures of TOL and the anhydroglucose unit of starch were covalently polymerized by the monomer to generate the three-block copolymer. The molecular weight, radius of gyration, and shape factor of the copolymers were fundamentally correlated to the structure of lignin and starch, as well as the polymerization outcomes. The deposition behavior of the copolymer, studied by a quartz crystal microbalance with dissipation (QCM-D) analysis, revealed that the copolymer with a larger molecular weight (ALS-5) deposited more and generated more compact adlayer than the copolymer with a smaller molecular weight on a solid surface. Owing to its higher charge density, molecular weight, and extended coil-like structure, ALS-5 produced larger flocs with faster sedimentation in the colloidal systems, regardless of the extent of agitation and gravitational force. The results of this work provide a new approach to preparing a lignin-starch polymer, i.e., a sustainable biomacromolecule with excellent flocculation performance in colloidal systems.

Cationic Pullulan Derivatives Based Flocculants for Removal of Some Metal Oxides from Simulated Wastewater

Modified polysaccharides have been increasingly used as flocculants in wastewater treatment due to their non-toxicity, low price, biodegradability, etc. However, the pullulan derivatives are less used in wastewater purification processes. Therefore, this article presents some data regarding FeO and TiO₂ particle removal from model suspensions by some pullulan derivatives with pendant quaternary ammonium salt groups, trimethylammonium propyl carbamate chloride (TMAP_x-P). The influence of the polymer ionic content, dose, and initial solution concentration as well as of the dispersion pH and composition (metal oxide content, salts, and kaolin) on the separation efficacy were considered. UV-Vis spectroscopy measurements have shown a very good removal efficacy of TMAP_x-P for the FeO particles (around 95% and more), irrespective of the polymer and suspension characteristics; a lower clarification of the TiO₂ particles suspension (removal efficiency between 68% and 75%) was noticed. Both the zeta potential and the particle aggregates size measurements revealed the charge patch as the main mechanism which governs the metal oxide removal process. The surface morphology analysis/EDX data provided supplementary evidence regarding the separation process. A good removal efficiency (90%) of the pullulan derivatives/FeO flocs for the Bordeaux mixture particles from simulated wastewater was found.

Experimentally Created Magnetic Force in Microbiological Space and On-Earth Studies: Perspectives and Restrictions

Magnetic force and gravity are two fundamental forces affecting all living organisms, including bacteria. On Earth, experimentally created magnetic force can be used to counterbalance gravity and place living organisms in conditions of magnetic levitation. Under conditions of microgravity, magnetic force becomes the only force that moves bacteria, providing an acceleration towards areas of the lowest magnetic field and locking cells in this area. In this review, we consider basic principles and experimental systems used to create a magnetic force strong enough to balance gravity. Further, we describe how magnetic levitation is applied in on-Earth microbiological studies. Next, we consider bacterial behavior under combined conditions of microgravity and magnetic force onboard a spacecraft. At last, we discuss restrictions on applications of magnetic force in microbiological studies and the impact of these restrictions on biotechnological applications under space and on-Earth conditions.

Dataset on rheological measurements of xanthan gum aqueous dispersions containing sodium chloride and settling dynamics of spheres and disks in these dispersions

This paper presents a dataset collected in laboratory experiments on the settling of solid spheres and disks in shear-thinning and viscoelastic aqueous solutions of xanthan gum with sodium chloride addition. Two types of spheres with density of 1.41 g/cm³ varying in diameter (3.00 mm and 1.59 mm) and four types of disks with density of 1.43 g/cm³ and thickness of 0.3 mm varying in diameter (1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm) were considered. A single particle was settling in a column filled with a test solution which varied in salt content (from 0 M to 0.9 M), while xanthan gum content was constant (1 g/L). The total of elven solutions were tested. For each experimental set, a sequence of images with a falling particle was captured using a camera with macro lenses. Dataset includes position of particle in time and enables the evaluation of settling velocity. Rheological measurements were carried out for each test solution to assess flow properties and viscoelasticity. The following measurements were performed: shear dependent viscosity, shear stress amplitude sweeps, frequency sweeps, the dependence of the first normal stresses difference on shear strain at constant frequency (1 Hz). Datasets may be useful in various areas on fluid mechanics and rheology, e.g., in research on the impact of salinity on rheological properties of exopolymer solutions, to develop numerical models on solid particles settling in non-Newtonian fluids, and in studies on the impact of exopolymers and electrolytes dissolved in water on settling dynamics of solid particles.

A Functionalized Polysaccharide from Sphingomonas sp. HL-1 for High-Performance Flocculation

The characterization and flocculation mechanism of a biopolymer flocculant produced by Sphingomonas sp. HL-1, were investigated. The bio-flocculant HL1 was identified as an acidic polysaccharide, mainly composed of glucose, and also contained a small amount of mannose, galacturonic acid and guluronic acid. The flocculating activity of the purified HL1 polysaccharide could be activated by trivalent cations, and its flocculation mechanism was mainly charge neutralization and bridging. The working concentration of fermentation broth HL1 in a kaolin suspension was only 1/10,000 (v/v), in which the polysaccharide concentration was about 2 mg/L. The bio-flocculant HL1 maintained high efficiency at a wide range of pH (pH 3-10). It also exhibited good flocculating activity at a temperature range of 20-40 °C; it could even tolerate high salinity and kept activity at a mineralization degree of 50,000 mg/L. Therefore, the bio-flocculant HL1 has a good application prospect in the treatment of wastewater over a broad pH range and in high salinity.

Bio-flocculation of Microcystis aeruginosa by using fungal pellets of Aspergillus oryzae: Performance and mechanism

Algal blooms caused by eutrophication are global phenomena that seriously threaten the sustainable use of freshwater resources. Traditional water treatment chemicals often typically lead to high levels of residue and cause damage to the morphology of algal cells. This study investigated an eco-friendly fungal bio-flocculant, Aspergillus oryzae, to remove the representative microalgae (Microcystis aeruginosa). Furthermore, it explored crucial flocculation parameters, adsorption kinetics, and thermodynamics of microalgae using A. oryzae. Accordingly, a flocculation efficiency of >95% was achieved when the fungus was cultured for six days, flocculant dosage was 11 g/L, rotation speed was 100 rpm, temperature was 25 °C, flocculation time was 5 h, and pH ranged between 4.0 and 9.0. KEGG analysis based on the genomic data, and chemical composition analysis revealed that proteins and polysaccharides were the major components of metabolites. Zeta potential analysis, scanning electron microscopy, three-dimensional fluorescence, X-ray spectroscopy, and infrared spectroscopy, electrostatic attraction revealed that electrostatic attraction promoted the destabilization and aggregation of microalgae. Additionally, hyphal surface adsorption and chemisorption from extracellular proteins and exopolysaccharides aided in the removal of microalgae. Therefore, fungi-based bio-flocculants have the potential to remove microalgae in a simple, effective, and eco-friendly manner without the complex extraction of extracellular metabolites.

Immune enhancement of N-2-Hydroxypropyl trimethyl ammonium chloride chitosan/carboxymethyl chitosan nanoparticles vaccine

The immunogenicity and toxicity of N-2-Hydroxypropyl trimethyl ammonium chloride chitosan/N, O-carboxymethyl chitosan nanoparticles (N-2-HACC/CMCS NPs) as a universal vaccine adjuvant/delivery system remains unclear. The present study indicated that the positively charged N-2-HACC/CMCS NPs showed a regular spherical morphology, with a particle size of 219 ± 13.72 nm, zeta potential of 37.28 ± 4.58 mV, had hemocompatibility and biodegradation. Acute toxicity, repeated dose toxicity, abnormal toxicity, muscle stimulation, whole body allergic reaction evaluation in vitro, and cytotoxicity in vivo confirmed N-2-HACC/CMCS NPs is safe and non-toxic. N-2-HACC/OVA/CMCS NPs were prepared to evaluate the immunogenicity, which showed a particle size of 248.1 ± 15.53 nm, zeta potential of 17.24 ± 1.28 mV, encapsulation efficiency of 92.43 ± 0.96 %, and loading capacity of 42.97 ± 0.07 %. Oral or intramuscular route with the N-2-HACC/OVA/CMCS NPs in mice not only induced higher IgG, IgG1, IgG2a, and sIgA antibody titers, but also significantly produced higher levels of IL-6, IL-4, IFN-γ, and TNF-α, demonstrating that the N-2-HACC/OVA/CMCS NPs enhance humoral, cellular, and mucosal immune responses. Our results not only support the N-2-HACC/CMCS NPs to be a safe and potential universal nano adjuvant/delivery system in vaccine development, especially mucosal vaccines, but also rich the database knowledge of adjuvant/delivery systems, and provide new direction to introduce more licensed adjuvants.

Cactus Cladode Juice as Bioflocculant in the Flocculation-Thickening Process for Phosphate Washing Plant: A Comparative Study with Anionic Polyacrylamide

In the phosphate industry, the thickening process is vital to increasing the solid slurry concentration and to recovering water that is as clear as possible. The performance of the thickening process depends mainly on the coagulation–flocculation effect. The thickening process is based on flocculant agents to concentrate particles: flotation and washing plant rejects as large flocs, which accelerate their sedimentation velocity. The phosphate industry worldwide uses synthetical flocculants such as polyacrylamides. These flocculants are non-biodegradable, limiting the process efficiency regarding cost and harmful effects on the environment. This study proposes cactus cladodes juice as an eco-friendly alternative to industrial flocculants. The particle size of the phosphate samples ranges from 0 μm to 160 μm, with a solid concentration of 8%. This bioflocculant allowed for an increase in sedimentation velocity of 95% compared with the case without flocculant. The optimal amount of cactus bioflocculant for decanting 1 tonne of phosphate pulp at pH 7–8 is 1.12 kg. Special attention is paid to understanding the flocculation mechanism. The results of the physicochemical characterization show that the flocculant biopolymers have similar characteristics to anionic polyacrylamide. This work indicates the promising application of the cactus juice bioflocculant in phosphate washing plants.

Grafted Pullulan Derivatives for Reducing the Content of Some Pesticides from Simulated Wastewater

The goal of the current article was to obtain data regarding the application of a series of grafted pullulan derivatives, as flocculating agents, for removal of some pesticide formulations from model wastewater. The pullulan derivatives are cationic polyelectrolytes, with various content and length of grafted poly[(3-acrylamidopropyl)-trimethylammonium chloride] chains onto the pullulan (P-g-pAPTAC)]. The commercial pesticides are either fungicide (Bordeaux Mixture) (BM) or insecticides (Decis (Dc)—active ingredient Deltamethrin, Confidor Oil (CO)—active ingredient Imidacloprid, Confidor Energy (CE)—active ingredients Deltamethrin and Imidacloprid and Novadim Progress (NP)—active ingredient Dimethoate). The removal efficiency has been assessed by UV-Vis spectroscopy measurements as a function of some parameters, namely polymer dose, grafted chains content and length, pesticides concentration. The P-g-pAPTAC samples showed good removal efficacy at dose_op, more than 94% for BM, between 84 and 90% for DC, CO and CE and around 93% for NP. The maximum percentage removal decreased with the pesticides (DC, CO, CE, NP) concentration declining; no effect of BM concentration in suspension on its removal efficiency process has been noted. Differences indicated by zeta potential and particle size distribution measurements regarding the pesticides removal mechanisms by pullulan derivatives (charge neutralization, bridging, etc.) are discussed.

Bioflocculant produced by Bacillus velezensis and its potential application in brewery wastewater treatment

This study was designed to evaluate the potential of bioflocculant producing strains isolated from wastewater sludge. According to the Plackett–Burman design, the response surface revealed glucose, magnesium sulfate, and ammonium sulfate as critical media components of the nutritional source, whereas the central composite design affirmed an optimum concentration of the critical nutritional source as 16.0 g/l (glucose), 3.5 g/l magnesium sulfate heptahydrate (MgSO₄.7H₂O), and 1.6 g/l ammonium sulfate ( (NH₄)₂SO₄), yielding an optimal flocculation activity of 96.8%. Fourier Transformer Infrared Spectroscopy (FTIR) analysis confirmed the presence of hydroxyl, carboxyl and methoxyl in the structure of the bioflocculant. Additionally, chemical analysis affirmed the presence of mainly a polysaccharide in the main backbone of the purified bioflocculant with no detection of protein. Energy Dispersive X-ray analysis affirmed the presence of chlorine, phosphorous, oxygen and chlorine as representatives of elemental composition. Thermogravimetric (TGA) analysis revealed over 60% weight was retained at a temperature range of 700 °C. The purified bioflocculant remarkably removed chemical oxygen demand, biological oxygen demand and turbidity in brewery wastewater. This study suggested that the bioflocculant might be an alternate candidate for wastewater treatment.

Putative functions of EpsK in teichuronic acid synthesis and phosphate starvation in Bacillus licheniformis

Extracellular polymeric substances (EPSs) are extracellular macromolecules in bacteria, which function in cell growth and show potential for mechanism study and biosynthesis application. However, the biosynthesis mechanism of EPS is still not clear. We herein chose Bacillus licheniformis CGMCC 2876 as a target strain to investigate the EPS biosynthesis. epsK, a member of eps cluster, the predicted polysaccharide synthesis cluster, was overexpressed and showed that the overexpression of epsK led to a 26.54% decrease in the production of EPS and resulted in slenderer cell shape. Transcriptome analysis combined with protein-protein interactions analysis and protein modeling revealed that epsK was likely responsible for the synthesis of teichuronic acid, a substitute cell wall component of teichoic acid when the strain was suffering phosphate limitation. Further cell cultivation showed that either phosphate limitation or the overexpression of teichuronic acid synthesis genes, tuaB and tuaE could similarly lead to EPS reduction. The enhanced production of teichuronic acid induced by epsK overexpression triggered the endogenous phosphate starvation, resulting in the decreased EPS synthesis and biomass, and the enhanced bacterial chemotaxis. This study presents an insight into the mechanism of EPS synthesis and offers the potential in controllable synthesis of target products.

Adsorption and interaction mechanisms of Chi-g-P(AM-DMDAAC) assisted settling of kaolinite in a two-step flocculation process

Flocculation has been widely employed in treatment of mineral tailings and water management. In this study, a chitosan-graft-poly(acrylamide-dimethyl diallyl ammonium chloride) (Chi-g-P(AM-DMDAAC)) was synthesized in-house. The adsorption and interaction mechanisms of Chi-g-P(AM-DMDAAC) and an anionic polyacrylamide (APAM) in a two-step flocculation process of kaolinite were explored using settlement tests, zeta potential measurement, quartz crystal micro-balance with dissipation (QCM-D) and atomic force microscopy (AFM) technique. The type of primary flocculant was critical for the two-step flocculation process. The treatment of the kaolinite suspension using 1 mg/L of Chi-g-P(AM-DMDAAC) followed by adding 2 mg/L of APAM displayed more efficient flocculation performance. QCM-D results showed that three dissipative layers were assembled on model kaolinite surface after sequentially injecting 3.5 mg/L of Chi-g-P(AM-DMDAAC), 0.05 wt% kaolinite suspension and 2.5 mg/L of APAM. The above total adsorption amount (Δf of -64.9 Hz) was much higher than that of using the two flocculants in reverse order (Δf of -23.1 Hz). This result indicated that the adsorption layer of the positively charged Chi-g-P(AM-DMDAAC) on kaolinite surface provided active adsorption sites for APAM. Further AFM measurement confirmed that the average adhesion between the silicon tip adsorbed Chi-g-P(AM-DMDAAC) and model kaolinite surface in 2.5 mg/L APAM solution increased from 0.25 ± 0.1 nN to 4.2 ± 0.3 nN with the effective interaction range of 700 nm, which was stronger than that measured between a bare silicon tip and silica substrate in single-component-flocculant solutions. The highly efficient two-step flocculation process could be ascribed to the strong electrostatic attraction between the kaolinite and the oppositely charged Chi-g-P(AM-DMDAAC) and APAM. Findings in this study will benefit the development of environmentally friendly flocculant for mineral tailings and water treatment.

Novel Copolymer Cationic from Agroindustrial Waste using Microwave

Background. A cationic copolymer has been developed as a substitute for synthetic coagulants, resulting in decreased pH, potential health problems, high costs, and large sludge volumes. Aim. This study evaluated the potential of banana pith in several treatments as a natural coagulant to reduce turbidity, COD, and color. Methods. The synthesis was carried out by inserting the cationic moiety of GTA (3-Chloro-2-hydroxypropyl trimethyl ammonium chloride) into the starch backbone by microwave radiation. Resulth. It has been found that the floculation characteristics depend on the charge neutralization, followed by the linkage between the copolymer chains. The results showed that the initial dose and concentration influenced the copolymer's flocculation performance. Conclusions. Natural polysaccharides can be modified becomes an effective flocculation material for treating clean water and wastewater

Biochemistry, Synthesis, and Applications of Bacterial Cellulose: A Review

The potential of cellulose nanocomposites in the new-generation super-performing nanomaterials is huge, primarily in medical and environment sectors, and secondarily in food, paper, and cosmetic sectors. Despite substantial illumination on the molecular aspects of cellulose synthesis, various process features, namely, cellular export of the nascent polysaccharide chain and arrangement of cellulose fibrils into a quasi-crystalline configuration, remain obscure. To unleash its full potential, current knowledge on nanocellulose dispersion and disintegration of the fibrillar network and the organic/polymer chemistry needs expansion. Bacterial cellulose biosynthesis mechanism for scaled-up production, namely, the kinetics, pathogenicity, production cost, and product quality/consistency remain poorly understood. The bottom-up bacterial cellulose synthesis approach makes it an interesting area for still wider and promising high-end applications, primarily due to the nanosynthesis mechanism involved and the purity of the cellulose. This study attempts to identify the knowledge gap and potential wider applications of bacterial cellulose and bacterial nanocellulose. This review also highlights the manufacture of bacterial cellulose through low-cost substrates, that is, mainly waste from brewing, agriculture, food, and sugar industries as well as textile, lignocellulosic biorefineries, and pulp mills.

Microalgae harvesting techniques: updates and recent technological interventions

Microalgal biomass has garnered attention as a renewable and sustainable resource for producing biodiesel. The harvesting of microalgal biomass is a significant bottleneck being faced by the industries as it is the crucial cost driver in the downstream processing of biomass. Bioharvesting of microalgal biomass mediated by: microbial, animal, and plant-based polymeric flocculants has gained a higher probability of utility in accumulation due to: its higher dewatering potential, less toxicity, and ecofriendly properties. The present review summarizes the key challenges and the technological advancements associated with various such harvesting techniques. The economic and technical aspects of different microalgal harvesting techniques, particularly the cationic polymeric flocculant-based harvesting of microalgal biomass, are also discussed. Furthermore, interactions of flocculants with microalgal biomass and the effects of these interactions on metabolite and lipid extractions are discussed to offer a promising solution for suitability in selecting the most efficient and economical method of microalgal biomass harvesting for cost-effective biodiesel production.

In situ utilization of biomass pretreatment liquor as a novel flocculant for anion dyes removal: Performance and mechanism

In this work, it was first found biomass pretreatment liquor (PL) produced from rice straw (RS) pretreatment with FeCl₃ and polyethylene glycol 400 co-solvent can be used in situ as a new flocculant to remove anionic dyes from wastewater. The removal performance of nine dyes was investigated using various PL doses at different pH values. The experiment indicated that the PL had different flocculation effects on these dyes (color removal efficiency: 42.58-99.84%). Positive color removal results for the dyes were unachievable with six commercial coagulants. Among the nine dyes treated by PL flocculation, the best removal efficiencies for color, turbidity and suspended matter were obtained for Congo red. In the flocculation process, Fe³⁺ plays a role in charge neutralization, lignin nanoparticles (LNP) relies on hydroxyl groups to react instantaneously with the amino groups on the dye, and are bridged together by π-π interactions to promote the formation of floc clusters until they completely settle. Utilization of PL as a flocculant helps pave the way to simultaneously treat waste biomass, waste treatment liquor and dye wastewater. This research is of great significance for future water environment remediation and material development.

Water-Soluble Starch-Based Copolymers Synthesized by Electron Beam Irradiation: Physicochemical and Functional Characterization

Modification of natural polymers for applications in the treatment of waste and surface waters is a continuous concern of researchers and technologists in close relation to the advantages they provide as related to classical polymeric flocculants. In this work, copolymers of starch-graft-polyacrylamide (St-g-PAM) were synthesized by electron beam irradiation used as the free radical initiator by applying different irradiation doses and dose rates. St-g-PAM loaded with ex situ prepared silver nanoparticles was also synthesized by using an accelerated electron beam. The graft copolymers were characterized by chemical analysis, rheology, and differential scanning calorimetry (DSC). The results showed that the level of grafting (monomer conversion coefficient and residual monomer concentration), intrinsic viscosity and thermal behavior (thermodynamic parameters) were influenced by the irradiation dose, dose rate and presence of silver nanoparticles. The flocculation performances of the synthesized copolymers were also tested on water from the meat industry in experiments at the laboratory level. In the coagulation–flocculation process, the copolymer aqueous solutions showed good efficiency to improve different water quality indicators.

The Use of Chitosan and Starch-Based Flocculants for Filter Backwash Water Treatment

Inorganic aluminum or iron salts supported with synthetic polymers are commonly used to eradicate colloidal particles from water in coagulation and flocculation processes. Nevertheless, these agents have several disadvantages, such as large volumes of sludge produced or environmental toxicity. Recently biodegradable polymers have been suggested as eco-friendly flocculants for water treatment. This study aimed to investigate the possibilities of using starch and chitosan and their oxidized derivatives as flocculants for filter backwash water treatment. Dialdehyde starch (DST) and dialdehyde chitosan (DCT) were synthesized by periodate oxidization of natural starch from corn and low molecular weight chitosan. The obtained materials have been characterized with scanning electron microscopy (SEM), ATR-FTIR spectroscopy, and thermogravimetric analysis (TGA). Furthermore, we studied the flocculation properties of polysaccharide flocculants in a series of jar tests. The effectiveness of chitosan and starched-based flocculants was compared to synthetic polymers commonly used to treat iron ions-rich filter backwash water. The environmental aspects of these chemicals, particularly the biodegradability of post-flocculation residues, were also addressed. It was found that oxidized starch and chitosan derivatives can be used as ecological flocculating materials to treat potable water or sludge.

Isolation and Optimization of Culture Conditions of a Bioflocculant-Producing Fungi from Kombucha Tea SCOBY

Biolocculants are gaining attention in research due to their environmental friendliness and innocuousness to human in comparison to the conventional flocculants. The present study aimed to investigate the ability of fungi from Kombucha tea SCOBY to produce effective bioflocculant in bulk. A 16S rRNA gene sequence analysis was utilized to identify the isolate. The medium composition (carbon and nitrogen sources) and culture conditions (inoculum size, temperature, shaking speed, pH, and time) were optimized using one-factor-at-a-time method. The functional groups, morphology, and crystallinity of the bioflocculant were evaluated using Fourier transform infrared (FT-IR), scan electron microscope (SEM) and X-ray diffractometry (XRD). The fungus was found to be Pichia kudriavzevii MH545928.1. It produced a bioflocculant with flocculating activity of 99.1% under optimum conditions; 1% (v/v) inoculum size, glucose and peptone as nutrient sources, 35 °C, pH 7 and the shaking speed of 140 rpm for 60 h. A cumulus-like structure was revealed by SEM; FT-IR displayed the presence of hydroxyl, carboxyl, amine, and thiocynates. The XRD analysis demonstrated the bioflocculant to have big particles with diffraction peaks at 10° and 40° indicating its crystallinity. Based on the obtained results, P. kudriavzevii MH545928.1 has potential industrial applicability as a bioflocculant producer.

Flocculation of combined contaminants of dye and heavy metal by nano-chitosan flocculants

In this study, two multifunctional nano-chitosan flocculants (CPAM-NCS1 and CPAM-NCS2) were made through the graft modification of cationic monomer and carboxymethylchitosan (CMCTS) to remove combined contaminants. The effects of various factors (pH, flocculant dosage and hydraulic mixing conditions) on the flocculation performance under single and composite pollution conditions were systematically investigated, the optimal chemical oxygen demand (COD) and the chromaticity removal rates in the dye wastewater were 79.9% and 83.9% at wastewater pH 7, the fast stirring rate 300 rpm, the fast stirring time 8 min, and the dosage of CPAM-NCS1 80 mg/L, respectively. The optimal removal rates of Cu (II) obtained by CPAM-NCS1 and CPAM-NCS2 at were 80.3% and 75.2% at 60 mg/L and the wastewater pH 7, respectively. The optimal removal rates of Cu (II) and disperse orange were 85.3% and 89.4%, respectively, in a composite pollutant system in which Cu (II) and disperse orange coexisted when the pH of the composite system was 9 and the dosage of CPAM -NCS1 was 60 mg/L. This study proved that nanoflocculants made by modifying CMCTS with different structures can demonstrate ideal flocculation removal performance for dye and heavy metal wastewaters.

Ubiquitous flocculation activity and flocculation production basis of the conglutination mud from Ruditapes philippinarum along the coast of China

Ruditapes philippinarum conglutination mud (RPM) is a typical waste by-product from manila clam R. philippinarum aquaculture. However, RPM from the clam at an aquaculture farm in Zhoushan, China, has been newly reported as a promising natural bioflocculant resource that contains effective flocculating polysaccharides from the clam associated bacteria. With an intent to figure out whether RPM flocculation activity is ubiquitous to the manila clam across a wide geographical range or only the Zhoushan location, and to explore the flocculation production basis and ultimately widen its exploitation scope, in this study, an extensive survey of RPMs from four representative locations along the coast of China was performed to determine their flocculation activity, polysaccharide constitution and bacterial community composition. Frozen preserved RPM samples from Zhoushan, Dalian, Weihai and Zhanjiang exhibited comparable flocculation activities (FRs) ranging from 61.9±2.4% to 73.2±0.9% at dosage of 8 g·L-1; while fresh RPMs from Zhoushan exhibited a much higher flocculation activity of 91.34±1.18% than its frozen counterpart. Polysaccharide extracts from the four locations showed similar monosaccharide constitutions to some extent. The geographical distribution led to certain variation in bacterial community structures. The similarity clustering of the polysaccharide compositions coincided with that of bacterial community structures from RPMs, suggesting that polysaccharides and respective bacterial communities might be the foundation of the flocculation activity for all RPMs. The overlapping OTUs across all the RPMs accounted for 44.6-62.22% of the overall sequences in each sample and contained the vast majority of the most abundant OTUs (Operational Taxonomic Units), forming a common "core microbiome" that is probably responsible for polysaccharide production and flocculation activity development.

Study on the influencing factors of natural pectin's flocculation: Their sources, modification, and optimization

Natural pectin, derived from fruit residue, presented a certain flocculation performance in previous studies. However, the process of extraction and treatment affected the flocculation performance considering the uncontrollable chemical composition and the molecule structure. In this study, degree of esterification (DE), degree of amidation (DA) were used as the internal factors affecting flocculation performance. The DE/DA values of pectin were obtained through FTIR, elemental analyses, H-NMR, and titration measurements. The kaolin suspension was employed for the coagulation jar tests, and the removal of NTU (Nephelometric Turbidity Unit) was used as the index of the flocculation performance. Results showed that the flocculation performance of pectin arising from different fruits was different, which was associated with the various preparation processes. By introducing polar groups into pectin, the flocculation was found to be related to bridging, adsorption, and charge neutralization. Based on the trends of three-dimensional response surfaces, the flocculation effect was improved with the decreased DE and the increased DA. The optimized amidated pectin was obtained by the amidation experiment, the turbidity reduction in wastewater was 99.63%. PRACTITIONER POINTS: The internal influencing factors of pectin as a flocculant were investigated. Different sources of pectin show different flocculation ability. Amidation modification can improve the flocculation performance of pectin. Response surface method to study the interaction of different influencing factors. Pectin may replace synthetic flocculants in water treatment.