arsenic removal using aged rapid sand filter media
TRANSCRIPT
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
BACKGROUNDBACKGROUND
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
BACKGROUNDBACKGROUND
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
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 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.
METHODOLOGYMETHODOLOGY
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
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 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.
METHODOLOGYMETHODOLOGY
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