Overview of flotation as a wastewater treatment technique

Rubio, J.; Souza, Maysa Lucena de; Smith, Ross

doi:10.1016/s0892-6875(01)00216-3

Cited by 765 publications

(350 citation statements)

References 42 publications

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“…The asymmetry can be made so great that the air appears to tear. This symmetry breaking may be important in numerous applications [15,16,17], and for understanding other physical processes which are modeled as the formation of a singularity, such as star or black hole formation [18] and supernova explosions [19]. Thus our experimental observation of the breakdown of cylindrical symmetry in the air bubble demonstrates a new view of dynamical singularities that may be relevant even on a celestial scale.…”

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confidence: 74%

Breakup of Air Bubbles in Water: Memory and Breakdown of Cylindrical Symmetry

et al. 2006

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Using high-speed video, we have studied air bubbles detaching from an underwater nozzle. As a bubble distorts, it forms a thin neck which develops a singular shape as it pinches off. As in other singularities, the minimum neck radius scales with the time until breakup. However, because the air-water interfacial tension does not drive breakup, even small initial cylindrical asymmetries are preserved throughout the collapse. This novel, non-universal singularity retains a memory of the nozzle shape, size and tilt angle. In the last stages, the air appears to tear instead of pinch.PACS numbers: 47.55.db, 47.55.df, 02.40.Xx The delightful tingling felt when drinking carbonated beverages, the glee of children blowing bubbles in a bathtub, and the importance of deep underwater fissures venting gasses into the oceans hint at the richness and significance of bubble formation in determining the texture and composition of our world. However, the process by which a bubble is formed is still full of surprises. A drop or bubble breaks up by forming a neck that thins to atomic dimensions, a process described as an approach towards a singularity where physical quantities such as stress or pressure grow infinitely large. Singularities often organize the overall dynamical evolution of nonlinear systems. Each symmetry in nature implies an underlying conservation law, so that the symmetries of the singularity associated with pinch-off naturally have important consequences for its dynamics. It was previously believed [1,2,3,4,5,6,7,8,9,10,11,12] that the pinching neck of any drop or bubble would become cylindrically (i.e. azimuthally) symmetric in the course of pinch-off. Recently, pinching necks of air in water were observed to lose cylindrical symmetry in the course of detachment [13,14].Here we show that this loss of symmetry is caused by a new form of memory in singular dynamics: even a small asymmetry in the initial conditions is preserved throughout bubble detachment. This novel singularity retains a memory of the nozzle shape, size and tilt angle. The asymmetry can be made so great that the air appears to tear. This symmetry breaking may be important in numerous applications [15,16,17], and for understanding other physical processes which are modeled as the formation of a singularity, such as star or black hole formation [18] and supernova explosions [19]. Thus our experimental observation of the breakdown of cylindrical symmetry in the air bubble demonstrates a new view of dynamical singularities that may be relevant even on a celestial scale.Singularities govern the dynamics in many familiar break-up events, such as the dispersal of oil drops into * Electronic address: nkeim@uchicago.edu vinegar during the making of a salad dressing, or the dripping of water from a leaky faucet. For many fluid pairs -for example, one viscous fluid breaking in a surrounding fluid of high viscosity [7,8,12] -the shape and dynamics of the pinching neck depend solely on the fluid parameters, as the breakup forgets its initial conditions on ...

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confidence: 74%

Breakup of Air Bubbles in Water: Memory and Breakdown of Cylindrical Symmetry

et al. 2006

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“…Meanwhile, the use of a centrifuge to enhance the oil and sludge separation is likely to increase the oil dispersion into smaller droplets (Floury et al 2000). In wastewater treatment, oil droplets less than 50 μm have been removed by packed bed filters and dissolved air flotation (DAF) (Rubio et al 2002); however, this method is not applicable for removing oils from OPDC. A decanter is used to treat the underflow of the clarification tank in order to reduce the use of dilution water as well as minimize oil loss in the OPDC.…”

Section: Fourier Transform Infrared Spectroscopy (Ftir) and Thermogramentioning

confidence: 99%

Physicochemical Characterization of Oil Palm Decanter Cake (OPDC) for Residual Oil Recovery

Sahad¹,

Som²,

Baharuddin³

et al. 2014

BioResources

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A characterization study on oil palm decanter cakes (OPDC) was performed to gain an in-depth understanding of the material's characteristics to aid in potential residual oil recovery. The OPDC was characterized by a high moisture content, high biodegradability, high organic content, and a nutrient-rich composition. Microscopic observation showed that the oil attachments in OPDC, and a vast majority of the droplets, were less than 50 μm in size. Furthermore, contact angle measurement revealed the hydrophilic and oleophilic characteristics of OPDC. Specifically, the contact angles of water and crude palm oil (CPO) with OPDC were both less than 45° with absorption rates of 0.0265  0.003 µL/s and 0.1042  0.05 µL/s, respectively. The OPDC is a fibrous material, and the surface area and pore size measured were 7.103 m 2 /g and 481.7 Å, respectively. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis results showed the functional groups and degradation properties of OPDC, respectively.

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“…Even though the average bubble production increased with the increase in pressure, the deviation between values of 552-621 kPa showed no significant difference (P > 0.05). Without surfactants, the minimum saturation pressure required for dissolution to occur was found to be 304 kPa which explained the lack of significant bubble production at pressures below 350 kPa [15].…”

Section: Pressurementioning

confidence: 98%

Optimizing the Air Dissolution Parameters in an Unpacked Dissolved Air Flotation System

Dassey

Theegala

2011

Water

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Due to the various parameters that influence air solubility and microbubble production in dissolved air flotation (DAF), a multitude of values that cover a large range for these parameters are suggested for field systems. An unpacked saturator and an air quantification unit were designed to specify the effects of power, pressure, temperature, hydraulic retention time, and air flow on the DAF performance. It was determined that a pressure of 621 kPa, hydraulic retention time of 18.2 min, and air flow of 8.5 L/h would be the best controlled parameters for maximum efficiency in this unit. A temperature of 7 °C showed the greatest microbubble production, but temperature control would not be expected in actual application. The maximum microbubble flow from the designed system produced 30 mL of air (±1.5) per L of water under these conditions with immediate startup. The maximum theoretical dissolved air volume of 107 mL (±6) was achieved at a retention time of 2 h and a pressure of 621 kPa. To isolate and have better control over the various DAF operational parameters, the DAF unit was operated without the unsaturated flow stream. This mode of operation led to the formation of large bubbles at peak bubble production rates. In a real-world application, the large bubble formation will be avoided by mixing with raw unsaturated stream and by altering the location of dissolved air output flow.

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Overview of flotation as a wastewater treatment technique

Cited by 765 publications

References 42 publications

Breakup of Air Bubbles in Water: Memory and Breakdown of Cylindrical Symmetry

Breakup of Air Bubbles in Water: Memory and Breakdown of Cylindrical Symmetry

Physicochemical Characterization of Oil Palm Decanter Cake (OPDC) for Residual Oil Recovery

Optimizing the Air Dissolution Parameters in an Unpacked Dissolved Air Flotation System

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