Slow Sand Filter AmendmentsSlow Sand Filter Amendments forfor

Clay Removal and Corrosion ControlClay Removal and Corrosion Control

Stephen J. RooklidgeBioengineering Department

Oregon State UniversityJune 23, 2003

OutlineOutline Filter DescriptionsFilter Descriptions Research OriginResearch Origin Laboratory ExperimentsLaboratory Experiments Field ExperimentsField Experiments SummarySummary

ObjectivesObjectivesExpand Slow Sand Filter use by:Expand Slow Sand Filter use by:

evaluating roughing filter pretreatment evaluating roughing filter pretreatment

evaluating limestone amendmentsevaluating limestone amendments

Slow Sand and Roughing FiltersSlow Sand and Roughing Filters

““Passive” treatment methodPassive” treatment method

RF/SSF - physical and biological processesRF/SSF - physical and biological processes

Appropriate for rural regions and developing nationsAppropriate for rural regions and developing nations

RawWater

Waste

Effluent

Roughing Filter Slow Sand Filter

Limestone AmendmentsLimestone Amendments

RawWater

Effluent

Roughing Filter

LimestoneContactor

SlowSandFilter

Two experimental and one EPA-approved limestone amendment positions to alter filter performance and effluent corrosion control

Research filter media materials are basalt, calcite, and dolomite limestone

Research OriginsResearch Origins Slow sand filters of the City of Salem, OR provide drinking Slow sand filters of the City of Salem, OR provide drinking

water for 155,000 residents from the Santiam Riverwater for 155,000 residents from the Santiam River

Research OriginsResearch Origins Santiam River produces filter effluent with pH < 7 Santiam River produces filter effluent with pH < 7

SSF were unable to treat water with > 140 ntu claySSF were unable to treat water with > 140 ntu clay turbidity during the flood of 1996turbidity during the flood of 1996

Research QuestionsResearch Questions

Will roughing filters amended with Will roughing filters amended with limestone enhance clay removal?limestone enhance clay removal?

Will a SSF amended with limestone Will a SSF amended with limestone enhance effluent corrosion control?enhance effluent corrosion control?

Laboratory ExperimentsLaboratory ExperimentsBench-scale RF clay turbidity challenge tests:Bench-scale RF clay turbidity challenge tests:

Compared clay removal of basalt and calcite media Compared clay removal of basalt and calcite media

Calcium Dissolution

48-minute Detention

Ca2+ (mg/L)

BASALT 1.55

CALCITE 8.42

X-Ray DiffractionX-Ray DiffractionQualitatively examined clay removal using changes in Qualitatively examined clay removal using changes in kaolinite and montmorillonite XRD peak area ratios (K/M)kaolinite and montmorillonite XRD peak area ratios (K/M)

Kaolinite ~ 25Kaolinite ~ 25o o / Montmorillonite ~ 27/ Montmorillonite ~ 27oo

0200400600800

100012001400160018002000

22 23 24 25 26 27 28 29 30

2-Theta (degrees)

Inte

nsit

y (c

ount

s)

Clay Removal TrendsClay Removal Trends

BASALTBASALT

CALCITECALCITE

0

1

2

3

4

5

6

7

8

K/M

Influent Effluent

012345678

0 100 200 300 400 500 600 700Time (minutes)

K/M

Pilot-scale ResearchPilot-scale Research Three RF/SSF configurations: Three RF/SSF configurations:

Basalt, Calcite, Calcite-amended Basalt Filter MediaBasalt, Calcite, Calcite-amended Basalt Filter Media 60-day study & 150 NTU clay challenge tests60-day study & 150 NTU clay challenge tests

Flow

To Waste

Overflow

Raw wa ter

Sample Tap

CalciteLimestone

Layer

EffluentPump

SSF

P1P2

P3

Roughing Filter Research ResultsRoughing Filter Research Results

Parameter River BRF/SSF CRF/SSF CBRF/SSFTurbidity (ntu) 150 -88.0 -95.3 -99.6

pH 7.3 -0.4 +14.4 +0.2

Ca2+ (mg/L) 4.1 -0.2 +73.4 +0.4

Alkalinity (mg/L as CaCO3) 30.1 -1.3 +47.8 +13.7Conductivity (S/cm) 36.6 +1.0 +43.7 +12.5

% change during challenge study

SSF Corrosion ControlSSF Corrosion Control

Effluent pH decreased by:Effluent pH decreased by: Microbial activityMicrobial activity COCO22 conversion conversion

Increase effluent pH by:Increase effluent pH by:

Installing dolomite layerInstalling dolomite layer

48 cm from schmutzdecke48 cm from schmutzdecke

EffluentTap

Sand

Dolomite

Sand

GravelWaste Waste

SampleTap

PolyethyleneTank

RawWater

Overflow

Corrosion Control ResultsCorrosion Control Results Effluent met OHD pH requirements for majority of 60-day study Effluent met OHD pH requirements for majority of 60-day study

Saturation Index, alkalinity, and hardness raisedSaturation Index, alkalinity, and hardness raised

5.5

6.0

6.5

7.0

7.5

8.0

8.5

0 10 20 30 40 50 60Time (days)

pH

Active LayerSSF Effluent

Mineral Service Life CalculationMineral Service Life Calculation Constant flow rateConstant flow rate Filter areaFilter area Range of dolomite packed densityRange of dolomite packed density Assumption of stoichiometric dissolutionAssumption of stoichiometric dissolution

CaMg(COCaMg(CO33))2 2

CaCa2+ 2+ + Mg+ Mg2+ 2+ + 2CO+ 2CO33

Verified by:Verified by: EDTA titration hardnessEDTA titration hardness vs. vs. Hardness by Calculation Hardness by Calculation

(P > 0.12)(P > 0.12)

7

8

9

10

1200 1300 1400 1500 1600 1700

Dolomite Density (kg/m3)

Serv

ice

Life

(yea

rs)

Effluent Limestone ContactorEffluent Limestone Contactor

Research study limestone media acquired from:

Ashgrove Rivergate Lime Plant, Portland, Oregon

Contactor Feasibility Decision TreeContactor Feasibility Decision Tree Design contactor length using EPA DESCON program Design contactor length using EPA DESCON program

Parameters needed:Parameters needed: pHpH Alkalinity (DIC)Alkalinity (DIC) CalciumCalcium IronIron ManganeseManganese

Available at Raymond Letterman’s website http://web.syr.edu/~rdletter/Available at Raymond Letterman’s website http://web.syr.edu/~rdletter/

Research ResultsResearch Results

Slow sand filters pretreated by calcite-amended roughing Slow sand filters pretreated by calcite-amended roughing filters comply with regulatory requirements for raw water filters comply with regulatory requirements for raw water clay turbidity <1 to 150 NTU, while enhancing effluent clay turbidity <1 to 150 NTU, while enhancing effluent corrosion control characteristics.corrosion control characteristics.

Dolomite-amended slow sand filters enhance effluent Dolomite-amended slow sand filters enhance effluent corrosion control, and amendment layer service life corrosion control, and amendment layer service life appears acceptable for engineering applications.appears acceptable for engineering applications.

Limestone contactors are an applicable corrosion control Limestone contactors are an applicable corrosion control engineering design for surface waters of the Pacific engineering design for surface waters of the Pacific Northwest.Northwest.

AcknowledgementsAcknowledgements Environmental & Water Resources Institute (ASCE)Environmental & Water Resources Institute (ASCE)

Oregon State University, Oregon State University, Dr. J. Ronald MinerDr. J. Ronald Miner

University of Notre Dame, University of Notre Dame, Dr. Lloyd H. Ketchum, Jr.Dr. Lloyd H. Ketchum, Jr.

City of Salem water operations and engineering staffCity of Salem water operations and engineering staff

Publications:Publications: Rooklidge, S., Ketchum, L., Burns, P. 2002. Clay Removal in Rooklidge, S., Ketchum, L., Burns, P. 2002. Clay Removal in

Basaltic and Limestone Horizontal Roughing Filters. Basaltic and Limestone Horizontal Roughing Filters. Advances in Advances in Environmental ResearchEnvironmental Research, 7/1, 231-237., 7/1, 231-237.

Rooklidge, S., Ketchum, L. 2002. Corrosion Control Rooklidge, S., Ketchum, L. 2002. Corrosion Control Enhancement from a Dolomite-amended Slow Sand Filter. Enhancement from a Dolomite-amended Slow Sand Filter. Water Water ResearchResearch, 36/11, 2689-2694., 36/11, 2689-2694.

Rooklidge, S., Ketchum, L. 2002. Calcite-Amended Roughing Rooklidge, S., Ketchum, L. 2002. Calcite-Amended Roughing Filtration for Clay Turbidity Removal. Filtration for Clay Turbidity Removal. Journal of Water Supply: Journal of Water Supply: Research and Technology- AquaResearch and Technology- Aqua, 51/6, 333-343., 51/6, 333-343.