Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.17 No.4 (December 2016) 35- 42 

ISSN: 1997-4884 

 
 
 
 
 

Performance Study of Electrodialysis for Treatment Fuel Washing 

Wastewater 

 
Basma A. Abdul Majeed

1
 and Maitham Adham Zubaidy

2
   

1
Chemical Engineering Department-College of Engineering-University of Baghdad-Iraq 

2
Department of Environment-Ministry of Industry and Minerals-Iraq  

 

Abstract 

In this work, electrodialysis (ED) has been demonstrated to be appropriate 

technique for reducing the electrical conductivity of real wastewater from fuel 

washing unit, which has been previously treated by other electrochemical technology 

(electrocoagulation and electrooxidation).  A five cell electrodialysis stack, with an 

active membrane area of 60 cm
2
 per cell was employed. During a batch recirculation 

mode ED system, the effects of parameters such as electrical potential applied (6-18 

V) and flow rate of streams (0.5-1.7 L/min.) on the performance of the total dissolved 

solids (TDS) separation and specific power consumption (SPC) were studied. The 

results indicate that the process of ED under potential (15 V) and flow rate (1.4 

L/min) are recommended as operation conditions. The removal of TDS achieved was 

about 95% throughout (80 min.) time of electrodialysis and (1.72 kWh/m
3
) of SPC. 

Moreover, SPC increased with an increase in the applied potential of ED stack, while 

it was not intensely responsive to the change in the flow rate. 

 

Key words: Electrodialysis, Real wastewater, Fuel washing, Ion exchange 

membrane. 

 

Introduction 

Water is a critical necessity for 

utilization of humanity. It is crucial for 

rural and modern development, and 

also to support developing populaces 

that requires a harmless drinking water 

supply [1].  

Water requirements are 

expanding quickly and thus the 

accessibility of good water sources is 

being brought down. Consequently, the 

reclamation and reuse of treated urban 

wastewaters is turning into an 

attractive study subject for tending to 

water lack. Desalination is a process 

that removes dissolved minerals from 

brackish water, sea water or treated 

wastewater [2]. There are essentially 

two groups of desalination innovations 

utilized all through the world today. 

These incorporate thermal technologies 

and membrane technologies. Thermal 

processes are those that evaporate 

water and gather condensed vapor to 

create distilled water. Infrequently, 

evaporation procedures are utilized to 

desalinate brackish water, as it is 

uneconomic for this purpose.  

Membrane technologies are 

much modern innovation than thermal 

procedures. It utilizes membranes to 

separate the inlet solution into two 

University of Baghdad 
College of Engineering 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 



 Performance Study of Electrodialysis for Treatment Fuel Washing Wastewater 
 

36                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

different solutions which are called 

product and concentrate. Reverse 

osmosis (RO) and electrodialysis (ED) 

are considered primarily membrane 

processes for desalination [3]. 

Electrodialysis procedure is more 

cost effective than reverse osmosis for 

desalination of the wastewater which 

contains TDS of   500 - 4000 ppm, 

thus, ED is generally utilized for 

desalination of industrial wastewater 

containing TDS of 500 ~ 1500 ppm 

[4]. 

The reclamation and reuse of 

wastewater by ED was widely reported 

in publications like in almond industry 

[5], wastewater plant [6] brine from a 

reverse osmosis [7] and nuclear power 

plant [8]. 

ED is an electrochemical 

separation process in which ions are 

traveled through ion exchange 

membranes by effects of a constant 

current or potential. Potential driving 

force is utilized to transfer dissolved 

ions from the feed water through 

cationic and anionic exchange 

membranes to form a concentrate and 

dilute streams [9]. 

An electrodialysis (ED) unit is 

made out of alternating anion and 

cation membrane sheets inserted 

between cathode and anode electrodes, 

these membrane sheets are separated 

from each other by spacers. Ionic 

species are depleted from dilute cells 

and collected in concentrate cells. 

Generally, several factors can 

affect the ED process performance 

such as stack design, length of the 

solution path in the stack, number of 

cells, feed concentration, flow rate and 

applied voltage, etc. [10, 11]. 

In this work, electrodialysis is 

proposed to be the procedure used for 

decreasing electrical conductivity by 

removing TDS from a real fuel oil 

washing wastewater (FWW) obtained 

from gas power station and pretreated 

by in situ electrocoagulation-

electrooxidation method.  

The aims of this work are to 

show that ED is an appropriate method 

for desalting fuel washing wastewater 

which is previously treated by other 

electrochemical techniques. The effect 

of applied potential and feed flow rate 

on the TDS removal efficiency has 

been studied to investigate the best 

conditions for the treatment at 

laboratory level. 

 

Materials and Method 

 

1. ED Set Up 
The ED setup consisted of: DC 

power supply (UNI-T, model: 

UTP3315FT-L), three glass tank each 

of 2 L was used for concentrate, feed 

(dilute) and electrode rinse, three 

diaphragm  pumps (type HF-9050, 

Taiwan) equipped each with a flow 

meter, three pressure gauges (0-2.5 

bar) to maintain the similar pressure 

drop across compartments. Three 

valves were used to control solutions 

flow rate in the concentrate, dilute and 

electrodes compartments of ED cell. 

Figure 1 shows a simplified diagram of 

the ED setup working in batch 

recirculation mode. 

 

 
Fig. 1: The ED experimental setup 

 

 

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Basma A. Abdul Majeed and Maitham Adham Zubaidy  

 

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2. Cell and Membranes 
The electrodialysis cell 

employed at present work was 

homemade designed and manufactured 

based on the research studies in the 

field of lab electro-membrane 

processes. The ED stack packed with 

five pair cells of cation and anion 

exchange membranes. Plastic spacers 

with 0.5 mm were placed between the 

membranes to form the flow paths of 

the dilute and concentrate streams.  

These spacers were designed to 

minimize boundary layer effects and 

were arranged in the stack so that all 

the dilute and concentrate streams were 

manifold separately. In this way a 

repeating section called a pair cell was 

formed; it consisted of a cation 

exchange membrane, a dilute flow 

spacer, an anion-exchange membrane, 

and a concentrate flow spacer. In this 

work, experiments were carried out by 

this stack equipped with six cation 

exchange membranes (CEM) and five 

anion exchange membranes (AEM) 

arranged as described in Figure 2. 

 

 
Fig. 2: The ED stack configuration 

 

Membranes used in these 

experiments were (anion 

AR204SXR412) and (cation CR67, 

MK111) manufactured by Ionics, 

Watertown, MA, USA. Table 1 shows 

the main characteristics of the 

membranes, according to the data 

provided by the supplier (membranes 

were supplied from Aldora refinery, 

Iraq). 

Table 1: Characteristics of the membranes 

Property Membrane 

 AR204SXR412 CR67,MK111 

Reinforcing 

fabric 
Acrylic Acrylic 

Specific 

weight 

mg/cm
2
 

13.7 13.7 

Thickness 

mm 
0.5 0.56-0.58 

Burst 

strength 

kg/cm
2
 

7 7 

Capacity 

meq/g 
2.8 2.4 

Chemical 

stability pH 
1-10 1-10 

 

The active membrane area was 

60 cm
2
 per cell, thus the total active 

area of the stack was 300 cm
2
. 

Stainless steel (316 L) and graphite 

were selected as cathode and anode 

electrodes respectively. 

Area of each electrode was 6 

cm×10 cm with a thickness of 0.3 cm. 

Thickness of dilution and concentrate 

cell were 0.15 cm with 0.6 cm
2
 cross 

sectional area of flow for each. 

Cathode and anode distances were 4 

mm from membrane in catholyte and 

anolyte compartments.  

 

3. Materials 
Sodium chloride (NaCl) with 

purity (99.5%wt.), product of Fisher 

chemicals (USA) was used to prepare 

concentrate solution at appropriate 

electrical conductivity. Sodium 

sulphate (Na2SO4) with purity (99.5% 

wt.), product of Fisher chemicals 

(USA) was used to prepare rinse 0.5 M 

solution. 

 

4. Analytical Method 
In all experiments, ion 

conductivity meter (CRISON Basic-

30, Spain), was used to measure the 

ionic concentration, TDS and 

conductivity of the solution during the 

experiments. Pros Kit MT 1210 

avometer was used to measure current 

passed through the ED stack circuit. 

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 Performance Study of Electrodialysis for Treatment Fuel Washing Wastewater 
 

38                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

5. Characterization of Wastewater 
The source of wastewater for the 

ED was a real fuel oil washing 

wastewater (FWW) obtained from the 

South Baghdad gas power station/2 

and pretreated by electrocoagulation-

electrooxidation in situ method at the 

best investigated conditions. About 20 

liters of pretreated FWW were 

produced and collected to be post 

treated by desalination in ED 

experiments. The main characteristics 

of the real and pretreated FWW are 

shown in Table 2. 

 
Table 2: Characteristics of pretreated FWW 

Parameter Real Pretreated 

pH 6.5-7.3 6.15 

Turbidity 

(NTU) 

785 24.3 

TSS (mg/L) 488 34 

Oil content 

(mg/L) 

586 1.1 

Conductivity 

(µS/cm) 

2350-2550 1722-1751 

COD (mg/L) 753-760 72-79 

TDS (mg/L) 1370 907-923 

  

6. Experimental Method 
In each experiment, the solutions 

employed were 1L of the wastewater 

(pretreated FWW) as a dilute, 1L of  

NaCl  895 mg/L (about 1700 µS/cm 

electrical conductivity) as a 

concentrate and 2L of Na2SO4 (0.5 M) 

as the electrolyte solution. In order to 

study the voltage effect on the ED 

process, a series of potentiostatic 

experiments with voltage range of (6, 

9, 12, 15 and 18 V) were carried out 

with fixed flow rate of 0.5 L/min for 

dilute and concentrate solutions. In 

order to study the flow rate effect on 

the ED process, several tests at the best 

selected voltage were approved with  a 

wide flow rate range (0.5, 0.8, 1.1, 1.4 

and 1.7 L/min.) The TDS 

concentration of salts as well as the 

conductivity of dilute and concentrate 

solutions were measured at 10 min. 

intervals, also the electrical current of 

the ED stack was recorded during the 

electrodialysis time. The time of 

treatment for each experiment was 60 

minutes. The flow rate of the 

electrolyte solution was fixed at 1.2 

L/min for all experiments. Moreover, 

pressure drop was maintained the same 

for all solution streams in each case. 

In this study, the quality 

characteristic was the separation 

percentage (SP) which was calculated 

as follows: 

 

  ( )  (  
  

  
)                 …(1) 

 

Where, Ct and Ci are timed and 

initial ionic salts concentrations (mg/l), 

respectively.  

Also, Specific power 

consumption (SPC) is an important 

parameter from the economical point 

of view, as it can be described as the 

energy consumed for desalting one m
3
 

of feed solution and it is calculated 

here as electrical energy consumed 

only in the cells (kWh/m
3
) 

 

    
 ∫    

 
 

        
                               …(2) 

 

Where E is the applied potential 

(volt), I is the current (ampere), Vd is 

the dilute stream volume (m
3
), and t is 

the time (hour) [12]. 

 

Results and Discussion 
 

1. Effect of Applied Voltage 
The treated FWW by EC-EO 

was further reclaimed by 

electrodialysis (ED) process in order to 

recycle and reuse water in the washing 

fuel system. The separation 

performance of dissolved salts from 

the treated FWW was investigated at 

constant voltage electrodialysis 

experimental studies through an 

unsteady state batch recycled run of 

the ED system. At time intervals of 10 

min, both TDS concentrations and 

electrical conductivity of concentrate 

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Basma A. Abdul Majeed and Maitham Adham Zubaidy  

 

-Available online at: www.iasj.net                    IJCPE Vol.17 No.4 (December 2016)                      39 
 

stream (C) and dilute stream (D) were 

measured.  

The operating time for each run 

was fixed at time (60 min.) while the 

flow rate was set at (0.5 L/min). 

Different voltages values (6,9,12,15 

and 18 V) were tested. The 

conductivity of concentrate and dilute 

streams versus time at different 

voltages was plotted as shown in 

Figure 3. It can be noticed from Figure 

3 that the conductivity of both dilute 

and concentrate streams were varying 

with different voltages. The 

conductivity of dilute stream decreased 

faster with increasing applied voltages 

which means higher transfer rate and 

lower duration time was needed to 

achieve a particular target at greater 

potential driving force. On the other 

hand, the slop of conductivity curves 

for concentrate stream was increased 

with increasing the applied voltage as 

consequence of mass balance of the 

transferred salts.     

 

 
Fig. 3: Curves of conductivity of dilute (D) and 

concentrate (C). vs. time at different voltages 

and constant flow rate (0.5 L/min.) 

 

Same conductivity behavior were 

illustrated by Valero et al [5] who 

studied the application of 

electrodialysis for the treatment of 

almond industry wastewater. The TDS 

removal efficiency of the dilute stream 

against time at different voltages was 

plotted in Figure 4. It can be shown 

from Figure 4 that the TDS removal 

efficiency (SP) was increased with 

increase of electrical potential. At 60 

min. of the process, the removal was 

45.8% at 6 volte while it were 74.93% 

and 75.2% at 15 and 18 voltages 

respectively. The convergence between 

two last curves may be attributed to 

approaching close the limiting current 

density of the ED process [13]. 

 

 
Fig. 4: TDS removal efficiency of dilute 

stream against time at flow rate 0.5 L/min. and 

different voltages range 

 

2. Effect of Flow Rate 
From economical point view, 

applied voltage (15 V) was selected to 

examine the effect of flow rate on the 

separation performance. At constant 

voltage, various flow rates (0.5, 0.8, 

1.1, 1.4 and 1.7 L/min) were tested. 

The conductivity of concentrate and 

dilute streams versus time at different 

flow rates was plotted in Figure 5. 

Figure 5 shows that the 

conductivity of dilute decreased while 

the conductivity of concentrate 

increased with the increasing flow rate. 

The TDS removal efficiency (SP) of 

the dilute stream against time at 

different voltages was plotted in Figure 

6. 

It can be shown from Figure 6 

that the TDS removal efficiency was 

increased with increasing of flow rate. 

After 60 min. of the process, the 

removal was 74.93% at flow rate (0.5 

L/min) while it was achieved 90.8% 

and 92.5% at 1.4 and 1.7 L/min 

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 Performance Study of Electrodialysis for Treatment Fuel Washing Wastewater 
 

40                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

respectively. Increasing the flow rate 

leads to increasing the linear velocity 

of solution across the membrane 

surface, which results in decreasing the 

boundary layer thickness and 

improving the mass transfer 

coefficient. Unless, in high flow rate 

the decrease of residence time in cells 

offsets the positive effect of layer 

thickness decrease. This behavior was 

reported as well by Gangchoon Lee 

[14]. 

 

 
Fig. 5: Curves of conductivity of dilute (D) and 

concentrate (C). vs. time at different flow rates 

and constant voltage (15 V) 

 

 
Fig. 6: TDS removal efficiency of dilute 

stream against time at applied voltage (15 V) 

and different flow rates range 

 

3. Specific Pwer Consumption 
For each set of potential and flow rate 

experiments, the specific power 

consumption (kWh/m
3
) was estimated 

based on Equation 2. The calculated 

SPC was plotted in Figure 7 for both 

potential and flow rate experiments.  

It can be seen form Figure 7-a 

that the SPC was drastically affected 

by the change in the applied potential 

force and the voltage line was 

extended for a wide range of SPC   

(0.287-1.94 Kw h/m
3
).  

In contrast, the SPC has 

negligible changes with flow rate 

chosen and the flow rate line has small 

range (1.39-1.69 Kw h/m
3
) in SPC 

scale as illustrated in Figure 7-b. 

Therefore it can be concluded that 

voltage has the higher effect on the 

SPC rather than the flow rate. This 

behavior was also observed by 

Demircioglu et al.[15] and Kabay et 

al.[16].  

 

 
(a) 

 

 
(b) 

 

Fig. 7: the SPC for (a) different potential (at 

flow rate = 0.5L/min.) and (b) different flow 

rate (at potential =15 volte)  

 

It can be seen that the best 

conditions of ED process which give 

the higher TDS removal at acceptable 

SPC and were 15 V and 1.4 L/min. 

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Basma A. Abdul Majeed and Maitham Adham Zubaidy  

 

-Available online at: www.iasj.net                    IJCPE Vol.17 No.4 (December 2016)                      41 
 

To investigate the possibility of 

achieving higher removal with 

increasing time, an experiment was 

conducted at the optimum conditions a 

long with electrodialysis process time 

as shown in Figure 8.  

The ED stack operated under 

potential of 15 V and the flow rate of 

1.4 L/min was able to remove about 

95% of TDS removal and reduces the 

dilute solution conductivity value from 

1538 µS/cm to 67 µS/cm during 80 

min of operation time with about 1.72 

kWh/m
3
 of SPC. It is clear that 

increasing time higher than 80 min has 

no effect on the removal efficiency and 

leading to dissipate the energy used for 

the system with marginal increment of 

removal efficiency.  
 

 
Fig. 8: TDS removal at voltage 15V , flow rate 

1.4 against time 

 

Conclusions 

A laboratory study was 

conducted to investigate the feasibility 

of electrodialysis process for treating 

the electrochemically pretreated fuel 

washing wastewater containing TDS 

concentration about 923 ppm.  

Removal efficiency was 

increased with the applied potential in 

the range 6-18 V due to strength of 

electrical potential as driving force for 

mass transfer. However, the increment 

of removal efficiency was diminished 

as the applied potential increases. 

Removal efficiency in dilute was 

enhanced with flow rate in the range of          

0.5-1.7 L/min due to the positive effect 

on removal rate of salts ion as a result 

of reducing the boundary layer 

thickness and improving the mass 

transfer coefficient. The 

inconsequential increment of removal 

rate higher than 1.4 L/min was come 

about because of the decline of 

residence time in cells. 

Based on the operation of the 

electrodialysis stack used in this work, 

the applied voltage 15 V and the flow 

rate of 1.4 L/min are recommended as 

suitable operating conditions for 

wastewater solutions which 

corresponds to about 95% of TDS 

removal and reduces the dilute solution 

conductivity around 23 times in 80 min 

of operation time.  

It was obtained that the specific 

power consumption (SPC) was 

influenced by the potential applied. 

While it was not intensely responsive 

to the change in flow rate. 
 

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42                                IJCPE Vol.17 No.4 (December 2016)              -Available online at: www.iasj.net 
 

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