Dissolved air flotation of polishing wastewater from semiconductor manufacturer

2006 ◽  
Vol 53 (7) ◽  
pp. 133-140 ◽  
Author(s):  
J.C. Liu ◽  
C.Y. Lien
Keyword(s):  
Removal Efficiency ◽  
Suspended Particle ◽  
Saturation Pressure ◽  
Silica Particles ◽  
Ammonium Bromide ◽  
Dissolved Air Flotation ◽  
Recycle Ratio ◽  
Semiconductor Manufacturer ◽  
Air Flotation ◽  
Dissolved Air

The feasibility of the dissolved air flotation (DAF) process in treating chemical mechanical polishing (CMP) wastewater was evaluated in this study. Wastewater from a local semiconductor manufacturer was sampled and characterised. Nano-sized silica (77.6 nm) with turbidity of 130±3 NTU was found in the slightly alkaline wastewater with traces of other pollutants. Experimental results indicated removal efficiency of particles, measured as suspended particle or turbidity, increased with increasing concentration of cationic collector cetyltrimethyl ammonium bromide (CTAB). When CTAB concentration was 30 mg/L, pH of 6.5±0.1 and recycle ratio of 30%, very effective removal of particles (> 98%) was observed in saturation pressure range of 4 to 6 kg/cm2, and the reaction proceeded faster under higher pressure. Similarly, the reaction was faster under the higher recycle ratio, while final removal efficiency improved slightly as the recycle ratio increased from 20 to 40%. An insignificant effect of pH on treatment efficiency was found as pH varied from 4.5 to 8.5. The presence of activator, Al3 +  and Fe3 + , enhanced the system performance. It is proposed that CTAB adsorbs on silica particles in polishing wastewater through electrostatic interaction and makes particles more hydrophobic. The increase in hydrophobicity results in more effective bubble-particle collisions. In addition, flocculation of silica particles through bridging effect of collector was found; it is believed that flocculation of particles also contributed to flotation. Better attachment between gas bubble and solid, higher buoyancy and higher air to solid ratio all lead to effective flotation.

Effects of floc and bubble size on the efficiency of the dissolved air flotation (DAF) process

2007 ◽  
Vol 56 (10) ◽  
pp. 109-115 ◽  
Author(s):  
Mooyoung Han ◽  
Tschung-il Kim ◽  
Jinho Kim
Keyword(s):  
Bubble Size ◽  
Saturation Pressure ◽  
Collision Efficiency ◽  
Water And Wastewater Treatment ◽  
Dissolved Air Flotation ◽  
Floc Size ◽  
Recycle Ratio ◽  
Air Flotation ◽  
The 1960S ◽  
Dissolved Air

Dissolved air flotation (DAF) is a method for removing particles from water using micro bubbles instead of settlement. The process has proved to be successful and, since the 1960s, accepted as an alternative to the conventional sedimentation process for water and wastewater treatment. However, limited research into the process, especially the fundamental characteristics of bubbles and particles, has been carried out. The single collector collision model is not capable of determining the effects of particular characteristics, such as the size and surface charge of bubbles and particles. Han has published a set of modeling results after calculating the collision efficiency between bubbles and particles by trajectory analysis. His major conclusion was that collision efficiency is maximum when the bubbles and particles are nearly the same size but have opposite charge. However, experimental verification of this conclusion has not been carried out yet. This paper describes a new method for measuring the size of particles and bubbles developed using computational image analysis. DAF efficiency is influenced by the effect of the recycle ratio on various average floc sizes. The larger the recycle ratio, the higher the DAF efficiency at the same pressure and particle size. The treatment efficiency is also affected by the saturation pressure, because the bubble size and bubble volume concentration are controlled by the pressure. The highest efficiency is obtained when the floc size is larger than the bubble size. These results, namely that the highest collision efficiency occurs when the particles and bubbles are about the same size, are more in accordance with the trajectory model than with the white water collector model, which implies that the larger the particles, the higher is the collision efficiency.

Effects of Al3 +  and hydraulic characteristics on the removal and behaviour of particles in dissolved air flotation

2006 ◽  
Vol 6 (3) ◽  
pp. 89-95
Author(s):  
Jungsoo Mun ◽  
Sungwon Park ◽  
Mooyoung Han
Keyword(s):  
Turbulent Flow ◽  
Removal Efficiency ◽  
Operating Conditions ◽  
Point Of Zero Charge ◽  
Hydraulic Characteristics ◽  
Dissolved Air Flotation ◽  
Floc Size ◽  
Saturated Water ◽  
Air Flotation ◽  
Dissolved Air

The removal efficiency of the dissolved air flotation (DAF) process to separate particles from water and wastewater depends on the size and zeta potential of bubbles and particles, the solution and operating conditions, hydraulic characteristics, etc. The effects of aluminium ions and turbulent flow-produced when air-saturated water was spouted into the reactor in the DAF process, on removal and, particle behaviour were on investigated. When bubble size was similar to particle size (10–50 μm), the maximum removal efficiency was 92% in a Kaolin solution of 10−3 M Al3 +  without pre-treatment for flocculation process, and, as time passed, the floc size was observed to increase at a pH of 8, which was the condition of high removal efficiency as seen through image analysis. When the air-saturated water was spouted into the reactor, the size of particle at p.z.c. (point of zero charge) seemed to increase to form a floc due to collision effects caused by turbulent flow. Consequently, floc formation by turbulent flow in the reactor seemed to positively affect removal efficiency.

Treatment Spent Filter Backwash Water using Dissolved Air Flotation (DAF) in Isfahan WTP

2008 ◽  
Vol 3 (3) ◽  
Author(s):  
Mohammad Hassan Mahmoodian ◽  
Mohammad Mehdi Amin ◽  
Mohammad Reza Shahmansouri ◽  
Mohammad Ghasemian
Keyword(s):  
Low Dose ◽  
Saturation Pressure ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Recycle Rate ◽  
Polyaluminium Chloride ◽  
Significant Concentration ◽  
Dissolved Air ◽  
Filter Backwash Water

Recovering spent filter backwash water is currently receiving a great deal of attention. EPA published the Filter Backwash-Recycling Rule (FBRR) in 2001. Recycle stream may contain significant concentration of pathogens, such as, cryptosporidium and Giardia. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation technology. In this study with using a pilot of DAF effluent turbidities of >20NTU could be easily obtained, when raw water turbidities were in excess of 800 NTU. Chemical requirements were low with only a single low dose of polyaluminium chloride (PACl) required binding the floc particles to form a solids matrix suitable for flotation. The results showed that the efficiency of continuous flow DAF with using PACl as coagulant for removal of Turbidity, COD, HPC, SS and MPN were 97, 72, 75, 95 and 100 percent, respectively. The statistical analyses indicated that the optimum saturation pressure is 4-5 atm, during recycle rate of 20-25 percent. The removal efficiencies of turbidity and bacteria in coagulation with sedimentation were reported up to 70 and 65 percent, while in this study using DAF with coagulant PACl could remove turbidity, COD, SS and bacterial up to 97,72, 95 and, 72 percent respectively.

scholarly journals KOMBINASI ULTRAFILTRASI DAN DISSOLVED AIR FLOTATION UNTUK PEMEKATAN MIKROALGA

REAKTOR ◽  
2014 ◽  
Vol 15 (1) ◽  
pp. 43
Author(s):  
I Nyoman Widiasa ◽  
A A Susanto ◽  
B Budiyono
Keyword(s):  
Organic Fertilizer ◽  
Saturation Pressure ◽  
Raw Material ◽  
Natural Food ◽  
Omega 3 ◽  
Dissolved Air Flotation ◽  
Microalgae Biomass ◽  
Air Flotation ◽  
Β Carotene ◽  
Dissolved Air

Abstrak Mikroalga merupakan mikroorganisme fotosintetik prokariotik atau eukariotik yang dapat tumbuh dengan cepat. Pemanfaatan mikroalga tidak hanya berorientasi sebagai pakan alami untuk akuakultur, tetapi terus berkembang untuk bahan baku produksi pakan ternak, pigmen warna, bahan farmasi (β-carotene, antibiotik, asam lemak omega-3), bahan kosmetik, pupuk organik, dan biofuel (biodiesel, bioetanol, biogas, dan biohidrogen. Studi ini bertujuan untuk menginvestigasi kombinasi ultrafiltrasi (UF) – dissolved air flotation (DAF) untuk pemekatan mikroalga skala laboratorium. Hasil penelitian menunjukkan bahwa penurunan fluks membran UF secara tajam sebagai akibat dari deposisi sel mikroalga terjadi pada 20 menit pertama proses filtrasi. Backwash pada interval 20 menit selama 10 detik dengan tekanan 1 bar memberikan pengendalian fouling yang efektif dalam nilai kestabilan fluks yang layak. Membran UF yang digunakan dapat memberikan selektivitas pemisahan biomassa mikroalga ~ 100%. Kualitas permeat sangat stabil, yaitu kekeruhan < 0,5 NTU, kandungan organik < 10 mg/L, dan warna < 10 PCU. Lebih lanjut, pemekatan retentat membran dengan DAF pada tekanan saturasi 6 bar dapat menghasilkan pasta mikroalga dengan konsentrasi 20 g/L. Koagulan PAC perlu ditambahkan kedalam umpan DAF dengan dosis 1,3–1,6 mg PAC/mg padatan tersuspensi.   Kata Kunci: ultrafiltrasi; dissolved air flotation; pemanenan mikroalga; pemekatan mikroalga   Abstract COMBINATION OF Ultrafiltration and Dissolved Air Flotation for Microalgae CONCENTRATION. Microalgae is a prokaryotic photosynthetic microorganism or eukaryotic microorganism  that proliferate rapidly. Cultivation of the microalgae is not only oriented  as natural food for aquacultures, but also developed  for animal food, color pigment, pharmaceutical raw material (β-carotene, antibiotic, fatty acid omega-3), cosmetic raw material, organic fertilizer, and biofuels (biodiesel, bioethanol, biogas, and biohydrogen. This study is aimed to investigate the potential of combination of ultrafiltration (UF) and dissolved air flotation  (DAF) for concentration of microalgae in laboratory scale. The experimental results showed that fluxes of the UF membrane decreased sharply due to deposition of microalgae biomass during first 20 minutes of filtration. Periodically backwash using the UF permeate (backwash  interval = 20 minutes;  backwash duration = 10 seconds;  backwash pressure = 1 bar) gave an effective fouling control to maintain reasonable stable fluxes. In addition,  the UF membrane gave separation of microalgae biomass ~ 100%. Permeate quality is strongly stable in which turbidity < 0.5 NTU, organic content < 10 mg/L, and color < 10 PCU.  Moreover, concentration of the UF retentate by DAF under saturation pressure of 6 bars was able to produced microalgae feedstock having 20 g/L dry microalgae. PAC is required for DAF feed with dosage of 1.3–1.6 mg PAC/mg suspended solids.

Dissolved Air Flotation with Spraying of Liquid

2017 ◽  
Vol 6 (2) ◽  
pp. 48-55
Author(s):  
Еськин ◽  
A. Es'kin
Keyword(s):  
Traditional Method ◽  
Saturation Pressure ◽  
Volumetric Method ◽  
Gas Content ◽  
Dissolved Air Flotation ◽  
Wall Area ◽  
Liquid Saturation ◽  
Flotation Cell ◽  
Air Flotation ◽  
Dissolved Air

This paper presents a new method of dissolved air flotation with spraying of liquid. Liquid that needs cleaning is sprayed inside an overhead reservoir through a hydraulic nozzle allowing to enlarge the contact area between phases in comparison with traditional method of saturation by barbotage. Suggested method makes it possible to increase the gas content of the liquid processed for cleaning into a flotation section. This paper also contains the results of experimental investigation of the effectiveness of liquid saturation inside the overhead reservoir using spray-centrifugal and spray-percussive nozzles. Volumetric method was used to measure the amount of air escaping during dissolved air flotation and the results of the measurement were used to calculate the speed of barbotage. It was identified that when the method of spraying of liquid is applied, the amount of soluble air increases on average by 33% in comparison with overhead reservoir of bubbling type. The speed of barbotage increases with growth of saturation pressure and significantly depends on the area of the flotation section. If the saturation pressure exceeds 2 bars, the speed of barbotage in the center of the flotation cell becomes significantly higher than in the wall area.

Flow structures in a dissolved air flotation pilot tank and the influence on the separation of MBBR floc

2002 ◽  
Vol 2 (2) ◽  
pp. 69-76 ◽  
Author(s):  
M. Lundh ◽  
L. Jönsson ◽  
J. Dahlquist
Keyword(s):  
Flow Structure ◽  
Removal Efficiency ◽  
Pilot Plant ◽  
Suspended Solids ◽  
Short Circuit ◽  
Flow Structures ◽  
Dissolved Air Flotation ◽  
Air Content ◽  
Air Flotation ◽  
Dissolved Air

The objective of the study was to find ways of improvement of the dissolved air flotation process by studying the flow structure. The paper presents experimental data on flow structures and the relation between the flow structure and the removal efficiency. Measurements have been performed in a pilot plant with an Acoustical Doppler Velocimeter. The water velocity was measured in a grid net, giving insight into the flow structure. The removal efficiency was analysed at Malmö wastewater treatment plant in Sweden. The pilot plant separated biological floc from a Kaldnes Moving Bio-Bed Reactor (MBBR). The efficiency of the separation was analysed by measurements of suspended solids in the influent and the effluent. Air content was measured inside the tank and in the re-cycle. The result showed that basically two flow structures existed; the stratified and the short-circuit flow structure. The stratified flow structure seemed correlated to efficient separation of particles while the short-circuit flow structure seemed to have a negative effect, especially when the flow structure was affected by varying the re-cycle rate, i.e. the air content. Conclusively, the flow structure seemed to be correlated to type of flow structure. However, studies with higher concentration of suspended solids for verification were suggested.

Oil removal efficiency forecast of a Dissolved Air Flotation (DAF) reduced scale prototype using the dimensionless number of Damköhler

2018 ◽  
Vol 23 ◽  
pp. 45-49 ◽  
Author(s):  
Fernanda Cristina P. Rocha e Silva ◽  
Nathalia Maria P. Rocha e Silva ◽  
Ivison Amaro da Silva ◽  
Pedro P. Ferreira Brasileiro ◽  
Juliana M. Luna ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Dimensionless Number ◽  
Oil Removal ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Reduced Scale ◽  
Dissolved Air

Optimizing dissolved air flotation design and saturation

2001 ◽  
Vol 43 (8) ◽  
pp. 145-157 ◽  
Author(s):  
L. A. Féris ◽  
C. W. Gallina ◽  
R. T. Rodrigues ◽  
J. Rubio
Keyword(s):  
Iron Hydroxide ◽  
Minimum Energy ◽  
Saturation Pressure ◽  
Complete Recovery ◽  
Capture Zone ◽  
Dissolved Air Flotation ◽  
Flotation Cell ◽  
Adhesion Zone ◽  
Air Flotation ◽  
Dissolved Air

Dissolved air flotation (DAF) of iron hydroxide precipitates at working pressures lower than 3 atm, using modified flotation units to improve the collection of fragile coagula, was studied. Conventional DAF flotation was studied as a function of saturation pressure in the absence and presence of surfactants in the saturator. Without surfactants, the minimum saturation pressure required for DAF to occur was found to be 3 atm. But, by lowering the air/water surface tension in the saturator, DAF was possible at a saturation pressure of 2 atm. This behavior was found to occur in both batch and pilot DAF operation tests and almost complete recovery of the precipitates was attained. Results are explained in terms of the minimum “energy” which has to be transferred to the liquid phase to form bubbles by a cavity phenomenon. Further, studies were conducted changing equipment design and feed bubbles size distribution (mixing micro and “mid-sized” bubbles). Thus, bubbles entrance position in the collision-adhesion zone (“capture” zone) was compared to bubble entrance position in the water flow inlet below the floating bed. A “mushroom” type diffuser was used for the “capture zone” experiment and better performance was obtained. Results are explained in terms of different mass transfer phenomena in the collection zone and in the separation zone. Finally, results obtained with the use of a column flotation cell working as normal DAF and with a wide bubble size range are presented. Results indicate good performance and some gains in process kinetics with middle size bubbles.

Algae, Bubbles, Coagulants, and Dissolved Air Flotation

1993 ◽  
Vol 27 (10) ◽  
pp. 67-81 ◽  
Author(s):  
J. K. Edzwald
Keyword(s):  
Conventional Treatment ◽  
Suspended Particle ◽  
Treatment Method ◽  
Air Bubbles ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
The Stability ◽  
Mass Volume ◽  
Bubble Attachment ◽  
Dissolved Air

This paper like Ken Ives' PhD research comments upon algae and their removal from drinking water. Specifically, algal properties, difficulties in removing algae by conventional treatment, and dissolved air flotation (DAF) as a treatment method are emphasized. The stability of algal suspensions may be due to surface charge, hydrophilic effects, or steric effects. Coagulation is required as a pretreatment step in DAF to destabilize algal particles relative to the microbubbles, and thus ensure particle-bubble attachment The air supplied in DAF may be expressed fundamentally as mass, volume, and number concentrations of air bubbles. Calculations show high bubble volume concentrations compared to suspended particle volumes. The effectiveness of flotation is examined in terms of dimensionless products and compared to other particle processes. DAF is compared to settling for algal separation in experiments with DAF operating at higher overflow rates and smaller flocculation times. DAF produced clarified waters with lower turbidities and algal counts.

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