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Journal of Engineering
Volume 15 December 2009
Number 4
4356
TREATMENT OF INDUSTRIAL WASTE WATER USING
REVERSE OSMOSIS TECHNIQUE
Nada S.Ahmedzeki, Sama M. Abdullah, Rasha H. Salman.
University of Baghdad, College of Engineering, Chem.Eng.Dep.
ABSTRACT
Reverse osmosis technique was used for the treatment of industrial waste water. Ions like
calcium, magnesium, sodium, sulfate, and nitrate were found in the waste water of the General
Company of Vegetable Oil with high concentrations which must be treated for reuse. Feed water
containing the above mentioned ions was fed to the RO unit at feed flow rates (0.4 and 0.8 lit/min)
and different operating pressure (2-4bar) .It is concluded that increasing operating pressure and
feed flow rate improved the separation by a decrease in the concentration of ions in the product.
High rejection was obtained for all ions present in feed water, ranging from (63.8-97.6%).
Rejection of TDS was 87% when the concentration of TDS was reduced from 1192 to 154.94 ppm.
ةصخلا
INTRODUCTION
The use of reverse osmosis (RO) to remove salts and impurities from water had been a
recognized technology to improve water quality therefore it had a valuable application in the reuse
of waste water streams. The benefit includes; reduced discharge, reduced purchases and the
conservation of water resources. In the reverse osmosis process, water passes through a semi-
permeable membrane which removes inorganic minerals like radium, sulfate, calcium, magnesium,
potassium, sodium, nitrate, fluoride and phosphorous. It also helps to remove some organic
compounds including some pesticides (Zibrida et al., 2000). RO can be used for the removal of
arsenic which occurs naturally and can contaminate drinking water through the erosion of rocks and
minerals or through human activities such as fossil fuel burning, paper production, cement
manufacturing, and mining. Natural contamination of groundwater by arsenic has become a crucial
water quality problem in many parts of the world (Pawlak, 2006). Often, reverse osmosis units are
used in combination with a mechanical filter and an activated carbon filter. The water passes
through the mechanical filter first, where sand and large particles are removed, then through the
reverse osmosis unit, and lastly through the activated carbon filter which removes organic
compounds (Daniels, and Mesner, 2005).
N. S.Ahmedzeki Treatment of Industrial Waste Water Using
S.M. Abdullah Reverse Osmosis Technique
R.H. Salman
4357
Applications of membrane technologies for water and wastewater treatment is growing due
to decreasing price of membranes and more stringent regulations for water quality. Membrane
separation processes have following advantages in industrial applications:
- appreciable energy savings , - clean and easy to apply technology, -replaces several
conventional processes like filtration, distillation, ion-exchange and chemical treatment with
smaller and more efficient equipment - produces high quality products - allows greater flexibility in
designing systems. During the last two decades significant advances have been made in the
development and application of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and
reverse osmosis (RO) processes. MF membranes reject suspended particles only, UF membranes
reject suspended particles and high molecular weight compounds, NF membranes also reject low
molecular weight compounds, and RO membranes also reject ions (Kochany, 2007, and Amjad and
Zibrida, 1998).
Over 100 different materials are used to make RO membranes, however the two most
commonly used membranes are made from cellulose acetate (CA) and polyamide thin film
composite (TFC). These may come in spiral, tubular hollow fiber, and plate and frame. Hollow
fiber (HF) and flat sheet are the most commonly used RO membrane configurations. Although HF
RO elements provide more surface area, they are more prone to fouling..
Most studies on industrial waste water using RO were limited on either feed containing
NaCl salt (Ahmed, 2000, and Mohammed, 2008) or feed containing dye (Mahmood, 2001). In the
present study, investigation of five different monovalent and divalent ions (Ca++, Mg++, Na+, SO4--,
NO3-) was the point of view in the treatment of industrial waste water. The important parameter to
be compared is the rejection percentage.
EXPEREMENTAL WORK:
(i) Experimental apparatus:
The Experimental apparatus consists of the following parts:
1) QVF feed tank with capacity of 20 liter.
2) Centrifugal pump is used to pump the feed at a pressure of 4-6 bar.
3) Rotameter of (0.2-2 lit/ min.).
4) 5-stage reverse osmosis system supplied by So-Safe Water Technologies.
1. Wound Polypropylene Yarn (WPP) or Spun Polypropylene (SPP) is used for pre-filtration to
remove the sediments.
2&3. Activated carbon (GAC) and dual purpose carbon (DPC) used for the purification for taste
and odor.
4. Desalination and purification using reverse osmosis membrane. Thin film composites membrane
(The spiral – wound module type TFC – 8822HR) is installed for best permeate water
quality.
5. Water polishing and purification unit using In-line granular activated post carbon cartridge
(ILGAC-10).
The schematic diagram of the experimental apparatus is shown in Fig. 1.
(ii) Experimental Procedure:
Industrial water from the factories of The General Company of Vegetable Oil was analyzed
for the specified ions; Ca++ , Mg++ , Na+ , SO4-- , NO3- . Feed solution to the RO unit, containing
the aforementioned was prepared. Table 1 shows the analysis of the prepared feed water. Salts of
analytical grades from Merck Company were used.
Feed solution containing the specified ions, with the appropriate concentrations, was
added to the 20 liter feed tank. The outlet valve was opened to fill the pipes with water. The pump
Journal of Engineering
Volume 15 December 2009
Number 4
4358
was switched on and the feed rate of 0.4 and 0.8 lit/min was set. Operating pressure range was (2-4
bar) for each flow rate. Concentrations of the product solution were analyzed using Atomic
absorption technique.
RESULTS AND DISCUSSIONS
Operating pressure affects the performance of RO units. Concentrations of the specified
ions as a function of the operating pressure were drawn for both feed flow rates. The results are
shown in Figs. (2-6).The effect of operating pressure and feed flow rate on the total TDS is shown
in Fig 7. It is obvious that increasing the operating pressure or feed flow rate improves the degree
of separation for each ion. However, the operating pressure has a pronounced effect compared with
feed flow rate. Increasing operating pressure offers a pressure gradient across the membrane and
the driving force will be higher, therefore water is forced to pass through the membrane and
%rejection is increased. Considerably high pressures are necessary to overcome osmotic pressure
which is mainly a function of concentration and molecular weight ( Amjad and Zibrida, 1998
;Singh and Heldman,1993).
When the feed rate was increased, concentration of ions in product solution and hence,
TDS, were decreased and %Rejection was increased. This means that the degree of separation is
increased by an increase of the throughput rate and increase of mass transfer coefficient between
the membrane and feed flow.
% Rejection for 0.8 lit/min flow rate is also calculated in order to investigate the degree of
separation for each ion as shown in Fig.8. 87% of TDS are rejected which is an acceptable value,
and for individual ions, it can be seen from Fig.9, that SO4-- and NO3- ions have the lower
%Rejection while, NO3- has the lowest. Nitrate is so soluble and non-reactive; therefore it is very
difficult to be removed from water. These results are in agreement with those obtained by Ellen,
2007. Therefore, it is possible to say that the best operating conditions are feed flow rate 0.8 lit/min
and operating pressure 4 bars.
CONCLUSIONS:
1. The concentration of ions in the product solution decreases with increasing operating
pressure. Increasing operating pressure are necessary to overcome the osmotic pressure and
the driving force will be higher, therefore, TDS decreased.
2. The concentration of ions in the product solution decreases with increasing feed flow rate.
3. The percent of rejection for each ion differ from each other. Sulfate and nitrate were lower
than other ions. Nitrate ions had the lowest % Rejection.
4. It is demonstrated that the RO process could effectively applied for the removal of calcium,
magnesium, sodium, sulfate, and nitrate ions. The best operating conditions are feed flow
rate of 0.8 lit /min and 4 bar operating pressure.
NOMENCLATURE
MF Microfiltration
NF Nanofiltration
ppm Part per million
RO Reverse osmosis
TDS Total dissolved solids
UF Ultrafiltration
N. S.Ahmedzeki Treatment of Industrial Waste Water Using
S.M. Abdullah Reverse Osmosis Technique
R.H. Salman
4359
REFERENCES
Ahmed F., 2000 “Study of factors affecting the efficiency of reverse osmosis process”
MSc.Thesis, University of Baghdad.
Amjad Z. and Zibrida J., 1998, Reverse Osmosis Technology: Fundamentals and Water
Applications. Association Water Technologies, Inc. Annual Convention, Washington, DC.
Barbara Daniels, and Nancy Mesner, 2005“Drinking Water Treatment Systems” Water
Quality, Utah state University extension., NR/WQ/2005-24.
Ellen R. Campbell 2007, “Removal is essential for excess nitrate” Water technology online.
www.watertechonline.com.
Kochany, J., 2007, “Wastewater Treatment by Membrane Technology” ONESTOGA-
ROVERS & ASSOCIATES, vol.7 No.3.
Mahmood M., 2001, MSc.Thesis, University of Baghdad.
Mohammed B., 2008, “Membrane separation process for treatment and reuse of water”
MSc.Thesis. University of Baghdad.
Pawlak Z., Żak S., Zabłocki L.2006, “Removal of Hazardous Metals from Groundwater by
Reverse Osmosis” Polish J. of Environ. Stud. Vol. 15, No. 4, , 579-583.
Singh, R.P. and Heldman, D.R. 1993. “Introduction to Food Engineering,” 2nd ed.
Academic Press, Inc., Harcourt Brace & Company, San Diego, California.
Zibrida J., Amjad Z., Zuhi R. and Lewis J. 2000, ““Advances In Reverse Osmosis;
Application in water reuse” Corrosion, paper No.314.
Journal of Engineering
Volume 15 December 2009
Number 4
4360
Fig. 1 Schematic diagram of reverse osmosis unit.
0
20
40
60
80
100
0 1 2 3 4 5
Operatin g pressure (bar)
Ca Concentration
Series1
Series3
0.4lit/min
0.8lit/min
Fig. 2Concentration of Ca++ vs operating pressure.
Feed Tank
-
-
-
-
-
Pump
Recycle valve
Rotameter
Reverse osmosis
unit
Pressure gauge
Product solution
(Permeate)
Concentrated
solution
N. S.Ahmedzeki Treatment of Industrial Waste Water Using
S.M. Abdullah Reverse Osmosis Technique
R.H. Salman
4361
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5
Operatin g pressure (bar)
Mg concentration
Series1
Series3
0.4lit/mi
n
0.8lit/mi
n
Fig. 3 Concentration of Mg ++ vs operating pressure.
0
20
40
60
80
100
0 1 2 3 4 5
Operatin g pressure (bar)
Na concentration
Series1
Series3
0.8lit/mi
n
0.4lit/mi
n
Fig. 4 Concentration of Na+ vs operating pressure.
0
100
200
300
400
500
600
700
0 1 2 3 4 5
Operatin g pressure (bar)
SO4concentration
Series1
Series3
0.4lit/min
0.8lit/min0.8lit/min
Fig. 5 Concentration of SO4-- vs operating pressure.
Journal of Engineering
Volume 15 December 2009
Number 4
4362
0
20
40
60
80
100
120
140
160
180
200
0 1 2 3 4 5
Operatin g pree sure (bar)
NO3 concentration
Series1
Series3
0.4lit/min
0.8lit/min
Fig. 6 Concentration of NO3- vs operating pressure.
0
200
400
600
800
1000
1200
0 1 2 3 4 5
operating pressure(bar)
TDS
Series1
Series2
0.4lit/min
0.8lit/min
Fig. 7 Total dissolved solids vs operating pressure.
0.6
0.8
1
012345
operating pressure (bar)
%TDS Rejection
Fig. 8 % TDS Rejection vs operating pressure.
N. S.Ahmedzeki Treatment of Industrial Waste Water Using
S.M. Abdullah Reverse Osmosis Technique
R.H. Salman
4363
0
0.2
0.4
0.6
0.8
1
012345
operatin g pressu re (bar)
% Rejection
Ca
Mg
Na
SO4
NO3
Fig. 9 % Rejection for different ions vs operating pressure.
Table 1. The initial concentrations of feed solution.
Feed water ion
Concentration (ppm)
Ca++
100
Mg++
100
Na+
90
SO4--
717
NO3-
185
TDS
1192