IMPACT OF REVERSE OSMOSIS ON PURIFICATION OF WATER

Abstract

With increasing demand for potable water in regions lacking fresh water sources, various potential technologies have been explored for eliminating water shortage. Raw water (from sea, and other water sources) emerged as a potential source for such water deprived areas. The development of raw water reverse osmosis technology proved to be a ground breaking innovation, making it easier to extract pure water from raw water (sea water and Brackish water). Raw water reverse osmosis technology has taken many leaps towards the development of energy efficient and high yielding systems. The reduction in energy consumption, improvement in membrane life and increase in energy recovery emerged as the primary criteria for research in this field. The key objective of the work involves the optimization of the variables involved in the pre-treatment process of different water sources (pond, canal and surface water) reverse osmosis plant which would lead to an increase in the membrane life by reducing solids content of the raw water. Experiments were carried out to ensure maximum total solids reduction and also reduction of different chemical parameters (BOD, TDS and Bacteria). These parameters were found to be desirable for the discharge from the pre-treatment to be fed into the reverse osmosis part of the plant and RO water plant is used drinking purpose and free from contaminants. INTRODUCTION More than 60% of the world's population resides in Asia, and the continent is fast becoming a powerful engine for global economic growth. Rapid economic growth can be buttressed only by the strong support of infrastructure like power and water facilities. Moreover, continuous population expansion calls for more and better quality fresh water, thereby underscoring the increasingly critical need for reliable sources of water. Given the fixed supply of fresh water globally from conventional sources like streams and underground aquifers, simple economic thinking dictates that to meet rising demand, supply from non-traditional sources must rise, such as sea water desalination. Global sea water desalination capacity has continuously increased over the past 30 years, especially in the past decade. This is a clear indication that drawing fresh water from the sea has gained traction in time in Asia, and today, sea water desalination in Asia accounts for almost 70 % of the global capacity [6]. Water is the most common liquid on our planet, vital to all life forms.

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Lamma OA et al. / Journal of Pharmaceutical Biology, 5(2), 2015, 108-112.
108
Journal of Pharmaceutical Biology
www.jpbjournal.com e-ISSN - 2249-7560
Print ISSN - 2249-7579
IMPACT OF REVERSE OSMOSIS ON PURIFICATION OF WATER
Lamma OA1*, Abubaker M. Outhman2, Lamma SA3
1Department of Soil and Water, Faculty of Agriculture, Bani Walid, Azzayatuna University, Libya.
2Faculty of Engineering &Technology, University of Sebha, Libya.
3Department of Environmental Sciences, Baniwalid, Libya.
ABSTRACT
With increasing demand for potable water in regions lacking fresh water sources, various potential technologies
have been explored for eliminating water shortage. Raw water (from sea, and other water sources) emerged as a potential
source for such water deprived areas. The development of raw water reverse osmosis technology proved to be a ground
breaking innovation, making it easier to extract pure water from raw water (sea water and Brackish water). Raw water reverse
osmosis technology has taken many leaps towards the development of energy efficient and high yielding systems. The
reduction in energy consumption, improvement in membrane life and increase in energy recovery emerged as the primary
criteria for research in this field. The key objective of the work involves the optimization of the variables involved in the pre-
treatment process of different water sources (pond, canal and surface water) reverse osmosis plant which would lead to an
increase in the membrane life by reducing solids content of the raw water. Experiments were carried out to ensure maximum
total solids reduction and also reduction of different chemical parameters (BOD, TDS and Bacteria). These parameters were
found to be desirable for the discharge from the pre-treatment to be fed into the reverse osmosis part of the plant and RO
water plant is used drinking purpose and free from contaminants.
Keywords: Reverse osmosis, Chlorination, BOD, Bacteria.
INTRODUCTION
More than 60% of the world’s population resides
in Asia, and the continent is fast becoming a powerful
engine for global economic growth. Rapid economic
growth can be buttressed only by the strong support of
infrastructure like power and water facilities. Moreover,
continuous population expansion calls for more and better
quality fresh water, thereby underscoring the increasingly
critical need for reliable sources of water. Given the fixed
supply of fresh water globally from conventional sources
like streams and underground aquifers, simple economic
thinking dictates that to meet rising demand, supply from
non-traditional sources must rise, such as sea water
desalination. Global sea water desalination capacity has
continuously increased over the past 30 years, especially
in the past decade. This is a clear indication that drawing
fresh water from the sea has gained traction in time in
Asia, and today, sea water desalination in Asia accounts
for almost 70 % of the global capacity [6]. Water is the
most common liquid on our planet, vital to all life forms.
It is the dispersion medium for all biochemical reactions
of the living process and takes part in many of these
reactions. In spite of the chemical simplicity of the water
molecule, its physical properties are quite remarkable.
Safe drinking water is essential to humans and other
lifeforms.To overcomes the problem of water scarcity, the
best way is to reuse the water. For this purpose the more
suitable plant is the RO plant. Reverse Osmosis is the
finest level of Filtration available. The RO membrane acts
as a barrier to all dissolved solids and inorganic molecules
with a molecular weight greater than approximately
100.Reverse osmosis system is a process of membrane
application. In this process water is passed through at a
high pressure (12, 13, and 14). Thus separating pure water
and dissolved salts. Water coming out is free from TSS,
BOD, and Bacteria and contains very low TDS. In this
technology, the reverse osmosis takes place with high
pressure and because of this the flow of water gets
reversed through the semi permeable membrane.
Corresponding Author:- Lamma O.A. E-mail:- osamalama3875@yahoo.com

Lamma OA et al. / Journal of Pharmaceutical Biology, 5(2), 2015, 108-112.
109
This assists us in clearing the water from excess
salts using the high pressure produce in the RO module.
The Reverse Osmosis System (RO) is designed to purify
water by forcing water through a semi-permeable RO
membrane. Water purified by reverse osmosis has
approximately 97-98% of the dissolved ions and
approximately 99% of most other contaminants removed.
The purified water exiting the system is referred to as
Permeate. Reverse osmosis (RO) desalination is one of
the main technologies for producing fresh water from
seawater and other saline water sources (2).
The membrane properties greatly affect the water
productivity and energy costs in the reverse osmosis
desalination processes. Recent years have seen significant
research efforts devoted to developing high-performance
RO membranes. The recent activities in the development
of RO membranes with improved flux and salt rejection,
chlorine tolerance, fouling resistance and thermal
stability. Membrane processes such as Reverse osmosis
(RO), Nano filtration (NF), and electrodialysis (ED) have
drawn more attention because of their strong separation
capabilities and exhibiting a great potential for the
treatment of water worldwide [1-5]. The scarcity of fresh
water problem may be overcome by using the alternative
membrane technology such as membrane distillation for
groundwater surface water, brackish water, sea water.
Hence, In the present study, an attempt has been
made to use of Reverse osmosis process for purification
of water collected from different sources (surface water of
ponds, canal, ground water and lakes).
MATERIALS AND METHOD
Collection of Water
Water is mainly collected from the different
sources surface water of pond surface, sea water and sea
water.
Para meters analyzed
Physical parameters like PH, Turbitity and
chemical parameters Nitrates, COD,BOD, sulfates,
acidity, alkalinity and total hardness according to APHA
(2005). Biological parameters identified (E.coli)
according standard protocol.
Operating procedure of Ro plant
Water is passed through at a high pressure. Thus
separating pure water and dissolved salts. This process
yields 75% permeate and 25% concentrate of the feed
volume. It depends upon the characteristics of the water
being passed. The typical single-pass RO system consists
of the following 5 steps:
Intake Type of the water intake mainly depends on the
pre and post treatment. The RO system is used for the
purification of water like river water, sea water ground
water, and brackish water.
Pretreatment
It is essential step in reverse osmosis. It is carried
out either by physical and chemical treatment or by
passing through filter beds. When working with RO and
Nano filtration (NF) membrane, pretreatment is essential
due to the nature of their spiral wound design.
By physical and chemical methods
Screening of solids
Solids within the water must be removed and the
water treated to prevent fouling of the membranes by fine
particle or biological growth, and reduce the risk of
damage to high-pressure pump components.
Cartridge filtration
Generally, string-wound polypropylene filters
are used to remove particles of 1–5 µm diameters.
Dosing Oxidizing biocides, such as chlorine, are added
to kill bacteria, followed by bisulfite dosing to deactivate
the chlorine, which can destroy a thin-film composite
membrane. There are also biofouling inhibitors, which do
not kill bacteria, but simply prevent them from growing
slime on the membrane surface and plant walls.
Pre filtration pH adjustment
If the pH, hardness and the alkalinity in the feed
water result in a scaling tendency when they are
concentrated in the reject stream, acid is dosed to
maintain carbonates in their soluble carbonic acid form.
CO32– + H3O+ = HCO3– + H2O
HCO3– + H3O+ = H2CO3 + H2O
Carbonic acid cannot combine with calcium to
form calcium carbonate scale. Calcium carbonate scaling
tendency is estimated using the Langelier saturation
index. Adding too much sulfuric acid to control carbonate
scales may result in calcium sulfate, barium sulfate or
strontium sulfate scale formation on the RO membrane.
Pre filtration anti-scalants
Scale inhibitors (also known as antiscalants)
prevent formation of all scales compared to acid, which
can only prevent formation of calcium carbonate and
calcium phosphate scales. In addition it inhibit sulfate and
fluoride scales, disperse colloids and metal oxides.
Despite it claims that antiscalants can inhibit silica
formation.
By passing through filter beds
Pressure Sand Water Filter
Sand filtration is frequently used and very robust
method to remove suspended solids from water. Raw

Lamma OA et al. / Journal of Pharmaceutical Biology, 5(2), 2015, 108-112.
110
water is passed through Multigrade Sand Filter at a
pressure of 3.5 kg / cm2 to reduce the suspended solids
present in the raw water. The filter will effectively
remove up to 30 – 50 micron of the suspended solids to
less than 5 ppm.
Activated Carbon Filtration System
The activated carbon filtration system is also one
type of filtration process to polish the treated water after
sand filtration system. By this process the odors, free
chlorine; present in the water will be reduced.
Start up procedure
Before starting up an RO system, it should be
verified that all pretreatment systems are working
according to their specifications On startup, the inlet
valve should open prior to the initiation of the high-
pressure pump, to completely fill the system with low
pressure water (<100 psi [< 7 Bars]). This “soft start” will
prevent hydraulic shock at startup. Pre-treatment chemical
making sure the chemicals are not over-injected.
High Pressure Pump
One No. of Vertical Mounted Multi stage
centrifugal High Pressure Pump with SS construction.
The High Pressure Pump supply raw water with pressure
of 12 to 15 kg/cm2 to RO Membranes, where permeate is
separated.
PROCESS
Reverse Osmosis (RO) water treatment process
involves water being forced under pressure (Osmotic
Pressure) through a semipermeable membrane. The
Reverse Osmosis Process is generally used for
desalination of Sea water treatment and Brackish Water
treatment for its conversion into potable water. In the
whole Water Treatment fields Reverse Osmosis water
treatment Process usage in Industrial water treatment and
Domestic water treatment is huge. Reverse Osmosis water
treatment is the main key of modern water treatments
field to solve water requirements.
In Reverse Osmosis water treatments, feed water
is pumped at high pressure through permeable
membranes, separating salts from the water. It is called
Desalination of Reverse Osmosis (RO) water treatment.
The feed water is pretreated to remove particles that
would clog the membranes.
Remineralisation and pH Adjustment
The desalinated water is very corrosive and is
stabilized to protect downstream pipelines and storages,
usually by adding lime or caustic to prevent corrosion of
concrete lined surfaces. Liming material is used to adjust
pH between 6.8 and 8.1 to meet the potable water
specifications primarily for effective disinfection and for
corrosion control.
Post-Treatment
Post-treatment consists of preparing the water for
distribution after filtration. It provides secondary
protection against compromised membranes and
downstream problems. Disinfection by means of UV
lamps. Store the treated water in storage tank before it is
supplied.
Table 1. Variation of pH at different sampling times the variation depends upon the pollutant concentration of the
raw water
S.No
Parameter
First week
Second week
Third week
WHO Standard value
Rw (ex v)
Ow(ex v)
Rw(exv)
Ow(ex v)
Rw (ex v)
Ow (ex v)
Ow (ex v)
1.
PH
6.0
7.8
6.25
8.0
6.45
8.2
8.4
7.5-8.5
2.
Turbidity
50
2.5
58
3.5
53
2.4
2.8
2.5
3
BOD
10.24
2.8
13.25
3.12
12.12
3.2
2.96
3
4.
COD
30.5
7.4
36.0
7.2
35.00
7.3
7.6
<10ppm
5.
TSS
1050
230
1000
270
1450
230
280
300-500
6.
TDS
550
300
650
240
700
260
220
500
7.
Chlorides
250(chl)
Nil
300(chl)
Nil
430(chl)
Nil
Nil
200
8.
Total
hardness
430
130
450
100
420
134.50
200
200
9.
E.coli
8per100ml
1per100ml
13per100ml
1per100ml
11per100ml
1per100ml
15
200
3.69
0.5per100ml
<20
1per100ml
RESULTS AND DISCUSSION
The study of physical and chemical
characteristics of water provides a clear idea about quality
of water present on the surface. (River, Lake, Ponds,
Oceans, Canals etc).
Some of the parameters tested are as follows:
pH Data presented in Table 1 shows variation of pH
at different sampling times the variation depends upon the
pollutant concentration of the raw water. pH in raw water
was varying from 6.0-6.25 and after RO treatment it is

Lamma OA et al. / Journal of Pharmaceutical Biology, 5(2), 2015, 108-112.
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found that the pH value is between 7.8-8.0 which is in
permissible limit.
Turbidity
Turbidity at different sampling times the
variation depends upon concentration of color causing
agents of the raw water. Turbidity in raw water was
varying from 55-60 and after RO treatment it is found that
the it is between 2.5-2.8which is in permissible limit.
Biological oxygen demand (BOD)
BOD at different sampling times the variation
depends upon the pollutant concentration and oxygen
availability of the raw water. BOD in raw water was
varying from 10.24-13.25 and after RO treatment it is
found that the BOD value is 2.8 which is in permissible
limit (1).
Chemical oxygen demand (COD)
COD variation depends upon the chemical
concentration of the raw water. COD in raw water was
30.5-36 and after RO treatment it is found that the COD
value is less than 7.4 which is in permissible limit (1).
Total suspended solids (TSS)
pH at different sampling times the variation
depends upon the pollutant concentration of the raw
water. TSS in raw water was varying from 1050-1400 and
after RO treatment it is found that the TSS value is less
than 400 which is in permissible limit.
TDS (Total dissolved solids)
TDS at different sampling times the variation
depends upon the pollutant concentration of the raw
water. TDS in raw water was up to 700 and after RO
treatment it is found to be less than 500 which is in
permissible limit.
Chlorides
Chloride should be removed from raw water
before enter in to the system by adding chlorides and anti
scalents because membranes are sensitive to chlorine.
Total Hardness
After RO treatment the values are reduced from
100-150 which is in permissible limits.
E.COLI After RO treatment the values are reduced from
12 per 100 ml _<1 per 100 ml,which is in permissible
limits The water quality is directly relate to health,
various chemicals releasing from the industries and
release from the domestic waste. I have examined some
parameters of raw water whose values are much more
than the permissible limit which causes diseases on
continuous exposure to untreated water. So that the
purification is necessary for raw water. By passing
through Ro plant the out-put water from the plant may
have the values with in permissible limit given by WHO,
so it is suitable for drinking.
The procedure of RO plant is well suited for
purification of raw water collected from the different
locations. The product water is free from the nutrients,
metal ions and bacteriological impurities. Some of the
important precautions taken during the storage of water is
to prevent from the bacterial attack and treated with
chlorine to disinfect that bacteria passes through the
membrane. The main disadvantage is the fouling of
membrane so is to prevent from fouling it requires
pretreatment of feed.
The present study on purification of raw water
by reverse osmosis plant in chemical laboratories has
been carried out at different locations surrounding located
at Vijayawada. Natural water bodies such as lakes,
ponds, streams, river and seas acquire microorganisms on
exposure to air. Water found in nature contains number
of impurities which are essential .Water should be free
from all objectionable matter. It is the best process for the
purification of the raw water. Reverse osmosis is a
process of flow of pure water from a dilute saline solution
through a membrane into a higher concentrated saline
solution is being forced under pressure through a semi
permeable membrane (7, 8, 9 and 10). The purification of
raw water is completed in three stages.1.Pretreatment 2.
RO treatment. 3. Post treatment. The product water from
the membrane assembly usually requires pH adjustment
and degasification before being transferred to the
distribution system for use as drinking water. In many
cases, this water is discharged to a storage cistern for later
use. The physical, chemical and microbiological
parameters are monitored.
CONCLUSION
It is well established that there is an evolving
lack of fresh water availability due to several reasons like
population blast, ground water depletion, climatic change,
global warming, etc. To meet this rising demand of
potable water, there is an ever-growing requirement of
novel, energy efficient, economically viable technologies
that would yield fresh water for domestic and industrial
consumption. Hence, Reverse osmosis technologies are
being worked upon all around the world to device an
efficient method to purify water for human consumption
.Pre-treatment of raw water is an absolute necessity
before sending in the feed for desalination into a RO
plant. Failing to do so exponentially reduces the
membrane, and hence, the plant life.The primary aim of
this entire process is to reduce the TS content of the water
as much as possible to make free from other
physicochemical parameters and potable for drinking.

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