Flocculating Activity Research Articles

Evaluation of Coagulation Activities of Moringa oleifera Seeds and Aluminium sulphate on the Treatment of Wastewater from Biodiesel Production

The production of clean biodiesel from vegetable oil generates a large quantity of toxic wastewater. Most researches have been focused on the technical process of biodiesel production but the environmental management of the wastewater generated from the production process has not been given adequate attention. In this study, treatment of wastewater from biodiesel production by coagulation activities of defatted Moringa oleifera seed (DMOS) and inorganic coagulant, Aluminium sulphate (AlSP) was examined. Proximate analysis was carried out on the DMOS powder; and it was also characterized by Fourier Transform Infra-Red (FTIR) analysis. The coagulation process was carried out within 48 hours in jar test apparatus using 0.1%, 0.2%, 0.3%, 0.4% and 0.5% (w/v) of DMOS and AlSP respectively. The results show that 84.54% and 85.65% turbidity reduction occurred at coagulant dosage of 0.2% within 12 hours by DMOS and AlSP respectively. The FTIR analysis of DMOS showed functional groups such as O-H, C-O, and N-H indicating the presence of carbohydrates, esters and proteins respectively. It was suggested that the presence of a cationic protein of high molecular weight destabilizes the dissolved particles in the wastewater, and by a process of neutralization and adsorption, the flocculation and sedimentation activities occurred. Hence, it can be indicated that DMOS powder can effectively be used in place of inorganic coagulant to remove turbidity in biodiesel wastewater.

Coagulant aids showed negligible effect on the flocculation capacity of the fermentation broth produced by a newly isolated strain of Serratia marcescens, XN-6

The flocculation process usually requires the addition of coagulants containing metal ions, which may lead to secondary pollution. In this study, the bio-flocculant produced by Serratia marcescens XN-6 did not depend on the coagulant. The optimal conditions for strain XN-6 to produce its fermentation broth for flocculation were as follows: 2.5% sucrose, 1% ammonium sulfate, 25 °C, pH 7.0, and 5% inoculum size, for which the highest flocculation efficiency of the fermentation broth achieved was 80.08%. The highest flocculation efficiency of the bacterial suspension that could be obtained was only 75.11% after supplementing the broth with 1% CaCl2. These results indicate that the flocculation activity of the fermentation broth was more efficient than that of bacterial suspension, even if CaCl2 was supplemented as a coagulant aid. This study may provide a novel type of bio-flocculant with coagulant aid-independence to be used for breaking down chemical pollution in the environment.

Isolation of Biofilm-Bioflocculant Producing Bacteria from Palm Oil Mill Effluent

A variety of flocculants have been used to treat wastewater by agglomerating various colloidal substances and cells. Due to the adverse effects and high cost of conventional flocculants, bioflocculant which are originally produced by microorganisms are gaining attention. Therefore, this study aimed to identify the biofilm-bioflocculant-producing bacteria which was isolated from palm oil mill effluent in Johor, Malaysia. The isolated bacteria were identified by their colony morphology, Gram-staining and 16S rRNA gene sequence analysis. All isolates were subjected to bioflocculant assay with kaolin clay suspension as a model of wastewater to assess the flocculation efficiency of the bacterial bioflocculants. Two different isolates were successfully identified as Gram-negative bacteria Stenotrophomonas koreensis TR6-01 and Alishewanella agri BL06. S. koreensis TR6-01 shows the highest flocculating activity at 82.79%, followed by A. agri BL06 with 78.52%, respectively. The strongest biofilm producer was shown by S. koreensis TR6-01 and thus, indicates good candidate for future wastewater treatment technology.

Insights into the rapid granulation for treating refractory wastewater under salt stress: Variation of sludge property, treatment performance and microbial community

Industrial effluents often contain high total dissolved solids, which exhibit negative effects on microorganisms. In this study, the granulation process under salt stress in the presence of aniline (a common organic pollutant in several types of industrial wastewaters) was evaluated. The sludge properties, removal performance of pollutants and microbial community structure were investigated. Two reactors, namely R1 and R2 were set up, and influent in R1 contained 15 g L−1 of NaCl while R2 was in the absence of salt as contrast. Results showed that aerobic granules appeared within 20 d under saline conditions with 30 min sludge volume index (SVI30) below 36 mL g−1. High salinity led to larger granule size and extracellular polymeric substances was 1.3 times higher than those in R2. However, part of Ca2+ ions in the bio-aggregate matrix of granules were replaced by Na+ ions in the saline environment, resulting in the modestly higher SVI30. Regarding the treatment performance, high removal efficiencies of aniline and COD were observed (~100% and 93.7%, respectively) after 4-h treatment under saline condition while both nitrification and denitrification were slightly retarded. The average concentration of NH4+-N and TN in the effluent of R1 after formation of granules were 1.2 ± 0.4 and 17.3 ± 1.7 mg L−1, respectively. Microbial community analysis indicated that saline condition could facilitate microorganisms with high flocculation activity and high tolerance to salinity such as Paraclostridium, Citrobacter, and Flavobacterium, which contributed to simultaneous removal of organics and nitrogen in AGS process for treating saline refractory wastewater.

Treatment of laundry wastewater using extracellular polymeric substances (EPS)

The problem of management and treatment of wastewater from commercial laundries is a matter of concern. The present study provides an effective and eco-friendly solution to the treatment of wastewater from commercial laundries in Quebec (Canada) by using the extracellular polymeric substance (EPS) as a bio-flocculant. EPS was produced from the valorization of crude glycerol and paper mill sludge by a bacterial strain (BS-04). Two different types of EPS: Slime EPS (S-EPS) and Broth EPS (B-EPS) were used for the treatment of commercial laundry wastewater (CLWW). This is the first study for the treatment of CLWW using bio-flocculant EPS. A comparison between the conventional treatment of laundry wastewater (LWW) by chemical coagulants (FeSO4, CaCl2, Alum) and enhanced treatment by bio-flocculant EPS has been drawn in the study. Moreover, LWW treatment by a combination of EPS and chemical coagulants was also investigated. It was observed that S-EPS (0.6 g/L) gave better flocculation activity (FA) than B-EPS. S-EPS alone can remove 83.20% of turbidity, 77.69% of suspended solids (SS), and 76.37% of chemical oxygen demand (COD). The best results were obtained by combining S-EPS (0.6 g/L) with alum (300 mg/L) at pH 7 for a treatment time of 30 min. This combination was able to remove 98% of turbidity, 95.42% of SS, and 83.08% of COD from LWW. When treatment time has been increased to 4 h at pH 7, it resulted in more than 88% COD removal from CLWW.Graphical

Kinetic modelling and process optimization of textile effluent treatment with bacterial gamma polyglutamic acid

Aim: The present study aims to synthesize gamma poly glutamic acid from the optimized starch-based glutamate-dependent medium for wastewater treatment with kinetic studies for an effective decolorization process. Methodology: Microbial coagulant (γ-PGA) was synthesized from the optimized glutamate-dependent medium with sago as a substrate and Bacillus subtilis as fermenter. Synthesized γ-PGA was harvested by ethanol precipitation and lyophilization method. The presence of γ-PGA was determined by UV-visible spectrum and ninhydrin analysis and its flocculating activity was screened by ninhydrin assay. Harvested γ-PGA was treated with different types of wastewater samples (Textile, tannery, dairy and sewage) in the preliminary screening. Process optimization was performed to screen the maximal decolorization for textile effluent (light and dark color). The physical and chemical characterization of treated wastewater samples with kinetic studies was performed to improve the treatment process. Results: The synthesized γ-PGA weighed as 41.20 g l-1 from the fermented medium and its presence was confirmed by characterization techniques. The flocculating activity of synthesized γ-PGA was 40.56 and 58.78 % against the kaolin suspension. The maximal decolorization percentage was 59.58% for γ- PGA treatment against textile effluent. The significance of optimized parameters such as pH, temperature, rotation speed and contact time were determined in the treatment of textile effluents (light and dark color) with maximal reduction of solids profile COD and BOD concentration. Kinetic studies revealed that the isotherm Langmuir isotherm was fit for the experimental data with R2 as 0.9943, 0.9692 and Pseudo second order fitted with R2 as 0.9871 and 0.9594 respective to light and dark color effluent. Interpretation: This study confirmed the maximal yield of γ-PGA from a sago-based glutamate-dependent medium and revealed its effective flocculating and decolorization activity against textile effluent which suggest them as a better alternative coagulants. Key words: γ- PGA, Bacillus subtilis, Kinetic modelling, Process optimization

Hyperproduction of extracellular polymeric substance in Pseudomonas fluorescens for efficient chromium (VI) absorption

A novel extracellular polymeric substance (EPS) with flocculating activity produced by Pseudomonas fluorescein isolated from soil was studied in this paper. Firstly, atmospheric and room temperature plasma (ARTP) was applied to get a mutant of P. fluorescein with higher EPS production. A mutant T4-2 exhibited a 106.48% increase in flocculating activity compared to the original strain. The maximum EPS yield from T4-2 was enhanced up to 6.42 g/L, nearly 10 times higher than the original strain on a 3.6-L bioreactor with optimized fermentation conditions. Moreover, the flocculating activity of the mutant reached 3023.4 U/mL, 10.96-fold higher than that of T4. Further identification showed that EPS from mutant T4-2 was mainly composed of polysaccharide (76.67%) and protein (15.8%) with a molecular weight of 1.17 × 105 Da. The EPS showed excellent adsorption capacities of 80.13 mg/g for chromium (VI), which was much higher than many reported adsorbents such as chitosan and cellulose. The adsorption results were described by Langmuir isotherm and pseudo-second-order kinetic model. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) revealed that the adsorption process was spontaneous and exothermic. Adsorption mechanisms were speculated to be electrostatic interaction, reduction, and chelation.Graphical

A bioflocculant from Corynebacterium glutamicum and its application in acid mine wastewater treatment.

Although many microorganisms have been found to produce bioflocculants, and bioflocculants have been considered as attractive alternatives to chemical flocculants in wastewater treatment, there are few reports on bioflocculants from the safe strain C. glutamicum, and the application of bioflocculants in acid wastewater treatment is also rare attributed to the high content of metal ions and high acidity of the water. In this study, a novel bioflocculant produced by Corynebacterium glutamicum Cg1-P30 was investigated. An optimal production of this bioflocculant with a yield of 0.52g/L was achieved by Box-Behnken design, using 12.20g/L glucose, 4.00g/L corn steep liquor and 3.60g/L urea as carbon and nitrogen source. The structural characterization revealed that the bioflocculant was mainly composed of 37.50% neutral sugar, 10.03% uronic acid, 6.32% aminosugar and 16.51% protein. Carboxyl, amine and hydroxyl groups were the functional groups in flocculation. The biofocculant was thermally stable and dependent on metal ions and acidic pH, showing a good flocculating activity of 91.92% at the dosage of 25mg/L by aid of 1.0mM Fe3+ at pH 2.0. Due to these unique properties, the bioflocculant could efficiently remove metal ions such as Fe, Al, Zn, and Pb from the real acid mine wastewater sample without pH adjustment, and meanwhile made the acid mine wastewater solution become clear with an increased neutral pH. These findings suggested the great potential application of the non-toxic bioflocculant from C. glutamicum Cg1-P30 in acid mine wastewater treatment.

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).

Structural characterization and partial properties of dextran produced by Leuconostoc mesenteroides RSG7 from pepino.

Exopolysaccharides (EPSs) produced by lactic acid bacteria possess various bioactivities and potential attractions for scientific exploration and commercial development. An EPS-producing bacterial strain, RSG7, was previously isolated from the pepino and identified as Leuconostoc mesenteroides. Based on the analyses of high-performance size exclusion chromatography, high-performance ion chromatography, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and methylation, the RSG7 EPS was identified as a dextran with a molecular weight of 5.47 × 106 Da and consisted of α-(1→6) glycosidic linkages as backbone and α-(1→2), α-(1→3), α-(1→4), and α-(1→6) glycosidic linkages as side chains. Scanning electron microscopy observed a honeycomb-like porous structure of RSG7 dextran, and this dextran formed aggregations with irregular hill-shaped lumps according to atomic force microscopy analysis. Physical-chemical investigations suggested that RSG7 dextran possessed excellent viscosity at high concentration, low temperature, and high pH; showed a superior emulsifying capacity of tested vegetable oils than that of hydrocarbons; and owned the maximal flocculating activity (10.74 ± 0.23) and flocculating rate (93.46 ± 0.07%) in the suspended solid of activated carbon. In addition, the dextran could coagulate sucrose-supplemented milk and implied potential probiotics in vitro. Together, these results collectively describe a valuable dextran with unique characteristics for exploitation in food applications.

Characteristics of exopolysaccharides produced by isolates from natural bioflocculant of Ruditapes philippinarum conglutination mud.

Three novel types of exopolysaccharides (EPS) EPS-S8, EPS-S5, and EPS-F10 were extracted and purified from bacterial isolates Bacillus sp. GHS8, Pseudoalteromonas sp. GHS5 and Psychrobacter sp. GHF10, which were originated from natural bioflocculant of Ruditapes philippinarum conglutination mud (RPM), respectively. The EPS had similar function groups C-H, N-H, C-O, and C = O. The EPS were composed of different monosaccharides (EPS-F10, Man: GlcN: GlcUA: GalUA = 1:0.66:5.75:0.51; EPS-S5, Man: Gal: GlcN: Rib = 1: 0.50: 2.94: 0.26; EPS-S8, Man: Gal: GlcN = 1:1.54:7.69). The molecular weights (Mw) of EPS were ordered as 51.4 kDa (EPS-S5) > 9.15 kDa (EPS-S8) > 4.41 kDa (EPS-F10). Three types of EPS all showed higher peak flocculation activities than the reported crude EPS from the RPM. Besides, the EPS also exhibited efficient decoloration and antioxidation activities, especially for EPS-S8, which might be due to the low Mw and specific monosaccharide composition.

Solving urban water microplastics with bacterial cellulose hydrogels: Leveraging predictive computational models

The prevalence of microplastics (MPs) in both urban and aquatic ecosystems is concerning, with wastewater treatment plants being considered one of the major sources of the issue. As the focus on developing sustainable solutions increases, unused remnants from bacterial cellulose (BC) membranes were ground to form BC hydrogels as potential bioflocculants of MPs. The influence of operational parameters such as BC:MPs ratio, hydrogel grinding, immersion and mixing time, temperature, pH, ionic strength, and metal cations on MPs flocculation and dispersion were evaluated. A response surface methodology based on experimental data sets was computed to understand how these parameters influence the flocculation process. Further, both the BC hydrogel and the hetero-aggregation of MPs were characterised by UV–Vis, ATR-FTIR, IGC, water uptake assays, fluorescence, and scanning electron microscopy. These highlights that the BC hydrogel would be fully effective at hetero-aggregating MPs in naturally-occurring concentrations, thereby not constituting a limiting performance factor for MPs' optimal flocculation and aggregation. Even considering exceptionally high concentrations of MPs (2 g/L) that far exceed naturally-occurring concentrations, the BC hydrogel was shown to have elevated MPs flocculation activity (reaching 88.6%: 1.77 g/L). The computation of bioflocculation activity showed high reliability in predicting flocculation performance, unveiling that the BC:MPs ratio and grinding times were the most critical variables modulating flocculation rates. Also, short exposure times (5 min) were sufficient to drive robust particle aggregation. The microporous nature of the hydrogel revealed by electron microscopy is the likely driver of strong MPs bioflocculant activity, far outperforming dispersive commercial bioflocculants like xanthan gum and alginate. This pilot study provides convincing evidence that even BC remainings can be used to produce highly potent and circular bioflocculators of MPs, with prospective application in the wastewater treatment industry.

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.

Biocoagulation of Dried Algae Chlorella sp. and Pellets of Aspergillus Niger in Decontamination Process of Wastewater, as a Presumed Source of Biofuel.

The removal of microalgae represents a problematic part of the water decontamination process, in which most techniques are expensive and non-ecological. In the paper, we focus on the synergistic relationship between microscopic filamentous fungi and algal culture. In the process of decontamination of a model sample containing ammonium ions, efficient biocoagulation, resp. co-pelletization of dried algae Chlorella sp. and Aspergillus niger sensu stricto are shown. The microscopic filamentous fungus species A. niger was added to a culture of an algal suspension of Chlorella sp., where the adhesion of the algal cells to the fungi subsequently occurred due to the electrostatic effect of the interaction, while the flocculation activity was approximately 70 to 80%. The algal cells adhered to the surface of the A. niger pellets, making them easily removable from the solution. The ability of filamentous fungi to capture organisms represents a great potential for the biological isolation of microalgae (biocoagulation) from production solutions because microalgae are considered to be a promising renewable source of oil and fermentables for bioenergy. This form of algae removal, or its harvesting, also represents a great low-cost method for collecting algae not only as a way of removing unnecessary material but also for the purpose of producing biofuels. Algae are a robust bioabsorbent for absorbing lipids from the environment, which after treatment can be used as a component of biodiesel. Chemical analyses also presented potential ecological innovation in the area of biofuel production. Energy-efficient and eco-friendly harvesting techniques are crucial to improving the economic viability of algal biofuel production.

Natural Flocculant from a Combination of Moringa oleifera Seeds and Cactus Cladodes (Opuntia ficus-indica) to Optimize Flocculation Properties

The lack of access to clean water worldwide and organic, inorganic as well as biological contamination of existing freshwater sources are a major problem for around 2 billion people, especially in the countries of the global south. One sign of polluted water is turbidity. It is generally caused by colloidal and particulate suspended solids. Chemical flocculants are often used to reduce turbidity and thus eliminate the mostly harmful substances that cause it. However, these have some disadvantages, such as cost and availability, so increasingly natural plant-based flocculants are coming into focus and are considered as an alternative option. In this study, Moringa seeds (Moringa oleifera) and cactus cladodes (Opuntia ficus-indica) were investigated as innovative and environmentally friendly flocculants for water treatment. The parameters investigated included absolute turbidity reduction and flocculation activity, as well as shear strength of the resulting flocs. The flocculation experiments were conducted as simultaneous tests in beakers. Experiments were conducted using both a laboratory-prepared model suspension with an initial turbidity of approximately 139 NTU and natural surface water with an initial turbidity of approximately 136 NTU. The flocculant dosages used ranged from 100 to 300 mg/L. The results show that although Moringa seeds had the highest flocculation activity (up to 93%), the flocs were very fragile and were destroyed again even at low induced shear forces. Flocculants from cactus yielded stable flocs, but the flocculation activity (maximum at 54%) was not as high as that of Moringa. The combination of the two materials resulted in a flocculant with sufficiently high flocculation activity (76%) and stable flocs, which could withstand higher shear forces potentially induced in further treatment steps.

New insights into the combination of Fe(III) and xanthan gum in dewatering of coal slurry: Molecular self-assembly

Aggregation is an economical and widely existing method to in fine coal particles dewatering, but the effect of cations on the flocculation activity of different bio-flocculant was inconformity. In this work, the aggregation behavior of coal slurry using XG combination Fe3+ was investigated. The adsorption of FeCl3·6H2O and XG was investigated via wetting heats, water contact angle, Zeta potential and SEM-EDS testing. The results show that the combination of FeCl3·6H2O and XG could build up layer-by-layer self-assembly multilayers on coal particles surface. Further, solution chemistry, FTIR and XPS analyses were performed to detect the adsorption mechanism. The results indicate that Fe(OH)3(s) covering and coordination reaction of the Fe active sites with the polar groups of XG are the main driving force for the self-assembly. The obtained settling tests results show a great potential of the combination of XG combination Fe3+ in the dewatering of coal slurry. The flocculation dewatering model of coal with FeCl3·6H2O and XG was drawn.

The effect of substrate consumption on the increasing of biofloculans productivity and activity of cultivation by Alcaligenes latus

The efficient technology cultivation is developed as a respond to the emergence of clean technology trend issue to produce biogically degraded product. This research aims to review the effect of sweet potato hydrolysis concentration on biofloculan cultivation productivity and its effect on flocculation activity. Cultivation starts from cell refreshment to propagation and inoculation into cultivation medium which has been sterilized. Enzymatically, the sweet potato starch hydrolyzate supernatant usage (S) as a cultivation medium is expected can substitute glucose (G) synthetic medium and able to increase bioflocculant activity and bioabsorbent formation, while the Nitrogen substrate usage from CSL (C) and yeast extract (Y) into the medium. Cultivation of Alcaligenes latus can stimulate the formation of acid biopolymers which have large molecular weights. Furthermore, made a notation like SC-10 which is a medium of glucose supernatant factor with Corn steep liquor (CSL) with an initial sugar concentration level of 10 g/l. Control process including the analysis of reduced sugar (RS) and nitrogen, viscosity, pH, measurement of dry cell weight (DC), and flocculation activity (AF) is conducted during cultivation. The research results indicates the usage of sweet potato supernatan hydrolysate is to subsitute the synthetic mediums due to its ability to increase biofloculan activity. The best medium for biofloculan cultivation is SC-10 with kinetic parameter μ, 0,0834 hours-1; Xmax,12,54 g/l; m, 0,641 and n, 0,0105 g product/g biomass/hours; α, 0,409 and β, 0,0006 g biomass/g substrate/ hours; Yp/s, 68%; Yx/s, 97%. There is no significant viscosity changes during cultivation so that it can not be used as a production index. Flocculation Activity resulting from the cultivation of SC-10 medium is the strongest process in forming flok-flok while SC-30 medium is the least.

Enhanced remediation of fracturing flowback fluids by the combined application of a bioflocculant/biosurfactant-producing Bacillus sp. SS15 and its metabolites.

Fracturing flowback fluids (FFFs), which is generated from the process of oil and gas exploitation, is one of the major environmental concerns. In this study, a bacterial strain, Bacillus sp. SS15, capable of producing both bioflocculant (BF) and biosurfactant (BS), was isolated from oil-contaminated mudflat sediment. The BS produced by SS15 was identified as lipopeptide, which could reduce the surface tension of water from 74.2mN/m to 36.6mN/m with a critical micelle concentration of 44.4mg/L. It also exhibited strong tolerance against a wide range of pH (2-12), temperature (4-60°C), and salinity (0-100g/L). Meanwhile, the BF produced by SS15 exhibited high flocculating activity (84.9%) for kaolin suspension, and was confirmed to be thermostable, salt-tolerant, and alkaliphilic. The combined treatment of bioremediation (introducing SS15 and BS) followed by flocculation (introducing BF) greatly promoted the removal of chroma (85.7% reduction), suspended solids (94.4% reduction), chemical oxygen demand (84.9% reduction), n-alkanes (50.0% reduction), and polycyclic aromatic hydrocarbons (66.5% reduction), respectively. The genome analysis showed that strain SS15 possessed abundant genes related to the synthesis of carbohydrate, protein, and lipid, which might play an important role in BF and BS synthesis. The findings in this study demonstrated that Bacillus sp. SS15 has promising prospect in the remediation of FFFs.

Isolation of a Marine Bacterium and Application of Its Bioflocculant in Wastewater Treatment

Bioflocculation has become the method of choice in wastewater treatment because of its effectiveness, environmental friendliness and innocuousness to humans. In this study, the bioflocculant-producing bacterium was isolated and its bioflocculant was used in wastewater treatment. The isolate was identified by 16S rRNA gene sequencing analysis. Its culture conditions (inoculum size, carbon and nitrogen sources, pH, temperature and time) were optimised using the one-factor-at-a-time assay. The cytotoxicity of the bioflocculant was assessed on human colorectal adenocarcinoma cells (Caco2) by tetrazolium-based colorimetric method. The ability of the bioflocculant to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in wastewater was evaluated using Jar test. The bacterium was identified as Bacillus subtilis CSM5 and the maximum flocculating activity of 92% was observed when fructose and urea were used as nutrients and the culture conditions were adjusted to 30 °C, pH 9, 160 rpm and 72 h of incubation. Caco2 exhibited 90% viability when the highest bioflocculant concentration of 200 µg/µL was used. The reduction of BOD and COD was achieved at 59 ± 3.1 and 75 ± 0.4%, respectively. In conclusion, B. subtilis CSM5 is a good candidate for bioflocculant production and its bioflocculant has good potential for use in wastewater treatment.

Isolation and Optimisation of Culture Conditions for a Marine Bioflocculant-Producing Bacterium and Application of Its Bioflocculant in Wastewater Treatment.

The application of bioflocculants has become an alternative to that of chemical flocculants in wastewater treatment due to their environmental friendliness and non-toxic effects. This study aimed at isolating a bioflocculant-producing bacterium from marine water, optimisation of its culture conditions, and investigation of the removal efficiency of its bioflocculant on pollutants in wastewater. The bacterium was identified by 16S rRNA gene analysis. Optimal carbon and nitrogen sources, inoculum size, temperature, pH, and time were determined by the one-factor-at-a-time assay. The cytotoxicity of the bioflocculant was assessed on African green monkey kidney and bovine dermis cells using a tetrazolium-based columetric (MTT) method. Its removal efficiencies on chemical oxygen demand (COD), biological oxygen demand (BOD) and sulphur were determined using the Jar test method. The bacterial isolate was identified as Ochrobactrum oryzae AB84113. A maximum flocculating activity of 92% and a yield of 3.768 g/L were obtained when a 1% (v/v) inoculum size was used in the presence of starch and yeast extract at pH 7, 30 °C, and after 72 h of cultivation. The bioflocculant demonstrated non-cytotoxic effects on bovine dermis and African green monkey kidney cells. The bioflocculant removed 98% COD, 91% BOD and 86% of Sulphur. The bioflocculant has potential for pollutant removal from industrial wastewater.