Willow Valley Water CompanyAlternative Oxidant & Corrosion Control – Studies, Strategies & Solutions - May 4, 2012
Willow Valley Water CompanyAlternative Oxidant & Corrosion Control – Studies , Strategies & Solutions
Joel Wade – Global Water Resources
Presentation Overview
Facility Information/Project BackgroundPrimary TechnologyBench Scale TestingFull Scale Pilot TestFull Scale ImprovementsResults - Capital / O&M CostsConclusions & Considerations
Willow Valley Water Company
Willow Valley Water CompanyChallenges with Newly Acquired Water System
Willow Valley Water CompanyUnder 2,000 customers5 - Active Groundwater WellsRated Capacity: 2-Sites 890 Kgal/dayPurchased by Global Water - 2006SWDA - Groundwater Rule – Disinfection Required.Tough Water!
Iron – 1.2 mg/lManganese – 1.5 mg/lTotal Organic Carbon - 3.2 mg/l
Good Oxidants – Doing Bad Things!
½” Iron Deposits
3-1/2”Manganese Deposits
2” Free Flow Area of Pipe
Fe & Mn RemovalCimarron / Unit 17
Built with limited controls and flexibilityExperiencing process stability issues using sodium hypochlorite as the oxidant at design capacityLimited contact time further stresses water clarityCapacity limited by organic and solids loading not hydraulics
Oxidant: Sodium hypochloriteOxidant Contact : 6 min (Unit 17), 0 min (Cimarron)Filtration: 2 Parallel Units -Manganese Dioxide Coated MediaDisinfection: Sodium Hypochlorite
Disinfection / Storage / Pressure Boosting
FiltrationOxidant /Contact Tank
Groundwater Well
Pureflow Filtration Technology
CORROISION CONTROL STUDY16 - Sample Points26 - Constituents 12 - Calculated Indices 2 – Chemistry Models
Material SurveyWater Age ModelPipe Velocity ContoursTrend Map – Cu+ hits
Copper 2.5 mg/l
Copper1.9 mg/l
Copper 2.1 mg/l
Water Age of High Copper Areas Residential Address Water Age (Hrs)System Address #1 - 1568 E. Puma Rd. 60System Address #2 - 1648 Valley Pkwy 70System Address #3 - 1770 Emily Dr. 58System Address #1 - 8170 Aspen 20System Address #2 - 1093 Pine 20System Address #3 - 7793 Green Valley 20System Address #4 - 467 Kingsley 30System Address #5 - 8663 ASH 35System Address #6 - 1430 E. Commercial St. 50
Typical Corrosion Sampling Suite
pH/ORPConductivity / Total Dissolved SolidsAlkalinity – Total / PhenolphthaleinTotal Hardness Lead/CopperSulfate/ SRBsDissolved Oxygen / Carbon Dioxide
Chlorine/Chloride-Nitrate/ Sulfate Iron / IRBs Total Organic Carbon (TOC) .Dissolved Inorganic Carbon (DIC)Calcium Bicarbonate/Magnesium Bicarbonate
Water Quality AveragesParameter Max Min Average
ORP (mV) 553 121 269Temp (deg C) 25.3 22.1 24.3
pH (units) 8.13 7.4 7.73Cond (uS/cm) 2500 1388 2004
TDS (ppm) 1770 973 1414 CO2 (mg/l) 25 10 17DO (mg/l) 10.8 3.7 6.2TOC (mg/l) 2.7 2 2.4DIC (mg/l) 75 53 65.4
T-Alk 320 168 255Ca- Hard 630 148 408Mg-Hard 246 62 152Sulfate 710 378 570
Phosphate 2.8 0.84 1.84Chloride 250 130 192
Manganese 1.24 0.035 0.306Iron 1.4 0.012 0.295Lead 0.6 0.012 0.088
Copper 2.57 0.014 0.595
RTW Water Chemistry Model Input
RTW Model Output Graph
Trussell Tech. Water Chemistry Model
Ionic StrengthDissolved Inorganic CarbonCaCO3 – Precipitation Potential
Water Quality IndexingWQ Index Max Min Average Indicator Range
pH (Units) 8.13 7.4 7.73
pHs (Units) 7.28 6.71 6.89
LSI (units) 1.38 0.45 0.84 -1.0 to +2.0
CCPP Index 78.92 21.4 50.42 4-10 mg/l
Ryznars Index 6.76 5.48 6.03 5 to 10
Aggressive Index 12.97 12.24 12.71 10 - 12 units
Ionic Strength (mol/l)
0.0416 0.0246 0.0344 0 - 0.05 mol/L
Larson Sklod Index
4.64 2.21 3.01 0.8 – 1.2
Baylis curve Scale Scale Scale Incrustation / corrosion
DIC (Calculated) (mg/l)
81.1 41 63.2 10 – 30 mg/l as C
Alk/Chloride + Sulfate Ratio
0.33 0.33 0.29 Greater than 5.0
Baylis Curve Zone A – No Corrosion
Non-Corrosive Water?? Not So Fast,
Average pH 7.7 – Check!Average Alkalinity 255 – Good!Average LSI - 0.84, Slightly Positive – Stable!Ryznars Index – 6.03 Mid range of stability – Check!Baylis Curve – Non-Corrosive – Deposition ZoneLarson Skold – 3.01 Not So Much!Alkalinity Chloride + Sulfate Ratio 0.29 – Way Out of Range!
Corrosion Control SummarySlow oxidation reactions due to high levels of TOC in the raw water cause overuse of oxidants related to Iron and Manganese removal. Increased DIC concentrations related to the iron and manganese filtration process, may be the leading cause of increased copper solvency of the contact water. High chloride and sulfate concentrations stripping away protective films, required to offset high oxidation potential & electro conductivity.
Elevated DIC – What to do?
How to fix itSimple Ratio - ALK/ (Cl- + SO4)
Increase Alk or Reduce Cl-, SO4-
DIC limits Alk – Beware of CSI!Use Polyphosphate as protective coatingEliminate NaOCl- – Reduce Chloride
Hydrogen Peroxide - Not effective with TOCOzone – Material compatibility issues, Can reform MnO4
Sodium Permanganate – Slow acting, Can reform MnO4
Chlorine Dioxide – Fast Acting, No THMs Ok, Lets try it!
Why Not NaOCl- ?
Chlorine Dioxide Advantages
Detention Time – ClO2 reactions are instantaneous, reducing contact time requirements and is 10 times more soluble in water than chlorine.Increased effectiveness with increasing pH (opposite of chlorine).More effective than chlorine for virus inactivation.Powerful enough to oxidize Iron Manganese in the presence of high TOC.Can inactivate THM precursors without forming THM or HAA5s.Improves taste and odor from organics, algae and sulfides.CLO2 provides a chlorine residual, while other oxidants may not.CT requirements are initiated at point of use, reducing the amount of chlorine required to meet CTCl2 gas can reduce disinfection costs by 2/3
DisadvantagesClO2 forms chlorite which is regulated constituent, limiting the concentration that can be fed.On-site generation process control can vary efficiency of product.Training, sampling and lab efforts are higher than that of Chlorine.On-site generation equipment capital costs are higher than NaOCl-
Cost per lb of oxidant is 4.3 times higher than the cost of NaOCl - , but dosage is 2.7 times less than NaOCl- .ClO2 decomposes in sunlight.Safety concern of ClO2 is greater than that of NaOCl- .When spilled or agitated, liquid ClO2 can produce chlorine gas.
Bench ScaleTesting Dissolved Mn vs. Oxidant Dose: Unit -17 Well
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.00.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
Oxidation of Mn2+ in raw water by Cl2 alone ,ClO2 alone and MnO4 + ClO2. For combined process, ClO2 dose was 1.5 mg/L. Initial Mn2+ = 1.35 mg/L. Temp. = 10 C, pH = 7.4 - 7.5. TOC = 3.56 mg/L.
Cl2 AloneCl2 + ClO2 (ClO2 dose = 1.5 mg/L)ClO2 AloneMnO4- + ClO2 (ClO2 dose = 1.5 mg/L)
Unit 17 - Oxidant Dose (mg/L)
Diss
olve
d M
n (m
g/L)
Bench Scale Testing Dissolved Mn vs. Oxidant Dose : Cimarron Well
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
Oxidation of Mn2+ in Cimmaron raw water by Cl2 alone, Cl2 + ClO2 and ClO2 alone and Detention time = 5 min. Initial Mn2+ = 0.626 mg/L. Temp. = 10 C, pH = 7.3 - 7.4. TOC = 2.45 mg/L.
ClO2 onlyCl2 AloneCl2 + ClO2 (ClO2 dose = 1.0 mg/L)
Cimarron Oxidant Dose (mg/L)
Diss
olve
d M
n (m
g/L)
Full Scale Pilot Test Liquid Chlorine Dioxide – Pentasodium Tripolyphosphate
Pilot TestingPilot Unit Overview
CDG Solution 3000 – Liquid Chlorine Dioxide 330-gallon toteVariable Speed DrivePeristaltic Pump SkidWestfall Static Mixers50 gallon NaMnO4 & PumpInjection QuillsRubbermaid Storage UnitNa4P2O7 – Mixing & Chemical Feed StationConcrete Pad
Pilot Test Equipment
Pilot Testing Summary
Cimarron Full-Scale Pilot Results
Constituent Before AfterFe Removal (%) 84.3 99.3
Mn Removal (%) 55.5 88.0TTHM (ug/l) 0.100 0.059TOC (mg/l) 2.7 2.4
Max Copper Sampled (mg/l)
1.30 0.35
Unit 17 Full-Scale Pilot ResultsConstituent Before After
Fe Removal (%) 91.0 98.1Mn Removal (%) 70.4 87.1
TTHM (ug/l) 0.120 0.056TOC (mg/l) 3.4 3.0
Max Copper Sampled (mg/l)
2.77 0.56
Storage Tank
To D
istrib
utio
n Sy
stem
‘
Well No. 1
Well No. 2
Raw Water
Treatment System Bypass
Iron & Manganese Treatment
Unit 17Distribution Pump Station
Onsite Chlorine Dioxide Oxidant Generator/Feed
System
Tetrasodium Pyrophosphate
Sodium Permanganate
Feed
Chlorine Gas Feed System
Full Scale Improvements
CDG Gas:Solid™ Process
Cl2 + 2NaClO2 2ClO2 + NaCl
Chlorine Gas Solid Sodium ChloriteSAF-T-CHLOR™
Chlorine Dioxide Gas Solid Sodium Chloride
½ lb gas chlorine passing through Sodium chlorite makes 1 pound of Chlorine Dioxide
Chemical Injection Unit 17
Static MixerUnit 17
Lab Requirements
Daily Chlorine Dioxide at EPDS – HACH Field KitDaily Chlorite at the EPDS – HACH AutoCat 900Monthly Chlorite – Third Party – Three Samples
Oxidant Dosage OptimizationParker THM Analyzer
Cimarron Site
Cimarron Site
Twin Feed – Chlorine Gas
Cimarron CLO2 Generator
Unit 17Full Scale Improvements
NaMnO4 & Na4P2O7 Feed Station
Great! But What Does It Cost?
Capital Costs – $172,000 ($0.38 per gallon)Chlorine Gas System - $37,800Chlorine Dioxide Generator - $67,300CC Pad & Tuff Shed Structure - $4,500Sodium Permanganate feed station - $750Tetrasodium Pyrophosphate Feed Station - $1,500Backflow, piping and static mixers - $15,000Electrical Improvements - $5,000Settling Tanks and Ancillary Equipment – $10,000In-House Labor - $30,000 - Constructed in 8-Weeks!
Production Costs ComparisonSite
LocationProduction
(Kgal)Oxidant&
Disinfection ($)
Power ($)
Prod Cost ($/kgal)
Unit 17 (2010) 104,209 11,823 26,152.38 $0.36
Cimarron (2010) 12,306 1,395.02 5,189.71 $0.54
SiteLocation
Production (Kgal)
Oxidant ($)
Disinfection ($)
Corrosion Inhibitor
($)
Power ($)
Prod Cost ($/kgal)
% CostIncrease
Unit-17 (3/2012)
5,976 1,848.62 305.31 87.41 1948.81 $0.70 94.4
Cimarron (3/2012)
872 258.67 42.64 11.78 576.03 $1.07 98.1
Yearly Production CostCimarron / Unit 17
Cimarron Jan Feb March April May June July Aug Sept Oct Nov Dec Total
Prod (Kgal) 741 671 807 743 898 944 935 1,229 1,121 1,112 801 724 5,792
Prod($) 2010
$400 $362 $436 $401 $485 $510 $505 $664 $605 $600 $433 $391 $5,792
Prod($) 2012
$793 $718 $863 $795 $961 $1,010 $1,000 $1,315 $1,199 $1,190 $857 $775 $11,477
Change($)
$393 $356 $428 $394 $476 $500 $496 $651 $594 $589 $425 $384 $5,685
Unit 17 Jan Feb March April May June July Aug Sept Oct Nov Dec Total
Prod (Kgal) 5,931 5,857 7,039 7,519 9,303 8,303 9,467 9,975 7,514 6,543 8,728 4,875 91,054
Prod($) 2010
$2,135 $2,109 $2,534 $2,707 $3,349 $2,989 $3,408 $3,591 $2,705 $2,355 $3,142 $1,755 $32,779
Prod($) 2012
$4,152 $4,100 $4,927 $5,263 $6,512 $5,812 $6,627 $6,983 $5,260 $4,580 $6,100 $3,413 $63,738
Change($) $2,017 $1,991 $2,393 $2,556 $3,163 $2,823 $3,129 $3,392 $2,555 $2,225 $2,968 $1,658 $30,958
ConclusionsFE & Mn Removal w/o Copper CorrosionAlternative Oxidants can Improve Fe & Mn Removal w/o TTHMCheck CPI Before considering Alkalinity AugmentationClO2 + MnO4 – Most effective in combinationCLO2 Can Be User Friendly
Acknowledgements
St. Mary's WTP - Flagstaff Az.Valencia Water Company Utilities Staff.Pureflow Filtration/Reaco Associates, LLC.Chemical Feeding Technologies, Inc.Parker Hannifin CorpCDG Environmental Steve Osborn, James Taylor – Global WaterWillow Valley Operations Staff
And Isn't This What It’s Really About??
Any Questions ??
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