THE INVESTIGATION OF INDUCED GAS 

FLOTATION (IGF) PERFORMANCE AT 

ELEVATED TEMPERATURES AND HIGH 

TOTAL DISSOLVED SOLIDS (TDS) 

PRODUCED WATER 

 

R.Mastouri1*,S.M. Borghei 2, F.Nadim3, E.Roayaei4

1

 Islamic Azad University , Arak Branch, Arak, Iran 

(E-mail: reza.mastoori@gmail.com) 

2

 Dept. of Chemical and Petroleum Engineering, Sharif University of 

Technology, Tehran, Iran 

(E-mail: mborghei@sharif.edu) 

3University of Connecticut, Department of Civil and Environmental 

Engineering, Storrs, 

Connecticut, USA (E-mail: fan02001@engr.uconn.edu) 

4

 Vice President in Project Studies, EOR Research Institude, National 

Iranian Oil Company, Tehran,Iran 

(E-mail :emad.roayaei@gmail.com) 

ABSTRACT 

Produced water is a major source of oily wastewater in oilfield sites. The volume 

and characteristics of this formation water differs in different parts of the world regarding 

the various geological specifications of the earth. However the crude oil desalting process 

and unit operation also impact the quality and quantity of the produced water. In the 

present study, the possibility of application of an innovative rotor/stator mechanical 

induced gas flotation(IGF) system was investigated for a somehow abnormal produced 

water in the Persian Gulf region with the temperature of about 100 oC and total dissolved 

solid content (TDS) of about 300 g/l. The results showed that at the temperature of 100 

oC and TDS of 300g/l, oil removal efficiency was 80% achieved when the impeller speed 

was set at 900rpm. In this case, without adding any chemicals such as flotation aids, the 

outlet oil content from a single flotation cell could not support the regional environmental 

discharge regulation of 15 mg/l and required the addition of at least one more flotation 

cell. 

Key Words: Induced Gas Flotation (IGF); Oily Wastewater; Produced Water; Wastewater 

temperature. 

 
 INTRODUCTION 

Extraction and desalination of oil and gas is usually accompanied by co-produced 

water (referred as produced water), well-water or formation water. The quantity of the 

produced water versus the produced oil or gas usually differs from one site to another site 

as well as its quality. Geological specifications of the reservoirs, the age of extracting 

period and different extraction/desalting processes may cause various oil/gas-water ratio 

values and characteristics. In crude oil wells, the percentage of water increases over time 

and the percentage of product declines. Lee al. (2002) (1) reported that U.S. wells 

produce an average of more than 7 bbl of water for each barrel of oil. For crude oil wells 

nearing the end of their productive lives, water can comprise as much as 98% of the 

material brought to the surface. Wells elsewhere in the world average 3 bbl of water for 

each barrel of oil (2). Coal bed methane (CBM) wells, in contrast, produce a large volume 

of water early in their life, and the water volume declines over time. 

After Saudi Arabia, Iran is OPEC’s second largest oil producer and holds 10 

percent of the world’s proven oil reserves. It has the world’s second largest natural gas 

reserves_ after Russia_ (3). Meanwhile, 90 percent of Iran’s crude oil export is carried 

out via Kharg Island oil terminal located in the Persian Gulf, 25 km off the coast of Iran’s 

mainland. Three oil refineries are located in Kharg Island named Aboozar, Doroud and 

Foroozan which totally produce an average amount of 350,000 BOPD desalinated crude 

oil. As a result, an average volume of about 70,000 BWPD is separated in the 

desalters/separators and drained and discharged to the Persian Gulf after passing a 

skimmer tank and storage pit. The temperature and total dissolved solids (TDS) of this 

stream is about 100oC and 300 g/l respectively. The average oil content of the skimmer 

tank effluent is measured as 150 mg/l. In order to make a correct treatment decision, it 

was investigated whether the mechanical induced gas flotation (IGF) system would be 

able to treat the aforementioned produced water and reduce the oil content up to 15 mg/l 

which is the regulated oil content for the discharge to the Persian Gulf marine 

environment according to the Article VI (Pollution from Land-Based Source) of the 

Kuwait Convention (4). The general characteristics of produced water and its 

accompanying oil at the outlet of skimmer tank are presented in Table 1 and Table 2 

respectively. In this paper, the results of the performance of an innovative IGF pilot plant 

for the treatment of synthetic produced water resembling Kharg Island oil refinery 

produced water which contains an average oil content of 150 mg/l and Total Dissolved 

Solids (TDS) of 200-300 g/l at different temperatures and varying impeller speeds (N) are 

presented. 

Induced Gas Flotation (IGF) 

IGF unit is an accelerated gravitational separation technique in which gas bubbles 

are induced into a water phase stream either by the use of an eductor device or by a 

vortex set up by mechanical rotor (impeller). The liquid phase (oily wastewater) usually 

contains immiscible liquid droplets (oil) or oily solid particles and that the gas bubbles 

attach themselves to the droplets. The oil appears lighter because the density difference 

between the oil agglomerate and water is increased. Consequently, the oil rises faster 
enabling a more rapid and effective separation from the aqueous phase. The oil droplets 

and oil-coated solids rise to the surface where they are trapped in the resulting 

foam/scum, and removed from the flotation chamber when the foam/scum is skimmed off 

(5, 6, 7, 8, 9). The nozzles, rotors, baffles and foam/scum skimmers for these units are 

patented designs (8). 

EXPERIMENTAL 

IGF pilot plant 

Fig. 1, shows a schematic diagram for IGF pilot plant. A transparent Plexiglas 

cylindrical column, 280 mm in height and 260 mm in diameter with the total volume of 

14.8 l was used as the flotation cell. Top of the cell could be fully dismantled from the 

body of the cell, allowing complete cleanup of the cells after each test. Different parts of 

the whole body were designed in such a way that would expand together in thermal 

shocks. The flotation cell was equipped with a variable speed motor (Bosch Drill, GSB 

13, 600Watt, coupled with a dimmer). The motor speed varied from 0 to 2000 rpm. The 

stirrer/rotor speed could be measured by a hand held digital laser tachometer (DT 2236B). 

A stainless steel flat blade rotor (blade diameter / tank diameter =1/3) with a proper 

height was used for agitation. A new stator was used to disperse the stream and gas 

bubbles. The novel combination of this rotor and stator in the flotation cell _so called 

Mastour flotation cell_ performed a very good bubble generation and dispersion in the 

flotation cell. Gorain et al.(1995) (10) applied four different types of impellers _Pipsa, 

Chile-X, Dorr-Oliver and OutoKumpo_ and showed that in spite of small differences in 

trends, the general performance of impellers in flotation process was independent of 

impeller type. Therefore, it is believed that the performance of Mastour flotation cell in 

different testing conditions is not limited to its type. Hydraulic retention time (HRT) for 

the IGF pilot was set at 1min as suggested by Movafaghian et al.(2003) (9), Arnold and 

Stewart (1998) (8) and Sylvester and Byeseda (1980) (11) and it was controlled and 

calibrated by the emulsion preparation tank outlet valve. Although in the oil-water 

separation devices, it is a rule that: “the longer the residence time, the greater the 

separation”(11, 12, 13),but it should be noted that IGF system is dominated for its small 

footprint in oil-fields and specially offshore platforms and if this trait is waned by long 

HRTs for the purpose of higher oil removal efficiency, as it is observed in the study of 

El-Kayar et al.(1993) (14), Fench and Aldrich(2000) (15), Melo et al.(2003) (16) and 

Ramaswamy et al.(2007) (17), Oliveira de Lima et al.(2008) (18), it is only worthful for 

laboratory pilot studies and it is not practical for IGF design in its commercial uses. 

Crude Oil 

Crude oil from Doroud oil field, Kharg Island was used for oil in water emulsion 

preparation. The properties of the crude oil are specified in Table 2. 

Produced water 
Tap water and table salt were used to prepare the saline water resembling the 

produced water. 

Feed Gas 

Pure nitrogen gas (N2) from a N2 capsule equipped with a regulator and flow 

indicator (FI) and pressure indicator (PI) was considered for supplying nitrogen as feed 

gas with the rate of 10 lit/min as suggested by Sylvester and Byeseda (1980) (11). A 

pressure indicator on the top of the cell was installed to control the positive pressure in 

the vapor space in the cell. The feed gas nitrogen capsule is shown in right side of Fig. 1. 

Procedure 

Oil-water emulsion preparation 

A polyethylene (PE) mixing tank with the capacity of 85 liters was used to store 

the O-W emulsion. It was gauged in different levels/capacities for further volumetric 

determinations. A 2000 Watt electric heater was used to heat the water and a temperature 

indicator (TI) instrument ranging from 0-120oC was applied to monitor the temperature. 

One variable speed mixer equipped with a glass stirrer was used to emulsify oil and salt 

in water. When the water in the preparation tank reached the intended temperature, the 

mixer started to work with the speed of 2000 rpm so that the oil droplets would 

completely be dispersed in water (19). Specified amount of the previously weighted salt 

was added to the heated water. After about 5 minutes, crude oil was gradually added to 

the tank and was allowed to mix for 30 minutes so that the oil droplets would completely 

disperse in water. The mixer speed was then reduced to 400 rpm. Although not 

measured but according to similar procedure, the mean diameter of oil droplets in this 

method would be about 20 μm and the maximum diameter of oil droplets would hardly 

exceed 100 μm (19, 20). The outlet valve was opened and the O-W emulsion was 

transferred to the flotation cell with constant flow rate of 14 lit/min. In the oil-fields, 

rarely the produced water is transferred to the IGF system directly and is usually 

pretreated with simple gravity separators such as API or parallel plate separators. The oilwater emulsions leaving these separators normally have oil droplets less than 30 μm in 

diameter and oil concentrations below 200 mg/l (11). Therefore the inlet oil content 

concentration for all the tests were fixed at 150 ± 5 mg/l. For reaching to the constant oil 

in water content of 150 ± 5 mg/l in all the tests, several samples were taken at the inlet of 

flotation cell for calibration. In order to determine the performance of IGF system in oil 

removal, samples were taken at the inlet and outlet of the flotation unit in each running 

process. The oil & grease measurements were made due to the methods presented in 

Standard Methods for the Examination of water and wastewater, 1992. It should be noted 

that the preparation of stable/similar emulsions is a very sensitive step as was experienced 

by the authors and other researchers (21). 

Results and Discussion 
Oil removal efficiency 

The oil removal efficiency (%E) was obtained using Eq. (1):

 (1) 

where Co is the initial concentration of oil present in the produced water and Cf

 is 

its concentration after the flotation process. 

The results of all the oil removal efficiencies and power consumption 

measurements are presented in Figs. 2 to 4. Each figure illustrates at a particular impeller 

speed, constant TDS, constant inlet oil content and feed gas, the oil removal efficiency of 

IGF and both gassed and ungassed conditions power consumption versus the effect of 

temperature variations. 

Effect of temperature on oil removal efficiency 

Figures 2a-2c show that with the test set ups, the IGF oil removal efficiency 

improves with increasing temperature from ambient temperature _ 20 oC_ up to a specific 

temperature and then the oil removal efficiency falls down. At the TDS of 200 g/l and 

temperature of 20-100 oC and the impeller speed of 450-2000 rpm (Fig. 2a), the best 

efficiencies are obtained at 70 oC which are equivalent to 76%, 76.67%, 85.33% and 

83.33% for N= 450, 900, 1450 and 2000 rpm respectively. At the TDS of 200 g/l, after 

the optimum temperature of 70 oC, at tested impeller speeds _N=450 to N=2000 rpm_ 

there is a small decrease in oil removal efficiency when the temperature exceeds 70 oC 

and reaches 100 oC. The maximum oil removal efficiency decrease in this case is 

observed in N=2000 rpm with the amount of 12.79%. At the TDS of 200 g/l, there is an 

exception in IGF performance at temperature of 80 oC at N=900 rpm in which the oil 

removal efficiency is similar to the conditions of T=70 oC and is equal to 76.67%. At 

TDS of 250 g/l, temperature of 20-100 oC,and the impeller speed of 450-2000 rpm, as it 

is depicted in Fig. 2b, the best results are again performed at the temperature of 70 oC in 

which the oil removal efficiencies equal to 78%, 80%, 86.67% and 85.33% for N=450, 

900, 1450 and 2000 rpm respectively. At TDS level of 250 g/l, IGF oil removal 

efficiency is reduced when the temperature increases from 70 oC to 100 oC. The 

maximum reduction in IGF oil removal efficiency in this case equals to 13.46%. At the 

TDS level of 300 g/l (Fig. 2c.), the best IGF performances are obtained at 80 oC which 

are equivalent to 87.33%, 90%, 81.33% and 78.67% for N= 450, 900, 1450 and 2000 rpm 

respectively. For TDS of 300 g/l, after reaching the optimum oil removal efficiency at 

the 80 oC, there is a small decrease when the temperature goes up to 100 oC. The 

maximum decrease in oil removal efficiency in this case is observed at 11.47% when 

N=1450 rpm. The results correspond with observations of Strickland (1980) (5) and 

Arnold and Stewart (2008) (22) which indicated that the operation of IGF systems 

increases when the brine temperature increases up to 60 oC. The temperature directly 

affects the density, viscosity and surface tension of both oil and water. Raising the 

temperature also increases the enhancement of bubble coalescence (23). According to the 

authors review, this is the first time that the oil removal performance of flotation cells in a 
wide range of temperatures, specially at elevated temperatures (higher than 60oC) is 

investigated. It was visually observed that at temperatures higher than 70 oC, water vapor 

appeared in the gas space above the produced water and during the induction of impeller, 

water vapor and moisture were drawn into the liquid instead of nitrogen gas. This 

phenomenon may also affect the gas bubble size, bubble formation and oil-bubble 

coalescence.

Effect of TDS and impeller speed on oil removal efficiency 

Fig. 3a-d shows the effect of TDS _200-300 g/l_ on the IGF oil removal 

efficiency at constant impeller speed _450-2000 rpm_ at constant temperatures. Fig. 3a 

indicates that at the constant impeller speed of 450 rpm, at the test set ups, the effect of 

TDS is not considerable when the temperature changes from 20 to 70 oC. At 

temperatures above 70 oC, and constant impeller speed of 450 rpm, the TDS increase 

from 200 to 250 rpm did not change the oil removal efficiency significantly. But, at the 

stated conditions, when the TDS increases from 250 to 300 rpm, the IGF oil removal 

efficiency increases in the constant temperatures of 80, 90 and 100 oC by the amount of 

13.9%, 12.61% and 11.43% respectively. 

Fig. 3b demonstrates that at the constant impeller speed of 900 rpm, at the test set 

ups, the effect of TDS is not considerable when the temperature changes from 20 to 70 

oC. At temperatures above 70 oC, and constant impeller speed of 900 rpm, the TDS 

increase from 200 to 250 rpm did not change the oil removal efficiency significantly. But, 

at the stated conditions, when the TDS increases from 250 to 300 rpm, the IGF oil 

removal efficiency increases in the constant temperatures of 80, 90 and 100 oC by 

15.38%, 9.40% and 11.11% respectively. When the temperature changes from 20 to 100 

oC, at the TDS of 200 to 300 g/l and N=900 rpm, there are two exceptions in which the 

IGF efficiency is reduced due to TDS increase, which takes place at the temperature of 20 

oC and 70 oC by the amount of 3.32% and 5% respectively when the TDS increases from 

250 to 300 g/l. 

The IGF oil removal efficiency at constant impeller speed of 1450 rpm and 

temperatures between 20-100 oC versus TDS (200-300 g/l) is depicted in Fig. 3c. As it is 

observed in Fig 3c., at the stated conditions, there is not any significant change in the 

performance of the IGF system when the TDS changes from 200 to 300 g/l in different 

conditions. The noticeable change in the performance of IGF system in this case is 

related to the reduction of efficiency when the TDS increases from 250 to 300 g/l at all 

testing temperature ranges. In this case, the maximum decrease takes place at the 

temperature of 20 oC and the minimum decrease is related to 50 oC, which is equal to 

15.37% and 1.34% respectively. 

Fig. 3d shows the effect of TDS on the IGF efficiency at constant temperatures at 

constant impeller speed of 2000 rpm and varying TDS levels (200-300 g/l). Similar to 

the results of N=1450 rpm in Fig. 3c and neglecting some discrepancies, there is no 

significant change in IGF efficiency while the TDS increases from 200 to 300 g/l at 

different constant temperatures. Again the noticeable change in the performance of IGF 

system in this case is related to the reduction of efficiency when the TDS increases from 

250 to 300 g/l at all testing temperature ranges. In this case, the maximum decrease takes 
place at the temperature of 20 oC and the minimum decrease is related to 100 oC, which 

are equal to 15.37% and 1.8% respectively. 

Some researchers have shown that the increase of NaCl concentration from about 

zero to 4% will reduce the bubble size in flotation cells and meanwhile increase the oil 

removal efficiency. In these researches, only minor increase in oil recovery was 

observed as the salt concentration increased beyond 4% (21, 24). According to the results 

of the present research, it could be concluded that at TDSs about 16.5% to 23% _high 

saline produced waters_ the effect of TDS/NaCl on the mechanically IGF systems could 

not be studied individually and should be regarded with other parameters as well as 

temperature and impeller rotational speed. 

Agitation can have two opposing effects. On one hand an increase in impeller 

rotational speed will bring about an increase in energy dissipation, and hence an increase 

in the number of bubble–bubble or bubble-oil collisions per unit volume per unit time 

(25, 26). While this may be expected to increase coalescence, the contact time will also 

be reduced, so the rate of coalescence is not expected to increase at the same rate as the 

number of collisions. On the other hand, an increase in energy dissipation will increase 

the rate of bubble break-up (27, 28, 29). As was mentioned above, the increase in TDS 

also decreases the bubble size in flotation cells. It should be noted that the gas bubble 

size is an important factor in flotation unit design. If the bubbles are too large, there will 

be too few bubbles and they will not attach efficiently to the oil droplets as they rise very 

fast. If the bubbles are too small, they will not rise quickly enough, allowing the oil and 

gas to be entrained in the outlet water stream. The best performance point will be 

achieved according to the physical characteristics of produced water and IGF impeller 

speed specifications. 

Environmental regulations and IGF global oil removal efficiency 

From environmental perspective, it is important to check whether the selected 

technology meets the regional environmental regulations or not. According to the inlet oil 

content of 150 mg/l, the minimum IGF oil removal efficiency at the TDS of 200-300 g/l 

and impeller speed of 450-2000 rpm with the N2 fuel gas flowrate of 10 l/m, was at 

temperature of 20 oC and impeller speed of 450 and 2000 rpm at TDS of 200 and 250 g/l 

which led to 96 mg/l outlet oil content and 36% oil removal efficiency. The maximum oil 

removal efficiency was due to impeller speed of 900 rpm and temperature of 80 oC which 

led to 15 mg/l and 90% oil removal efficiency. At the temperature of 100 oC and the TDS 

of 300 g/l_ Kharg Island produced water case_ the minimum oil removal efficiency took 

place at N=1450 rpm which was equivalent to 72% and 42 mg/l oil in outlet stream and 

the maximum efficiency was achieved at N=900 rpm with 80% oil removal efficiency 

and 30 mg/l outlet oil content. Therefore if the goal is to use IGF system for the 

discussed specific produced water at high temperatures (70 oC or higher) and TDSs (200 

g/l or higher) without the use of any chemicals, a single flotation cell could not guarantee 

the outlet oil content of 15 mg/l which is the regulated oil content for the discharge to the 

Persian Gulf marine environment according to the Article VI of the Kuwait Convention 

and should be followed by at least one more flotation cell. 
Conclusion 

 

 Regarding the conditions of test procedures discussed in this article, at constant 

TDS levels of 200 and 250 g/l, different impeller speeds_ N=450 to N=2000 rpm_ the 

IGF oil removal efficiency increases when the temperature increases from 20 oC to 70 oC. 

At the constant TDS level of 300 g/l, at different impeller speeds _ N=450 to N=2000 

rpm_ the IGF efficiency increase continues from 20 to 80 oC. After these points, the oil 

removal efficiency is usually diminished. 

According to the test set ups, at a constant temperature between 20-100 oC, at 

different impeller speeds_ N=450 to N=2000 rpm_ the IGF oil removal efficiency was 

not so dependent on TDS when the TDS is very high_ 250-300 g/l_, specially at lower 

temperatures_20-60 oC_ and at lower impeller speeds (i.e., <1450 rpm). 

At the temperature of 100 oC and TDS of 300 g/l, oil removal efficiency would 

reach 80% when the impeller speed was set at 900 rpm. In this case, without adding any 

chemicals such as flotation aids, the outlet oil content from a single flotation cell could 

not support the regional environmental discharge regulation of 15 mg/l according to the 

Article VI of the Kuwait Convention and should be followed by at least one more 

flotation cell. 

It is recommended to run the tests with different types of crude oil to check 

whether the results are reproducible in different iol field settings. 
Table 1. Characteristics of Kharg Island produced water at the outlet of skimmer tank 

Specifications of Produced 

Water 

Value 

Temperature (oC) 90-110 

pH 7.02 

Suspended Solids (mg/l) 30-60 

TDS @ 180 oC (g/l) 250-310 

Oil Content (mg/l) 100-200 

Table 2. Characteristics of Kharg Island crude oil 

Specifications of crude oil Value

SGr @ 60/60 oF (ASTM D4052) 0.85 

API gravity (ASTM D4052) 

Kinematic Viscosity @ 20 oC(cSt.)(ASTM D-445) 

34 

8.01 

Figure 1. IGF pilot set up: IGF flotation cell and the nitrogen capsule Feed Gas 


Figure 2. IGF oil removal vs. temperature at different impeller speeds at constant 

inlet oil content of 150 mg/l and constant N2 fuel gas(10 l/min) at: 

(a)TDS=200 g/l; (b)TDS=250 g/l; (c)TDS=300 g/l 



Figure 3. IGF oil removal efficiency vs. TDS at different temperatures at constant inlet oil content of 150 mg/l an

at: (a)N=450 rpm; (b)N=900 rpm; (c)N=1450 rpm; (d)N=2000 rpm 

(d)
REFERENCES CITED 

1. Lee, R., Seright, R., Hightower, M., Sattler, A., Cather, M., McPherson, B., 

Wrotenbery, L., Martin, D., Whitworth, M., “Proceedings of the Ground Water 

Protection Council Produced Water Conference”, Colorado Springs, 16- 17 

(2002). 

2. Khatib, Z., Verbeek, P., “Water to Value — Produced Water Management for 

Sustainable Field Development of Mature and Green Fields,” Journal of 

Petroleum Technology, 55, 26–28 (2003). 

3. EIA (Energy Information Administration), 2009, Iran, Background, Available at 

http://www.eia.doe.gov/emeu/cabs/Iran/Background.html. Accessed October 10

(2009). 

4. Kuwait Convention, Kuwait regional convention for co-operation on the 

protection of the marine environment from pollution, Environmental Treaties 

and Resource Indicators 

(ENTRI),<http://sedac.ciesin.columbia.edu/entri/texts/kuwait.marine.pollution.19

78.htm.(1978). 

5. Strickland, W.T., “Laboratory results of cleaning produced water by gas 

flotation”. Society of Petroleum Engineering Journal, 20, 175–190. (1980) 

6. Moosai,R., Dawe, R.A.,” Oily wastewater clean up by gas flotation”.West Indian 

J. Eng.25 (1),pp 25-41 (2002) 

7. Kitchener, J.A.,.” The froth flotation process: Past, present and future-in brief”. 

In: The Scientific Basis of Flotation, Part 1. NATO Advances Study Institute, pp. 

1–26. (1985) 

8. Arnold, K.E. Stewart, M.,. “Surface production operations-Design of Oil”, 

Handling Systems and Facilities, vol. 1, second ed., Gulf Publishing Co, 

Houston, Texas (1998). 

9. Movafaghian,Sh.,Chen,J.,Wheeler,S.S.,Guidry,R.W.,.”Pilot testing of a new 

generation of induced gas flotation equipment”, SPE 87630,Soc. Pet. Eng. J,19 

(1),9-13 (2004). 
10. Gorain,B.K. ,Franzidis,J.P. ,Manlapig,E.V.,.”Studies on impeller speed and air 

flow rate in an industrial scale flotation cel”l, Part 1:Effect on bubble size 

distribution. Mineral Engineering. 8:6:615-635 (1995). 

11. Sylvester, N. D. and Byeseda, J. J.. “Oil Water Separation by Induced Air 

Flotation”. SOC. Pet. Eng. J. 20, 579 – 590 (1980).

12. Angelidou,Keshavarz, E., Richardson, M. J., Jameson, G. J., “The Removal of 

Emulsified Oil Particles from Water by Flotation” Ind. Eng. Chem. Process Des. 

Dev., 16,4: 436-441 (1977); 

13. Cline,J.T.,”Survey of gas flotation technologies for treatment of oil & 

grease”.Presented at the 10th produced water seminar,Houston.TX.Jan.19-21 

(2000). 

14. El-Kayar,A.,Hussein,M.,Zatout,A.,Hosny,A.Y. and Amer,A.A., , “Removal of oil 

from stable oil-water emulsion by induced air flotation technique”, Separation 

Technology,3, pp.25-31 (1993). 

15. Fench,D.,Aldrich,C., “Removal of diesel from aqueous emulsions by flotation”. 

Seperation science and technology, 35(13),pp.2159-2172 (2000). 

16. Melo,M.V., Sant’Anna Jr,G.L., Massarani,G.,.”Flotation techniques for oily 

water treatment” .Environmental technology,24,pp 867-876 (2003). 

17. Ramaswamy, B., Kar, D.D., De, S., ”A study on recovery of oil from sludge 

containing oil using froth flotation”, Journal of environmental management, 85, 

pp 150-154 (2007). 

18. Oliveira de Lima, L.M., da Silva, J. H., Ribeiro Patricio, A.A., de Barros Neto, 

E.L., Dantas Neto, A.A., de Castro Dantas, T.N. and de Alencar Moura, M C. P., 

“ Oily Wastewater Treatment through a Separation Process Using Bubbles 

without Froth Formation”, Petroleum Science and Technology. 26:9:994-1004 

(2008). 

19. Bing,L.,Tian,L.,Tian,W.,Ying,W,Hua,Z.,”Separation of oil from wastewater by 

column flotation”. Journal of China University of Mining & 

Technology,17(4),546-551 (2007). 

20. Pal, R., Masliyah, J. “Oil recovery from oil in water emulsions using a flotation 

column”, The Canadian Journal of Chemical Engineering. 68:959-967 (1990). 
21. Van Ham, N. J. M., Behie, L. A. , Svrcek, W. Y., “The Effect of Air Distribution 

on the Induced Air Flotation of Fine Oil in Water Emulsions”, Can. J. Chem. 

Eng. 61:514-547 (1983). 

22. Arnold, K.E. Stewart,M.,” Surface production operations-Design of Oil Handling 

Systems and Facilities”, vol. 1, third ed., Gulf Publishing Co, Houston, Texas, 

(2008). 

23. Ribeiro Jr.,C.P., Mewes, D.,” On the effect of liquid temperature upon bubble 

coalescence”, Chemical Engineering Science. 61:5704-5716 (2006). 

24. Takahashi, T., Miyahara, T., Nishizaki, Y.,”Separation of oily water by bubble 

column”, journal of chemical engineering of Japan, Vol. 12 (5), 394-399 (1979). 

25. Abrahamson, J.,”Collision rates of small particles in a vigorouslyturbulent fluid”, 

Chem. Eng. Sci. 30, 1371–1379 (1975). 

26. Prince, M.J., Blanch, H.W., Bubble coalescence and break-up in air-sparged 

bubble columns. AIChE J. 36, 1485–1499 (1990). 

27. Calderbank, P.H., “Interfacial area in gas–liquid contacting with mechanical 

agitation”, Trans. Inst. Chem. Eng. 36, 443–463 (1958). 

28. Parthasarathy, R., Jameson, G.J., Ahmed, N., “Bubble breakup in stirred vesselsPredicting the Sauter mean diameter”, Transactions IChemE 69, pp 295–301 

(1991). 

29. Deglon, D.A., O'Connor, C.T., Pandit, A.B., “Efficacy of a spinning disc as a 

bubble break-up device”, Chem. Eng. Sci. 53, 59–70 (1998).