Polyferric Sulfate Research Articles

Effects of suspended particulate matter from natural lakes in conjunction with coagulation to tetracycline removal from water

Coagulation is a common method used to remove suspended particulate matter (SPM) from the water supply. SPM has preferable adsorption ability for antibiotics in water; therefore, SPM adsorption and coagulation may be a possible way to remove tetracycline (TC) from water. This study carried out coagulation experiments combining SPM collected from a natural lake at a location with three common coagulants—polyaluminum sulfate, polyaluminum chloride, and polyferric sulfate—under different pH values, exploring the adsorption of TC by SPM, coagulation of SPM with TC, and the primary influencing factors of this process. The maximum removal rate of TC can reach 97.87% with an SPM concentration of 1000 mg/L. Multi-factor analysis of variance showed the importance of various TC removal factors, which were ranked as follows: SPM concentration ≫ initial TC concentration > type of coagulant > pH values. The higher the SPM concentration, the better the TC removal (p < 0.001). Fourier infrared spectroscopy results demonstrated the strong adsorption effect of SPM on TC after being combined with a coagulant, and scanning electron microscopy also indicated that SPM becomes effective nuclei in the coagulation process, which is a possible reason for better TC removal. However, the effluent turbidities under 1000 mg/L SPM concentrations were high without coagulant aid. With the addition of coagulant aid anion polyacrylamide, the TC removal remained unchanged, effluent turbidity significantly reduced, and the TC desorption became low. These results indicate that applying SPM from natural lakes in the coagulation process could potentially remove TC in water.

Hydrothermal synthesis, structure and variable temperature magnetic performance of polyferric sulfate with µ 3-O2- and µ 3-OH--centered Trinuclear Ferric(III)

A novel inorganic coordination polymers crystal is grown from ferric sulfate solution under hydrothermal condition in the presence of adipic acid. The single crystal structure analysis shows that 0.5[Fe6(μ3-O2-)2(μ3-OH-)2(SO4)6].2H2O 1 is composed of µ 3-O2- and µ 3-OH--centered Trinuclear Ferric(III) secondary building units (SUBs) to form two dimensional network, and the lattice parameters are a = 18.223(13) Å, b = 7.670(5) Å, 9.932(7) Å, α = β= γ = 90°, orthorhombic crystal system, Cmc21 space group, V = 1388.3(17) Å3. Squid-VSM magnetic measurement system is used for characterizing the variable temperature magnetic properties measurement of reaction products, and the result indicates that the magnetic susceptibility is obvious reduced with the increasing of test temperature. Noticeably, the higher magnetic susceptibility is acquired at about 0 K. Consequently, the products can be used as a good candidate for magnetic memory materials.

Study of PFS and PAC coagulation effect on Pi River water

Using poly-aluminum chloride (PAC) and poly-ferric sulfate (PFS) as coagulants, the effects of the dosage of PAC and PFS on the removal of turbidity, chromaticity and UV254* in water were investigated by using the method of enhanced coagulation. The results show that when the raw water is neutral and the turbidity is less than 20NTU, and the pH value does not decrease much after coagulation and sedimentation, PAC and PFS are separately added to 7.5mg/l, 35mg/l. The removal rate of turbidity and chromaticity in the water sample can reach 83.75% and 48.47%, respectively, but the removal rate of UV254* is less than 30%, the mass ratio of PAC to PFS is 1:1 to 6:1, the removal efficiency of turbidity and Chroma increased by about 10%, but the removal efficiency of UV254* did not change or even decreased, both PFS and PAC can effectively remove the turbidity and Chroma in the micro polluted Pi River, but the removal effect of UV254* is not good, and the removal effect of PAC is better than PFS.

Efficiency and Mechanism of Advanced Treatment for Phosphate Wastewater by High Efficiency and Low Consumption Coagulation and Phosphorus Removal System

Beaker coagulation experiments were carried out using polyaluminium chloride (PAC), polyferric sulfate (FPS), polyacrylamide (PAM), polyaluminum chloride (PAFC), polyaluminum sulfate (PAFS) and polyacrylamide (PAFC). The phosphorus removal effects of several flocculants were compared. The best combination coagulant PAM-PAC/PFS with high efficiency and economy was selected. The best ratio of PAC/PFS is 1:1, and the dosage of PAM is 1mg/L. The experiment determined the optimal hydraulic conditions: fast agitation and addition of PAC/PFS at a speed of 400 r/min for 1 min. PAM was added during slow agitation at a speed of 100 r/min for 6 min. The phosphorus removal system has a good effect on the removal of total phosphorus and other water quality indicators in the mine drainage of many phosphate mines, and all of them can meet the discharge standards.

Synchronization of dehydration and phosphorous immobilization for river sediment by calcified polyferric sulfate pretreatment

Disposal of dredged river sediment requires decreases in both water content for reduction in disposal area, and the amount of eutrophication pollutants at risking of leaching. The effects of CaCl2, polyferric sulfate (PFS) and calcified polyferric sulfate (CaPFS) on dewatering and phosphorus immobilization were examined. Upon CaPFS dosage of 1.88 mg Ca + Fe kg−1 raw sediment (RS) the moisture content of the sediment was 41.1 wt% after pressure filtration, with filtrate dissolved inorganic phosphorus (DIP) of 6.1 mg L−1; better outcomes than for equivalent dosages of CaCl2 or PFS. On CaPFS dosage of 4.98 mg Ca + Fe kg−1 RS, DIP in the filtrate was <0.5 mg L−1. Dosages of CaCl2 and PFS required to achieve <0.5 mg L−1 DIP were 6.79 mg Ca kg−1 RS and 5.64 mg Fe kg−1 RS. CaPFS aids particle surface charge neutralization and sweep flocculation by polymeric iron, improving dehydration efficiency. Synergistic effects of aqueous Ca and Fe promote P stability reducing DIP mobility. For treatment of 10000 m3 of this dredged sediment, CaPFS has the potential to reduce the discharge of eutrophicated water by 74 ± 6% compared with PAC + PAM conditioning, demonstrating the promising application of CaPFS conditioning.

Mechanistic insights into the effect of poly ferric sulfate on anaerobic digestion of waste activated sludge

Poly ferric sulfate (PFS), one of the typical inorganic flocculants widely used in wastewater management and waste activated sludge (WAS) dewatering, could be accumulated in WAS and inevitably entered in anaerobic digestion system at high levels. However, knowledge about its impact on methane production is virtually absent. This study therefore aims to fill this gap and provide insights into the mechanisms involved through both batch and long-term tests using either real WAS or synthetic wastewaters as the digestion substrates. Experimental results showed that the maximum methane potential and production rate of WAS was respectively retarded by 39.0% and 66.4%, whereas the lag phase was extended by 237.0% at PFS of 40 g per kg of total solids. Mechanism explorations exhibited that PFS induced the physical enmeshment and disrupted the enzyme activity involved in anaerobic digestion, resulting in an inhibitory state of the bioprocess of hydrolysis, acidogenesis, and methanogenesis. Furthermore, PFS's inhibition to hydrogenotrophic methanogenesis was much severer than that to acetotrophic methanogenesis, which could be supported by the elevated abundances of Methanosaeta sp and the dropped abundances of Methanobacterium sp in PFS-present digester, and probably due to the severe mass transfer resistance of hydrogen between the syntrophic bacteria and methanogens, as well as the higher hydrogen appetency of PFS-induced sulfate reducing bacteria. Among the derivatives of PFS, “multinucleate and multichain-hydroxyl polymers” and sulfate were unveiled to be the major contributors to the decreased methane potential, while the “multinucleate and multichain-hydroxyl polymers” were identified to be the chief buster to the slowed methane-producing rate and the extended lag time.

Removal of viscous and clogging suspended solids in the wastewater from acrylonitrile-butadiene-styrene resin production by a new dissolved air release device

The suspended solids in the acrylonitrile-butadiene-styrene(ABS) wastewater are in the form of viscous latex, which strengthens the blocking phenomenon of the release device, increases the suspended solids in the return water and reduces the removal effect of the air flotation apparatus. Therefore, we designed a new release device. To achieve the goal of controlling the bubbles in the target diameter and enlarge the hole size as much as possible to reduce blockage, we studied the relationship between the geometry structure and performance of the new, which could be describeed by fixed polynomials. The best demulsification effect could be obtained by the hybrid of the polyferric sulfate and FO4440SSH, and the highest removal rate was 92.51 %. After a long-running in the ABS sewage treatment plant of the petrochemical industry, the removal rate of the new could maintain at a high level(>90 %), and the removal effect was stable. Compared with other release devices that reported in the literatures, the new one had advantages significant in both removal efficiency and operation cost.

The effect of polyferric sulphate treated farm dairy effluent and clarified water on leaching losses, greenhouse gas emissions and pasture growth

ABSTRACT A lysimeter experiment was conducted to investigate the environmental effects of applying farm dairy effluent (FDE) treated with a chemical coagulant (polyferric sulphate) to land. The coagulant was administered as part of an effluent treatment system known as ClearTech. Two products are produced from the treatment process; treated effluent (TE) and clarified water (CW). Applications were applied in May. When compared to FDE, TE and CW reduced E. coli, Total-P and dissolved reactive P (DRP) leaching losses. Escherichia coli leaching losses were reduced by 99.97% and 99.99% for TE and CW, respectively. This was because of the acidity of the added coagulant and the encapsulation of the bacteria in the flocculated sediment. Compared to FDE, Total-P leaching losses were reduced by 90.5% and 85.7% for TE and CW, respectively. DRP leaching losses were also reduced under TE and CW by 99.5% and >99.99%, respectively. Reductions in phosphorus leaching were attributed to the reduced P solubility, resulting from the iron added in the coagulant binding to the phosphorus. There was no significant difference between treatments in the amount of iron leached, greenhouse gas emissions or Mineral-N leached (except where additional ammonium-N was added to the clarified water).

High-Performance Flocculants for Purification: Solving the Problem of Waste Incineration Bottom Ash and Unpurified Water.

The silicon–aluminum–iron flocculant (PAFSi) combines the most abundant resources of waste incineration bottom ash and unpurified water, being regarded as one of the most promising approaches toward water purification. Herein, in this research, waste incineration bottom ash was employed to produce a cost-effective and highly efficient flocculant. PAFSi with a particle size of 214 nm and a zeta potential of 8.63 mV reached the optimum performance using a dosage of 2 mL/50 mL at pH from 8 to 11. The results with the copolymer exhibited the following: (1) a good flocculation efficiency over a wide pH range, (2) superior flocculation performance compared to those of polyaluminum chloride and polyferric sulfate, (3) three-dimensional branching structure of PAFSi micelles with a high aggregation degree, (4) charge neutralization and bridging as the main flocculation mechanism, and (5) recycling the floc. Thus, this work provides an attractive solution to the pressing global clean water shortage problem.

Treatment of potato starch wastewater by dual natural flocculants of chitosan and poly-glutamic acid

Starch wastewater treatment required extensive optimization because of its high concentrations of organic compounds and concentrated emissions. An environmental friendly dual flocculant, composed of cationic chitosan and anionic poly-glutamic acid, was investigated. Initial mechanistic studies involving independent injections of chitosan and poly-glutamic acid revealed their primary mechanisms of charge neutralization and bridging respectively. The highest removal rates of turbidity by chitosan and poly-glutamic acid were 90.1% and 91.8%. Dosing pattern studies showed that initial chitosan dosing provided the highest removal rate and widest effective pH range. Mechanistic studies using zeta potential and floc measurements, confirmed that chitosan neutralized negative charges, while long-chained poly-glutamic acid aggregated particulates. The effects of wastewater quality storage time, compound ratio, and total dosage were studied, with optimization at 0 h, 1:1, and 80 mg L−1, which outperformed traditional flocculants polyaluminium chloride and polyferric sulfate. The removal rates of chemical oxygen demand, total nitrogen, total phosphorus and turbidity were 44.8, 53.4, 28.1, and 98.3%. The sediment was detected containing 95% of organic matters and 5.6% of total nutrients making it an excellent organic fertilizer. This dual system is promising in starch wastewater treatment and resource recovery considering its eco-friendly and effective flocculation performance.

Upcycling of Electroplating Sludge to Prepare Erdite-Bearing Nanorods for the Adsorption of Heavy Metals from Electroplating Wastewater Effluent

Electroplating sludge is a hazardous waste produced in plating and metallurgical processes which is commonly disposed of in safety landfills. In this work, electroplating sludge containing 25.6% Fe and 5.5% Co (named S1) and another containing 36.8% Fe and 7.8% Cr (S2) were recycled for the preparation of erdite-bearing particles via a facile hydrothermal route with only the addition of Na2S·9H2O. In the sludges, Fe-containing compounds were weakly crystallized and spontaneously converted to short rod-like erdite particles (SP1) in the presence of Co or long nanorod (SP2) particles with a diameter of 100 nm and length of 0.5–1.5 μm in the presence of Cr. The two products, SP1 and SP2, were applied in electroplating wastewater treatment, in which a small portion of Co in SP1 was released in wastewater, whereas Cr in SP2 was not. Adding 0.3 g/L SP2 resulted in the removal of 99.7% of Zn, 99.4% of Cu, 37.9% of Ni and 53.3% of Co in the electroplating wastewater, with residues at concentrations of 0.007, 0.003, 0.33, 0.09 and 0.002 mg/L, respectively. Thus, the treated electroplating wastewater met the discharge standard for electroplating wastewater in China. These removal efficiencies were higher than those achieved using powdered activated carbon, polyaluminum chloride, polyferric sulfate or pure Na2S·9H2O reagent. With the method, waste electroplating sludge was recycled as nanorod erdite-bearing particles which showed superior efficiency in electroplating wastewater treatment.

Recovery of the fibrolytic microorganisms from rumen fluid by flocculation for simultaneous treatment of lignocellulosic biomass and volatile fatty acid production

Large volumes of rumen fluid are continuously discharged from slaughterhouses, which are typically transported to facilities for treatments of lignocellulosic biomass. Recovery of fibrolytic microorganisms from the rumen fluid enables to reduce the load for wastewater treatment and transportation of rumen fluid. However, there is no standardized method for recovering ruminal microorganisms. Here, we established a flocculation-based method with an optimized flocculant concentration required to recover ruminal microorganisms with fibrolytic activity. Rumen fluid was flocculated with poly-ferric sulfate at 0.4%, 0.7%, 1.0%, and 2.0% and with an inorganic neutral flocculant at 13.0%. Poly-ferric sulfate at 0.4%, 0.7%, and 1.0% effectively recovered ruminal microorganisms, which resulted in an 85.6%, 77.3%, and 75.6% reduction in rumen fluid volume, respectively. These recovered microorganisms retained the endoglucanase activity at 52 kDa and 53 kDa in size. In addition, recovery of ruminal microorganisms allowed for substantial reductions in the solids and organic compound concentrations of the filtrates after the flocculation. As a practical demonstration of this method, tomato leaves were treated with the flocculated rumen fluid at 37 °C for 48 h. Hydrolysis of the tomato leaves using the rumen fluid flocculated with 0.7% poly-ferric sulfate demonstrated elevated endoglucanase activity at 37 kDa, 46 kDa, 57 kDa, 61 kDa, and 66 kDa in size during treatment. Therefore, 0.7% poly-ferric sulfate is the optimal concentration for recovering ruminal microorganisms while maintaining their fibrolytic activity. This is the first study which suggest a novel method to efficiently recover ruminal microorganisms from huge amounts of rumen fluid offers a practical and sustainable solution to reduce the load for wastewater treatment at slaughterhouses and in the transportation of rumen fluid.

Recycling of groundwater treatment sludge to prepare nano-rod erdite particles for tetracycline adsorption

Groundwater treatment sludge was a ferrihydrite-rich solid waste and abundantly generated for potable water production in groundwater treatment plant. Here we demonstrated an alternative strategy to reuse the sludge for preparing nano-rod erdite particles (EPs) via a facile hydrothermal method with only adding Na2S. The produced EPs were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The SEM results showed that with the molar ratio of N2S to Fe in the sludge increasing from 1 to 2, the product EPs grew long from 0.5-1 μm to 1–4 μm. The product EP-0.2, prepared at the molar ratio of 0.2, was amorphous aggregates with dotted distribution of hexahedral pyrite. With the molar ratio increasing to 2, the product EP-2 was in the form of nanorod, and exhibited high TC adsorption capacity of 1960.8 mg/g, approximately 15 times of that of EP-0.2. By adding 0.02g EP-2, the removal rate of TC was 92.5% at the initial TC concentration of 1000 mg/L, higher than that of active carbon, diatomite, polyaluminium chloride and polyferric sulfate, and nearly 100% TC and 51.5% total organic carbon were removed from pharmaceutical wastewater. EP-2 was completely hydrolyzed to yield Fe oxyhydroxide in TC-containing solution, which exhibited adequate hydroxyl groups to link the –NH2 group at the side chain of TC molecules, resulting in high TC adsorption. This is the first report of recycling groundwater treatment sludge for preparing nano-rod erdite particles, which can be serve as low-cost materials in wastewater treatment.

Removal of hard COD from biological effluent of coking wastewater using synchronized oxidation-adsorption technology: Performance, mechanism, and full-scale application

Efficient removal of the non-biodegradable organics from the biological effluent of industrial wastewater is becoming more and more important with the increasing demand for stringent discharge regulation. In this study, a synchronized oxidation-adsorption (SOA) technology was proposed for the removal of hardly biodegradable COD (hard COD) from the biological effluent of coking wastewater, and its performance was verified in a full-scale coking industrial park wastewater treatment plant (Q = 5,000 m3/d). The SOA was performed by coupling oxidation by hydroxyl radical (molar ratio of Fe2+ to H2O2 of 1:1 and pH = 5.0 ± 0.2) and adsorption by in-situ-formed nano hydrolyzed Fe3+ particles (nano-FeOOH). The nano hydrolyzed Fe3+ particles formed during the SOA exhibited a much higher specific surface area (22.83 m2/g) than the particles (10.87 m2/g) formed during the polyferric sulfate coagulation (PFSC). In comparison to PFSC, SOA performed better in terms of average COD removal (39% vs 18%) from the biological effluent. Wastewater fractionation result showed that SOA performed better in the removal of the hydrophobic acid matters, which was supported by the experiment using fulvic acid as the model organics. Mechanism studies using both biological effluent and fulvic acid solution showed that more carboxylic substances were adsorbed by the in-situ-formed nano-hydrolyzed Fe3+ particles formed by SOA than by PFSC, which was likely due to the generation of carboxylic substances by hydroxyl radical oxidation. In the full-scale, the COD was reduced from 118.5–198.0 mg/L in the PFSC-pretreated effluent to 61.5–104.0 mg/L through SOA treatment. The SOA treatment characterized with a mild pH condition (pH 5) and low molar ratio of Fe2+ to H2O2 (1:1) is particularly suitable for the polishing purpose to remove limited amount of organic pollutants from wastewater before discharge.

Experimental Research on Removal of UV254 by PFS in Pi River water with low turbidity

Through beaker test, it was analyzed the effect on the removal of turbidity, chroma and UV254 in PI River water with low turbidity by poly-ferric sulfate(PFS).The results showed that it has good effect on removing turbidity and chroma by adding PFS, but it was normal to UV254, not exceed 50%,with the increase of PFS dosage, the turbidity and chroma removal trend is similar to that of UV254. For turbidity removal, the optimal dosage of PFS was 70 mg / L, and for UV254 removal, the optimal pH value range is not neutral, and it is speculated that PFS mainly neutralizes pollutants during coagulation in PI River water.

Analysis of the Influence of Coagulant on Phosphorus in Landscape Water Environment

This study selected three kinds of inorganic polymer coagulant: polyferric sulfate, polyaluminium chloride, polyaluminium ferric chloride, two inorganic low molecular coagulants: aluminum chloride and aluminum sulfate. The coagulation experiment of lake water without “water bloom” was carried out. The results were analyzed by multivariate linear regression and principal component regression analysis. It showed that the effects of the five coagulants on the phosphorus were the same when the landscape water was treated with different dosages of coagulants. The sequence was: total nitrogen (TN) > dosage > ammonia nitrogen > CODcr > turbidity > PH. Among them: the highest effect of total nitrogen on phosphorus was aluminum chloride (71.73%). The most obvious effect of dosage on phosphorus was polyaluminium chloride (34.68%). The most significant effect of ammonia nitrogen on phosphorus was polyaluminum chloride (16.98%).

Analysis of the Sedimentation Characteristics of Ultrafine Tailings Based on an Orthogonal Experiment

Due to continuous improvements in the beneficiation process, the size of tailings has decreased. In many mines, more than 50% of the total tailings are finer than 74 μm. Ultrafine tailings exhibit a slow settling velocity and uneven settling, which pose new challenges to the safety and stability of tailings dams. In this paper, ultrafine iron tailings from the Makeng Iron Mine in Longyan City, Fujian Province, were used as the research object. A four-factor, three-level orthogonal test method was used to study the sedimentation characteristics of ultrafine tailings with four common curing agent materials, including polyacrylamide, polyaluminum chloride, polyaluminum sulfate, and polyferric sulfate. The results show that when the pulp concentration is 30%, the polyacrylamide is cationic and the molecular weight is 10 million, the optimal content of the flocculant is 3‰, the optimum dose of the polyaluminum chloride with a content of 28 is 0.1‰, the optimum dose of polyaluminum sulfate is 1‰, and the optimum dose of polymeric ferric sulfate is 1‰. When the flocculant is mixed according to the proportion of 2‰ polyacrylamide, 0.05‰ polyaluminum chloride, 1‰ polyaluminum sulfate, and 1.0‰ polyferric sulfate, the sedimentation speed of the ultrafine tailings is fast, and the supernatant liquid is clear. The results of multivariate nonlinear regression analysis of the sedimentation curve show that the primary and secondary factors affecting sedimentation are polyacrylamide &gt; polyaluminum sulfate &gt; polyaluminum chloride &gt; polyferric sulfate. When the optimal ratio is applied, the cohesion (c) of ultrafine tailings increases from 27 kPa to 68.75 kPa and the internal friction angle (φ) increases from 25.53° to 27.53°, which shows that the shear strength improves and the stability of the tailings dam increases. The economic analysis of the composite flocculant with the optimal ratio shows that the flocculant with the optimal proportion has an obvious economic advantage over polyacrylamide alone.

Synthesis of Poly-Alumino-Ferric Sulphate Coagulant from Acid Mine Drainage by Precipitation

The wastes generated from both operational and abandoned coal and metal mining are an environmental concern. These wastes, including acid mine drainage (AMD), are treated to abate the devastating effects they have on the environment before disposal. However, AMD contains valuable resources that can be recovered to subsidize treatment costs. Two of the major constituents of coal AMD are iron and aluminium, which can be recovered and engineered to function as coagulants. This work examines the potential of producing a poly-alumino-ferric sulphate (AMD-PAFS) coagulant from coal acidic drainage solutions. The co-precipitation of iron and aluminium is conducted at pH values of 5.0, 6.0 and 7.0 using sodium hydroxide in order to evaluate the recovery of iron and aluminium as hydroxide precipitates while minimizing the co-precipitation of the other heavy metals. The precipitation at pH 5.0 yields iron and aluminium recovery of 99.9 and 94.7%, respectively. An increase in the pH from 5.0 to 7.0 increases the recovery of aluminium to 99.1%, while the recovery of iron remains the same. The precipitate formed at pH 5.0 is used to produce a coagulant consisting of 89.5% and 10.0% iron and aluminium, respectively. The production of the coagulant is carried out by dissolving the precipitate in 5.0% (w/w) sulphuric acid. Subsequently, the treatment of the brewery wastewater shows that the AMD-PAFS coagulant is as efficient as the conventional poly ferric sulphate (PFS) coagulant. The turbidity removal is 91.9 and 87.8%, while the chemical oxygen demand (COD) removal is 56.0 and 64.0% for AMD-PAFS and PFS coagulants, respectively. The developed process, which can easily be incorporated into existing AMD treatment plants, not only reduces the sludge disposal problems but also creates revenue from waste.

A novel scheme for flotation tailings pulp settlement and chemical oxygen demand reduction with polyferric sulfate

Abstract In most of the mining industries, lime is widely used to settle flotation tailings pulp. However, this conventional method has some drawbacks, as it increases pH, organic matter content and chemical oxygen demand (COD) of tailings dam wastewater (TDW) and further treatment is required. Therefore, current research provides an innovative and environmentally friendly technology that uses polyferric sulfate (PFS) instead of lime for pulp settlement. A series of laboratory tests showed that the final settlement effects of PFS and lime for tailings pulp settlement were comparable. However, the COD of tailings water by PFS settlement was considerably reduced compared with that of lime settlement. Total organic carbon and fluorescence excitation–emission matrix analysis showed that organic matter content in tailings water by PFS settlement was also significantly lower than that of lime settlement. Lead nitrate and benzohydroxamic acid (Pb-BHA) synthetic solutions analysis showed that increasing or decreasing the pH dissolved Pb-BHA precipitates into water, leading to an increase in COD. Therefore, in lime settlement, the pH value significantly increased, which dissolved the remaining Pb-BHA precipitates in the pulp into water, resulting in an increase in COD. In PFS settlement, the pH change was small, and polynuclear hydroxyl complex generated by the hydrolysis of PFS adsorbed part of the organic matter to precipitate, resulting in COD reduction. Results of laboratory tests were further verified by an industrial test. The COD and pH of the TDW significantly decreased from 110 mg/L before the industrial test (lime settlement) to 68 mg/L and from 11.8 to 7.1, respectively, after the industrial test (PFS settlement).

Comparison of coagulative colloidal microbubbles with monomeric and polymeric inorganic coagulants for tertiary treatment of distillery wastewater

The flotation using coagulative colloidal gas aphrons (CCGAs) is of great potential in effectively removing the recalcitrant dissolved organic matter (DOM) and colorants from the bio-chemically treated cassava distillery wastewater. As bubble modifier, the monomeric and polymeric inorganic coagulants need to be studied considering their distinct influence on the surfactant/coagulant complex, the properties of colloidal aphrons as well as the process performance and mechanisms. Such studies help to create robust CCGAs with high flotation potential. In this work, the commonly-used monomeric and polymeric Al(III)- and Fe(III)-coagulants were combined with the cationic surfactant – cetyl trimethylammonium bromide (CTAB) to generate CCGAs. The CCGAs functionalized with Al(III)-coagulants (both monomeric and polymeric ones) were featured as small bubble size, strong stability and high air content. Particularly, the monomeric Al(III)-coagulant (AlCl3 in this work) resulted in low surface tension and high foamability when being mixed with CTAB in the bubble generation solution. Those CCGAs achieved high removal efficiencies of DOM and colorants at low coagulant concentrations. The molecular weight of DOM in effluent was well controlled below 1 kDa by CCGAs. For the flocs obtained from CCGA-flotation, the characteristic Raman band of DOM and colorants showed the layer-by-layer variation of Raman intensity which decreased from the outer layer to the center. In contrast with the conventional coagulation-flotation, the reduction of coagulant dosage by CCGAs was 67% (AlCl3), 25% (polyaluminum chloride), 60% (Fe2(SO4)3) and 40% (polyferric sulfate). The sludge production could then be largely reduced, and meanwhile, the retention time was shortened by 9.5 min.