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Issam Najm, Nancy Patania Brown WQTS; Los Angeles, California
American Water Works Associa�on CA-‐NV Sec�on Fall Conference
Sacramento, California October 1 – 3, 2013
Nicole Blute, Xueying Wu Hazen and Sawyer; Los Angeles, California
Sami Kader Water Works Engineers; Redding, California
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(Water Research Founda�on Project 4450)
Par�cipa�ng Agencies:
City of Davis, CA Indio Water Authority, CA City of Riverside, CA City of Sacramento, CA MWD of Southern California, CA Palmdale Water District, CA City of Norman, OK Truckee Meadows Water Authority, NV Yucaipa Valley Water District, CA Zone 7 Water Agency, CA California American Water Co.
Project Advisory Commi�ee:
Eugene Leung – California DPH Joe Drago – Kennedy/Jenks Steve Via – AWWA Tom Schrempp – WaterOne Tom Sorg – US EPA
Water Research Founda�on: Alice Fulmer Mary Smith
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1. Configura�on of a WBA treatment system 2. Cr(VI) Removal Performance 3. Es�ma�ng resin replacement frequency 4. Capital & Annual O&M Costs 5. Overall Strengths & Weaknesses
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N
H
H
H+ + N
H
H
H+ + N
H
H
H+ HCrO4–
Ini�al Neutral Func�onal Group
Protonated Func�onal Group
Cr(VI)
Acid (e.g., HCl or H2SO4)
HCrO4 –
At the surface of the resin, Cr(VI) is reduced to Cr(III):
HCrO4 + 4H+ + 3e– Cr(OH)3(s) + H2O –
STEP 1:
STEP 2:
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Cost of CO2 to lower pH to 6.0
Resin replacement & disposal cost
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Purolite S106 Nitrate = 0.1 mg/L Sulfate = 19 mg/L
DOW PWA7 Nitrate = 0.1 mg/L Sulfate = 19 mg/L
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pH = 6.0 SO4 = 165 mg/L NO3 < 1 mg/L
pH = 6.0 SO4 = 17 mg/L NO3 < 1 mg/L
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Cr= 40 µg/L SO4 = 38 mg/L NO3 = 40 mg/L
Cr(VI) = 45 µg/L SO4 = 21 mg/L NO3 = 2.2 mg/L
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Cr= 57 µg/L SO4 = 20 mg/L NO3 = 2.5 mg/L
Cr(VI) = 48 µg/L SO4 = 21 mg/L NO3 = 2.2 mg/L
0.2 lbs/�3 0.2 lbs/�3
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u For up to 150,000 BVs, there was no discernable effect of nitrate or sulfate (up to 165 mg/L)
u pH 6.0 is op�mal for Cr(VI) removal with WBA resin
u Spent resin contains high loads of Cr(VI) and other metals
u Resin replacement frequency depends mostly on Cr(VI) concentra�on
u Es�mated Cr(VI) load at breakthrough ≅ 0.2 lbs/�3
u This translates into an approximate resin u�liza�on rate of:
�3/MG = 24
Cr(VI) Conc., µg/L
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Parameter Value Well Capacity 1,000 gpm
U�liza�on Rate 60%
Cr Level 15 µg/L
pH 8.2
Alk., as CaCO3 197 mg/L
Conduc�vity 520 µS/cm
Nitrate 22 mg/L
Sulfate 33 mg/L
Uranium 5 µg/L
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Treatment System
1,000 gpm Cr(VI) = 15 µg/L
500 gpm (By-‐Pass) Cr(VI) = 15 µg/L
500 gpm Cr(VI) = 1 µg/L
1,000 gpm Cr(VI) = 8 µg/L
u MCL = 10 µg/L
u Treated Water Goal = 80% of MCL (8 µg/L)
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u Two 10-‐� diameter lead-‐lag pressure vessels u Resin replacement projected at ~345,000 BVs (might be too
op�mis�c?) u That’s about 8 years of opera�on! u 77-‐ton onsite CO2 storage tank (48-‐� long) u 22-‐ton CO2 delivery every 3 weeks (375 mg/L CO2) u Indoor area Required ≅ 1,000 �2 u Outdoor area Required ≅ 2,000 �2 u Waste Brine contains 0.28% Uranium (LLRW)
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WBA System: Spent resin disposed as LLRW SBA System: 1. Waste brine is treated on-‐site to remove Cr
2. Sludge is dewatered and disposed as non-‐RCRA California hazardous waste
3. Clarified brine is hauled away for off-‐site disposal at $230/1000 gal.
RCF System: 1. Waste backwash water is clarified onsite
2. Sludge is dewatered and disposed as non-‐RCRA California hazardous waste
3. Clarified water is returned to head of the plant
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Strengths Weaknesses
1. No significant liquid residuals
2. Minimal operator a�en�on required
3. Very few “moving parts”
4. No hazardous chemicals on site
1. Requires high CO2 dose to lower pH to 6.0, especially in waters with high alkalinity
2. Frequency of CO2 truck deliveries may become prohibi�ve
3. Resin is very costly (~$500/�3), and its disposal cost is another $300 to $400/�3
4. Uranium accumula�on on the resin may greatly limit the spent resin disposal op�ons
