Water reclamation system presentation.

China Steel Corporation India Private Limited
Water reclamation system
China steel corporation India Pvt
Ltd (Taiwan)
Prepared & Presented by : Jaypalsinh Boradhara
Dept- W22
EMPLOYEE CODE :
Y00550
DECEMBER-2016

1. Schematic diagram of Utility water complex.
2. Water reclamation system AIM & Cost Calculation chart.
3. Schematic diagram of water reclamation system.
4. Fiber filtration operation, monitoring & cleaning.
5. Ozonation process.
6. BAC Filtration process.
7. Ultra filtration operation, monitoring & cleaning.
8. Reverse Osmosis operation, monitoring & cleaning.
9. How to reduce the costs of RO water treatment.
10.Q & A
Presentation outline

H2
STATION
UTILITY SCHEMATIC DIAGRAM
G.I.D.C
WATER
INTAKE
N2 & O2
STATION
#100
AREA TW
SUPPLY
SYSTEM
UTILITY
CONTROL
ROOM
#400 AREA
DMW SUPPLY
SYSTEM
#800 AREA PA
SUPPLY
SYSTEM
#700 AREA WASTE WATER
TREATMENT SYSTEM
NG STATION
G.I.D.C EFFLUENT LINE

WATER RECLAMATION SYSTEM AIM…
What is role of water reclamation system and how it affect
to our system ?

RAW WATER COST CALCULATION
1. Raw water intake limit is 1680 CMD
2. Raw water charges – Rs28.99/m3 & revision once in every year.
Example : (i) September month RW consumption : 16228 m3/month
So if we calculate Raw water cost = (Raw water consumption) * (28.99)
= (16228) * (28.99)
= 4,70,450 INR.

RAW WATER COST CALCULATION
January 10914 5372
February 7927 4323
March 12427 4631
April 12139 4833
May 9703 5717
June 16239 6545
July 11127 5362
August 14616 6777
September 16228 5561
October 16079 4681
November 19130 3050
Total 146529 56852
Month-
2016
Raw water
consumption
RO water
7927
12427 12139
9703
16239
11127
14616
1622816079
4323 4631 4833
5717
6545
5362
6777
5561
4681
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
February March April May June July August
Raw water vs. product water
Raw water consumption RO water

G.I.D.C DRAINAGE (W/W)COST CALCULATION
1. Maximum discharge limit : 265 CMD
2. Drainage charge : 8.80/m3. Rate revision once in every year
(i) Example : September month Raw consumption = 16228 m3.
So if we calculate drainage cost = (RW consumption ) * (8.80)
= (16228) *(8.80)
= 1,42,806 INR.

SCHEMATIC DIAGRAM OF WATER
RECLAMATION SYSTEM
1st.
REACTION
TANK
SAND FILTER
OZONE FEED
TANK 1st. BAC
TANK
UF FEED
TANK
2nd. BAC
TANK
CONCENTRATE
TANK
GAC FILTER
RO FEED
TANK
RO SYSTEM
RO TANK
DISINFECTION
TANK
TREATED
W/W TANK
P-7R23A/B
RW BUFFER TANK
RO CIP
TANK
INHIBTOR
W/W TANK
FIBER
FILTER
FIRE WATER
POND
TW RESERVOIR
UF CIP TANK
NaOCl
NaOH
BIOCIDE SBS
UF SYSTEM
OZONE
GENERATOR
2nd.
REACTION
TANK
CAPACITY : 1000CMD
RECOVERY RATE : 76% (DESIGN)
AREA : 1440m2

FILTRATION SPECTRUM

FIBER FILTRATION OPERATION
 The fiber filter is a type of “pressure” cum
“gravity” type filtration equipment using soft
wadding and bundled fiber as filtration
materials with very small diameter (several
micrometers).
 The filtration material is made of long strand
PP (Polypropylene) fiber which is resistance to
certain acids and alkaline and are highly
absorbent. The density of the filtration
material is adjusted by the incoming water
pressure (level) to be filtered.
 Suspended solids with 2µm-diameter and
above can be intercepted & finally removed

FIBER FILTRATION PROCESS
The filters retain aqueous suspended solids besides
organic substances, colloid, iron, manganese and other
pollutants with high effectiveness.
Iron and colloid particles are not removed by
conventional sand filters but are removed effectively by
fiber filters.
The fibers have good absorbing quality for oils and
washing the fibers with oil removal will regain the
absorbability of the fibers

• Filtering: The adjustable plate is driven down by water inlet,
squeezing the fibers downwards to achieve filtration
effectiveness. The height of the adjustable plate will meet the
required accuracy of filtration. Fiber filter removes almost 10%
of suspended solid & mainly for oil & grease contents.
FIBER FILTRER OPERATION
(FILTRATION-BACKWASH-RINSING

• Backwash: Filter water and air enters from the bottom due to which
the adjustable plate floats up and loosen the fibers. The air bubbles
prevents the fibers to rub against each other to reach the scouring
(cleaning) effect. Water enters from the bottom again after
backwash, to push the remaining air out.
• Water Cleaning (Rinsing): Water enters from the top and goes out
from the bottom, squeezing the fibers and removing the solid
particles sticked to the fiber surface.
(FILTRATION-BACKWASH-RINSING

(FILTRATION-BACKWASH(WATER & AIR)-RINSING
Operation mode Backwash mode
V1-Feed water inlet
V2-Filter water outlet
V3- Backwash water inlet
V4- Backwash water outlet
V5-Water rinse valve
V6- Air release valve
V7-Air inlet Valve
V8- Normally open during
Filtration & Closed during
backwash process.

OPERATIONAL CONTROLS & BACKWASH STEPS
V1 V2 V3 V4 V5 V6 V7 V8 FeedPunp B/Wpump Blower
1 Filtration ● ● ● ●
2 Lowerlevel ● ●
3 Firstrinse ● ● ● ● ● ●
4 B.W-1 ● ● ● ● ● ●
5 B.W-2 ● ● ● ● ●
6 Circulation
7 Finalrinse ● ● ● ● ● ●
8 Exhaust ● ● ● ●
9 Fastrinse ● ● ● ●
90Sec
30Sec
60Sec
SR.No
Backwash
120sec
60Sec
60Sec
60Sec
2(times)
Steps
Time
duration(Sec)
Description
240Min

CHEMICAL CLEANING OF FIBER FILTER
Prepare 2000 ppm(0.2%) in 2m3 chemical solution of
NaOCl for biological cleaning.
 Take a regular backwash before chemical cleaning.
Soak for 60-90 minutes.
backwash with water & blower air to wash chemical .
Final rinse & let system stable and observed water
quality.

 The Ozone Generator is a device that produces
ozone gas using electrical discharge. A high
voltage with high frequency is applied between
two electrodes to produce a discharge space.
Oxygen gas and air is then passed through the
space and some of the oxygen is converted to
ozone.
 The waste water after processing from the fiber
filter and the concentrate (reject) water from RO
will undergo ozone reaction to reduce the COD
and to perform the chain scission degradation of
the hardly biodegradable organics.
 Capacity: 4 kg-O3/hour( dosing concentration as
required. Max doing 50 ppm )
OZONE GENERATION SYSTEM

OZONE GENERATION SYSTEM

OZONE GENERATION SYSTEM PLC

ADVANTAGES & DISADVANTAGES OF OZONE
Advantages:
 Purifies the water and has a very strong oxidizing power with a short reaction time.
 To get rid of mold and fungus. It is effective over a wide pH range and rapidly reacts
with bacteria, viruses, and protozoans.
 To clean and purify the air. The treatment process does not add chemicals to the water.
 Cleanse and sterilize cuts and wounds. Ozone can eliminate a wide variety of inorganic,
organic and microbiological problems and taste and odor problems.
Disadvantages:
 Ozonation provides no germicidal or disinfection residual to inhibit or prevent regrowth.
 The system may require pre-treatment for hardness reduction or the additional of
polyphosphate to prevent the formation of carbonate scale.
 Potential fire hazards and toxicity issues associated with ozone generation.

BAC FILTRATION PROCESS
 Biological filters remove contaminants by three main
mechanisms: biodegradation, adsorption of micro pollutants, and
filtration of suspended solids. The microbial growth attached to
the filter media (biofilm) consumes the organic matter that would
otherwise flow through the treatment plant and ultimately into
the distribution system.
 BAC system uses activated carbons to adsorb the organic
materials in the water. In the meantime, microorganisms at the
surface of activated carbons can also degrade the organic
materials and reduce COD to extend the cycle life of activated
carbons.

BAC FILTER OPERATION CONTROLS &
BACKWASH STEPS
V1 V2 V3 V4 V5 V6 Blower FeedPump
1 Filtration ● ● ●
2 Settledown ●
3 AIRB.W ● ●
5 Exhaust ●
6 Rinse ● ●
6 Wait ●
B/WPump
Description
Backwash
SR.No Steps
Time
duration
72hours
45Sec
200Sec
150Sec
240Sec
120Sec
●

ULTRAFILTRATION
 Ultrafiltration (UF) is a pressure driven purification process that separates
particulate matter from soluble components. Membrane reject particulates
that are 0.01 microns and larger facilitating high removal capacity for
bacteria, viruses, colloids, silt and more

WHAT IS A MEMBRANE
Thin barrier or film of material that allow certain
substances to pass through while rejecting other
substances.

FILTRATION SPECTRUM
Ultrafiltration do not remove any dissolved salt, dissolved
organic or other species like true color & taste, odor

ULTRAFILTRATION MEMBRANE

• The model no. of the UF membrane that is used in our water
reclamation system is DOW’s IW74-1100. (PVDF hollow fiber
membranes).
• In our system, it has 2 skids of 11 nos. (total of 22 nos.) of
membrane in each skid with flow rate of 25 CMH per skid.
• 74 m2 of filtration area in a short module format.
• 0.03 µm pore size which enables removal of bacteria up to 6 log,
removal of viruses up to 2.5 log and < 2.5 SDI (Silt Deposition
Index) filtrate quality.
• PVDF fibers free of macro voids which offers excellent break
resistance, chemical and fouling resistance.
• Outside-In flow configuration which allows higher TSS feed water
while producing high quality filtrate.
• It is an ideal choice for containerized system designs where its
large filtration area and short height.
UF MEMBRANE FEATURES

Chemistry ( PVDF, PAN, PES, PP, etc.)
Operating Mode ( Cross-flow, dead end)
Pressurized vs. Submerged
Flow Configuration (Inside-out, Outside-
in)
Pore Size
Fiber Orientation
Backwash (Air, Water, Both)
ULTRAFILTRATION FUNDAMENTAL

UF MEMBRANE CHEMISTRY
Polyvinylidene Fluoride (PVDF) Fibers maintain their strength under
continuous harsh chemical cleaning conditions, better than any
other membrane material.
Chemical formula : (C2H2F2)n

OPERATING MODE
In dead-end filtration, fluid flow
is perpendicular to the filter
surface
• High collection rate (almost 100%)
• Low cost
Advantages:
Disadvantages:
• Filters must be replaced often
Cannot be used if large amounts of insoluble materials are present

OPERATING MODE
 Entire Flow Passes Through
Membrane
 Filter Cake Builds Up
 Requires Periodic
Backwashing
 Fairly Good Quality Feeds
 Simple Operation
 Good Recovery >95%
 No Concentration of Feed
Stream

In cross flow filtration, fluid flows parallel to the filter
surface and particles become more concentrated as
filtrate leaves through the filter's pores

Pressurized vs. Submerged
Pressurized Hollow fiber modules where water is
forced either into or out of the lumen under pressure

Hollow fiber configurations where water
is pulled into the fiber lumen by suction
Submerged (or Immersed)
 Usually for larger WTPs
 Higher Capacity Trains
 Lower Pressure Range

Flow Configuration (inside-out, outside-in)
Inside out
Outside in

UF MEMBRANE PRODUCT SPECIFICATION
Expected Filtrate Turbidity
Expected Filtrate SDI
≤ 0.1 NTU
≤ 2.5
Maximum Operating TMP 2.1 bar
Maximum Inlet module pressure 5.0 bar
Maximum Particle Size 300 μm
Confugration(Fluid flow)
Base Polymer
Nominal pore diameter
Hollow fibre ID
pH
NaoCl cleaning mixture
2to 11
2000 ppm
Fiber Physical Properties
Operating Ranges
Typical filtrate flux at 25ºC 40-90L/m2/h
Temperature range 1-40ºC
Hollow fibre OD
Hollow fibre (outside in
H-PVDF
0.03 micron
0.70 mm
1.30 mm

ULTRAFILTRATION TERMS
 Recovery : Ratio of filtrate flow to feed flow [%].
 TMP : Trans Membrane Pressure. The pressure that is needed to
press water through a membrane is called Trans Membrane
Pressure (TMP).
TMP = Filtrate water pressure(bar) – Feed water pressure(bar)
TMP increases as membrane fouls.
Maximum Operating TMP 2.1 bar.
 SDI : Silt Density Index. SDI is measure for the fouling capacity of
water.
 Flux : Permeate Flow Divided by Membrane Area, [l/m2/h or gfd]
Flux means that quantity of gallons of water is passing through
each square foot of each membrane per day
 CEB & CIP : Chemical enhanced backwash & Clean in Place

ULTRAFILTRATION TERMS
 Clean-in-place (CIP) is a method of cleaning the interior surfaces of
pipes, vessels, process equipment, filters and associated fittings,
without disassembly.
 Osmotic pressure : Osmotic pressure is the minimum pressure which
needs to be applied to a solution to prevent the inward flow of water
across a semipermeable membrane
 Net driving pressure(NDP) :The net driving pressure refers to the
difference between the feed pressure and the osmotic pressure. The
net driving pressure is the measure of the actual driving pressure
available to force the water through the membrane. As net driving
pressure increases, the flux increases proportionally (given all other
factors are held constant).

OPERATIONAL CONTROLS & BACKWASH & CEB
STEPS
V1
From 1st BAC Tank
(Feed water)
Backwash
water out
Backwash
air inV3
Process Flow
V2
Product
water
Backwash
water in
V5
V4 Up backwash &
reject water
V6

OPERATIONAL CONTROLS & BACKWASH & CEB
STEPS
V1 V2 V3 V4 V5 V6
NaoCl
Pump
NaOH
pump
B/Wpump
1 Filtration ● ●
2 AIRB.W ● ● ●
3 UpB.W ● ● ● ● ●
4 DownB.W ● ● ● ● ●
5 Wait(CEB)
6 UpB.W(CEB) ● ● ●
7 DownB.W(CEB) ● ● ●
8 Rinse ● ●15Sec
40min. ●
●
15Sec
20Sec
300Sec
40Sec
15Sec
SR.No Steps
Time
duration
Description
Feed
Pump
20Sec

CEB (Chemically Enhanced Backwash):
 When the nos. of backwash are up to 30, the 31st
time will conduct CEB in auto process.CEB is online
process.
Alkali:
NaOH @ 250 ppm & NaOCl @ 500 ppm.
Frequency is typically every 16 – 20 hours or when
necessary.
Removes organics and boifoulants from membrane.
Residual Chemical is removed with Back Wash step.

TOP BACKWASH & CIP

BOTTOM BACKWASH & CIP

When to Clean UF Membrane
Feed water flow decrease to 20% to 25%
When TMP exceeds 1.0 bar above starting TMP (at
same temperature)

WHY to Clean UF Membrane
For best efficiency of cleaning procedure, elements
must be cleaned before fouling has fully developed. If
cleaning is postponed for too long it will be difficult or
impossible to completely remove foulants from
membrane surface and to re-establish full
performance
Fouling is “the most common” problem in
Ultrafiltration process

FOULING
 Plugging of the membrane surface by feed water
suspended substances and sticky polymeric
precipitated.
 The surface of Ultrafiltration (UF) membranes is
subject to fouling by foreign materials that may
be present in the feed water, such as suspended
solids, colloids, organics and biological matter. The
term “fouling” includes the build-up of various kinds
of layers on the membrane surface.

FOULING
 There are four types of fouling common to UF operations
including particulate, biological, inorganic, and organic.
Particulate fouling is caused by suspended solids, colloids, and
turbidity that can be reduced by coagulation, The common
cleaning method for particulate fouling is air scour and backwash.

FOULING
Biological fouling is caused by the growth of microorganisms
that can be reduced by using in-line chemical feed of chlorine or
biocide or by elimination of nutrients by using PAC, GAC,BAC
filtration. The common cleaning method for removal of biological
fouling is Chemically Enhanced Backwash (CEB) with oxidizers or
biocides (Cl2, H2O2, SBS).

FOULING
 Inorganic fouling is caused by the precipitation of
inorganics on the membrane that can be reduced by using
oxidation/precipitation and filtration as pretreatment to the
UF or in some cases using low hardness water for the alkali
chemically enhanced backwash. The common cleaning
method for removal of inorganic fouling is chemically
enhanced backwash with acid at pH 2 (HCl, H2SO4, Citric,
Oxalic Acid)

FOULING
Organic fouling is caused by organics adsorbing on the
membrane (silt, organic acids, humus) that can be
reduced by using PAC, GAC, or coagulation. The common
cleaning method for removal of organic fouling is CEB
with alkali at pH 12 (NaOH).

Summary of Cleaning Process
Acid:
• HCl, H2SO4@ 2000ppm
• Oxalic acid or Citric acid @ 2%
• Target pH: 2 to 2.5
Alkali:
• NaOH @ 1000 ppm
• NaOCl @ 2000 ppm
• Target pH :11.5 – 12
• Alkali CIP step is done at first and then acid ( If required)
• CIP to remove the biomass particles initially by alkali.

Summary of Cleaning Process

UF CIP PROCEDURE
• Make-up cleaning solution:.
• Regular Backwash, pre-CIP: Conduct a regular backwash of the UF
skid to remove loose contaminates prior to the CIP. (3-5 times before
starting CIP)
• Drain Out water in UF skid: Residual water in UF skid will dilute the
concentration of cleaning solution.
• Low flow pumping : Pump cleaning solution through the feed side of
the UF modules at conditions of low flow rate.
• Recycle: Recycle the solution at recommended flow for about 1 – 1.5
hrs.
• Soak: Typically 2 hrs. (Means to hold the chemical inside the system)
• Flush Out: RO permeate preferred to prevent reaction of impurities in
the flush out water with the remaining solution.
• Regular backwash after 30 mins of circulation, post CIP.

UF CIP TIPS
• Often it is required a two step cleaning process, alkaline
cleaning followed by acidic cleaning. Acid cleaning must
only be done if it is known that only calcium carbonate or
iron is present on membrane surface.
• If the pH varies more than 1 pH units during cleaning,
add more chemical.
• Inspect the appearance of the CIP solution at various
points during the recycle and soak steps.
• Fresh cleaning solution must be prepared when the
solution becomes turbid.
• Air supply must be given in between during soaking to
benefit the cleaning effectiveness.

OPERATING LIMITS

Reverse Osmosis is a technology that is used to
remove a large majority of contaminants from water by
pushing the water under pressure through a semi--
‐permeable membrane.
BASICS OF REVERSE OSMOSIS

 Osmotic pressure is the minimum pressure which
needs to be applied to a solution to prevent the inward
flow of water across a semi permeable membrane. It is
also defined as the measure of the tendency of a solution
to take in water by osmosis.
Examples of osmosis are when plant roots absorb
water from the soil and our kidneys absorb water from
our blood.
Osmotic Pressure

Osmotic Pressure –Thumb rule
• Convert TDS to Osmotic Pressure:
 TDS in ppm divided by 100: Osmotic Pressure in PSI
 TDS in ppm divided by 1400: Osmotic Pressure in Bar
 Examples:
 100 ppm TDS = 1 PSI Osmotic Pressure = 0.07 bar
 1000 ppm TDS = 10 PSI Osmotic Pressure = 0.7 bar
 35000 ppm TDS = 350 PSI Osmotic Pressure = 25 bar
TDS = 0.67 * Conductivity

Reverse Osmosis principles
Application of pressure greater than osmotic pressure
of solution
Operated in cross flow mode to sweep away
concentrated salts

How does Reverse Osmosis work?
Reverse osmosis works by using a high pressure
pump to increase the pressure on the salt side of
the RO and force the water across the semi
permeable RO membrane, leaving almost all
(around 95% to 99%) of dissolved salts behind in
the reject stream. The amount of pressure required
depends on the salt concentration of the feed
water. The more concentrated the feed water, the
more pressure is required to overcome the osmotic
pressure.

How does Reverse Osmosis work?
In very simple terms, feed water is pumped into a
Reverse Osmosis (RO) system and you end up with
two types of water coming out of the RO system:
good water and bad water. The good water that
comes out of an RO system has the majority of
contaminants removed and is called permeate.
Another term for permeate water is product water
The ‘bad’ water is the water that contains all of the
contaminants that were unable to pass through
the RO membrane and is known as the
concentrate, reject, or brine.

Reverse Osmosis Membrane
Model no : BW-30XFR-400/34i (Polyamide Thin-Film Composite).
Brackish water Active area(ft2)
37 (m2)
Feed spacer thickness(mil)
In our system, it has 3 skids of 24 nos. of membrane in each skid
(total 72 nos.) with feed flow rate of 25 CMH per skid.
34 mil feed spacer to reduce the impact of fouling and enhance
cleaning effectiveness.
Design feed water conductivity is 3500 µs/cm for 75 % of
recovery ratio & max allowable feed water conductivity is <6000.
µs/cm.

Reverse Osmosis operating range
Description Range
Maximum operating temperature 45◦C
Maximum operating Pressure 41 bar
Maximum element pressure drop 1.0 bar
pH range continues range 2 to 11
pH range short term chemical range 1 to 13
Maximum feed SDI SDI 5
Feed chlorine tolerance <0.1 ppm
Chemical Name
Chemical dosage
concentration
Dosage
ppm
Dosing
m3/hr
Biocide 100% 5 ppm 0.0006
Inhibitor 20% 5 ppm 0.0006
SMBS 20% 5 ppm 0.0006
Chemical dosing in feed water

Reverse Osmosis Performance & Design
Calculations
 There are a handful of calculations that are used to judge
the performance of an RO system and also for design
considerations.
1. Feed pressure (bar)
2. Permeate pressure (bar)
3. Concentrate pressure (bar)
4. Feed conductivity(µs/cm)
5. Permeate conductivity(µs/cm)
6. Feed flow(m3/hr)
7. Permeate flow(m3/hr)
8. Temperature(◦C)

Reverse Osmosis Performance
Salt rejection :This equation tells you how effective the RO
membranes are removing contaminants. A well--‐designed RO
system with properly functioning RO membranes will reject 95% to
99%of most feed water contaminants (that are of a certain size and
charge).
Salt Rejection % = Conductivity of Feed Water – Conductivity of Permeate Water x 100
Conductivity of Feed
The higher the salt rejection, the better the system is performing.
A low salt rejection can mean that the membranes require cleaning
or replacement.

Salt Passage % : This is simply the inverse of salt rejection
described in the previous equation. This is the amount of salts
expressed as a percentage that are passing through the RO system.
The lower the salt passage, the better the system is performing. A
high salt passage can mean that the membranes require cleaning or
replacement.
Salt Passage % = (1-Salt Rejection%)

Recovery % : Percent Recovery is the amount of water that is
being ‘recovered’ as good permeate water. Another way to think of
Percent Recovery is the amount of water that is not sent to drain as
concentrate, but rather collected as permeate or product water. The
higher the recovery % means that you are sending less water to
drain as concentrate and saving more permeate water. However, if
the recovery % is too high for the RO design then it can lead to larger
problems due to scaling and fouling.
% Recovery = Permeate Flow Rate (m3/hr) x 100
Feed Flow Rate (m3/hr)

Concentration Factor : The concentration factor is related to
the RO system recovery and is an important equation for RO system
design. The more water you recover as permeate (the higher the %
recovery), the more concentrated salts and contaminants you collect
in the concentrate stream. This can lead to higher potential for
scaling on the surface of the RO membrane when the concentration
factor is too high for the system design and feed water composition.
Concentration Factor = (1 / (1-Recovery %)
Example : A concentration factor of 4 means that the water going
to the concentrate stream will be 4 times more concentrated than the
feed water is. If the feed water in this example was 500 ppm, then the
concentrate stream would be 500 x 4 = 2,000 ppm.

 Flux : Permeate Flow Divided by Membrane Area, [l/m2/h or
gfd] Flux means that quantity of liter of water is passing through
each square meter of each membrane per hour
Flux (l/m2/hr) : Permeate Flow
Membrane Area
This number could be good or bad depending on the type of feed
water chemistry and system design.

Summary of the parameters influencing RO
performance:

Understanding the difference between passes and stages
in a Reverse Osmosis (RO) system
In a one stage RO system, the feed water enters the RO system
as one stream and exits the RO as either concentrate or permeate
water.
 In a two‐stage system the concentrate (or reject) from the first
stage then becomes the feed water to the second stage. The
permeate water is collected from the first stage is combined with
permeate water
from the second stage. Additional stages increase the recovery
from the system.

Cross-section of Thin Film Composite
Membrane

Reverse Osmosis membrane

Reverse Osmosis skid

FOULING
 Plugging of the membrane surface and/ or
feed spacer by feed water suspended
substances and sticky polymeric precipitates.

Biofouling Occurs due to
High bio growth potential in
feed water
 Improper operation and
procedures
Dead legs in system
Typical: ΔP increase of front
elements
FOULING

Organic Fouling
Natural organic matter in the
feed water
 humic substances
 Polluted raw water
 Oil, grease
Polyelectrolytes in
flocculation/coagulation pre-
treatment
 Scaling inhibitors
 Flocculation aids
FOULING

FOULING
Water flux (gfd or l/m2/hr)
Cross flow (gpm or m3/hr)
 Fouling rate controlled by
 Membrane fouling commonly caused by ineffective
or defective pre- treatment.

Water Flux
gfd(S.I unit)
Gallons of permeate per square foot of
membrane per day
l/m2/hr(metric unit)
Litters of permeate per square meter of
membrane per hour

Water Flux
2.00 m3/hr 1.96 m3/hr 1.92 m3/hr 1.88m3/hr 1.85m3/hr 1.82 m3/hr
18.25m3/hr 11.43m3/hr
6.25m3/hr

Cross flow

Feed water
Reject water
Permeate water
Bio Fouling
Fouling
organic Fouling

SCALING
Precipitation of dissolved feed water substances
due to concentration within an RO unit above
their saturation limit.

Starts in tail end of the
system
Caused by:
 Raw water changes
 Improper dosage of
scaling inhibitor
 Too high recovery
SCALING

Feed water
Reject water
Permeate water
SCALING
Scaling
organic Fouling

Mechanical Damages
Telescoping : Axial displacement of the scroll by high
pressure differential feed-concentrate caused by
Water hammer
High feed flow rate
Feed channel plugging
Missing thrust rings

Chemical Damages
From Chemicals
• in feed water
• in cleaning solutions
• in disinfecting solutions
• in preservation solutions
Oxidation of the barrier
layer by
• free chlorine, ozone
• other oxidizing agents
Strong acids (pH<1)
Strong alkaline (pH>13)
Solvents

When to Clean
1.Normalized permeate flow drops 10-15 %
NPF measures that amount of permeate water that RO is producing. If the
NPF drops 10 to 15% below the base line value (NPF reading at start up with
new membrane were replaced or cleaned) then this indication fouling or
scaling of the RO membrane and the RO membrane should be cleaned.
 If NPF increases then this implies that there is damage to RO membrane. This
damage can be caused by chemical attack (from oxidizer or a mechanical issue
like O-ring failure) on the membrane.

Normalized permeate flow
2.Pressure drop across any stage increases 15% to 25%
3.Normalized salt passage increases 5% to 10%

Foulants
 Microorganism
Solubility
pH
Dissolved
Precipitated
 Can be removed by caustic & detergents

 Silica
Solubility
pH
Foulants

Foulants Removal
Right Cleaner
High temperature
Optimum Flow rate

Scaling
Cations + Anions
Calcium(ca+2) + Carbonate(co3
-2)
CaCO3
 The most common scale is calcium carbonate & easy
to remove
ca+2 co2
 Can be removed by hydrochloric acid, or citric acid

Scaling
Cations + Anions
Calcium(ca+2) + Sulfate(so4
-2)
CaSO4
ca+2 so4
-2
 Can be removed by citric acid

Scalant Removal
Right Cleaner
High temperature
Time

Temperature
Every 10◦C increase in temperature
chemical reaction rates double
Find out limit of your membrane
elements your membrane manufacturing
45◦C 35◦C 25◦C
Element
Type
pH pH pH
A,B,C 1 to 10.5 1 to12 1 to 13
X,Y,Z 3 to 10 1 to11 1 to12

Clean in Place basic steps
Mix chemical solution
Low pumping flow
Recycle or Circulation
Soak
Flush out
Use permeate water during CIP process

Clean in Place (CSCI)
1. Before CIP make sure that Skid put in local mode and close feed water
valves and close RO permeate valve.
2. RO Skid flush with RO water or TW water
3. Chemical cleaning with NaOH(1000 ppm), in 2 m3 volume, pH range 11.0
to 11.5 , required temperature 35◦C. Recycle for 1 hour. Follow this step
3 times.
4. Keep Ro skid for soaking for 2 to 4 hours. Long time soaking give better
result.
5. Chemical cleaning with NaOH, pH range 11.0 to 11.5 , required
temperature 35◦C. Recycle four 1 hour.
6. Flush RO skid with RO water or TW water.
7. Chemical cleaning with HCl(2000),2 m3 volume & pH range 2.0 to 2.5 ,
required temperature 35 ◦C and recycle four 30 mins to 1 hour.
8. Flush RO skid with RO water or TW water, until flushing water pH is
between 7 to 8.
9. After CIP finish closed both stage CIP calve & open service valve

Clean in Place effectiveness
Determined after 24 to
48 hours of operation
Normalized permeate
flow return to new or near
new performance
Pressure drop return to
new or near new
performance

How to care RO membrane in shut down
1. < 48 hours permeate or good quality feed water
2. > 48 hours 1.0% sodium bisulfite replace solution.
Note :
(1)As microorganism can grow within pH range 6 to 8. So to prevent
RO membrane from microorganism growth inside skid, skid
solution need to be pH between 1 to 2
(2) As chlorine, oxygen, ozone(oxidizing agent) can oxidize
membrane and damage so to prevent against such oxidizing
agent skid solution is maintain with 1.0 % sodium bisulfate
(pH<3)

How to reduce the cost of RO water
treatment
Cost saving categories
1. People : People are greatest recourse , likely know where cost
reductions can be found. Well trained and proficient people. Use
them to identify cost reduction opportunities
2. Water & Waste water minimization :
 Recycle
 Reuse
 Concentrate
3. Design : Poor design can cost money
 inadequate RO pre-treatment( particulate fouling)
 Under design media filter ( in other words loading rates to
high)
 High fouling RO unit design

How to reduce the cost of RO water
treatment
4. Operation : (a)Over capacity – intermittent operation
(b) Variable flow rates
Example : Change water flux rate, change cross
flow rate , due to that increase fouling /scaling
(c) Element placement
5. Effective chemical cleaning : Example chemical cleaning
problem
 Waiting too long to clean
 Inadequate cleaning pump
 Not cleaning back to new /near new performance

6. Power : Power is frequently the higher cost for RO water
treatment & power cost can very with time of day. Typically
more expensive during normal working hours
Power cost reduction
(1) Energy Cost = Total KWH*Energy Charge(4.3Rs/KWH)
= 1,821,300*4.3 = 7,831,590 Rs.
(2) Night Hour Rebate = Night Hour KWH*0.4Rs/KWH
= -585,480*0.4 = -234,192 Rs.
(3) Total Energy Cost = Energy Cost(1)+Night Rebate(2)
= 7,831,590-234,192 = 7,597,398 Rs.
(4) Pick Hour Charge = Pick Hour KWH*0.85Rs/KWH
= 604,560*0.85 = 513,876 Rs.
(5) Fuel Charge = Total KWH*1.63Rs/KWH (Review Quarterly)
= 1,821,300*1.63 = 2,968,719 Rs.

Category Time Period Tariff
Peak Hour 7 AM to 11 AM,
6 PM to 10 PM
+0.85 Rs./KWH (Extra)
Normal
Hour
6 AM to 7 AM,
11AM to 6 PM
Night Hour 10 PM to 6 AM -0.40 Rs./KWH (Rebate)
Time Per Unit Cost Remark
From To Rs.
12 AM 6 AM 5.53 Night Hour
6 AM 7 AM 5.93
7 AM 11 AM 6.78 Pick Hour
11 AM 6 PM 5.93
6 PM 10 PM 6.78 Pick Hour
10 PM 12 AM 5.53 Night Hour
Tabel-1 Different Time Period Different Rate
Tabel-2 Time Period wise Per Unit Cost
• Note:
• Try to reduce Peak hour consumption,
it will save 0.85 Rs./KWH
• Try to increase Night hour
consumption, it will save 0.40
Rs./KWH
• Try to shift Peak hour consumption to
Night hour consumption, it will save
1.25Rs./KWH
Power cost reduction

How to reduce the cost of water
treatment
7. Optimum usage of dosing Chemical : Example
Sulfite : Underfeeding sulfite will cause membrane damage
Overfeeding sulfite can cause increase bio fouling
Scale inhibitor : If scale inhibitor is being pumped above
the design dosage it means increased cost. It takes really
understanding the feed water and good controlled
operation to minimize SI dosage.

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