RO Recordkeeping and Normalization

Steven Coker

Topics

RO basic system design

RO operating data recording

Factors influencing RO system

performance

RO operating data normalization

FTNORM an easy method for

conducting normalization

calculations

2

Performance Monitoring

To track performance of RO system trends

To decide when to clean

To decide when to replace membranes

Useful information in troubleshooting

Required in event of warranty claim

3

Why?

Performance Monitoring

Record operating data

Manually on log sheet

Automatically in SCADA system

Normalize data to account for variation in feed water

pressure, temperature, concentration and recovery

Graph salt passage, product flow and DP vs. time

4

How?

Basic RO System Design

5

Pump

Concentrate

Feed

Water Permeate

RO Array

Temperature, C

Conductivity, S/cm

Flow Rate, gpm

Pressure, psig Conductivity, S/cm

Flow Rate, gpm

Pressure, psig

Conductivity, S/cm

Flow Rate, gpm

Pressure, psig

Factors Influencing RO Performance

Increasing Permeate Salt

Flow Passage

Effective Pressure

Temperature

Recovery

Feed Salt Concentration

6

Data Normalization

7

Why Normalize?

Fluctuations in operating conditions cause permeate flow

and salt passage to change.

Performance changes due to membrane properties

might go undetected.

Normalization eliminates the effects of fluctuating

operating conditions and allows monitoring of the

membrane properties.

Example: Raw Data from RO system

8

90%

91%

92%

93%

94%

95%

96%

97%

98%

99%

100%

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

Reje

ctio

n (

%)

Tem

pera

ture

(

)

Date

RO operation performance

Temperature Permeate Conductivity

RO membrane properties virtually constant, but the observed performance is changed by the variation of temperature.

What is Data Normalization?

Normalization is a calculation method to express measured

membrane performance variables in terms of a set of reference

conditions.

This allows the user to determine whether observed changes in

membrane performance (flow and/or rejection) are normal

variation due to a change in operating conditions or may be an

indication of fouling, scaling, or damage to the membrane.

Typical Reference Conditions:

Stabilized start-up performance data

Computer model (ROSA) projected performance at standard

conditions or start-up performance conditions

9

Homogenous Solution Diffusion Model

10

Fw - solvent flux [gallons per square foot per day, gfd]

A - solvent mass transfer coefficient [gfd/psi]

TCF - temperature correcting factor

DP - transmembrane pressure differential [psi]

Dp - osmotic pressure differential [psi]

Water and Solute Flux

Fw = A * TCF * (DP - Dp)

Fs = B * TCF * (DC) Fs - solute flux [pounds per square foot per day, lbfd]

B - solute mass transfer coefficient [gfd]

DC - transmembrane concentration differential [lb/gal]

The effect of temperature and operating pressure on the membrane performance can be calculated to avoid interfering with the membrane property evalution.

TCF = exp{ Bm * [1/298.15 - 1/(Tf +273.15)]}

TCF temperature correction factor

Bm membrane TCF coefficient

Tf feed temperature, C

RO Permeate Flow Normalization

NDP = Pf Pfb Pp + p

NDP net driving pressure, psig

Pf feed pressure, psig

Pfb - feed brine differential pressure, psig

Pp - permeate pressure, psig

p - permeate osmotic pressure, psig

RO Permeate Flow Normalization

12

act

ref

act

refact norm

NDP

NDP

TCF

TCF Q Q

Q - flow rate, gpm

TCF - temperature correction factor

NDP net driving pressure, psig

norm - normalized

act actual measured variable

ref - reference condition

Increasing Permeate

Flow

Effective Pressure

Temperature

Recovery

Feed Salt Conc.

RO Normalized Salt Rejection

13

)TCF

TCF

Q

Q

c

c

c

c( - 1 100 (%) SR

act

ref

ref

act

act fc,

ref fc,

ref f,

act p,norm

cp - permeate salt concentration

cf - feed salt concentration

cfc - feed-concentrate salt concentration

Q - permeate flow rate

TCF - temperature correction factor

act - actual condition

ref - reference condition

norm - normalized

When should I clean my RO?

14

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Feed

Pre

ssu

re, p

sig

Days of Operation

Feed Pressure vs. Time

Feed Pressure

When should I clean my RO?

15

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Te

mp

era

ture

, C

Feed

Pre

ssu

re, p

sig

Days of Operation

Feed Pressure vs. Time

Feed Pressure Feed Temp (C)

16

100

150

200

250

300

350

400

0 50 100 150 200 250 300

Flo

w (

gp

m)

Operating Time (days)

Normalized Permeate Flow

FTNorm for RO Operation Data Normalization

FTNORM Data Normalization Program

Based on ASTM D 4516

Written as Excel spreadsheet

Data normalized to start-up conditions

Designed for manual data entry but can be incorporated into

SCADA system

Automatic graphing includes:

Normalized permeate flow

Pressure drop

Normalized salt rejection

Graphs of other variables can be easily added

18

FTNORM - 1 Stage Data Entry Section

19

Reverse Osmosis Plant

Operating Data Normalization

Plant Identification: Train 1 C

Start-Up Date: 5/1/14 0:00 Feed Conductivity / Feed TDS: 1.43446

Date

Permeate

Flow

Concentrate

Flow

Feed

Pressure

Concentrate

Pressure

Permeate

Pressure

Calculated

Feed TDS

Feed

Conductivity

Calculated

Perm TDS

Permeate

Conductivity

Feed

Temp (C)

1/5/14 14:00 297.4 379.1 55.1 54.12 3.7 35205 50500 582 1178 25.4

2/5/14 13:00 298.2 378.7 55.0 53.96 3.4 35414 50800 573 1161 25.5

3/5/14 22:00 296.6 378.3 55.0 54.00 3.5 35275 50600 564 1142 25.5

4/5/14 22:00 295.7 378.4 54.9 53.86 3.3 35344 50700 559 1133 25.3

5/5/14 13:00 297.7 378.6 55.1 54.12 3.6 35275 50600 557 1129 25.5

7/5/14 22:00 296.7 377.3 55.1 54.12 3.7 35344 50700 629 1270 25.3

8/5/14 22:00 297.4 378.6 55.1 54.16 4.3 34926 50100 643 1297 25.3

9/5/14 21:00 296.5 377.3 54.8 53.86 3.9 34787 49900 606 1224 25.3

10/5/14 21:00 297.0 377.7 54.7 53.71 4.0 34717 49800 593 1200 25.6

11/5/14 17:00 300.8 386.7 54.2 53.19 3.4 34577 49600 573 1161 25.7

12/5/14 21:00 296.4 376.9 54.7 53.75 3.9 34647 49700 575 1163 25.6

13/5/14 14:00 298.5 378.9 55.4 54.36 4.3 34577 49600 578 1170 25.9

14/5/14 13:00 296.4 377.3 54.9 53.86 4.1 34787 49900 578 1169 25.9

15/5/14 22:00 297.6 378.1 54.8 53.82 3.6 34717 49800 559 1133 25.4

16/5/14 18:00 297.4 378.8 55.0 54.06 4.0 34647 49700 556 1127 25.4

17/5/14 21:00 296.9 376.6 55.0 53.96 3.8 34856 50000 552 1118 25.3

18/5/14 16:00 296.2 376.4 54.7 53.71 3.7 34787 49900 552 1119 25.6

19/5/14 16:00 297.2 378.1 54.9 53.88 3.7 34856 50000 548 1110 25.6

22/5/14 21:00 297.0 376.3 55.0 54.02 3.9 35414 50800 605 1222 25.3

23/5/14 19:00 296.1 377.9 54.9 53.92 4.0 35205 50500 585 1183 25.3

24/5/14 13:00 296.4 380.0 55.1 53.96 4.0 35275 50600 575 1163 25.5

25/5/14 14:00 297.3 378.2 54.8 53.77 3.7 35344 50700 569 1152 25.5

26/5/14 16:00 297.6 378.5 55.2 54.22 4.0 35344 50700 561 1136 25.5

27/5/14 19:00 295.4 378.2 54.9 53.90 4.1 35275 50600 561 1137 25.3

28/5/14 17:00 297.1 378.6 55.3 54.26 3.9 35414 50800 555 1124 25.4

29/5/14 21:00 297.7 378.5 54.7 53.65 3.5 35344 50700 551 1117 25.3

30/5/14 13:00 297.3 378.6 54.9 53.92 3.9 35344 50700 551 1117 25.5

31/5/14 17:00 296.9 378.7 54.8 53.82 3.8 35344 50700 547 1109 25.4

FTNORM - 1 Stage Calculation Section

20

Reverse Osmosis Plant

Operating Data Normalization

Plant Identification: Train 1 C

Feed

Flow

Days of

Operation

Recovery

(%)

Differential

Pressure

Temperature

Correction

Factor

Calculated

Feed/Brine

Avg Conc

Feed/Brine

Osmotic

Pressure

Permeate

Osmotic

Pressure

Net Driving

Pressure

Normalized

Permeate

Flow

Normalized

Permeate

Salt Passage

Normalized

Permeate

Salt

Rejection

677 1 44% 0.99 1.012 46378 38.6 0.5 12.9 297 1.7% 98.3%

677 2 44% 1.03 1.015 46688 38.8 0.5 12.7 301 1.6% 98.4%

675 3 44% 0.99 1.015 46464 38.6 0.4 12.8 298 1.6% 98.4%

674 4 44% 1.01 1.009 46525 38.7 0.4 12.8 297 1.6% 98.4%

676 5 44% 1.01 1.015 46491 38.7 0.4 12.8 297 1.6% 98.4%

674 7 44% 0.99 1.009 46583 38.7 0.5 12.7 302 1.8% 98.2%

676 8 44% 0.97 1.009 46022 38.2 0.5 12.6 304 1.8% 98.2%

674 9 44% 0.91 1.009 45842 38.1 0.5 12.9 297 1.7% 98.3%

675 10 44% 1.02 1.018 45756 38.0 0.5 12.6 300 1.7% 98.3%

688 11 44% 1.03 1.021 45474 37.8 0.5 13.0 295 1.7% 98.3%

673 12 44% 0.98 1.018 45665 38.0 0.5 12.8 295 1.6% 98.4%

677 13 44% 1.03 1.027 45589 37.9 0.5 13.1 288 1.7% 98.3%

674 14 44% 1.01 1.027 45839 38.1 0.5 12.6 299 1.6% 98.4%

676 15 44% 1.01 1.012 45765 38.0 0.4 13.1 292 1.6% 98.4%

676 16 44% 0.97 1.012 45650 37.9 0.4 13.1 292 1.6% 98.4%

674 17 44% 1.01 1.009 45963 38.2 0.4 12.9 296 1.6% 98.4%

673 18 44% 1.02 1.018 45855 38.1 0.4 12.9 294 1.6% 98.4%

675 19 44% 1.01 1.018 45936 38.2 0.4 12.9 294 1.6% 98.4%

673 22 44% 0.99 1.009 46709 38.8 0.5 12.2 313 1.6% 98.4%

674 23 44% 1.01 1.009 46366 38.5 0.5 12.3 309 1.6% 98.4%

676 24 44% 1.11 1.015 46416 38.6 0.5 12.4 307 1.6% 98.4%

676 25 44% 1.02 1.015 46580 38.7 0.5 12.3 311 1.5% 98.5%

676 26 44% 0.99 1.015 46582 38.7 0.4 12.5 306 1.5% 98.5%

674 27 44% 0.97 1.009 46429 38.6 0.4 12.2 313 1.5% 98.5%

676 28 44% 1.03 1.012 46656 38.8 0.4 12.5 306 1.5% 98.5%

676 29 44% 1.02 1.009 46585 38.7 0.4 12.4 311 1.5% 98.5%

676 30 44% 1.01 1.015 46570 38.7 0.4 12.2 313 1.5% 98.5%

676 31 44% 0.99 1.012 46555 38.7 0.4 12.2 312 1.5% 98.5%

FTNORM 1 Stage

21

0

100

200

300

400

500

0 5 10 15 20 25 30 35

Perm

eate

Flo

w (

m3/h

r)

Operating Time (days)

Normalized Permeate Flow

FTNORM 1 Stage

22

95.0%

96.0%

97.0%

98.0%

99.0%

100.0%

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

0 5 10 15 20 25 30 35

Salt

Reje

cti

on

(%

)

Salt

Pas

sa

ge (

%)

Operating Time (days)

Normalized Salt Passage and Salt Rejection

Salt Passage Salt Rejection

FTNORM 1 Stage

23

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25 30 35

Pre

ssu

re (

bar)

Operating Time (days)

Differential Pressure

FTNORM available from the web:

Go to: www.dowwaterandprocess.com

Click on Answer Center and enter FTNORM in search field

Click on FTNORM System Data Normalization Download

Download and save FTNORM spreadsheet appropriate for your system

Follow instructions for setup and entering data into FTNORM

One-stage system:

US Units (gpm psig)

Metric Units (m3/hr bar)

Metric Units (m3/hr kg/cm2)

Two-stage system:

US Units (gpm psig)

Metric Units (m3/hr bar)

Metric Units (m3/hr kg/cm2)

Additional FTNORM features available from DWPS TS&D:

Three-stage systems

Permeate backpressure

Boost pumps

Energy recovery devices

Data entry macro

Normalized DP

Specific flux

http://www.dowwaterandprocess.com/

Conclusions

Track the performance of RO trains in order to identify

problems early.

RO systems react to variation in feed water

characteristics and operating conditions.

RO data normalization allows the RO operator to

distinguish between normal variation in performance and

potential problems.

Use normalization software such as FTNORM to easily

trend the important performance variables and review

the data frequently.

25

Questions?

26

Thank You!

Steven D. Coker sdcoker@dow.com

http://www.dowwaterandprocess.com/