Andy Komor, MS, PE

Pacific Advanced Civil Engineering, Inc. (PACE)

2013 CA-NV AWWA Fall ConferenceSeptember 30 – October 3, 2013Sacramento, California

Keisuke Ikehata, PhD, PE, PEng

Fiona (Yao) Jin, MS, EIT

James A. Mattews, PE

Janet A. Fordunski, MS, PE

Outline Background shows multiple problems: Fe, Mn, Ur,

THMs, Hardness

On-site pilot test of expansion: NF versus GAC

Results: water quality, costs, maintenance

Conclusions

Existing Well Water Contains Mn, Fe, Uranium, Hardness, and Recently THMsParameters Unit Well Water

pH - 7.8

Total Dissolved Solids (TDS)

mg/L 722

Alkalinity mg/L as CaCO3 150

Hardness mg/L as CaCO3 310

Iron mg/L 0.23

Manganese mg/L 0.154

Uranium µg/L 72

Total Organic Carbon (TOC)

mg/L 1.4

Abbreviation: MCL = maximum contaminant level, NA = not applicableNote: *Secondary MCL

Existing Treatment Reduces Manganese, Iron, and Uranium Only

MnO2 Filter

NaOCl(~2 mg/L)

Wells

Ion Exchange

NaOCl(~ 2 mg/L)

Distribution System

Fe and Mn Removal(Pre-oxidation + Reactive

Media Filtration)

Uranium Removal (Anion

Exchange)

Secondary Disinfection

Existing Potable Water System Doesn’t Provide Softening of Hardness

Existing Filtration Plant Removes Mn, Fe, and U… but not Hardness or TOCParameters Unit Well Water

TreatedWater

Federal MCL

pH - 7.8 7.9 6.5-8.5*

Total Dissolved Solids (TDS)

mg/L 722 713 500*

Alkalinity mg/L as CaCO3 150 170 NA

Hardness mg/L as CaCO3 310 270 NA

Iron mg/L 0.23 <0.02 0.3*

Manganese mg/L 0.154 0.022 0.05*

Uranium µg/L 72 11 30

Total Organic Carbon (TOC)

mg/L 1.4 1.4 NA

Abbreviation: MCL = maximum contaminant level, NA = not applicableNote: *Secondary MCL

Trihalomethanes Were Emerging…TOC Removal Required

Disinfection by-products

Total trihalomethanes (TTHM) in drinking water exceeded maximum contaminant level (MCL): 80 µg/L

Brominated THMs

Bromodichloromethane (CHBrCl2)

Dibromochloromehtane (CHBr2Cl)

Bromoform (CHBr3)

TOC (THM precursors) must be removed

NF and GAC Were Selected for Pilot Testing

Options for organics removal

Nanofiltration (NF)

Granular activated carbon (GAC)

Ozone

Not suitable because of high bromide (Br-) concentration (>0.6 mg/L)

High risk of bromate (BrO3-) formation

Coagulation

Not suitable because of the site-specific limitations

NF vs. GACNF GAC

Pros

Lower media replacement cost

Removes not just organics

Reduces scaling at point of use

Cons

Higher capital cost

More elaborate operations

Water loss (generally)

Pros

Lower capital cost

No additional water loss

Simpler operation

Cons

Media disposal and replacement

Higher operational cost

Removes only organics

NF Provides Additional Benefits

Removal of hardness and salinity with less water loss compared to existing Hot Water RO and IX Polishing at Point of Use

Take uranium treatment process offline, decreasing salt addition from regeneration, radioactivity of spent material, and maintenance

MnO2 Filter for Iron and Manganese

Removal

Ion Exchange for Uranium

Removal

NaOCl

P

Nanofiltration

DistributionSystem

NF-treated Water

NF Concentrate

GAC-treated Water

CartridgeFilters

Antiscalant

Wells

NaOCl

Existing Water Treatment Plant

Nanofiltration(NF)

Granular Activated Carbon

(GAC)

P

GAC-1GAC-1GAC-1GAC-2GAC-2GAC-2

On-site Pilot Test

On-site Pilot Test

NF System Configuration Membrane element (Dow Filmtech NF90-2540)

Size

Diameter: 2.5 inches

Length: 40 inches

Type: thin-film composite

Material: polyamide

Feed flow rate: 6 gpm

Stabilized MgSO4 rejection: >97.0%

Five elements in-series

Concentrate recirculation

NF System Configuration Cartridge filters

Outside diameter = 2.5 inches

Inside diameter = 1 inch

Lengths = 9.75 inches

5 µm & 1 µm

Antiscalant injection

SpectraGuardTM from Professional Water Technologies, Inc.

GAC Media GAC-1

Norit DARCO® 12x20 Lignite coal

Mesh size : 12 x 20

Larger mesh size

Acid wash carbon

GAC-2

Siemens AquaCarb® 1230AWC Coconut shell

Mesh size : 12 x 30

Smaller mesh size

Acid wash carbon

Operation Parameters

NF

NF recovery rate = 85%

Hydraulic pressure = 150 ~ 170 psi

Feed flow rate = 1.2 gpm

GAC

Flow rate = 0.15 gpm

Pre-chlorine injection was halted during the pilot test to protect the NF membrane

Monitoring Parameters Trihalomethane formation potential (THMFP)

Organics

Chemical oxygen demand (COD)

Total organic carbon (TOC)

Iron

Manganese

Uranium

Total dissolved solids (TDS)

MnO2 Filter for Iron and Manganese

Removal

Ion Exchange for Uranium

Removal

NaOCl

P

Nanofiltration

DistributionSystem

NF-treated Water

NF Concentrate

GAC-treated Water

CartridgeFilters

Antiscalant

Wells

NaOCl

Existing Water Treatment Plant

Nanofiltration(NF)

Granular Activated Carbon

(GAC)

P

GAC-1GAC-1GAC-1GAC-2GAC-2GAC-2

Sampling Locations

Note: Samples were also collected at the existing RO plant.

THMFP Was Reduced by Both GAC and NF

0

10

20

30

40

50

60

THM

Fo

rmat

ion

Po

ten

tial

(µ

g/L

)

Sampling Point/Treatment

Chloroform (µg/L)

Dichlorobromomethane (µg/L)

Chlorodibromomethane (µg/L)

Bromoform (µg/L)

< 1 µg/L < 1 µg/L < 1 µg/L

*

Note: *RO feed already contained THMs.

THM Precursors Were Removed by Both NF and GAC

ParametersFeed

WaterNF

TreatedGAC*

Treated

COD (mg/L) 2.7 <0.7 <0.7

TOC (mg/L) 1.4 <1.0 <1.0

Note: *No difference between two GAC media.

Uranium Was Removed by NF and GAC

0

10

20

30

40

50

60

70

80

Feed NF Treated GAC-1 GAC-2

Ura

nim

(µ

g/L

)

Treatment

1st Week

2nd Week

< 1 µg/L < 1 µg/L

USEPA Primary MCLfor Uranium (30 µg/L)

Note: GAC adsorbed uranium and spent media exhibited a hazardous level of radioactivity.

Only NF Removed Iron and Manganese

0

0.01

0.02

0.03

Feed NF Treated GAC-1 GAC-2

Iro

n (

mg

/L)

and

Man

gan

ese

(m

g/L

)

Treatment

Iron

Manganese

Note: As iron and manganese may precipitate and foul NF membranes, MnO2 filters will be necessary regardless.

MnO2 Filter Performance during Pilot Test without Pre-chlorination

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Iro

n a

nd

Man

gan

ese

(m

g/L

)

Date/Time

Iron - Raw Well WaterMn - Raw Well WaterIron - After Iron & Mn FiltersMn - After Iron & Mn Filters

US EPA Secondary MCL for Iron (0.3 mg/L)

US EPA SecondaryMCL for Manganese (0.05 mg/L)

NF Removed Majority of TDS and Hardness

0

100

200

300

400

500

600

700

800

Co

nce

ntr

atio

n (

mg

/L)

Orthophosphate

Nitrate

Sulfate

Chloride

Bicarbonate

Magnesium

Calcium

Manganese

Iron

Potassium

Sodium

Note: The PACE pilot NF unit was operated at 85% recovery, while the Hot Water RO was operated at 50% Recovery.

Cost Estimate

TreatmentOptions

Capital Cost Annual O&M

GAC $ 309,900 $ 83,500/year

NF $589,300 $ 68,000/year

Note: Assuming GAC media replacement every ~2 months.

NF has the Following Benefits

Better water quality

Lower TDS and hardness

Lower O&M costs

May replace existing ion exchange for uranium removal and hot-water RO with NF

Reduce flow to WWTP by 20%

New

NF

Conclusions Both NF and GAC achieved satisfactory levels of

organics and THMFP removal

NF was recommended because it would provide additional benefits Removal of uranium, hardness and TDS No hazardous (radioactive) spent media

Lower O&M costs No frequent media replacement

Reduced scaling without RO/IX

Decommission existing uranium removal

Reduces flow to WWTP

Conclusions (Continued) GAC has been selected,

designed and constructed

Lower capital cost

Less operational complexity

However, replacement of the existing RO facility with smaller NF is being considered

Thank you!

Contact Information

Andy Komor, MS, PE

Email: akomor@pacewater.com

Phone: 714-481-7225