arsenic removal using aged rapid sand filter media

Arsenic Removal Using Aged Arsenic Removal Using Aged Rapid Sand Filter MediaRapid Sand Filter Media

bybyC. Menard, D. Burt, M.R. CollinsC. Menard, D. Burt, M.R. Collins

Water Treatment Technology Assistance CenterWater Treatment Technology Assistance CenterDepartment of Civil EngineeringDepartment of Civil Engineering

University of New HampshireUniversity of New Hampshire

Summer 2007Summer 2007

OUTLINEOUTLINE

BACKGROUNDBACKGROUNDRESEARCH OBJECTIVERESEARCH OBJECTIVE

Assess coating characteristics of ‘aged’ rapid sand filter Assess coating characteristics of ‘aged’ rapid sand filter media.media.

Quantity Arsenic removal potentials using “aged” rapid Quantity Arsenic removal potentials using “aged” rapid sand filter.sand filter.

Evaluate interferences associated with the adsorption Evaluate interferences associated with the adsorption capacity of the metal oxide coating.capacity of the metal oxide coating.

CONCLUSIONCONCLUSION

BACKGROUNDBACKGROUND

Reduction/Elimination of ArsenicReduction/Elimination of Arsenic

Ion exchangeIon exchange

Coagulation / FiltrationCoagulation / Filtration

Membrane filtration (Reverse Osmosis)Membrane filtration (Reverse Osmosis)

Innovative adsorbents, e.g. metal oxidesInnovative adsorbents, e.g. metal oxides


Conventional Water Treatment (Pathogen Removal)Conventional Water Treatment (Pathogen Removal)

––

CoagulantsCoagulantsAluminum SulfateAluminum SulfateFerrous Sulfate, Ferric Sulfate, and Ferric Ferrous Sulfate, Ferric Sulfate, and Ferric ChlorideChloride

––

Slow sand filtration processSlow sand filtration process


Natural Aging of Metal Hydroxides to More Stable Natural Aging of Metal Hydroxides to More Stable Metal OxidesMetal Oxides

Al(OH)Al(OH)3 3 →→→→→→→→→→→→AlAl22

OO33

Fe(OH)Fe(OH)3 3 →→→→→→→→→→→→FeFe22

OO33

REMOVAL ENHANCEMENT POSSIBILITY!!!REMOVAL ENHANCEMENT POSSIBILITY!!!Make use of metal oxide coatings that form Make use of metal oxide coatings that form ‘naturally’ over many ‘naturally’ over many yearsyears on filter media in WTP on filter media in WTP from carryover of metal hydroxide flocs produced from carryover of metal hydroxide flocs produced from “sweepfrom “sweep--floc” coagulationfloc” coagulation

RESEARCH OBJECTIVESRESEARCH OBJECTIVES

Explore the Arsenic removal potential of ‘naturally’ Explore the Arsenic removal potential of ‘naturally’ coated, regenerable sand filter media.coated, regenerable sand filter media.

1)1)

Assess coating characteristics of ‘aged’ Assess coating characteristics of ‘aged’ rapid rapid sand filter media.sand filter media.

2)2)

Quantify Arsenic removal potentials using Quantify Arsenic removal potentials using ‘aged’ sand ‘aged’ sand filter media.filter media.

3)3)

Evaluate interferences associated with the Evaluate interferences associated with the adsorption capacity of the metal oxide coating. adsorption capacity of the metal oxide coating.

METHODOLOGYMETHODOLOGY

Materials used for Objective 1Materials used for Objective 1

Filter MediaFilter Media––

Portsmouth, NH WTP sand Portsmouth, NH WTP sand ––

Philadelphia, PA WTP sand Philadelphia, PA WTP sand

Characterization MethodsCharacterization Methods––

SEM analysis SEM analysis ––

Electron microprobe analysisElectron microprobe analysis Portsmouth, NH Philadelphia, PA

Average Metal Coating Content ofAverage Metal Coating Content of Selected Rapid Sand Filters Selected Rapid Sand Filters ––

SEM pictureSEM picture

Portsmouth, 1996

Average Metal Coating Content ofAverage Metal Coating Content of Selected Rapid Sand Filters Selected Rapid Sand Filters ––SEM pictureSEM picture

Philadelphia, 2006

Average Metal Coating Content ofAverage Metal Coating Content of Selected Rapid Sand Filters Selected Rapid Sand Filters ––SEM pictureSEM picture

Philadelphia, 1996

Average Metal Coating Content ofAverage Metal Coating Content of Selected Rapid Sand Filters Selected Rapid Sand Filters

Philadelphia, 1996

Electron Microprobe

picture

Silica

grain

A

C

GF

E

D

B

Average Metal Coating Content ofAverage Metal Coating Content of Selected Rapid Sand Filters Selected Rapid Sand Filters

Philadelphia, 1996

W eight Oxide Percent

0

20

40

60

80

100

120

A B C D E F G

Layer Level

Per

cent

of O

xid

Al2O3MnOFeOSiO2



1)1)


2)2)

Quantify Arsenic removal potentials using Quantify Arsenic removal potentials using ‘aged’ sand filter media.‘aged’ sand filter media.

3)3)

Evaluate interferences associated with the Evaluate interferences associated with the adsorption capacity of the metal oxide coating. adsorption capacity of the metal oxide coating.


Experimental SetExperimental Set--UpUp

Backwash (BW) ProcedureBackwash (BW) Procedure––

50/100 mL sand in 500/1000 mL buffered water50/100 mL sand in 500/1000 mL buffered water––

Backwash at target pH’s for 1 hourBackwash at target pH’s for 1 hour

Equilibration ProcedureEquilibration Procedure––

Buffered water at the pH of the Challenge solutionBuffered water at the pH of the Challenge solution

Challenge ProcedureChallenge Procedure––

Arsenic Solution according to the array Arsenic Solution according to the array

Backwash/Regeneration SetBackwash/Regeneration Set--UpUp

pH controller

AcidBase

Motor with paddle

BufferedWater

Media(Sand)

Pumps

Challenge SetChallenge Set--UpUp

Filter1

Filter2

Filter3

Filter4

Effluent to Autosampler

Pump

Reservoir

pH controller

AcidBase



1)1)


2)2)

Quantify Arsenic removal potentials using Quantify Arsenic removal potentials using ‘aged’ sand filter media.‘aged’ sand filter media.

3)3)

Evaluate interferences associated with the Evaluate interferences associated with the adsorption capacity of the metal oxide coating.adsorption capacity of the metal oxide coating.


L 16 ORTHOGONAL ARRAYL 16 ORTHOGONAL ARRAY5 5 parametersparameters

––

EBCTEBCT––

pH of the challenge solutionpH of the challenge solution––

PresencePresence

of sulfateof sulfate––

PresencePresence

of of naturalnatural

organicorganic

mattermatter––

pH of the pH of the backwashingbackwashing

2 2 levelslevels

RESULTSRESULTSARSENIC REMOVED / BED VOLUME ARSENIC REMOVED / BED VOLUME atat

95 BV (g/m95 BV (g/m33))

[As]removed/ BVRUN/BV EBCT pH SO4 NOM BW 95

RUN1 2.5 6 0 0 8 3363

RUN2 2.5 6 0 6 8 3176

RUN3 2.5 6 200 6 8 3593

RUN4 2.5 6 200 6 11 3502

RUN5 2.5 8 200 6 11 2302

RUN6 2.5 6 200 0 8 3361

RUN7 2.5 6 0 0 11 3521

RUN8 2.5 8 0 0 8 2351

RUN9 5 6 200 6 11 3413

RUN10 5 8 200 6 8 3011

RUN11 5 8 0 6 11 1755RUN12 5 6 0 0 8 5873RUN13 5 8 0 0 8 4216

RUN14 5 8 0 0 11 3980

RUN15 5 8 200 0 11 4531

RUN16 5 8 200 6 11 3327

RESULTSRESULTSARSENIC REMAINING VERSUS BED VOLUME

arsenic restant vs bed volume

00,10,20,30,40,50,60,70,80,9

11,11,21,31,41,51,61,7

0 20 40 60 80 100 120

bed volume

[As]

(mg/

L

RUN1

RUN2

RUN3

RUN4

RUN5

RUN6

RUN7

RUN8

RUN9

RUN10

RUN11

RUN12

RUN13

RUN14

RUN15

RUN16

feed average

PREDICTION PROFILERPREDICTION PROFILER

INTERPRETATIONINTERPRETATIONar

seni

c re

mov

ed/

BV

(mg/

L) 6004.27

1729.2

3809.291±728.51

EBCT

1 2

pH

1 2

SO4

1 2

NOM

1 2

BW

1 2

EBCT(0.0113) > pH (0.0186) > NOM (0.0227) >> SO4 (0.3028) > BW (0.6037)

MODEL EQUATIONMODEL EQUATIONINTERPRETATIONINTERPRETATION

1000

2000

3000

4000

5000

6000

arse

nic

rem

oved

/ BV

(mg/

L) A

ctua

l

1000 2000 3000 4000 5000 6000arsenic removed/ BV (mg/L) PredictedP=0.0284 RSq=0.67 RMSE=670.91

Y = - 608,5*EBCT + 549,8*pH + (-213,7*SO4) + 526,7*NOM + 99,7*BW + 3454,6

SUMMARYSUMMARYSand coating composed mainly with aluminum, manganese Sand coating composed mainly with aluminum, manganese oxide with a beginning of small ratio of iron oxidesoxide with a beginning of small ratio of iron oxides

EBCT, pH and NOM: most important effectEBCT, pH and NOM: most important effect

Slight positive impact with the presence of sulfateSlight positive impact with the presence of sulfate

No significant effect of BW pH: in the range of recommended No significant effect of BW pH: in the range of recommended pH for aluminum coated sandpH for aluminum coated sand

RecommendationsRecommendationsAdditional experiments to analyze more precisely effect Additional experiments to analyze more precisely effect of sulfate but also others anions like phosphateof sulfate but also others anions like phosphate

Additional experiments to determine durability of Additional experiments to determine durability of coatings, test raw watercoatings, test raw water

Pilot or Full scale demonstrationPilot or Full scale demonstration

AnalyseAnalyse

Portsmouth sand with Electron microprobePortsmouth sand with Electron microprobe

arsenic removal using aged rapid sand filter media

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