Effects of water conductivity on microbubble size and distribution for seawater flotation in desalination pretreatment processes (original) (raw)
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SPE Production & Operations, 2020
SummaryFlotation is an important segment of water treatment. Bubbles are generated and dispersed in water where they capture oil and solids residuals and lift them up to the surface. Bubbles are generated either mechanically by agitation or hydraulically by induced gas ejectors. The bubble size has a crucial role in this kind of separation. In general, the smaller the bubbles, the better separation. Water chemistry has an important role in bubble formation and size. A laboratory scale flotation unit was developed to generate the microbubbles with diameters of 10 to 100 µm. The effects of salinity, coagulant, temperature, and ethanol on bubble size were investigated. The addition of 5000 mg/L of sodium chloride (NaCl) affected mainly bubble size with 50 µm diameter, whereas bubble size reduced and diameter decreased by one-half with the addition of NaCl. The bigger bubbles (100 µm size) were affected only at a salinity of 40 000 mg/L, whereas the smaller bubbles (20 to 30 µm) remaine...
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2020
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Raw water clarification by flotation with micro and nanobubbles generated with a multiphase pump
Water Science and Technology, 2017
Raw water clarification by flotation was studied by injecting air into a centrifugal multiphase pump to generate microbubbles (MBs) and nanobubbles (NBs). Measurements of gas dispersion parameters were performed and optimal conditions were obtained using a pump pressure of 4 bar. Values showed a bubble Sauter diameter of 75 μm, an air holdup of 1.2%, a bubble surface area flux of 34 s−1 and an NB concentration of 1 × 108 NBs mL−1 (measuring 220 nm). Then, a study compared flotation with bubbles formed with the multiphase pump (F-MP) to lamellar settling at the clarification stage of a water treatment plant (WTP), in Brazil. The F-MP showed a higher separation efficiency at high hydraulic loads (9–15 m h−1), even without the use of a polymer, reaching 2 NTU (10–25 NTU raw water feed), which was much lower than the technical goal of the WTP (5 NTU). The results and the technical aspects are discussed, and it is concluded that the employment of MBs and NBs with pumps widens new researc...
Heliyon, 2020
Microbubble technology dramatically raises the efficiency of the flotation and aeration processes of water treatment plants (WTPs), which see extensive use in developed countries. A local institution, Indonesia Water Institute, has tried to investigate microbubble technology intended for lab-scale WTP. However, the current reactor system does not yet meet the microbubble criteria, especially as it has had few investigations of its abilities in flotation and aeration. This study aims to analyze the effect of size variations that affect the rising velocity and mass transfer coefficient (kLa) of aeration contact time. Three local spargers were used to produce microbubbles. Bubble diameters were measured optically and analyzed using ImageJ software. The dissolved oxygen (DO) concentration was measured every minute using an automated sensor so that the kLa could be determined. Of the three spargers, the smallest bubble size was produced by the vortex type with an average bubble diameter of 89 μm and the slowest rising velocity of 17.67 m/h. It also yielded the highest kLa of 0.297/min, which gave an aeration contact time of 3.64 minutes. The experimental uses of three local spargers revealed that the smaller the microbubble diameter, the higher the mass transfer coefficient in flotation and aeration processes. This research can be the basis for developing microbubble technology for WTP in Indonesia.
TecnoLógicas
The current issues of climate change and high freshwater demand worldwide have promoted the implementation of wastewater reclamation technologies. This study aims to review the efficiency of the dissolved air flotation (DAF) technique in a wide variety of applications in the agricultural, industrial, domestic, and municipal sectors, which have high freshwater consumption worldwide. We made a systematic review of the DAF technique in wastewater treatment in 2015-2021. We reviewed six indexed databases and governmental statistical reports; we used the keywords: dissolved air flotation, microbubbles, wastewater treatment, and the main operating and design parameters involved in the effectiveness of the flotation process. Additionally, we conducted a review of the most common synthetic coagulant studies used with DAF, as well as natural coagulants that promise to mitigate current climate change. Finally, we discussed advantages, disadvantages, and potential future studies. DAF to have c...
Treating of Waste Water Applying Bubble Flotation
Water Treatment, 2013
Water Treatment 168 from polluted bionetwork. Therefore, advances in possible water treating improvements are issued in this chapter. 2. Treating of waste water applying bubble flotation From the time when natural resources started to exploit in a massive way, water is used as a vehicle to transport and process materials. Water is the most important solvent in nature, and the contact of water with a variety of substances makes it the origin of water pollution through the formation of dissolved solutes solutions which decrease the quality of the liquid. Water is often encountered with high concentration of pollutants that could be in solution or dispersed as insoluble phases frequently forming emulsions and colloids. Among pollutants encountered in fresh water are heavy metals and organics. These materials regularly are difficult to process because to the enormous amounts of water that is produced by urban and industrial activities; therefore, the ideal process to clean polluted water should be operating in a continuous way to minimise fixed and operating costs. 2.1. Lead carbonate colloid in residual water: continuous ion flotation The ion flotation term was first introduced by Sebba [1], defined it as a technique used to collect a material which is in solution in an aqueous phase, and it may be even in a colloid structure. By adding modifiers of the chemical conditions of the aqueous media, and with the addition of a collector reagent, adequately electrically charged, the dissolved substance, or the colloid, is transformed in a product with hydrophobic sites which promotes its adsorption on the liquid/vapour "surface" of a gas bubble and, therefore, to float in the aqueous media up to its surface producing a foam that contains a concentrate of the original substance which can be collected. By looking into the previous statement, it can be thought that there is a concentration relationship between the amount of dissolved substance and the required amount of collector reagent to create hydrophobic sites. Therefore, ion flotation technique is restricted to treat dilute aqueous solutions of such ion or colloid material, otherwise, the required amount of collector reagent may exceed the micelle critic concentration and the desired process would not be attained.
Dispersed air flotation as a pretreatment process for seawater desalination
Water Science & Technology: Water Supply, 2012
Pretreatment of seawater before reverse osmosis (RO) processes with dispersed air flotation involves a change in oxygen concentration in seawater. In order to understand this phenomenon, a series of experimental aeration studies was conducted. Aeration tests were performed under different operating conditions of seawater temperature, flow rate of the air and depth of the water in the aeration tank. The experimental results show that the overall mass transfer coefficient increases by increasing air flow rate. A measured increase in the overall mass transfer coefficient was observed with elevation of the temperature from 24 to 38 °C. The estimated value of activation energy of oxygen absorption in seawater is 42.5 kJ/mol. The value of the overall mass transfer coefficient is found to be affected by diffuser type and stirrer speed as these parameters influence the bubble size and the surface area available for mass transfer of oxygen from air bubbles to seawater.
DESALINATION AND WATER TREATMENT, 2019
The amount of the precipitated air inside a flotation tank has a significant effect on the removal efficiency of a dissolved air flotation (DAF) system. For the first time, this study examined the effect of salinity (35 g L-1) and temperature variations (10°C-40°C) on air solubility in an unpacked air saturator of a real-scale DAF system for different range of pressures (300-600 kPa) and recycle ratios (10%-40%). The amount of dissolved air inside the air saturator was measured using the liquid displacement method. The results indicated that, under equilibrium conditions, salinity and temperature are inversely proportional to air solubility. However, under non-equilibrium status, with increases in temperature, the amount of dissolved air declines to its minimum value at 20°C and then increased again. The observed behaviour was attributed to the effect of temperature on volumetric gas/liquid mass transfer (K L a). The effects of recycle ratio and pressure was also investigated for non-equilibrium conditions and it was observed that the temperatures was below 20°C, an increase in recycle ratio and saturator pressure can compensate the lack of air caused by salinity and increase of temperature. However, for temperatures above 20°C, it is not necessary to increase the recycle ratio and saturator pressure as the rise of temperature by itself increases air concentration. Finally, the size distribution of microbubbles was also investigated and it was found that temperature does not affect the average size of microbubbles noticeably whereas salinity prevents coalescence and contributes to smaller size bubbles.
Micro-Bubble-Flotation-Technology-in-Secondary-Tertiary-Produced-Water-Treatment-English-A4
Over the years a variety of oil/water separation methods have been developed throughout the world, including gravity separation, corrugated plate interceptors, centrifugal separation, hydrocyclones, and induced gas flotation. With increasingly tight legislative limits on OIW (Oil in Water) discharges, it is important that operators have an effective produced water treatment system which enables compliance with regulatory overboard discharge limits, meets specifications for re-injection, steam generation, irrigation and any other downstream process.
Recent Advances and Applications of Dissolved Air Flotation for Industrial Pretreatment
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