Solid-liquid Separation Processes Research Articles

Experimental Investigation on Abstraction of Phenol Onto Micrococcus lylae and Cetyl Trimethyl Ammonium Bromide

Air floatation, an efficient solid–liquid separation process, was tested as a post treatment technique for phenol removal. The results consider about the practical solutions for certain operations such as efficient solid–liquid separation, attainment of maximized percentage removal, phenol rich solution with Micrococcus lylae cells, and pure water without M. lylae cells. The two processes, biosorption and flotation, can effectively operate in combination and both the sorbent and treated water can be recycled. The effect of various operating parameters, such as initial feed concentration, equilibrium time, biosorbent dose, pH, liquid pool height, surfactant concentration, and air flow rate, was experimentally investigated. The maximum sorption capacity was found to be 303 mg/g at pH 7 and an initial phenol concentration of 500 mg/L. The higher floatability of M. lylae was obtained in a maximum time of 10 min. In addition, the adsorption isotherm and kinetic studies revealed that the biosorption process followed the Dubinin–Radushkevich model (R2 = 0.982) and pseudo‐first order kinetics with a kinetic constant of 2.6537/day. The adsorbed chemical species was identified by Fourier transform infrared (FTIR) spectroscopy. Electrokinetic measurements were carried out to determine the isoelectric point of the bacteria. The zeta potential profile of the bacteria was affected by the presence of phenol at different pH values. The recovery of phenol loaded biomass and final traces of phenol by flotation were found to be 99.91%.

Impact of organic polyelectrolytes on coagulation of source-separated black water

ABSTRACTHousehold wastewater is originated from common people's activities and has a potential harmful impact on the environment if discharged directly without proper treatment. Toilet wastewater or black water (BW) contains urine, faeces, toilet paper and flushing water and it contains the majority of pollutants obtained from a single household. In this study, the focus was on BW treatment using chemical methods. The main goal of current research was to define the possibility and applicability of conventional coagulants and flocculants in direct chemical treatment of vacuum-collected BW to remove particles, organic matter and phosphorous. After the definition of dosing ranges, based on the equivalent doses in conventional municipal and industrial wastewater treatment data, aluminium and iron coagulants, organic polyelectrolytes (polymers with anionic, neutral and cationic charge with different molecular weights) and their various combinations were tested using the well-known jar-test laboratory method to study aggregation and solid–liquid separation processes in raw BW. The most important process parameter during the coagulation was pH level, dependent on the type and doses of metal salts. Some side processes were found to occur while using iron-based coagulants. Dosing of either single coagulants or single polymers did not give satisfactory results, while a combination of aluminium salts and cationic polymers showed high removal rates in total suspended solids, total chemical oxygen demand and ortho-phosphates, reaching 97.8%, 92% and 98.6%, respectively, with the optimal doses of chemicals. Cationic polymers with the lowest molecular weight and highest charge density were the most efficient in combination with aluminium coagulants.

Flocs in Water Treatment

Flocs in Water Treatment is the first of its kind - serving as a valuable aide-memoire for scientists, process engineers and other professionals engaged in water treatment. The framework described in Flocs in Water Treatment can also be applied to aggregated solids found both in the natural environment, and within a broad range of industries. Flocs (aggregated solid matter) resulting from the combined influence of coagulation and flocculation play a vital role in solid-liquid separation processes. The design and operation of water treatment plants demands a proper understanding of the ways in which flocs affect treatment systems and how their properties can be manipulated to increase treatment efficiency. Flocs in Water Treatment provides a comprehensive account of the ways in which flocs are formed, their characterization, and how they behave in practice. Flocs are complex entities, whose properties defy easy description and measurement. In spite of this, the authors provide a clear and discerning account of the current state of knowledge; this is rooted in science and draws on many disciplines. Based on their experiences in research and the workings of full scale treatment plants, the authors offer candid advice on tasks such as the measurement of floc properties and guidance on problems involving the use of chemicals for controlling floc properties within treatment systems. This title belongs to WERF Research Report Series ISBN: 9781843390633 (Print) ISBN: 9781780402000 (eBook)

Residual moisture content and separation efficiency optimization in pilot-scale vibrating screen

Vibrating screening is still one of the main operations considering solid–solid and solid–liquid separation processes. Although it is an equipment of simple design and execution, the full description of a screening unit operation may be difficult to predict, considering that several operational variables can influence it. Therefore, the main objective of this work was to evaluate the best possible combination between the process variables screen aperture size, the volumetric concentration of solids in the feed, and the g-force (measurement of the vibration). This configuration predetermined values for moisture content of the retained material over the screen and separation efficiency regarding particle size. For this, a suspension of phosphate rock concentrate (with a particle density of 3.25g/cm3 and average particle size of 95μm) was diluted in water to perform the experiments in a pilot-scale vibrating screen. The results were analyzed statistically and correlations for each response were fit. The highest values of separation efficiency were found with the lowest values of cut-size diameter, which is desirable in terms of separation. A multi-objective optimization in the experimental range was developed, finding the optimal point for the moisture content of 17.29% and the separation efficiency of 86.88%. The effects of screen aperture size and g-force had important roles in this study.

Application of response surface method of optimization in flocculant assisted filtration of uranium bearing alkaline leach slurry of limestone origin

Leach slurries of alkaline nature often show very low rate of filtration due to high pulp viscosity contributed by dissolved solutes in solution and very fine grained nature of the unleached solids. Maximisation of filtration performance generally needs exhaustive experimentation involving various parameters which influence the solid–liquid separation process. The study reported in this paper pertains to optimisation of parameters in vacuum filtration of uranium bearing alkaline leach slurry generated from a brecciated limestone ore using response surface methodology. The d80 size of solids in the leach slurry is 60 μm and the pH of the pulp is 9·5–10. Initial screening of various commercial flocculants of anionic, cationic and non-ionic nature was carried out using the capillary suction time (CST) as basis. Minimum CST was achieved using a combination of anionic and non-ionic flocculant namely the Indfloc (IF) 477 and Guargum. The dosages of the flocculant combination and the slurry temperature were optimised to achieve maximum rate of filtration with optimal cake moisture under vacuum filtration conditions.

The influence on biogas production of three slurry-handling systems in dairy farms

Handling systems can influence the production of biogas and methane from dairy farm manures. A comparative work performed in three different Italian dairy farms showed how the most common techniques (scraper, slatted floor, flushing) can change the characteristics of collected manure. Scraper appears to be the most <em>neutral</em> choice, as it does not significantly affect the original characteristics of manure. Slatted floor produces a manure that has a lower methane potential in comparison with scraper, due to: a lower content of volatile solids caused by the biodegradation occurring in the deep pit, and a lower specific biogas production caused by the change in the characteristics of organic matter. Flushing can produce three different fluxes: diluted flushed manure, solid separated manure and liquid separated manure. The diluted fraction appears to be unsuitable for conventional anaerobic digestion in completely stirred reactors (CSTR), since its content of organic matter is too low to be worthwhile. The liquid separated fraction could represent an interesting material, as it appears to accumulate the most biodegradable organic fraction, but not as primary substrate in CSTR as the organic matter concentration is too low. Finally, the solid-liquid separation process tends to accumulate inert matter in the solid separated fraction and, therefore, its specific methane production is low.

Fast and efficient cesium removal from simulated radioactive liquid waste by an isotope dilution–precipitate flotation process

The performance of an isotope dilution–precipitate flotation process for Cs-137 removal from low-level liquid radioactive waste is evaluated in this study using sodium tetraphenylborate (NaTPB) as the precipitating agent. In absence of Fe(III), neither the anionic sodium lauryl sulfate (SLS) nor the cationic cetylpyridinium chloride (CPC) could float the CsTPB precipitate over the studied pH range of 2.5–11.9. It is proposed that iron oxide coated CsTPB particles are formed upon addition of Fe(III) solution and their floatability is greatly dependent on the solution pH and the Fe(III) content. At the optimum conditions, remaining Cs-137 activity values <1.3nCi/L (SLS, pH ∼6.8) and <2.3nCi/L (CPC, pH ∼10.2) are achieved from radioactive wastewater within half a minute which are below its discharge limits. The mechanism of flotation is proposed and cesium removal is suggested to proceed via flotation of iron oxide coated CsTPB. Flotation technique is compared to other conventional solid–liquid separation processes (decantation, centrifugation and filtration) for separation of the iron oxide coated CsTPB particles. The results showed that the best separation was attained by flotation process. The data obtained by the present combined process, precipitation followed by flotation, for Cs-137 from radioactive wastewater are also compared to those reported by other treatment methods. Based on the data obtained, the combined process has great potential as a radioactive wastewater treatment technology.

A low-cost solid–liquid separation process for enzymatically hydrolyzed corn stover slurries

Solid–liquid separation of intermediate process slurries is required in some process configurations for the conversion of lignocellulosic biomass to transportation fuels. Thermochemically pretreated and enzymatically hydrolyzed corn stover slurries have proven difficult to filter due to formation of very low permeability cakes that are rich in lignin. Treatment of two different slurries with polyelectrolyte flocculant was demonstrated to increase mean particle size and filterability. Filtration flux was greatly improved, and thus scaled filter unit capacity was increased approximately 40-fold compared with unflocculated slurry. Although additional costs were accrued using polyelectrolyte, techno-economic analysis revealed that the increase in filter capacity significantly reduced overall production costs. Fuel production cost at 95% sugar recovery was reduced by $1.35 US per gallon gasoline equivalent for dilute-acid pretreated and enzymatically hydrolyzed slurries and $3.40 for slurries produced using an additional alkaline de-acetylation preprocessing step that is even more difficult to natively filter.

Permeate Flux Measurement and Prediction of Submerged Membrane Bioreactor Filtration Process Using Intelligent Techniques

Recently, membrane technology has become more attractive particularly in solid-liquid separation process. Membrane bioreactor (MBR) has found to be a reliable technology to replace the conventional activated sludge (CAS) process for water and wastewater treatment by adopting membrane filtration technology and bioreactor. However, numerous drawbacks arise when using membrane which includes high maintenance cost and fouling problem. An optimal MBR plant operation is needed to be determined in order to reduce fouling and at the same time reduce the cost of running the MBR. It is crucial to have a reliable MBR filtration prediction that can measure and predict the filtration dynamic performance especially the effect of fouling to the filtration and cleaning operations. With this prediction tool, suitable action can be taken to improve the operation in order to find the optimum setting of the filtration process. This paper presents the permeate flux measurement and prediction development for submerged membrane filtration process. Three input filtration parameters were used to predict the permeate flux in the filtration process. This work employed feed forward artificial neural network (FFNN) and radial basis function neural network (RBFNN) for the prediction purpose. The permeate flux prediction method was developed using operation settings such as aeration airflow, suction pump voltage and transmembrane pressure (TMP) under schedule relaxation condition. The result shows that FFNN method gives better performance compared with RBFNN method in terms of accuracy and reliability.

Expert Control Tuning of an Industrial Thickener

Water consumption has become an important issue for the mineral processing industry. This situation has led to an increased effort for recovering the maximum amount of water in the solid-liquid separation process. Thickeners are designed to separate clear and reusable water from concentrate underflow. Conventional feedback control has not been effective in stabilizing the process operation when the characteristics of the feed changes over time, since process dynamics exhibits high non-linearity. This work presents an expert system for an industrial thickener. Main results are a reduction in flocculants consumption and a more stable operation, with few emergency conditions.

Modification of Activated Sludge Cohesion by Enzymatic Catalysis Process and Perspectives

It is possible to transform the structure of organic compounds so as to modify some of their properties to make them more “elastic”, for example. Many solid-liquid separation processes use the cohesion property of the solid in suspension to increase the performance of the separation system. In this work, we examine some beneficial aspects that enzyme catalysis may reveal when acting on the strength of cohesion of a suspension. The topic concerns the activated sludge (AS) produced by wastewater of urban (or industrial) treatment plants. We used urban sludge and industrial liquid enzymes produced by the firm NOVO. To accelerate the research process, we employed enzyme mixtures (we called “enzyme cocktails”) that highlighted the active mixtures, but until now we have not characterized specifically active enzymes. Despite a significant number of experiences, it is clear that given the number of different enzymes available and the almost infinite possible ratios of cocktails, only a small number of conceivable methods have been tested (and even less optimized). Nevertheless, a few cocktails were active and promising enough to improve solids contact processes in various industrial processes. We have found a range of combinations that increases the sludge cohesion coefficient and considered this enzyme treatment to strengthen the separation by solid contact structures mainly to tackle important hydraulic shock.

Evaluation of Soxhlet extractor for one-step biodiesel production from Zanthoxylum bungeanum seeds

Soxhlet extractor was applied for biodiesel production from Zanthoxylum bungeanum seeds containing high amount of free fatty acids (FFA) using methanol and ethanol as both extractants and reactants. The yields, fatty acid concentration and acid values of Z. bungeanum seed oil (ZSO) extracted with different solvents were determined. With a solvent-to-seed ratio of 6 (ml/g), extraction time of 4h and water bath at 95°C, the yields of ZSO with methanol and ethanol reached above 20%, which was almost as efficient as n-hexane, and the acid values of the corresponding ZSO were 56.9 and 41.9mgKOH/g, respectively. The final acid values of ZSO were reduced to below 10mgKOH/g when sulfuric acid was used as a catalyst presented in receiver flask in 4h extraction and reaction. After 12h of extraction and transesterification in a Soxhlet extractor with methanol and ethanol, the conversion of ZSO from Z. bungeanum seeds into ZSO biodiesel was almost complete as confirmed by 1H NMR. Application of the Soxhlet extractor for one-step biodiesel production from Z. bungeanum seeds containing high FFA avoided solid–liquid separation process and solvent wash, showing great potential of reducing the production cost of biodiesel.

Obtaining Constitutive Equations for Thickening and Filtration Non-Newtonian Fluids

The study of filtration and thickening of particulate systems are used in many industrial processes involving processes of solid-liquid separation, such as in sedimentation ponds, filters, the drilling of oil wells, among others. This paper aims to advance the empirical mechanisms involved in the processes of solid-liquid separation and obtain constitutive equations relating the pressure in solids and porous media permeability from non-Newtonian fluids. In the experiments used aqueous solutions of xanthan gum concentration of 0.1% in weight basis in order to ensure non-newtonian means. For the preparation of suspensions, was used calcium carbonate as particulate material in the separation process involved an initial concentration of 12% by volume. The concentrated sediment was maintained between 30 and 48% by volume. Settling tests were carried to term and sediments resulting from each test were evaluated by making use of the Gamma Rays Attenuation Technique (GRAT). The results show that GRAT is effective in determining sediment concentration distributions formed from non-Newtonian solutions, allowing the constitutive equations to obtain pressure and the solid porous medium permeability, very important for simulations of solid-liquid separation processes.

Technological Study of Titanium Slag Production from Titanium-Bearing Blast Furnace Slag

Titanium-bearing blast furnace slag in which TiO2 content reaches to 20%~23% is a kind of precious secondary resource. The research utilizes the stable characteristic of TiO2 in hydrochloric acid to digest acid-soluble matters in slag. Titanium-bearing slag is obtained after solid-liquid separation process. The optimum acidolysis reaction condition can be known through analysis of raw material granularity, acid-slag ratio, reaction temperature and effect caused by reaction time on TiO2 content in slag. XRD image analysis can prove that the chemical compounds of Al、Mg、Fe are totally acid-thinned and TiO2 content in slag reaches to above 40%. This technology provides a valuable new way for the comprehensive utilization of titanium-bearing Slag.

Combination of Natural and Thermosensitive Polymers in Flocculation of Fine Silica Dispersions

A novel strategy for faster and better flocculation in solid-liquid separation processes is reported: the use of the natural polyelectrolyte chitosan (CH2500) in combination with the biocompatible thermosensitive polymer poly(N-vinylcaprolactam) (PNVCL). Silica dispersions (Aerosil OX50) were used as model and evaluated by means of analytical centrifuge, laser diffraction, and turbidimetry studies. Results show that the sedimentation velocity is doubled by addition of PNVCL and that at 45°C the density of the sediment is 33% higher, as compared to the use of CH2500 only. This results from the temperature sensitive behavior of PNVCL that phase-separate expelling water at temperatures higher than its LCST (32–34°C) leading to compaction of the flocs. By using this strategy the sediment is more compact, contains less water, and contains a very small amount of biodegradable CH2500 and biocompatible PNVCL.

Simple mass balance controllers for continuous sedimentation

The rational use of water in the mineral processing industry has become an important issue due to the geographical location of many plants. The increase of capacity in many copper concentrators has lead to an increased effort for recovering the maximum amount of water in the solid–liquid separation process. Thickeners work continuously to produce a concentrated underflow and a water overflow free from particulate matter. The behavior of many processes can be represented by a set of intensive and extensive variables. In this case, practice has shown that standard feedback control based on intensive variables has not been very easy to tune and effective in providing consistent operations. In many plants, thickeners operate with poor standards, with high dosages of flocculants, overflows with high fine particles contents and highly variable underflows. This work presents a novel nonlinear PI controller which is able to stabilize thickener operation using a simple control structure. An internationally accepted model and calibration using plant data is used to illustrate the design methodology and the level of performance attained by the controllers. The analysis of the results points out the improved performance by using extensive variables. In addition some guidelines concerning controllers tuning are also provided.

Probing Adsorption of Polyacrylamide-Based Polymers on Anisotropic Basal Planes of Kaolinite Using Quartz Crystal Microbalance

Quartz crystal microbalance with dissipation (QCM-D) was applied to investigate the adsorption characteristics of polyacrylamide-based polymers (PAMs) on anisotropic basal planes of kaolinite. Kaolinite basal planes were differentiated by depositing kaolinite nanoparticles (KNPs) on silica and alumina sensors in solutions of controlled pH values. Adsorption of an in-house synthesized organic-inorganic Al(OH)3-PAM (Al-PAM) as an example of cationic hybrid PAM and a commercially available partially hydrolyzed polyacrylamide (MF1011) as an example of anionic PAM was studied. Cationic Al-PAM was found to adsorb irreversibly and preferentially on tetrahedral silica basal planes of kaolinite. In contrast, anionic MF1011 adsorbed strongly on aluminum-hydroxy basal planes, while its adsorption on tetrahedral silica basal planes was weak and reversible. Adsorption study revealed that both electrostatic attraction and hydrogen-bonding mechanisms contribute to adsorption of PAMs on kaolinite. The adsorbed Al-PAM layer was able to release trapped water overtime and became more compact, while MF1011 film became more dissipative as backbones stretched out from kaolinite surface with minimal overlapping. Experimental results obtained from this study provide clear insights into the phenomenon that governs flocculation-based solid-liquid separation processes using multicomponent flocculants of anionic and cationic nature.

臭氧–气浮分离在水处理中应用研究进展

臭氧作为一种强氧化剂，在水处理中得到了广泛的应用，有明显的杀菌消毒作用，同时臭氧又有较强的助凝作用，能够促进气浮工艺的处理效果，气浮分离由于不但可以明显的降低水中的悬浮物，而且COD也可得到一定的去除。臭氧–气浮工艺则结合二者优点，将臭氧氧化技术与气浮分离技术相结合，采用臭氧化空气为气源，去除悬浮颗粒物同时又分解大量有机物，且有明显的杀菌消毒作用，在一个操作单元内实现了破乳或絮凝、固液分离、除色、嗅、昧、消毒等多个过程。 As a strong oxidant, Ozone which was widely used in wastewater treatment played an important role in dis-infection and coagulation aid to promote the flotation separation effect in the flotation process. Flotation can signifi-cantly reduce the suspended solids in water, and COD can be removed in a certain degree. The ozone followed a flota-tion process is a combination of the two advantages. The combination of ozone oxidation and flotation separation tech-niques can use ozone as gas source, and remove suspended particles while decomposition of large amounts of organic disinfection. As a result, it can get emulsion breaking and flocculation, solid-liquid separation, decolorization, deodorant, disinfection and other process in one operating unit.

Atomization of petroleum-coke sludge slurry using effervescent atomizer

Experimental investigations were carried out on a bench-scale atomization test facility to explore the atomization performance of petroleum coke sludge slurry (PCSS) which comprises pulverized petroleum coke, sewage sludge, water and a certain amount of chemical additives. In the experiments, effervescent atomizer was employed to spray the petroleum coke sludge slurry. And effects of air injection pressure, air-to-liquid mass flow rate ratio (ALR), exit orifice diameter and rheological properties of petroleum coke sludge slurry with different amount of sewage sludge on the Sauter Mean Diameter (SMD or D32) of the atomized droplets were investigated. Results suggest that petroleum coke particles have strong hydrophobic surface. Solid–liquid separation occurs between petroleum coke particles and water film during atomization. Sewage sludge is viscoelastic non-Newtonian fluids, which would influence the solid–liquid separation process when pulverized petroleum coke and sewage sludge are blended to prepare petroleum coke sludge slurry for atomization. SMD of atomized petroleum coke sludge slurry droplets decreases with ALR increase. However, SMD increases with spray axial distance downstream from the nozzle tip primarily and then decreases. Reduction of exit orifice diameter and increase of air injection pressure could improve the atomization performance, while sewage sludge would weaken the influence on variation of the atomized droplets diameters with increase of the spray axial distance and ALR.

Analysis of the Use of a Filtering Medium in Different Parts of a Centrifugal Separator

Hydrocyclones are devices used in solid-liquid, liquid-liquid, and solid-liquid gas separation process applied in several industry fields such as mining, food and petrochemical. With the rising need of diminishing energy consumption and enhancing process efficiency, modifications on these equipments have been proposed in order to elevate their performance. It can be found in literature optimized geometric relations for a hydrocyclone (designated CH11), aiming to conjugate low energy consumption and small cut size diameters. Hence, the purpose of this paper is to study the influence of filtration on CH depending on where the filtering wall is settled (cylindrical or conical part). The main experimental results suggest that the placement of the permeable region (conical or cylindrical parts) influenced the performance of the equipment regarding the main variables. In conclusion, setting a filtering wall brought expressive changes for the separation process.