Pellet Softening: Hardness, Iron and Manganese Removal

Pellet Softening: Pellet Softening: Hardness, Iron and Hardness, Iron and Manganese RemovalManganese Removal

Janet Snedecor, P.E.Tom Peters, P.E.Milt Larsen, P.E.

Discussion OutlineDiscussion Outline

▼ Set the Stage…l Tuolumne, CA – Water Quality and Pre-design

Analysis.

▼ Traditional Softening Processes Evaluated

▼ What is Pellet Softening?l Advantagesl Possible Applications

▼ Tuolumne, CA Water Treatment Facilityl Pilot Study Results l Design and Construction l Facilities in Operation

Tuolumne, CATuolumne, CA

Background

▼ Client: Tuolumne Economic Development Authority (TEDA)

▼ Source: Groundwater Wells

▼ Problem: Hardness and Iron/Manganese Concentrations above SMCL’s.

l Hardness: 97 to 238 mg/L (moderately hard to very hard)l Iron: ND to 0.9 mg/L (SMCL = 0.3 mg/L)l Manganese: ND to 0.35 mg/L (SMCL = 0.05 mg/L)

Sacramento

TuolumneTuolumne

Modesto

Stockton

San Francisco

San Jose

California

Tuolumne, CA Tuolumne, CA -- PredesignPredesign

▼ Pre-design Evaluation: l Space considerations, quantity and type of waste stream,

ease of operation, operational & maintenance considerations

l Evaluate Softening ProcessesPellet SofteningIon ExchangeMembrane

l Evaluate Fe/Mn Removal ProcessesGreensandPyrolusite

Traditional Softening ProcessesTraditional Softening Processes

▼ Chemical Softening:l Precipitation created through chemical addition (lime, soda ash

or caustic soda)l Large quantities of sludge producedl Land intensive

▼ Ion Exchange:l Generally used in industry and small home unitsl Smaller footprintl High strength liquid waste stream (acid & brine)

▼ Membrane:l Smaller footprintl High strength liquid waste stream (acid & brine)

Backwash WaterWater

Raw WaterRaw WaterFinished WaterFinished Water

Reusable Pellets

Reusable Pellets

Process Flow DiagramProcess Flow Diagram

ChlorineChlorine

Raise pHRaise pH

Lower pHLower pH

Pellet Reactor

Pellet Reactor Polishing

FilterPolishing

Filter

Softened WaterSoftened Water

What is Pellet Softening?What is Pellet Softening?

▼ Fluidized Bed, Up-Flow Reactor

l Catalyst material (sand)

l Raise pH using NaOH or CaOH2 to promote crystallization of calcium on to the catalyst.

l Treated water from top of reactor, enlarged catalyst removed from bottom of reactor

l Softened water pH adjusted using CO2 or acid

Advantages of Pellet SofteningAdvantages of Pellet Softening

▼ Continuous Water Treatment

▼ Operator Effort Minimized

▼ Easily Managed Waste Stream: Water and Sand

▼ Minimal Environmental Impactsl No high strength liquid waste stream

l Environmentally benign solids – essentially damp sand

l Potential solids reuse opportunitiesLime in process, agricultural lime, acid wastewater neutralizer,animal feed additive, road building or cement making.

ApplicationsApplications

▼ Water Softeningl Reduced TDS and Chlorides

▼ Iron/Manganese Removal

▼ Phosphorus Removal

▼ Process Water Treatment

▼ Sulfate Removal

▼ Heavy Metals

Pellet Softening Pilot StudyPellet Softening Pilot Study

▼ Pilot Study Objectives

l Reduce hardness range to 60 – 75 mg/L

l Reduce iron and manganese concentrations below SMCL, 0.3 mg/L and 0.05 mg/L, respectively.

l Assess overall system performance

l Determine operational considerations for full scale process

Water Quality Water Quality –– Before & AfterBefore & After

▼ Two of five wells piloted – Well 6 and Well 3

0.0180.280.015-0.0190.28-0.36Manganese (mg/L)

0.000.070.03-0.100.51-0.96Iron (mg/L)

53-81212-25360 - 72188-210Hardness (mg/L)

8.0-8.47.38.2-8.97.1-7.8pH

FinishedRawFinishedRawParameterWell 3Well 6

Pilot Study Results Pilot Study Results

Results:▼ Optimum pH for softening: 9.5 to 9.6▼ Optimum stabilized pH 8.2 to 8.4▼ Hardness within target range of 60-75 mg/L▼ Iron and manganese removed to below SCML.

Conclusion:▼ Process met pilot test objectives of softening water

and removing iron/manganese.

Tuolumne Plant DesignTuolumne Plant Design

▼ Capacity: 120 GPM (initial), 240 GPM (future)

▼ Major Components:l Equalization Tankl Softening Reactor (Pressure Vessel)l Polishing Filter (Pressure Vessel)l Infiltration Basin for backwash disposall Chemical Feed and Storage

Tuolumne Water Treatment FacilityTuolumne Water Treatment Facility

Tuolumne Water Treatment FacilityTuolumne Water Treatment Facility

Softening Facilities in OperationSoftening Facilities in Operation

Hollywood, Florida

Softening Facilities in OperationSoftening Facilities in Operation

▼ Hollywood, Floridal Startup – 1960’s through 1970’sl Capacity – 10 MGD

▼ Valencia Water Company, Santa Clarita, CAl Startup – May 2008l Capacity – 800 GPM (1.2 MGD)

▼ Tuolumne Water Treatment Facility, Tuolumne, CAl Startup – May 2008l Capacity 120 GPM Initial, 240 GPM Build-Out (0.18-0.36

MGD)

Questions?Questions?