Developing efficient methods of mixing during chemical treatment of wastewater suspension

2021 ◽  
pp. 48-54
Author(s):  
А.Н. Григорьева ◽  
Р.Ш. Абиев ◽  
Ф.И. Лобанов ◽  
О.Ю. Тарарыков
Keyword(s):  
Angular Velocity ◽  
Chemical Treatment ◽  
Rotation Speed ◽  
Solid Phase ◽  
Particle Diameter ◽  
Wastewater Sludge ◽  
Similarity Criteria ◽  
Sludge Disposal ◽  
Work Done ◽  
Municipal Economy

Проблема утилизации осадка сточных вод в последние годы становится все более актуальной для коммунального хозяйства. Приведены результаты исследования процесса суспендирования осадка известьсодержащим реагентом Дезолак, определены размеры твердых включений, что позволило рассчитать необходимую скорость вращения перемешивающего устройства: средний заутеровский диаметр частиц составил 55 мкм, плотность твердой фазы – 2211 кг/м3. Для эффективного суспендирования реагента необходимо обеспечить угловую скорость мешалки не менее 0,03 м/с. Исследованы основные критерии подобия для масштабирования аппаратов, определено, что при выборе мешалки следует учитывать критерий Фруда Fr, так как именно этот показатель для трех исследованных реакторов практически постоянен. На основании проделанной работы определено, что отношение мощности к объему перемешиваемой жидкости не может являться критерием для расчета аппаратов, оснащенных перемешивающими устройствами GMS: для данных мешалок справедливо снижение мощности на перемешивание с увеличением размеров аппарата. In recent years the problem of wastewater sludge disposal has become more and more urgent for the municipal economy. The results of a study of the process of sludge suspending with Dezolak, a lime-containing agent, are presented; the size of solid inclusions is determined to provide for calculating the required rotation speed of the mixing device: the average Sauter particle diameter was 55 μm, the density of the solid phase was 2211 kg/m3. For effective chemical suspending the angular velocity of the mixer should be more than 0.03 m/s. The main similarity criteria for scaling the apparatus were investigated; it was determined that while choosing a mixer, the Froude criterion Fr should be taken into account, since that very indicator was practically constant for the three investigated reactors. Based on the work done, it was determined that the ratio of power to the volume of the mixed liquid cannot be a criterion for calculating devices equipped with GMS mixing devices: for these mixers, a decrease in the mixing power with an increase in the size of the device is valid.

Consolidation Features of Aluminum-Alumina Compositions by Powder Metallurgy Methods

2016 ◽  
Vol 254 ◽  
pp. 110-115
Author(s):  
Mihai Ovidiu Cojocaru ◽  
Mihaela Raluca Condruz ◽  
Florică Tudose
Keyword(s):  
Solid Phase ◽  
Particle Diameter ◽  
Aluminum Matrix ◽  
Aluminum Matrix Composites ◽  
Average Particle ◽  
Matrix Composites ◽  
Aluminum Particles ◽  
Transmission Electron ◽  
Tapped Density ◽  
Powder Metallurgy Methods

In this paper was followed the processing flow of aluminum-alumina compositions (10÷20% alumina) in powder state, aiming to obtain aluminum matrix composites reinforced with alumina particles, starting from selecting and mixing the grading fraction of both components reaching up to sintering; it was analyzed the way in which reflects the variation of grading fraction ratio (expressed through average particle diameter in the analyzed fractions limits) on the level of technological interest features: apparent density, tapped density, flowability, presability and on densification after sintering (in various environments). By transmission electron microscopy was observed that aluminum particles showed on the surface a nanoscale oxide film, so the sintering occurs between congeneric areas – by solid phase sintering mechanisms [1, 2, 3]. The analysis of thermophysical properties revealed a decrease of thermal diffusivity at an increase of alumina, simultaneous with the decrease of the densification level.

Experiments on the lift and drag of spheres suspended in a Poiseuille flow

1964 ◽  
Vol 20 (3) ◽  
pp. 513-527 ◽  
Author(s):  
R. Eichhorn ◽  
S. Small
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Rotation Speed ◽  
Fluid Dynamic ◽  
Particle Diameter ◽  
Dynamic Forces ◽  
Shear Parameter ◽  
Fluid Properties ◽  
Approach Velocity ◽  
Lift And Drag

An experimental investigation of the fluid dynamic forces on spheres suspended in a Poiseuille flow was performed. Small spheres of polystyrene, nylon, and Lucite, having diameters ranging from 0.061 in. to 0.126 in. were suspended in Poiseuille flows in a 0.419 in. diameter tube. Variations in particle size and density, the fluid properties, and the angle of inclination of the tube, resulted in a sphere Reynolds number (based on particle diameter and approach velocity) ranging from 80 to 250. The results are presented as curves which include the coefficients of lift and drag, and the dimensionless rotation speed plotted versus Reynolds number and a dimensionless shear parameter.

Wastewater sludge as a resource: sludge disposal strategies and corresponding treatment technologies aimed at sustainable handling of wastewater sludge

2002 ◽  
Vol 46 (10) ◽  
pp. 295-303 ◽  
Author(s):  
H. Ødegaard ◽  
B. Paulsrud ◽  
I. Karlsson
Keyword(s):  
Wastewater Sludge ◽  
Treatment Concept ◽  
Sludge Treatment ◽  
Disinfection Methods ◽  
Sludge Disposal ◽  
Treatment Technologies

The paper discusses different strategies for the disposal of wastewater sludge, particularly the “use on land” strategy and the “productification” strategy. In the “use on land” strategy the new regulations in Europe call for stabilization as well as disinfection of sludge to be used on land. The paper discusses the design and operation experiences with stabilization/disinfection methods in Norway where such treatment has been compulsory since 1995. In the “productification” strategy it is differentiated between the production of “bio-soils” and production of specific products (energy, nutrients, coagulants etc) and the “marketability” of these products is evaluated. An example of a sludge treatment concept aimed at recycling - the KREPRO process - is presented.

Reuse of Municipal Wastewater Sludge for Construction Material

2010 ◽  
Vol 156-157 ◽  
pp. 939-942 ◽  
Author(s):  
Deng Ling Jiang ◽  
Guo Wei Ni ◽  
Guan Yi Ma
Keyword(s):  
Municipal Wastewater ◽  
Raw Materials ◽  
Construction Material ◽  
Construction Materials ◽  
Matter Content ◽  
Wastewater Sludge ◽  
Dry Matter Content ◽  
Sludge Disposal ◽  
Paper Wastewater ◽  
Feasible Alternative

Treatment of municipal wastewater results worldwide in the production of large amounts of sewage sludge. The major part of the dry matter content of this sludge consists of nontoxic organic compounds, in general a combination of primary sludge and secondary (microbiological) sludge. The sludge also contains a substantial amount of inorganic material and a small amount of toxic components. The large volume of wastewater sludge generated requires enormous landfill space for disposal. Diverting the wastewater sludge from landfill would alleviate the shortage of landfill sites. Thus alternative applications have to be considered for the wastewater sludge diverted away from the landfills. The use of wastewater sludge for the production of construction materials is reviewed in this paper. Wastewater sludge can be used as raw materials for making bricks, concrete filler and concrete aggregates. The study reveals that the reuse of wastewater sludge as construction materials offers a technically feasible alternative for sludge disposal.

scholarly journals Pretreatments for enhancing sewage sludge reduction and reuse in lipid production

2020 ◽  
Author(s):  
Jiaxin Chen ◽  
Ji Li ◽  
Xiaolei Zhang ◽  
Zhaoyang Wu
Keyword(s):  
Lipid Content ◽  
Solid Phase ◽  
Lipid Production ◽  
Oxygen Demand ◽  
Rhodotorula Glutinis ◽  
Wastewater Sludge ◽  
Sludge Reduction ◽  
Acid Pretreatment ◽  
Sludge Management ◽  
Biological Sludge

Abstract Background: Converting wastewater sludge to lipid is considered as one of the best strategies of sludge management. The current problem of lipid production from wastewater sludge is the low yield (0.10-0.16 g lipid/g dry sludge) due to the low availability of easily uptaken materials (such as soluble monosaccharide and oligosaccharide) in sludge to oleaginous microorganism (Rhodotorula glutinis, Trichosporon oleaginosus, Lipomyces starkeyi). Pretreatments are efficient methods to improve sludge bioavailability. This study is aimed to achieve high lipid production from sludge and high sludge reduction. Results: In this study, it was observed that the soluble chemical oxygen demand (SCOD) had significantly increased after different pretreatment. The SCOD in the supernatant was increased from 32.64 to 180.25 mg/L, 924.16 mg/L, 1029.89mg/L and 3708.31 mg/L after acidic (pH 2 for 2 h), alkaline (pH 12 for 2 h), microwave irradiation (15 min with 5 min interval), and ultrasonication (30 min at 450 W and 20 kHz frequency with 5 s on and 2 s off mode) pretreatment, respectively. Pretreatments have also increased the release of total nitrogen (TN) and total phosphorus (TP) from solids. The sludge after different pretreatments were used as medium for lipid production, and the highest lipid content (36.67% g/g) was obtained in the fermentation with ultrasonication pretreatment sludge, and the sludge reduction was 63.10%. For other pretreatments, the lipid content and sludge reduction were 18.42% and 32.63% in acid pretreatment case, 21.08% and 36.44% in alkaline pretreatment case, and 26.31% and 43.03% in microwave pretreatment case, respectively.Conclusion: It was found that ultrasonication pretreatment was the most efficient way to increase the sludge biodegradability (SCOD) and to release TN and TP from solid phase to liquid phase. Pretreated sludge for lipid production achieved significant improvement in lipid yield and sludge reduction. Lipids produced from pretreated sludge were transesterified to biodiesel and the analysis showed that the biodiesel had a similar composition as commercial biodiesel. The study reveals that pretreatment on sludge is a promising method for enhancing biological sludge management efficiency.

Management of Wastewater and Faecal Sludge in Southern Africa

2007 ◽  
Vol 2 (4) ◽  
Author(s):  
Heidi G. Snyman
Keyword(s):  
South Africa ◽  
Southern Africa ◽  
Management Practices ◽  
Land Application ◽  
Wastewater Sludge ◽  
Sludge Disposal ◽  
Legislative Framework ◽  
Sanitation Systems ◽  
The Impact ◽  
Faecal Sludge

This paper deals with the trends, legislative framework and current sludge management practices in southern Africa. Recognising that a large percentage of the Southern African population is not serviced with full waterborne systems, a paper on the management of sludge in the region would not be complete without discussing the management of faecal sludge (FS) from on-site sanitation systems as well. The first half of the paper focuses on the management of wastewater sludge from waterborne sewage systems. The research papers from the region focus primarily on the impact of sludge application on land and agricultural use. The wastewater sludge disposal practices and legislative trends in South Africa are discussed in detail including an overview of the technologies that are used to stabilise, dewater and dry the wastewater sludge. The majority of plants in South Africa do not treat the sludge further than the traditional anaerobic digestion and activated sludge extended aeration. Final disposal methods are still dominated by on-site disposal methods including direct land application (dedicated land disposal) and stockpiling of the sludge on site. The second half of the paper focuses on the management of FS from on site sanitation systems. The FS, which is often contaminated with domestic waste, originating from these on-site sanitation systems requires responsible handling and disposal. The problems and challenges in FS management are highlighted as well as the recommended legislative trends.

Radar Icing Algorithm: Algorithm Description and Comparison with Aircraft Observations

2021 ◽  
Author(s):  
David J. Serke ◽  
Scott M. Ellis ◽  
Sarah A. Tessendorf ◽  
David E. Albo ◽  
John C. Hubbert ◽  
...  
Keyword(s):  
Solid Phase ◽  
Weather Prediction ◽  
Relative Size ◽  
Particle Diameter ◽  
Area Under The Curve ◽  
Mixed Phase ◽  
Small Drop ◽  
Large Drop ◽  
Statistical Measures ◽  
Research Aircraft

AbstractDetection of in-flight icing hazard is a priority of the aviation safety community. The ‘Radar Icing Algorithm’ (RadIA) has been developed to indicate the presence, phase, and relative size of supercooled drops. This paper provides an evaluation of RadIA via comparison to in-situ microphysical measurements collected with a research aircraft during the 2017 'Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment' (SNOWIE) field campaign.RadIA uses Level 2 dual-polarization radar moments from operational National Weather Service WSR-88D radar and a numerical weather prediction model temperature profile as inputs. Moment membership functions are defined based on the results of previous studies, and fuzzy logic is used to combine the output of these functions to create a 0 to 1 interest for detecting small-drop, large-drop and mixed phase icing.Data from the 2D-S particle probe on board the University of Wyoming King Air aircraft were categorized as either liquid or solid phase water with a shape classification algorithm and binned by size. RadIA interest values from 17 cases were matched to statistical measures of the solid/liquid particle size distributions (such as maximum particle diameter) and values of LWC from research aircraft flights. Receiver Operating Characteristic Area Under the Curve (AUC) values for RadIA algorithms were 0.75 for large-drop, 0.73 for small-drop, and 0.83 for mixed-phase cases. RadIA is proven to be a valuable new capability for detecting the presence of in-flight icing hazards from ground-based precipitation radar.

Numerical Study of Conduction and Convection Between Immersed Object and Gas Fluidized Bed

Volume 1 ◽  
2004 ◽  
Author(s):  
W. M. Gao ◽  
L. X. Kong ◽  
P. D. Hodgson ◽  
B. Wang
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Solid Phase ◽  
Numerical Study ◽  
Particle Diameter ◽  
Conductive Heat ◽  
Gas Temperature ◽  
Transfer Coefficients ◽  
Immersed Surfaces ◽  
Particle Layer

To analyze the heat transfer mechanism between fluidised beds and surfaces of an immersed object, the heat transfer and gas flow was numerically simulated for different particle systems based on a double particle-layer and porous medium model. It is fund that the conductive heat transfer occurs in the stifling regions between particle and the immersed surface, which have different temperature. The diameter of the circular conduction region, dc, is a function of particle diameter, dp, and can be given by dc/dp = 0.245dp−0.3. In other areas, the heat transfer between the dense gas-solid phase and the immersed object surface is dominated by convection from the moving gas in the tunnel formed by the first-layer particles and the immersed surfaces. The average dimensionless gas velocity, εmfU/Umf, in the tunnel is a constant of about 4.6. The virtual gas temperature at the free stream conditions can be given by the surface temperature of the first-layer particles. The heat transfer coefficient on the conductive region is about 6∼10 times of that on the convection region. The Nusselt numbers for calculating the instantaneous conductive and convective heat-transfer coefficients were theoretically analysed respectively.

scholarly journals Reduced particle settling speed in turbulence

2016 ◽  
Vol 808 ◽  
pp. 153-167 ◽  
Author(s):  
Walter Fornari ◽  
Francesco Picano ◽  
Gaetano Sardina ◽  
Luca Brandt
Keyword(s):  
Solid Phase ◽  
Density Ratio ◽  
Mean Square Displacement ◽  
Particle Diameter ◽  
Finite Size ◽  
Mean Square ◽  
Rigid Spheres ◽  
The Mean ◽  
Settling Speed ◽  
Quiescent Fluid

We study the settling of finite-size rigid spheres in sustained homogeneous isotropic turbulence (HIT) by direct numerical simulations using an immersed boundary method to account for the dispersed solid phase. We study semi-dilute suspensions at different Galileo numbers, $Ga$. The Galileo number is the ratio between buoyancy and viscous forces, and is here varied via the solid-to-fluid density ratio $\unicode[STIX]{x1D70C}_{p}/\unicode[STIX]{x1D70C}_{f}$. The focus is on particles that are slightly heavier than the fluid. We find that in HIT, the mean settling speed is less than that in quiescent fluid; in particular, it reduces by 6 %–60 % with respect to the terminal velocity of an isolated sphere in quiescent fluid as the ratio between the latter and the turbulent velocity fluctuations $u^{\prime }$ is decreased. Analysing the fluid–particle relative motion, we find that the mean settling speed is progressively reduced while reducing $\unicode[STIX]{x1D70C}_{p}/\unicode[STIX]{x1D70C}_{f}$ due to the increase of the vertical drag induced by the particle cross-flow velocity. Unsteady effects contribute to the mean overall drag by about 6 %–10 %. The probability density functions of particle velocities and accelerations reveal that these are closely related to the features of the turbulent flow. The particle mean-square displacement in the settling direction is found to be similar for all $Ga$ if time is scaled by $(2a)/u^{\prime }$ (where $2a$ is the particle diameter and $u^{\prime }$ is the turbulence velocity root mean square).

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