Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.

Shear hydrophobic flocculation and flotation of ultrafine Anshan hematite using sodium oleate

Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that these parameters significantly affect the shear hydrophobic flocculation of ultrafine hematite. The optimum conditions for the flocculation are： stirring speed 1 400 r/min, flocculation time 20 min, pH 9 and sodium oleate concentration 3.94×10-4 mol/L; the flotation recovery of hematite flocs is remarkably high compared with non flocculated ultrafine hematite. According to the extended DLVO theory, the total interaction potential of Anshan ultrafine hematite was determined. The calculation results indicate that the hydrophobic flocculation state of the ultrafine hematite-sodium oleate system is mainly dominated by electric double layer repulsive interaction potential and hydrophobic interaction potential. A mechanical agitation is required to impart particles a kinetic energy to overcome potential barrier between them due to the existence of electric double layer repulsive interaction potential. Those particles further approach to form flocs due to the significant increase of the hydrophobic interaction potential.

Dynamic experiments on flocculation and sedimentation of argillized ultrafine tailings using fly-ash-based magnetic coagulant

In order to accelerate the sedimentation of super-large-scale argillized ultrafine tailings with bad features such as low settling velocity, muddy overflow water, and large flocculant dosage, a fly-ash-based magnetic coagulant （FAMC） was used in a dynamic experimental device. To obtain the best possible combination of the impact factors （magnetic intensity, FAMC dosage, flocculant dosage, and feed speed） for minimum overflow turbidity, a response surface methodology test coupled with a four-factor five-level central composite design was conducted. The synergy mechanism of FAMC and flocculant was analyzed based on the potential measurement and scanning electron microscopy. The results show that the flocculant dosage, overflow turbidity, and solid content can be reduced by 50%, 90%, and 80%, while the handling capacity per unit and efficiency of backfill and dry stacking can be promoted by 20%, 17%, and 13%, respectively, with a magnetic intensity of 0.3 T, FAMC dosage of 200 mL/t, flocculant dosage of 30 g/t, and feed speed of 0.6 t/（m^2·h）. Therefore, synergy of FAMC and flocculant has obvious efficiency in saving energy and protecting the environment by allowing 70×10^6 t/a of argillized ultrafine tailings slurry to be disposed safely and efficiently with a cost saving of more than 53×106 Yuan/a, which gives it great promise for use in domestic and foreign mines.

Biological preparation and application of poly-ferric sulfate flocculant

A novel inorganic polymer flocculant,poly-ferric sulfate（BPFS） was prepared by oxidation of ferrous sulfate using domestic Thiobacillus ferrooxidans（T·f） under acid condition.The optimal conditions for the preparation were pH value of 1.5,（NH4）2SO4 dosage of 0.5 g/L,initial Fe2＋ concentration of 45g/L,inoculum 10%,rotating speed of 120 r/min,reaction time of 5-6 d and reaction temperature of 30 ℃.Under the optimal conditions,the BPFS product with pH value of 1.5-2.2,basicity of 17.5%-22.7% and total iron content of 43.87-45.24 g/L was obtained.The application of the BPFS to three wastewaters was carried out,and the removal efficiencies of COD,decolorization and Zn2＋ by BPFS can be reached 70%,90% and 99%,respectively.The result suggests that the BPFS is an excellent flocculant for water treatment.

Screening of One Microbial Flocculant for Treatment of Methyl Orange Wastewater and its Decolorization Effect

[Objective] To screen out a microbial flocculant with good decolorization effect on methyl orange wastewater,and study the effect of different cultural conditions on decolorization effect of methyl orange.[Method] Absorbance of methyl orange solution before and after decolorization was determined by spectrophotometer,and the decolorization rate was calculated to compare the effects of different cultural conditions on removal rate of methyl orange.[Result]An optimal actinomycete stain（F-1-2） was screened out,and the best cultural condition was as follows：with sucrose as carbon source and NaNO3 as nitrogen source,cultured in constant temperature oscillator at 150 r/min,30℃ for 72 h.Under the optimal condition,the removal rate against methyl orange could reach 68.4%.[Conclusion]Different culture conditions have great impact on decolorization effect of strain.

Isolation and Identification of Bioflocculant Producing Stain and Analysis on Its Flocculating Characteristics

[Objective] The aim was to indentify a bioflocculatnt producing strain W5 isolated from soil samples and analyze its flocculating characteristics. [Method] The universal primers of bacterial 16S rDNA were used for PCR amplification of its genome; effects of the medium pH,carbon and nitrogen sources on its flocculating activity were analyzed by using single factor method; and infrared spectroscopy was used for functional groups analysis. [Result] The results of homology comparison showed that strain W5 belonging to Gram-negative,long bacilli and had 98.34% of homology with Hymenobacter gelipurpurascens,. In addition,the optimum carbon source,nitrogen source,pH for fermentation condition were glucose,yeast extract and pH 7.04,respectively. Microbe flocculant produced by W5 strain （MBF-W5） was extracted and purified to obtain reddish and flocculent products. Fourier-transform infrared （FTIR） spectroscopy indicated that the major functional groups of MBF-W5 were hydroxyl,carboxyl and amino. [Conclusion] More than 85% of flocculating activity was achieved under the conditions of 150-500 μl bioflocculation dosage,5-65 ℃ temperature and pH 2-10.

Screening of a Novel Bioflocculant-producing Strain and Research on Its Flocculation

[Objective] This study aimed to screen a bacterial strain capable of producing bioflocculant. [Method] A bacterial strain T-11 capable of producing bioflocculant was isolated from activated sludge. Detailed tests on the morphological, physiological and biochemical characteristics were carried out and identification was performed to identify the strain. Finally, the bioflocculant was isolated and purified, and the flocculating activity and chemical characteristics were measured. [Result] It was identified as Serratia plumuthica based on its morphological, physiological and biochemical characteristics. This strain secreted flocculant best in a culture medium which included sucrose and NaNO3. The maximal cell growth was achieved within 10 h and the flocculating activity paralleled to it. It was found to be effective for flocculation of kaolin suspension, when added at a final concentration of 0.7 mg/L, over a range of pHs （2-7）, and temperature （approximately 30-80 ℃）. Chemical analysis indicated that the bioflocculant was an acidic polysaccharide consisting of glucose, glucuronic acid and galactose, talose and altrose. Infrared spectrum analysis also revealed typical characteristics of polysaccharides. [Conclusion] The biofloccu- lants produced by strain T-11 can greatly improve the ability of activated sludge to settle.

Effects of water hardness on selective flocculation of diasporic bauxite

The effect of electrolyte on settling behavior of kaolinite was studied. Effects of hard water on selective flocculation of diasporic bauxite was tested and the measures were taken to eliminate the effects of Ca2＋ and Mg2＋ in hard water. The results indicated that, not only the concentration of electrolyte ions but also the ionic valence of the electrolyte ions affects the settling behavior of kaolinite; hard water significantly affects its selective flocculation owing to Ca2＋ and Mg2＋; general dispersants could not eliminate the effects of Ca2＋ and Mg2＋. Self-made softening agent in our lab could weaken or eliminate the effects of hard water on flocculation processes. The results of molecular dynamics simulation show that softening agent molecules could restrict Ca2＋ and prevent them from playing their roles, so as to eliminate the effects. The continuous pilot experiment results of bauxite flocculation were even better than those obtained in laboratory.

Treatment of Wastewater in Chemistry Laboratory through Flocculent Settling and Constructed Wetlands

The basic chemistry laboratories of three colleges and universities in Guizhou Province were investigated completely,especially the pollution situations of the basic chemistry projects were counted,and the discharge amounts of the poisonous and harmful pollutants in the waste liquid from laboratories were monitored and analyzed.On the basis of the summing-up and analysis of the current research findings,a simple and feasible treatment scheme through flocculating,precipitating and constructed wetlands was designed to control the three kinds of excessive pollutants.

Isolation and Identification of a Flocculant Producing Strain TS-1

[Objective] The purpose was to select out and identify a flocculant producing strain which could produce high active flocculant.[Method] The strain producing high active flocculant was isolated out and purified through medium culture and the selected strain was identified through observing its culture characters and determining its physiological and biochemical property.[Result] Fourteen strains of bacteria with flocculant producing function were isolated from tested soil samples through isolation,purification and preliminary screening using dilution-spread plate method and plate streaking method.Five strains of flocculant producing bacteria showing higher flocculation activity were selected out after second screening and their flocculation rates were higher than 70%;the flocculation activity of one strain among them was still stable after multiple subculturings,its flocculation rate was always above 90% and it was marked as TS-1.TS-1 was encapsulated Gram-positive bacillus and there was no lipid in it,such as poly-β-hydroxybutyric acid.TS-1 was Bacillus amyloliquefaciens,so it was named Bacillus TS-1.[Conclusion] The strain selected out in this experiment could be used in the flocculation and biochemical treatment of wastewater from starch industry.

Floc flotation of marmatite fines in aqueous suspensions induced by butyl xanthate and ammonium dibutyl dithiophosphate

The hydrophobic flocculation of marmatite fines in aqueous suspensions induced by butyl xanthate （KBX） and ammonium dibutyl dithiophosphate （ADD） was investigated using laser particle size analysis, microscopy analysis, electrophoretic light scattering, contact angle measurement and infrared spectroscopy. The studies were performed on single minerals with size 〈20 μm by varying several parameters, including pH, collector concentration and kerosene addition. The results show that the floc fotation closely correlated with the size of flocs and the particle hydrophobicity, but was not lowered with increasing the particle surface charges due to collector adsorption. Under good operating conditions, the floc flotation of marmatite fines as a function of KBX and ADD can all reach floatability over 90%, in comparison with conventional flotation obtaining floatability of about 60%. It also has been found that a small addition of kerosene greatly improved the floc flotation because of the formation of oil films on marmatite particles. The results of FTIR spectra indicate that adsorption of the two collectors onto marmatite were chemical adsorption.

Experimental Research on the Dewatering of Dredged Sediment from Dianchi Lake

[Objective] The technological parameter suitable for the dewatering of dredged sediment from Dianchi Lake was studied.[Method] By means of the treatment method of sewage sludge in sewage treatment plant,flocculants including FeCl3,Al2(SO4)3 and PAM were taken as dewatering agents which were added in dredged sediment.[Result] The results showed that Al2(SO4)3 had better dewatering effect than FeCl3 and PAM,and the optimum dosing quantity of Al2(SO4)3 in dredged sediment was 170 mg/L,in addition,the water quality of supernatant met the first class B standard of GB18918-2002 and could be directly discharged to nature water without pollution.[Conclusion] The study could provide a simple and feasible way for the rapid dewatering of dredged sediment from Dianchi Lake,which would be convenient for the disposal and resource utilization of dredged sediment.

Microbial flocculant and its application in environmental protection

The microbial flocculant is a kind of natural bio polymer and has promising future to be used in the fermentation industry and wastewater treatment. It has been studied in details in many countries, such as U.S.A, Japan. This paper reviewed the development on microbial flocculant basic studies and applications, including flocculant production microorganisms, chemical and components of microbial flocculants, flocculation mechanism of microbial flocculants, capability of microbial flocculants and influence factors, and culture conditions for flocculant production. The application cases of microbial flocculants were also discussed.

Settling characteristics of ultrafine iron ore slimes

The slurry settling characteristics are the most important to design a thickener in process industries. In this work, the iron ore slurry from the screw classifier overflow was used for the settling study. It was observed that the original slurry exhibited a low settling velocity and a turbid supernatant during the settling process. Commercial flocculating agents with anionic, cationic, and nonionic characters were used to improve the settling behavior of suspensions, which were added into the slurry at different ranges of slurry pH values, respectively. The settling results show that the use of flocculants increase the settling rate by several times. Compared with the cationic and non-ionic flocculants, the anionic flocculant is more effective in enhancing the slurry settling rate. The small dose of the anionic flocculant is found to be more effective, but the other flocculants are less effective even at higher dosages. The simulation of an industrial thickener was carried out based on the laboratory settling data, and the appropriate design and selection parameters of the industrial thickener were estimated.

The effect of coupling coagulation and flocculation with membrane filtration in water treatment:A review

Water supply and sanitation demands are foreseen to face enormous challenges over the coming decades to meet the fast growing needs in a global perspective. Significant growth in the industry is predicted and membrane separation technologies have been identified as one of the possible solutions to meet future demands. Application and implementation of membrane technology is expected both in production of potable water as well as in treatment of wastewater. In potable water production membranes are substituting conventional separation technologies due to the superior performance, potential for less chemical use and sludge production, as well as the potential to fulfill hygienic barrier requirements. Membrane bio-reactor （MBR） technology is probably the membrane process which has had most success and has the best prospects for the future in wastewater treatment. Trends and developments indicate that this technology is becoming accepted and is rapidly becoming the best available technology for many wastewater treatment applications. A major drawback of MBR systems is membrane fouling. Studies have shown that fouling mitigation in MBR systems can potentially be done by coupling coagulation and flocculation to the process.

Features and mechanism for coagulation－flocculation processes of polyaluminum chloride

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Characterization of a bioflocculant from a newly isolated Vagococcus sp. W31

Screening of microorganisms producing flocculating substances was carried out. A strain secreting a large amount of bioflocculant was isolated from wastewater samples collected from the Little Moon River in Beijing. Based on the morphological properties and 16S rDNA sequence analysis, the isolate (designated W31) was classified as Vagococcus sp. A bioflocculant (named MBFW31) produced by W31 was extracted from the culture broth by ethanol precipitation and purified by gel chroma-tography. MBFW31 was heat-stable and had strong flocculating activity in a wide range of pH with relatively low dosage re-quirement. MBFW31 was identified as a polysaccharide with molecular weight over 2×106. It contained neutral sugar and uronic acid as its major and minor components, respectively. Infrared spectra showed the presence of hydroxyl, carboxyl and methoxyl group in its molecules. The present results suggested that MBFW31 had potential application in wastewater treatment.

Ability of Bacillus mucilaginosus GY03 Strain to Adsorb Chromium Ions

A research with Bacillus mucilaginosus cultured in nitrogen-free medium for forming a flocculant material to adsorb Cr+6 was conducted to determine the effects of different pH, volume, treatment time, and chromium (VI) concentrations on chromium (VI) adsorption by microbial flocculant (MBF), which was produced from the B. mucilaginosus GY03 strain. The results showed that MBF had outstanding flocculation on chromium (VI). Based on the results of a oneway experiment and actual wastewater treatment conditions, the optimum conditions, obtained by using orthogonal experiments, for chromium (VI) adsorption by MBF were: Cr6+ solution pH of 9, flocculant material volume of 15 mL, treatment time of 12 h and chromium ion concentration of 30 mg L-1. The results demonstrated that the MBF produced from GY03 could be used in the chromium-containing wastewater treatment. Meanwhile, after extraction and analysis of the MBF polysaccharides, it was found that MBF was mainly composed of glycoprotein. Analysis on constituents of monosaccharide showed that polysaccharides of B. mucilaginosus were composed of rhamnose, glucose etc. Thus, because it was applied over a wide range of pH, in small amounts and had a rapid flocculation speed the flocculant used in this experiment had a vast field of application potential.

Coagulation behavior of polyaluminum chloride: Effects of pH and coagulant dosage

Coagulation mechanisms of polyaluminum chloride(PACl) at various dosages were studied using a conventional jar test at different final and initial pH values during treating kaolin suspension. The optimal final pH and dosages for PACl were obtained based on residual turbidity and zeta potential of flocs. The coagulation zones at various PACl dosages and solution p H values were developed and compared with those of alum. It is found that the optimal mechanism under acidic condition is charge neutralization, while alkaline condition will facilitate the coagulation of PACl. Both charge neutralization coagulation and sweep coagulation can achieve high coagulation efficiency under the alkaline condition ranging from final p H 7.0 to 10.0. Stabilization, charge neutralization destabilization, restabilization and sweep zones occur successively with increasing PACl dosages with the final p H values fixed at 7.0 and 8.0, but restabilization zone disappears at final p H 10.0. When the final p H is not controlled and consequently decreases with increasing PACl dosage, no typical sweep zone can be observed and the coagulant efficiency decreases at high PACl dosage. It seems that the final pH is more meaningful than the initial p H for coagulation. Charge neutralization coagulation efficiency is dominated by zeta potential of flocs and PACl precipitates. The charge neutralization and sweep coagulation zones of PACl are broader in the ranges of coagulant dosage and p H than those of alum. The results are helpful for us to treat water and wastewater using PACl and to understand the coagulation process of PACl.

Influence of coarse tailings on flocculation settlement

The composition of tailings particles in mines plays a key role in the flocculation settlement of slurries.To study the influence of coarse particle tailings(CPTs)on the flocculation settlement of tailings slurries(TSs),static flocculent settling tests,scanning electron microscopy observations,and laser particle size analyses were conducted using the tailings obtained from a copper mine.The results demonstrate that(i)in the accelerated and free settling process,CPTs did not directly settle at the bottom of graduated cylinders;instead,they were netted by the flocculent structures(FSs)and settled together more quickly.The CPTs accelerate the rapid settlement of TSs;the acceleration effect is more obvious when the CPTs content is greater than 50 wt%.(ii)The most appropriate flocculant unit consumption(FUC)is 20 g·t-1,and no substantial increase is observed in the flocculant settling velocity with an increase in the flocculant because the effective FSs did not substantially change and thus did not lead to a notable increase in the settling velocity of the solid–liquid interface(SLI).(iii)In the effective settling space of the thickening facility,free water quickly flowed from the pores of FSs,which is reflected in the period from 0 to 1 min.