Raw Water Quality Not Textbook? Just Pilot! Iron Removal with High p. H Raw Water March 27, 2008 Sandy Kutzing, P. E. , CDM Eric Hahn, P. E. , NJAW American Water
Today’s Presentation u Background u Treatment Alternatives u Oxidation and Filtration u Fe and Water Chemistry u Pilot Test u Design American Water
New Jersey American Water u Serves more than 2 million people in 180 communities u 623, 800 connections u 8, 100 miles (12 000 km) of main from 2” to 72” (5 to 183 cm) in size u 170, 000 valves, including hydrant branch valves Current Operations New Jersey American Water
Background Monterey Beach, NJ u Existing well – PRM u Allocation limit of 900 GPM u SOS is limited on Barrier Island u Location u Large seasonal demand fluctuation American Water
Project Location American Water
Problem / Water Quality u Current Treatment u u Sequestration Customer Issues u Discoloration of laundry u Staining of sink u Taste and Odor American Water
Iron Levels u Iron Requirement u u u NJDEP Secondary Contaminant – Recommended Upper Limit = 0. 3 (mg/L) With Sequestration Treatment – Recommended Upper Limit = 0. 6 (mg/L) When Upper limit is exceeded, Treatment must be added to reduce levels below 0. 3 mg/L Monterey Well Iron Levels Year Iron Levels (mg/L) 2002 2003 2004 2005 2006 2007 0. 9 0. 7 1. 0 0. 8 American Water
Treatment Alternatives u Evaluated treatment methods u u u Membranes – eliminated due to space limitations and cost Biological removal – eliminated due to increase in O&M Oxidation with filtration – treatment method of choice American Water
Oxidation with Filtration u Basics of treatment process u u u Oxidation of iron and manganese with the addition of chlorine Dual media filtration of precipitates Manganese dioxide coating on sand acts as catalyst for oxidation and reduction of iron and manganese American Water
Greensand. Plus Technology u Selected in previous study u Greensand. Plus media u u u Silica sand Manganese dioxide coating Ordinary Manganese Greensand versus Greensand. Plus American Water
GREENSAND+ American Water
Existing Operations Chemical Injection 2. Tank (300 K gal) 1. Well Head 3. Booster Station 4. Discharge to Distribution System American Water
Location Details NJAW Monterey Well Site NJAW Vacant Lot American Water
Proposed Site American Water
Proposed Operations Chemical Injection 2. Greensand. Plus Filters 3. Tank (300 K gal) Prechlorination 1. Well Head 4. Booster Station 5. Discharge to Distribution System American Water
Iron and Water Chemistry u Surface Water Iron u u u Oxidized form as precipitate Typically removed by conventional clarification Groundwater Iron u Deprived of Oxygen u Reduced Form (2+) and in solution American Water
From “Water Treatment Handbook”, Degremont, 1979 American Water
Oxidation and Filtration u Most widely used treatment u Manganese Dioxide (Mn. O 2) or green sand u u u Oxidizes iron (II) and Manganese Precipitated and retained by the filter media Prechlorination oxidizes iron at Monterey Beach American Water
Abnormal Water Quality and Filtration u Effectiveness varies with p. H and oxidation-reduction potential (EH 2) u Monterey, NJ Well u Possibly collodial or complex iron u High p. H (above 7. 5) – Iron Fe 2+ (dissolved) most likely but not a guarantee American Water
Potential (Volts) Iron: p. H and Oxidation-Reduction Potential p. H American Water
American Water
Bench Scale Test u Prechlorinate to oxidize iron u Filter u Test for removal of Iron u Confirm: Iron form likely Fe 2+ American Water
Pilot Test u Higher Loading Rates u u 5 to 7 gpm/ft 2 Confirm Iron and Manganese Removal u Prechlorinate u Impact of Mn. O 2 coated green sands American Water
Pilot Study American Water
Pilot Study Results u Effluent Iron concentrations u u Effluent Manganese concentrations u u 0. 05 mg/L 0. 02 mg/L Headloss American Water
Pilot Study Results 0. 9 0. 8 0. 7 Iron (mg/L) 0. 6 0. 5 0. 4 NJDEP Secondary 0. 3 0. 2 Raw, 5 gpm/sf Raw, 7 gpm/sf Effluent, 5 gpm/sf Contaminant Level Effluent, 7 gpm/sf NJAW Performance Requirement 0. 1 0 0 10 20 30 40 Filter Run Time (Hours) 50 60 70 American Water
Frequency Pilot Study Effluent Iron Concentration American Water
Design u Greensand. Plus filters u Regular operation u Backwash operation (one filter backwashing) u Benefits of higher loading rate u Recycle 85% backwash flow American Water
Recap u Background u Treatment Alternatives u Oxidation and Filtration u Fe and Water Chemistry u Bench Scale & Pilot Tests u Design Questions? American Water
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