Iron and Manganese Treatment and Removal Options for Groundwater

Jon Oldham, P.E. Bowen, Collins & Associates

2013 AWWA IMS Annual Conference

Overview

• What are Iron and Manganese? • Regulatory Standards • Effects of Iron and Manganese in Drinking

Water • Well Source Options • State of Idaho and State of Utah Allowed

Treatment Control/Removal Systems • Preventing Problems in Distribution Mains

Iron and Manganese

Iron and Manganese

Iron, Fe • Silvery-gray, lustrous

metal • 5% of earth’s crust • Usually in oxidized form

(rusty)

Manganese, Mn • Gray-white metal,

similar to iron • Hard, very brittle • 0.1% of earth’s crust

Forms of Iron and Manganese in Water

• Ferrous Fe2+, Manganous Mn2+ (clear water) – Dissolved; forms rust colored particles when

exposed to atmosphere – Most common form in ground water

• Ferric Fe3+, Manganic Mn4+ (red water) – Not dissolved; reddish-brown/black particles

settle to bottom

Forms of Iron and Manganese in Water (continued)

Forms of Iron and Manganese in Water (continued)

• Iron Bacteria – Not harmful to health – Grow on water system

components (toilet tank) – Gelatin/slimy, suspended in

water – Brown, red or white

• Organic Iron – Shallow wells and surface water – Brown, yellow

Regulatory Standards Safe Drinking Water Act

• Primary Standards (health related) – None

• Secondary Standards (aesthetics) – Iron: 0.30 mg/L (300 ppm) – Manganese: 0.05 mg/L (50 ppm)

Effects of Iron and Manganese in Drinking Water

• Aesthetics (taste and appearance) – Metallic and unpleasant

taste – Iron-rusty color;

Manganese-black color – Stain laundry, toilet boils,

sinks etc – Customer complaints

Customer Complaint Resolution

Effects of Iron and Manganese in Drinking Water (continued)

• Physical Effects – Damage water equipment

and reduce treatment efficiency for other contaminants

– Increased costs for operations

Effects of Iron and Manganese in Drinking Water (continued)

• Health – Essential nutrients at lower doses; multivitamins – No known adverse health effects for levels

typically found in drinking water

Well Source Options

• Retrofit well to “zone off” metals-producing zones

• Drill new well to isolate zones • Treatment

Treatment Control and Removal Options

Idaho Administrative Code, 58.01.08 Section 535 Utah Rule R309-535

• Treatment Control – Sequestration with Polyphosphates – Sequestration with Sodium Silicates (Idaho only)

• Treatment Removal – Oxidation, Detention, Filtration – Manganese Coated Media Filtration – Ion Exchange – Biofiltration (Idaho Only)

Treatment Control Sequestration with Polyphosphates

• Combined Iron and Manganese below 1.0 mg/L

• Must chlorinate and maintain residual

• Inject after iron/manganese removal treatment

• Inject before aeration, oxidation, or disinfection

• Breaks down in water heaters

• Wastewater nutrient concern

Treatment Control Sequestration with Sodium Silicates

• Combined Iron and Manganese below 2.0 mg/L • Requires on-site pilot tests • Must chlorinate and maintain residual • Inject after iron or manganese removal

treatment • Less effective for treating manganese • Better in water heaters than polyphosphates

Treatment Removal Oxidation, Detention and Filtration

• Oxidation – aeration or chemicals

• Detention time- – Utah-20 min – Idaho-30 min – Pilot test can shorten

or eliminate this • Sedimentation basins,

sludge removal • Pressure Filtration

Treatment Removal Manganese Coated Media Filtration

• Continuous or batch feed potassium permanganate to coated filter media

• Can use other oxidants (chlorine, aeration) to supplement process

• Greensand Filtration

Treatment Removal Ion Exchange

• Water softeners • Not acceptable where

either raw water or wash water contains dissolved oxygen or other oxidants

• Ferrous (dissolved) iron only

Treatment Removal Biofiltration

• On-site pilot testing to determine effectiveness • Customized filter design

Preventing Problems in Distribution Mains

• Prior Treatment • Protective pipe linings • Noncorrodible pipe materials • Raise pH • Avoid dead-end mains • Reduce disturbances in flow • Regular Flushing

Summary

• What are Iron and Manganese? • Regulatory Standards • Effects of Iron and Manganese in Drinking

Water • Well Source Options • State of Idaho and State of Utah Allowed

Treatment Control/Removal Systems • Preventing Problems in Distribution Mains

Questions?