Nanofiltration Membrane Pilot Studies for Disinfection By-Product Control

by Eric Lynne, EIT

B.S. – Civil and Environmental Engineering (2007) South Dakota State University

Introduction

Objective Preliminary Tests Screening Tests Large Scale Pilot Tests Conclusions

(Bergantine 2007)

Restrictions

Stage 2 D/DBP Rule< 80 μg/L TTHM< 60 μg/L HAA5

Big Sioux River < 1000 mg/L TDS

Energy EfficientHigh Flow at Low Applied Pressure

Background

DBP Problem

Treatment Methods: ChloraminationNF Membranes

Pilot Plant Testing

Background

Chloramination

Low DBPs CreatedEffective

Background – Spiral Wound Membrane

(Hydranautics 2008)

1 2 3

4 5

Background

Membranes

PermeateConcentrateRecoveryStages

(AWWA 1999)

Nanofiltration

PermeateConcentrate

(AWWA 1999)

Background

Membrane Problems

Inorganic ScalingOrganic Fouling

Microbial or Silt Fouling

(Malki 2008, Dow 2008)

Preliminary Testing

Water QualityTOCUV254

SDIAmmonia

Chloramination

Preliminary Testing

ResultsWater Quality

• Well Specific

• UV254 TOC

• SDI: Raw < 5; Feed ~ 1• Naturally occuring ammonia

a) WTP Influent

b) Filter Effluent

Chloramination

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 1 2 3 4 5 6 7 8 9 10 11 12Chlorine : Ammonia Ratio

Res

idua

l (m

g/L

)

Free Chlorine Total ChlorineMonoChloramine Free Ammonia

Chloramination56, 59 μg/L TTHM

Chloramination

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 1 2 3 4 5 6 7 8 9 10 11 12Chlorine : Ammonia Ratio

Res

idua

l (m

g/L

)

Free Chlorine Total ChlorineMonoChloramine Free Ammonia

Chloramination56, 59 μg/L TTHM

10 μg/L TTHM

Preliminary - Conclusions

Source Water for NF Pilot Plant Direct Nanofiltration of raw water is feasible Filter Effluent is preferred

Chloramination viable alternative with 82% TTHM reduction

NF Membrane Pilot Plants

Phase I – ScreeningKoch TFC-SR2 (K2)Koch TFC-SR3 (K3)Trisep XN45-TSF (T)Hydranautics ESNA1-LF (HE)Hydranautics HydraCoRe-70pHT (HH)Dow/Filmtec NF270 (DF)

(Trisep 2008)

Phase I – Screening

Hold flux constant Vary recovery for each membrane tested

Phase I – Results

TOC and UV254 removal

NF Membrane and Percent Recovery

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

15 50 80 15 50 80 15 50 80 15 50 80 15 50 80 15 50 80K2 K3 T HE HH DF

Per

cen

t R

emov

alTOC UV254

Phase I – Results

TTHM reduction

NF Membrane and Percent Recovery

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

15 50 80 15 50 80 15 50 80 15 50 80 15 50 80 15 50 80K2 K3 T HE HH DF

Per

cen

t R

emov

al87% Minimum Rejection Allowed

Phase I – Results

Concentrate TDS concentration

0

200

400

600

800

1000

1200

K2 K3 T HE HH DF

NF Membrane

Tot

al D

isso

lved

Sol

ids

(mg/

L)

Disposal limit 1000 mg/L

Phase I - Conclusions

Membrane TDS < 1000 mg/L >87% TTHM reduction

Koch TFC-SR2 NO NO

Koch TFC-SR3 NO YES

Trisep XN45-TSF YES YES

Hydranautics ESNA1-LF NO YES

HydraCoRe-70pHT YES NO

Dow/Filmtec NF270 NO YES

Phase II 85% recovery

Variable Flux: 9, 12, 15 gfd

Determine design criteria

Photographs of Pilot Plant

Phase II - Results

TOC and UV254 removal

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

9* 12 15 9 12 15 9 12 15

K3 T HE

NF Membrane and Flux Rate (gfd)

Per

cen

t R

emov

al

TOC UV254

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

9* 12 15 9 12 15 9 12 15

K3 T HE

NF Membrane and Flux Rate (gfd)

Per

cen

t R

edu

ctio

n

Phase II - Results

TTHM reduction

87% Minimum Rejection Allowed

Phase II - Results

Adjusted Specific Flux

0.00

0.05

0.10

0.15

0.20

0.25

9* 12 15 9 12 15 9 12 15

K3 T HE

NF Membrane and Flux Rate (gfd)

Adj

uste

d Sp

ecif

ic F

lux

to 2

5°C

(gf

d/ps

i)

Phase II - Results

Ammonia (NH3-N) Removal

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

9* 12 15 9 12 15 9 12 15

K3 T HE

NF Membrane and Flux Rate (gfd)

Per

cen

t R

ejec

tion

Phase II – Results

Fouling

0

0.05

0.1

0.15

0.2

0.25

0 100 200 300 400 500 600 700 800

Hours

Ad

just

ed S

F (

gfd

/psi

)

.

T HE

Phase II – Results

Fouling

0

50

100

150

200

250

300

350

400

0 5 10 15 20 25 30

Days

Con

du

ctiv

ity

(μS

/cm

)

TriSep XN45-TSF

Hydranautics ESNA1-LF

Phase II - Conclusions

Blend Ratio: 44%/56%

Concentrate TDS Increased SF decreased with increasing flux Design Criteria

Applied pressures ranged from 64-165 psi Specific flux values ranged from 0.13-0.21 gfd/psi System recovery rate of 85% Permeate TTHM values ranging from 1.1-2.5 μg/L

No substantial fouling observed

Phase II - Conclusions

Highest Specific Flux = Trisep XN45-TSF Highest TTHM rejection = Hydranautics ESNA1-LF

Membrane Optimum Setting Costs

Koch TFC-SR3 __ gfd ??

Trisep XN45-TSF __ gfd ??

Hydranautics ESNA1-LF __ gfd ??

Recommendations

Cost Data Verify 15 gfd @ 80% recovery Select Hydranautics ESNA1-LF

15 gfd @ 85% recovery (costs?) Consistent Source Water One Membrane for Phase II Challenge Membrane to Foul

Questions