Prediction and Measurement of Bubble Formation in Water Treatment

Scardina, Paolo; Edwards, Marc

doi:10.1061/(asce)0733-9372(2001)127:11(968)

Cited by 19 publications

(13 citation statements)

References 11 publications

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“…The waters were then rapid‐mixed at 300, 1,000, or 16,000 s −1 , and turbidity was measured following settling. Plotting Amirtharajah and Mills's (1982) settled turbidity (after 90 min of settling) versus the bubble formation potential calculated using the model outlined by Scardina and Edwards (2001) for water initially at equilibrium with the atmosphere shows that trends in the Amirtharajah and Mills work are consistent with the observations of this study (Figure 7). In other words, settled turbidity increased when the potential for bubble formation was higher.…”

Section: Resultssupporting

confidence: 82%

“…Because water treatment plants typically operate as closed systems (Letterman & Shankar, 1996), dissolved gases may preferentially form as bubbles, rather than transferring at the interface, to alleviate dissolved gas supersaturation. Heterogeneous nucleation is the mechanism by which bubbles are expected to form at water treatment plants; that is, dissolved gases diffuse into air cavities (nucleation sites) located on imperfections of solid surfaces (Scardina & Edwards, 2001). As supersaturated dissolved gas diffuses into the nucleation site, gases collect in an air cavity and eventually create a bubble that can detach.…”

Section: Bubble Formation and Dissolved Gas Supersaturationmentioning

confidence: 99%

“…An alternative form of determining bubble formation potential is the bubble apparatus described by Scardina and Edwards (2001). This method is less expensive to build and may give a better indication of actual bubble formation in the water treatment plant.…”

Section: Measuring Dissolved Gas Supersaturationmentioning

confidence: 99%

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Practical implications of bubble formation IN CONVENTIONAL TREATMENT

Scardina¹,

Edwards²

2002

Journal AWWA

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Air entrainment and ozonation are the key causes of dissolved gas supersaturation and eventual bubble formation in water treatment plants. Total dissolved gas probes directly measure supersaturation and have many advantages over conventional gas measurement techniques. Experiments conducted during this study found that bubble formation during coagulation/flocculation hindered particle sedimentation—producing settled turbidity levels double those of solutions without dissolved gases. In a filtration experiment, the run time to one half of initial flow was decreased by 54% when the source water was increased from 0.1 to 0.2 atm supersaturation. Even at only 0.05 atm supersaturation, run length decreased to only 21 h in solutions without added particulate matter. A case study at a utility confirmed that bubble formation from supersaturated gases can interfere with coagulation and filtration processes at conventional water treatment plants.

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Section: Resultssupporting

confidence: 82%

Section: Bubble Formation and Dissolved Gas Supersaturationmentioning

confidence: 99%

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Practical implications of bubble formation IN CONVENTIONAL TREATMENT

Scardina¹,

Edwards²

2002

Journal AWWA

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“…On the one hand, both the direct impact and the lateral outflow of the micro-jets on the coating surface are influenced by the initial surface roughness. In this manner, the surface of the coating after 80 grit grinding contains more pre-existing defects, as shown in Figure 4a, where nucleation, growth and collapsing of bubbles are more likely to occur [32]. In addition, the rougher surface with more pre-existing defects will entrap the lateral outflow of the water impacts and, in turn, the more cavitation erosion damage of the coating.…”

Section: Cavitation Erosion Behavior Of the Coatingsmentioning

confidence: 89%

Effect of Initial Surface Roughness on Cavitation Erosion Resistance of Arc-Sprayed Fe-Based Amorphous/Nanocrystalline Coatings

et al. 2017

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Abstract:The arc spraying process was used to prepare Fe-based amorphous/nanocrystalline coating. The cavitation erosion behaviors of FeNiCrBSiNbW coatings with different surface roughness levels were investigated in distilled water. The results showed that FeNiCrBSiNbW coating adhered well to the substrate, and was compact with porosity of less than 2%. With increasing initial surface roughness, the coatings showed an increase in mass loss of cavitation erosion damage. The amount of pre-existing defects on the initial surface of the coatings was found to be a significant factor for the difference in the cavitation erosion behavior. The cavitation erosion damage for the coatings was a brittle erosion mode. The evolution of the cavitation erosion mechanism of the coatings with the increase of the initial surface roughness was micro-cracks, pits, detachment of fragments, craters, cracks, pullout of the un-melted particle, and massive exfoliations.

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“…Large phytoplankton blooms can occur, and the waterbodies are subject to an extreme climate with hot summers and ice-covered winters. DO is additionally important in drinking water reservoirs as dissolved gas supersaturation can be an issue in water treatment [7]. Low oxygen can also induce release of nutrients, and sulphide production.…”

Section: Introductionmentioning

confidence: 99%

Modelling Dissolved Oxygen/Sediment Oxygen Demand under Ice in a Shallow Eutrophic Prairie Reservoir

Terry

Sadeghian

Lindenschmidt

2017

Water

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Dissolved oxygen is an influential factor of aquatic ecosystem health. Future predictions of oxygen deficits are paramount for maintaining water quality. Oxygen demands depend greatly on a waterbody's attributes. A large sediment-water interface relative to volume means sediment oxygen demand has greater influence in shallow systems. In shallow, ice-covered waterbodies the potential for winter anoxia is high. Water quality models offer two options for modelling sediment oxygen demand: a zero-order constant rate, or a sediment diagenesis model. The constant rate is unrepresentative of a real system, yet a diagenesis model is difficult to parameterise and calibrate without data. We use the water quality model CE-QUAL-W2 to increase the complexity of a zero-order sediment compartment with limited data. We model summer and winter conditions individually to capture decay rates under-ice. Using a semi-automated calibration method, we find an annual pattern in sediment oxygen demand that follows the trend of chlorophyll-a concentrations in a shallow, eutrophic Prairie reservoir. We use chlorophyll-a as a proxy for estimation of summer oxygen demand and winter decay. We show that winter sediment oxygen demand is dependent on the previous summer's maximum chlorophyll-a concentrations.

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Prediction and Measurement of Bubble Formation in Water Treatment

Cited by 19 publications

References 11 publications

Practical implications of bubble formation IN CONVENTIONAL TREATMENT

Practical implications of bubble formation IN CONVENTIONAL TREATMENT

Effect of Initial Surface Roughness on Cavitation Erosion Resistance of Arc-Sprayed Fe-Based Amorphous/Nanocrystalline Coatings

Modelling Dissolved Oxygen/Sediment Oxygen Demand under Ice in a Shallow Eutrophic Prairie Reservoir

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