Ferric Flocs Research Articles

Efficacy and mechanism of enhanced Sb(V) removal from textile wastewater using ferric flocs in aerobic biological treatment

Antimony contamination from textile industries has been a global environmental concern and the existing treatment technologies could not reduce Sb(V) to meet the discharge standards. To overcome this shortcoming, ferric flocs were introduced to expedite the biological process for enhanced Sb(V) removal in wastewater treatment plant (WWTP). For this purpose, a series of laboratorial-scale sequential batch reactor activated sludge processes (SBRs) were applied for Sb(V) removal with varied reactor conditions and the transformation of Fe and Sb in SBR system was investigated. Results showed a significant improvement in Sb(V) removal and the 20 mg L−1 d−1 iron ions dosage and iron loss rate was found to be only 15.2%. The influent Sb(V) concentration ranging 153–612 μg L−1 was reduced to below 50 μg L−1, and the maximum Sb(V) removal rate of the enhanced system reached about 94.3%. Furthermore, it exhibited high stability of Sb(V) removal in the face of antimonate load, Fe strike and matrix change of wastewater. Sludge total Sb determination and capacity calculation revealed decreasing in Sb adsorption capacity and desorption without fresh Fe dosage. While sludge morphology analysis demonstrated the aging and crystallization of iron hydroxides. These results verify the distinct effects of fresh iron addition and iron aging on Sb(V) removal. High-throughput gene pyrosequencing results showed that the iron addition changed microbial mechanisms and effect Fe oxidized bacterial quantity, indicating Sb(V) immobilization achieved by microbial synergistic iron oxidation. The present study successfully established a simple and efficient method for Sb(V) removal during biological treatment, and the modification of biological process by iron supplement could provide insights for real textile wastewater treatment.

The influence of physical floc properties on the separation of marine microalgae via alkaline flocculation followed by dissolved air flotation

Flocculation achieved by raising the pH, termed alkaline flocculation is a sustainable way of inducing flocculation in marine microalgae. Flocs formed post-alkaline flocculation have the potential to be harvested via dissolved air flotation (DAF) or sedimentation. While DAF results in faster separation and biomass with a higher solids content compared to sedimentation, it has not been tested in saline environments, particularly when combined with alkaline flocculation. DAF processes, like most separation techniques, are heavily dependent on physical floc properties. In this study, the impact of alkaline floc properties on the performance of DAF versus sedimentation was evaluated to harvest marine Nannochloropsis oculata, benchmarking against the well-studied ferric chloride flocculation. This was followed by the use of the DAF white-water model to illustrate how alkaline and ferric floc properties impact bubble-particle attachment and DAF separation efficiencies. Alkaline flocs were smaller (peakmax < 300 μm; majority flocs 130–470 μm), stronger (~70 % strength factor) and more compact (scattering exponent > 2.30) compared to ferric flocs which were larger (peakmax ~ 1700 μm; >65 % of flocs >1000 μm), relatively weaker (<40 % strength factor), less compact (scattering exponent 1.49–2.30). However, as both flocs were hydrophilic, sedimentation yielded ~15 % greater efficiency than DAF. Stoke's Law suggested that sedimentation benefited due to alkaline floc compactness and large sizes of ferric flocs. Nonetheless, maximum separation efficiencies of ~80–85 % were still obtained via the DAF process. From the white-water model, bubble-floc attachment efficiency of alkaline flocs (0.01–0.001 %) was observed to be at least an order of magnitude greater than ferric flocs (0.001–0.0001 %) despite both methods resulting in comparable DAF separation efficiencies. For alkaline flocs, elevated bubble-floc attachment efficiency compensated low hydrophilicity; for ferric flocs, low bubble-floc attachment was compensated by large floc sizes. Overall, it is suggested that the determination of floc properties post-coagulation-flocculation could be used to optimise separation processes.

Concentration of MS2 phage in river water by a combined ferric colloid adsorption and foam separation-based method, with MS2 phage leaching from ferric colloid

The concentration of MS2 phage as a model RNA virus in river water using a combined ferric colloid adsorption and foam separation-based method was examined. The MS2 phage concentrations were determined by the plaque-forming unit (PFU) method and reverse transcription quantitative PCR (RT-qPCR) analysis. When ferric colloid adsorption was performed prior to foam separation, MS2 phage was effectively removed from river water and concentrated in the generated foam within 7min. The removal efficiency was >99% at the optimum iron and casein concentrations of 5mg-Fe/L and 10mg/L, respectively. Furthermore, based on the analysis of the collected ferric colloid dissolved using deferoxamine, the MS2 concentration in the colloid-dissolved solution was 190-fold higher than that found in raw water according to RT-qPCR analysis. This is a novel method for concentrating RNA viruses to facilitate their detection in river water using coagulation and foam separation combined with chelate dissolution of ferric flocs.

Effect of iron oxide nanocluster on enhanced removal of molybdate from surface water and pilot scale test

Abstract A novel combination of magnetic adsorptive and coagulative strategy which was applied to remove molybdenum (Mo) ions from surface water was investigated in this study. The ferromagnetic nanoclusters and ferromagnetic nanoclusters-ferric flocs composite coagulant were characterized in terms of typical properties, structure and morphological analysis (TEM, XRD, M – H hysteresis curves, particle size distribution). Different removal agents of Mo was investigated that the removal rate of Mo was ferromagnetic nanoclusters-FeCl 3 > FeCl 3 > AlCl 3 > TiCl 4 . Jar tests were employed to evaluate the removal performances. The coagulation performances of ferromagnetic nanoclusters-ferric flocs were compared under different pH conditions and dosages. Various factors influencing the removal of Mo(VI), e.g. pH, the dose of ferromagnetic nanoparticle, FeCl 3 , were conducted using a 3 3 full factorial design approach. The results show that the newly addition of ferromagnetic nanoparticles obviously had a trend to form cluster, especially magnetic force acted as a key role that may promote the formation of ferromagnetic nanoclusters. The better removal performance of Mo could be attributed to the co-effect of ferromagnetic nanoclusters and ferric flocs. Meanwhile, in order to satisfy the national drinking water criterion, the reinforce effect of ferromagnetic nanoclusters on reducing the concentration of ferric (Fe) ions in effluent makes sure that the content of ferric ions under 0.3 mg/L. The experimental results indicated that mechanism of the molybdate removal was a physical surface adsorption which might combine with chemical action.

Concentration of Cryptosporidium oocysts from river water by coagulation and foam separation combined with acid dissolution of ferric flocs

Cryptosporidium is an extremely virulent microorganism; contamination of water works systems by Cryptosporidium oocysts is a serious issue in public health. However, a great deal of effort is required to detect oocysts in source water for drinking, because the oocysts have to be concentrated from a large volume of water before detection. In this study, the concentration of oocysts in oocyst-polluted artificial river water was examined by coagulation and foam separation. The oocysts concentrated in the foam water were purified using immunomagnetic separation and assessed using epifluorescence microscopy. When ferric coagulation was performed prior to foam separation, oocysts were effectively removed from the river water and concentrated in the foam within 10 min. The removal efficiency was greater than 96% at the optimum iron and casein concentrations of 5 mg-Fe L−1 and 20 mg L−1, respectively. Furthermore, the number of recovered oocysts in the solution obtained by the dissolution of the collected ferric flocs from foam water was the same as that obtained using the Japanese standard procedure for detection of Cryptosporidium in water using membrane filtration. This is a novel method of concentrating Cryptosporidium oocysts for detection in river water using a coagulation and foam separation combined with acid dissolution of ferric flocs; the method is easy to use, rapid, and efficient.

The advantages of a superconducting magnetic intensity greater than 1 T for phosphate–ferric flocs separation in HGMS

High-gradient magnetic separation (HGMS) is widely used for water treatment. However, the effects of high magnetic intensities on removing magnetized flocs are unclear. In this study, separating phosphate–ferric flocs via HGMS at different magnetic intensities and gradients were evaluated. The TP removal efficiencies in the 5% #1 steel wool matrix were 65.1%, 82.1%, 89.1%, and 97.5% when the magnetic intensity was 0, 1.0, 3.5 and 5.5T, respectively. The TP removal rate increased by 21.9% when the magnetic gradient increased from 6×103 to 15×103 at 5.5T. The magnetic susceptibility of flocs in 1.0-T HGMS effluents was 1.5emu/g, and saturation magnetization was not observed at 5.0T. The volume mean particle size D(4,3) of the phosphate–ferric flocs decreased as the magnetic intensity increased. Magnetite was the primary mineral phase in the 0-T HGMS effluents, whereas no mature crystals were detected in the 1.0-T HGMS effluents. Microanalysis showed that magnetite particles in phosphate–ferric flocs were captured by the steel wool matrix by the magnetic force. It is expected that some of the phosphate–ferric flocs will break into magnetite and ferric precipitates. Increasing the magnetic intensity from 1.0T to 5.5T captured more ferric precipitates, which subsequently improved the TP removal efficiency.

Full Scale Evaluation on Anionic Polyacrylamide Applied in Ferric Flocs Sludge Treatment

The Polyacrylamide (PAM) is a frequently used flocculant for high concentration suspensions removal in water treatment characterized by the generation of large and dense flocs. In this paper, by using the anionic PAM as flocculant, a full-scale experimental study was carried out on flocculating ferric flocs sludge with pelleting flocculation blanket process under scale of 19~38 m3/h. The investigation aimed to optimum the dosage of the PAM and evaluate the application of the PAM in ferric flocs sludge treatment. The experimental results indicated that the increasing of PAM dosage could improve both outlet turbidity and thicken sludge concentration obviously, under the raw wastes concentration of 285~1022 mg/L, the system could achieve ideal operation effect with PAM dosage of 0.3~2.7 mg/L and treatment unit surface loading of 19~38 m3/m2·H. The investigation results also proved that there exists an approximately linear relationship between optimal PAM dosage and raw sludge concentration, that is, the increasing of raw sludge concentration would require synchronously rising of the optimal dosage. While the relationship between maximum surface loading and raw sludge concentration appeared negatively linear dependence, the maximum surface loading would decreased linearly with the increasing of inlet sludge concentration.

Full Scale Optimization of Flocs Blanket Process Applied in Ferric Flocs Sludge Treatment

The flocs blanket process is a traditional technology for high concentration suspensions removal. In this paper, by thickening ferric flocs sludge, the flocs blanket process was optimized with a scale of 19~38 m3/H to achieve more satisfied operational condition. Under the raw sludge concentration of 100~1200 mg/L, an increase in polymer dosage would improve outlet turbidity, the moderate mechanical agitating strength of 3 rpm could achieve best operational results. The experimental results also revealed an approximately linear relationship between raw water concentration and optimum PAM dosage, that is, the optimum dosage of PAM increased synchronously with the increasing raw sludge concentration. While the relationship between raw sludge concentration and maximum up-flow rate reflected negatively linear dependence, the maximum up-flow rate would decrease linearly with the increasing raw sludge concentration. The experimental results proved that the flocs blanket process could be applied to thicken the ferric flocs sludge as a highly efficient technology.

Pilot scale evaluation on ferric floc sludge concentration with pelleting flocculation blanket process

Pelleting flocculation blanket (PFB) process has been successfully applied to high turbidity suspensions for high efficient solid/liquid separation. In this paper, by using the PFB process, a dynamic experimental study was carried out on concentrating ferric flocs sludge with a scale of 1.3-5.4 m(3)/h. The pilot experiment aimed to optimize the conditioning system and determine the operational parameters. Under the raw sludge concentrations of 103-1,154 mg/L, the system could achieve ideal conditioning effect with polyacrylamide (PAM) dosages of 0.3-2.7 mg/L, agitation speed of 10 rpm, and water up-flow rates of 18-48 m/h. Under the experimental conditions, the increase of polymer dosage would improve effluent turbidity and pellets settling behaviour, the moderate up-flow rate had no marked effect on treatment results, while too large surface loading could worsen effluent turbidity. The experimental results also revealed that there existed an approximately linear relationship between the raw sludge concentration and optimum PAM dosage, that is, the optimum dosage of PAM increased synchronously as the raw sludge concentration increased. While the relationship between the raw sludge concentration and maximum up-flow rate reflected another linear dependence, namely, the maximum up-flow rate would decreased linearly as the raw sludge concentration increased.

Settling behaviour of pellet flocs in pelleting flocculation process: analysis through operational conditions

Pellet flocs' settling velocity is an important parameter in the pelleting flocculation blanket (PFB) process, hence, it is necessary to investigate flocs' settling behaviour to achieve the optimum operation parameters of the process. To investigate the settling behaviour of pellets under different operational conditions, a dynamic experiment was carried out to concentrate ferric flocs sludge by pelleting flocculation blanket (PFB) process with the scale of 0.5-1.2 m3/h. Under different operating conditions such as raw water concentration, polyacrylamide (PAM) dosage, up-flow rate, and agitation speed, pellet particles were sampled from different locations of the blanket in various operating stages to analyze pellet size, setting velocity, and porosity. Experimental results indicated that, when the PAM dosage increased from 0.59 mg/L to 1.18 mg/L, pellets size would flocculated from 2.25 mm to 3.52 mm with the settling velocity accelerated from 3.28 mm/s to 7.37 mm/s, while under the same up-flow rate, agitation intensity and PAM dosage, accompany with the raw water concentration increased from 216 mg/L to 840 mg/L, pellets settling velocity would improved from 6.03 mm/s to 13.6 mm/s. Under the experimental condition, along with the up-flow rate increased from 13.3 m/h to 40 m/h, pellets settling velocity would decreased from 4.39 mm/s to 3.42 mm/s due to its lower density.

Influence of structural properties of alum and ferric flocs on sludge dewaterability

Sludges are made of flocs produced during the coagulation stage. Their dewatering not only depends on the equipment used but also on the chemical, structural and physical characteristics of flocs. In this study, the relation between floc structure and sludge dewaterability is investigated beside the influence of the operating conditions during coagulation. Eight synthetic clay flocs families are produced using clay suspensions with four initial solids concentrations ranging from 0.5 to 5 g L −1 and two coagulants (Al 2(SO 4) 3 and FeCl 3). Flocs structure is characterised by their fractal dimension and by the size of the basic units (clusters, aggregates) they are made from. Fractal dimension values about 2.5 are indicative of rather compact structures with slightly looser flocs obtained when using FeCl 3. Except for clusters, larger in ferric flocs, the basic units sizes are similar whatever the coagulant used and they decrease when the solids concentration during coagulation is increased. Sludge dewaterability is estimated from the bound water content and the capillary suction time (CST) giving respectively information on the extent and on the rate of water removal. Ferric flocs contain about 20% less bound water but exhibit higher CST values and therefore higher resistance to water removal than alum ones. Flocs structure and sludge dewaterability are found linked. The sludge bound water content is found to decrease with the floc fractal dimension: less compact flocs contain more water but less bound water. And the capillary suction time is lower when sludges are made of smaller flocs.

Effect of shear on concentrated hydrous ferric floc rheology

The primary interest of this work is to determine the effect of continuous shear, variable shear rate, and shear history on concentrated hydrous ferric floc rheology. The floc suspensions are strongly shear degrading with the behaviour being adequately described by a power law model. This is supported by images of the floc particles, which indicate a breakdown in floc structure, with the release of water and formation of smaller particles, after the application of shear. A shear rate sweep of the sample produces a hysteresis loop due to the time dependency of the samples. Higher shear rates are shown to destroy more structure, resulting in an overall decrease in floc viscosity. This is irreversible, and occurs due to a breakdown in floc structure to release trapped water and produce smaller floc particles. Shear also causes an instantaneous reduction in viscosity. This effect is instantaneously recoverable, and is due to a decrease in floc particle aggregation. Floc behaviour within the shear rate range 20–250 s −1 is also adequately modelled by the Sisko model.

Effect of floc concentration on the rheology of a ferric floc

AbstractThe primary interest of this work is to determine the effect of floc concentration on ferric floc particle interactions and hence, rheology. In accordance with established theory, ferric floc viscosity exhibits a non‐linear increase with solids content, with the viscosity increasing sharply above a concentration of 12 000 ppm. Shear effectively breaks down floc structure, and thus reduces viscosity, the extent of which is independent of solids content. The effect of shear is also observed to diminish over time and can be adequately characterised by a power law model. Addition of aluminium nitrate to ferric floc increases the quantity of water bound within the floc, and thus produces suspensions which are more viscous in nature. Copyright © 2003 Society of Chemical Industry

Effect of freeze-thaw process on partitioning of contaminants in ferric precipitate

The primary interest of this work was to determine the processing conditions which will provide the most water removal from the precipitate after freezing and thawing. The work examined the effect of variables such as freezing time, freezing temperature, and pre-treatment steps, e.g. agitation or concentration, on the freeze thaw process of ferric precipitates. The extent of dewatering of freeze thawed samples was not significantly affected by freezing rate or curing time, provided the floc was completely frozen. However, a pre-concentration step was found to produce a more concentrated residual. The relatively low degree of structure within the ferric flocs makes them particularly suitable for freeze-thaw conditioning. Only a slight increase in leach out of contaminant from the floc was observed. Thus, the experiments indicate that this is a very simple and effective method of dewatering precipitates, which does not require the use of additional additives.

Effect of shear and washing on metal retention in ferric flocs

Flocculative wastewater residues present a serious threat to the environment and a costly disposal problem to industry. The composition of the sludges makes them a particularly intractable problem due to the need for either recovery or permanent isolation of the bound contaminant. The primary interest of this work was to determine the effect of conditioning processes such as shear and washing on the retention of heavy metal contaminants (nickel, cadmium, copper, zinc) within ferric flocs. Shear was found to produce an increase in the leach-out of certain heavy metals, including cadmium and nickel. Copper and nickel were unaffected by the application of shear. The extent of contaminant leaching, due to shear, increased with increasing contaminant to floc ratio. Repeated washing of the floc readily removed sodium ions, however, contaminant metal ions reformed an equilibrium with the washwater and the floc with every washing. © 2002 Society of Chemical Industry

The potential for phosphorus release across the sediment–water interface in an eutrophic reservoir dosed with ferric sulphate

Alton Water, Suffolk, UK is a pumped storage reservoir that has a history of cyanobacterial blooms. Dosing of the input water with ferric sulphate to control external phosphorus loading has occurred since 1983. A detailed study of the sediment chemistry of the site was carried out between May 1995 and July 1997. Sequential phosphorus fraction analysis indicated a decrease along the length of the reservoir in sediment labile phosphorus content from 0.62 to 0.08 mg P g −1 dw and iron-bound phosphorus content from 3.22 to 0.46 mg P g −1 dw. These gradients positively correlated with water column chlorophyll a concentrations reported in a parallel study. Labile and iron-bound sediment phosphorus contents were in a dynamic equilibrium due to diffusional release, contributing to internal loading to the water column. Equilibrium phosphorus concentrations (EPC) determined from phosphorus adsorption capacity (PAC) experiments were lower inside the bunded region (0.01–0.03 mg P-PO 4 l −1) where iron content was greatest compared to outside the bund (0.15–0.20 mg P-PO 4 l −1) suggesting greater potential for diffusional release of phosphorus at the latter site. PAC experiments indicated that anaerobic and pH-mediated loadings were of less importance than diffusional release, although the latter may have contributed to internal loading in the main reservoir. Sulphate concentrations may act to increase the potential for anaerobic internal loading near to the pumped input in microstratified sediment. Sediment iron content decreased from 250±13.1 to 51±4.0 mg Fe g −1 dw across the line of a constructed bund at the north-west end near to the pumped input, which indicated successful control of dispersal of the fine ferric floc. The management implications with regard to phosphorus loadings indicated by these results are discussed.

The production of flocs for water treatment by electrodialysis in a diaphragm cell

This paper considers a novel system of producing flocs for water treatment as part of a larger process of recycling the floc chemicals rather than dumping the waste at the treatment site. The cell produces high pH conditions in the cathode side of the cell and a porous diaphragm allows the passage of the cations to this side where they are precipitated. In several instances the apparent current efficiency of the process is over 100% owing to a contribution of bulk diffusion of iron from the anode to the cathode chamber. The process has some drawbacks. Firstly an alkali has to be fed into the cathode chamber and secondly bulk transport of water due to electroosmosis forces fluid from the cathode to the anode. This causes membrane fouling in a number of cases. Both aluminium and ferric iron flocs have been studied in this investigation. The process is more suitable for the production of ferric flocs.

Application of high gradient magnetic separation to ferric hydroxide filtration

Ferric Hydroxide is a good scavenger for trace concentrations of both heavy metals and many radio nuclides, its precipitation from waste streams could be used as an effective method of clean up if a satisfactory process for the recovery of the ferric floc was available. This paper examines the use of HGMS for this operation and concludes that a practical plant design is feasible for ferric floc separation but would require a large installation. The work is continuing and more recent developments have shown how significant improvements can be made by precipitating the iron as magnetite instead of ferric hydroxide.

Some Chemical Aspects of Rapid Sand Filtration

This article considers past efforts and present knowledge concerning the filtration process, with particular emphasis on particle removal mechanisms, and presents the results of research demonstrating chemical effects in the filtration of ferric floc suspensions. The results of this research provide experimental evidence that the surface properties of ferric floc particles markedly affect their filtrability, and that these properties depend on the chemical composition of the aqueous phase. These chemical effects in the filtration process are considered to result from interactions between the surfaces of the filter medium and the suspended floc particles; this conclusion lends strong experimental support to adsorption as a predominant removal mechanism in rapid sand filters. The data presented in this article indicate to the authors that rapid sand filtration can be chemically controlled through the influence of selected chemicals on the adsorption of suspended particles to the filter media.

Removal of Copper Sulfate from Water by Ferric Floc

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRemoval of Copper Sulfate from Water by Ferric FlocC. J. BrockmanCite this: Ind. Eng. Chem. 1934, 26, 9, 924Publication Date (Print):September 1, 1934Publication History Published online1 May 2002Published inissue 1 September 1934https://doi.org/10.1021/ie50297a005RIGHTS & PERMISSIONSArticle Views57Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (172 KB) Get e-Alerts