filter media choices and filter optimization
TRANSCRIPT
11
FILTER MEDIA CHOICES FILTER MEDIA CHOICES
AND FILTER OPTIMIZATIONAND FILTER OPTIMIZATION
Marvin Gnagy, P.E.Marvin Gnagy, P.E.
Water Resources ManagerWater Resources Manager
URS Corporation URS Corporation -- ToledoToledo
22
AgendaAgenda
•• Importance of filter optimizationImportance of filter optimization
•• Filter coring techniquesFilter coring techniques
•• Floc retention profilesFloc retention profiles
•• Bed depth evaluations Bed depth evaluations
•• Backwash duration testsBackwash duration tests
33
AgendaAgenda
•• Bed expansion evaluationsBed expansion evaluations
•• Sieve analysesSieve analyses
•• Water temperature effects on wash rateWater temperature effects on wash rate
•• FilterFilter--toto--waste simulationswaste simulations
•• Media growth / acid solubilityMedia growth / acid solubility
•• Media design parametersMedia design parameters
44
Importance of Filter Importance of Filter
OptimizationOptimization
•• Optimize filtration and backwashOptimize filtration and backwash
•• Improve filter effluent qualityImprove filter effluent quality
•• Reduce filter ripening timeReduce filter ripening time
•• Reduce turbidity / particle count spikesReduce turbidity / particle count spikes
•• Meet lower turbidity standardsMeet lower turbidity standards
•• Prevent exceptions reportingPrevent exceptions reporting
55
Importance of Filter Importance of Filter
OptimizationOptimization
•• Identify filter operating problemsIdentify filter operating problems
•• Identify current media conditionsIdentify current media conditions
•• Define proper bed depthDefine proper bed depth
•• Establish operating adjustmentsEstablish operating adjustments
•• Predict media replacement needsPredict media replacement needs
•• Optimize particle/microbial removalsOptimize particle/microbial removals
66
Filter Exceptions ReportingFilter Exceptions Reporting
• Exceed filter effluent turbidity limits in 2
consecutive samples taken 15 minutes
apart…
•• Filter profileFilter profile
•• Filter self assessmentFilter self assessment
•• ThirdThird--party Comprehensive Performance party Comprehensive Performance
Evaluation (CPE)Evaluation (CPE)
77
Turbidity MonitoringTurbidity Monitoring
•• Continuous turbidity monitoring of Continuous turbidity monitoring of
individual filter effluents individual filter effluents
•• 0.3 NTU in 95% samples taken0.3 NTU in 95% samples taken
•• Maximum 1 NTU at any timeMaximum 1 NTU at any time
1515
Filter Coring TechniquesFilter Coring Techniques
•• Electrical conduit makes good coring Electrical conduit makes good coring
devicedevice
•• Core in same spot each depthCore in same spot each depth
•• Samples in individual marked bagsSamples in individual marked bags
•• Samples washed and turbidity Samples washed and turbidity
measuredmeasured
1616
Floc Retention ProfilesFloc Retention Profiles
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200
NTU/100 grams
Bed Depth, inches
Less than 3,500 NTU/100
grams
Less than 150 NTU/100
grams at midpoint
No apparent potential for
breakthrough
1717
Floc Retention ProfilesFloc Retention Profiles
0
3
6
9
12
15
18
21
24
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000
NTU/100 grams
Bed Depth, inches
More than 3,500
NTU/100 grams
No apparent potential for breakthrough
Less than 150 NTU/100
grams at midpoint
1818
Floc Retention ProfilesFloc Retention Profiles
0
3
6
9
12
15
18
21
24
0 200 400 600 800 1,000 1,200 1,400
NTU/100 grams
Bed Depth, inches
Less than 3,500
NTU/100 grams
More than 150 NTU/100
grams at midpoint
Apparent breakthrough due
to excessive run time
1919
Backwash ProfilesBackwash Profiles
0
3
6
9
12
15
18
21
24
0 10 20 30 40 50 60 70 80
NTU/100 grams
Bed Depth, inches
Clean Range
Increased
surface wash
time needed
2020
Backwash ProfilesBackwash Profiles
0
3
6
9
12
15
18
21
24
0 10 20 30 40 50 60 70 80 90 100 110 120
NTU/100 grams
Bed Depth, inches
Clean Range
Poor bed expansion (16%)
lead to incomplete wash
2121
Backwash ProfilesBackwash ProfilesFLOC RETENTION GUIDELINES FOLLOWING BACKWASH
NTU/100 GRAMS MEDIA CONDITION ACTIONS NEEDED
Less than 30 Very clean Bed is too clean – examinethe wash rate and duration-
this bed will not ripen quickly.
30 to 60 Clean A well cleaned and ripenedbed – no action needed.
60 to 120 Slightly dirty Slightly dirty bed – reschedule
a backwash retention analysissoon.
Greater than 120 Dirty Dirty bed – re-evaluate the
backwash system andoperating procedures.
Greater than 300 Mud ball problems Mud balls are most likely
present – consider filterrehabilitation or rebuilding.
Greater than 2,000 Extreme mud ball
problems
Bed must be taken off line and
rebuilt to new specifications.
2525
Bed Depth EvaluationsBed Depth Evaluations
•• Minimum bed depthMinimum bed depth
• Mono/dual media L/D10 Ratio 1,000
• Multimedia L/D10 Ratio 1,250
• Provides 15% excess - media loss
•• Based on L/DBased on L/D1010 for each media layerfor each media layer
• 12-inches * 25.4 mm / inch = 304.8 mm
• 304.8 mm ÷ 0.45 mm (ES) = 677.3
2626
Bed Depth EvaluationsBed Depth Evaluations
Original Original
Media Media
DepthDepth
Depth Depth
with with
Media Media
LossLoss
Particle travelParticle travel
2727
Backwash Duration TestsBackwash Duration Tests
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
0 1 2 3 4 5 6 7
Backwash Duration, minutes
Turbidity, NTU
10 NTU reached at 4.5 minutes
2828
Backwash Duration TestsBackwash Duration Tests
020406080100120140160180200220240260280300320340360380400420440
0 1 2 3 4 5 6 7 8 9 10
Backwash Duration, minutes
Turbidity, NTU
Too many rate changes in wash cycle
10 NTU reached at 8.5
minutes
2929
Bed Expansion EvaluationsBed Expansion Evaluations
•• Determine actual bed expansionDetermine actual bed expansion
•• 30% expansion accepted as standard30% expansion accepted as standard
•• Simple device used to check expansionSimple device used to check expansion
•• Expansion observed on clean filterExpansion observed on clean filter
•• Rate adjustments should be obviousRate adjustments should be obvious
3232
Bed Expansion EvaluationsBed Expansion Evaluations
Gravel displacementGravel displacement60%60%
Excessive media lossExcessive media loss50%50%
Ineffective cleaningIneffective cleaning40%40%
Normal rangeNormal range30% to 35%30% to 35%
3333
Sieve AnalysesSieve Analyses
•• Indicates current condition of filter Indicates current condition of filter
mediamedia
•• Defines effective size and uniformity Defines effective size and uniformity
coefficientcoefficient
•• Perform every two years on each layer Perform every two years on each layer
of representative filter bedof representative filter bed
•• Helps define interfacial mixingHelps define interfacial mixing
3434
Sieve AnalysesSieve Analyses
Grain Size Distribution Curve
0
10
20
30
40
50
60
70
80
90
100
0.1001.00010.000
Diameter, mm
Percent Passing Sieve
3535
Sieve AnalysesSieve Analyses
Grain Size Distribution Curve
0
10
20
30
40
50
60
70
80
90
100
0.1001.00010.000
Diameter, mm
Percent Passing Sieve
0.62 mm
3636
Sieve AnalysesSieve Analyses
Grain Size Distribution Curve
0
10
20
30
40
50
60
70
80
90
100
0.1001.00010.000
Diameter, mm
Percent Passing Sieve
0.62 mm1.44 mm
3737
Sieve AnalysesSieve Analyses
•• DD1010 0.62 mm0.62 mm
•• DD6060 1.44 mm1.44 mm
•• ES = DES = D1010 0.62 mm0.62 mm
•• UC = DUC = D6060 ÷÷ DD1010
• 1.44mm ÷ 0.62mm = 2.32
3838
Temperature Effects on Temperature Effects on
Washwater RateWashwater Rate•• Decrease in temperature decreases the Decrease in temperature decreases the
effective backwash rateeffective backwash rate
•• Change wash rate 2% for each 1Change wash rate 2% for each 1ooC C
changechange
•• Lower rate in winterLower rate in winter
•• Higher rate in summerHigher rate in summer
•• UC also affects backwash rateUC also affects backwash rate
3939
Temperature Effects on Temperature Effects on
Washwater RateWashwater Rate
ABC WATER TREATMENT PLANT
ANTHRACITE SAND
D10, effective size, mm 0.85 0.45
D60/D10, uniformity coefficient 1.40 1.50
D90 calculated, cm 0.15 0.09
Media specific gravity 1.6 2.6
Water temp, 0C 2.0 2.0
Water viscosity, g/(cm-s) 0.01676 0.01676
Galileo Number 6,949 3,881
Fluidization Velocity, Vmf 0.45 0.43
Desired Bed Expansion, % 30% 30%
Backwash Velocity, Vmf 0.58 0.56
Backwash rate, gpm/ft2 * 8.6 8.2
Backwash rate, in/min 13.7 13.2
BACKWASH MODEL FOR RAPID RATE FILTRATION
RECOMMENDED MEDIA DESIGN BASED ON MEDIA AVAILABILITY
4040
Temperature Effects on Temperature Effects on
Washwater RateWashwater Rate
ABC WATER TREATMENT PLANT
ANTHRACITE SAND
D10, effective size, mm 0.85 0.45
D60/D10, uniformity coefficient 1.40 1.50
D90 calculated, cm 0.15 0.09
Media specific gravity 1.6 2.6
Water temp, 0C 28.0 28.0
Water viscosity, g/(cm-s) 0.00835 0.00835
Galileo Number 28,051 15,618
Fluidization Velocity, Vmf 0.79 0.80
Desired Bed Expansion, % 30% 30%
Backwash Velocity, Vmf 1.03 1.03
Backwash rate, gpm/ft2 * 15.1 15.2
Backwash rate, in/min 24.2 24.4
BACKWASH MODEL FOR RAPID RATE FILTRATION
RECOMMENDED MEDIA DESIGN BASED ON MEDIA AVAILABILITY
4141
Filter Efficiency EvaluationsFilter Efficiency Evaluations
•• Filter efficiency calculationFilter efficiency calculation
•• Gross Water Production (GWP)Gross Water Production (GWP)
%100=−
x
filteredGallons
backwashgallonsfilteredGallons
runftgalftgpmtimerunFilter //60*/*22
=
4242
Filter Efficiency EvaluationsFilter Efficiency Evaluations
•• Filter efficiency greater than 95%Filter efficiency greater than 95%
•• GWPGWP
• Monomedia 5,000 gal/ft2/run
• Dual media 10,000 gal/ft2/run
4343
Filter Efficiency EvaluationsFilter Efficiency Evaluations
•• Filter run timesFilter run times
• 48 hrs. monomedia
• 72 hrs. dual media or multimedia
• Marvin’s maximum - 150 hours
•• Washwater usageWashwater usage
• 2% to 4% raw water pumpage
• 100 gal / ft2 to 150 gal / ft2
4444
FilterFilter--toto--Waste SimulationsWaste Simulations
0.060
0.080
0.100
0.120
0.140
0.160
0.180
0 10 20 30 40 50 60 70 80 90
RUN TIME, minutes
NTU
4545
FilterFilter--toto--Waste SimulationsWaste Simulations
0.060
0.080
0.100
0.120
0.140
0.160
0.180
0 10 20 30 40 50 60 70 80 90
RUN TIME, minutes
NTU
4646
FilterFilter--toto--Waste SimulationsWaste Simulations
0.060
0.080
0.100
0.120
0.140
0.160
0.180
0 10 20 30 40 50 60 70 80 90
RUN TIME, minutes
NTU
6363--minute ripening timeminute ripening time
4747
Filter ProfilingFilter Profiling
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 10 20 30 40 50 60 70 80 90 100
Filter run time, hours
Turbidity, NTU
Increased flow due to
filter wash
Terminal head loss,
terminate filter run
4848
Media Growth / Acid SolubilityMedia Growth / Acid Solubility
•• Check growth rate every yearCheck growth rate every year
• Media above ES range• Consider replacement / acid cleaning
• Growth increases ES and UC
•• Keep COKeep CO33 deposition to a minimumdeposition to a minimum
• CO3 alkalinity ≤35 mg/L applied
• Perform acid solubility every year
• Solubility less than 2% per year
4949
Media Design ParametersMedia Design Parameters
•• ES ranges ES ranges
• 0.40 mm to 0.55 mm sand
• 0.80 mm to 1.20 mm anthracite
• 0.45 mm to 2.0 mm GAC (cap vs. monomedia)
•• UC less than 1.65 UC less than 1.65
• Consider low UC for anthracite to reduce
backwash rate
•• Minimum 12Minimum 12--inches filter sand (24inches filter sand (24--inches inches
monomedia)monomedia)
5050
Media Design ParametersMedia Design Parameters
•• Typical bed depth 24Typical bed depth 24--inches to inches to
6060--inchesinches
•• Match ES and UC for each layer to Match ES and UC for each layer to
obtain similar backwash rateobtain similar backwash rate
•• L/DL/D1010 ratio defines minimum bed depthratio defines minimum bed depth
•• Critical bed depth at lower L/DCritical bed depth at lower L/D1010 rangerange
5151
Media Design ParametersMedia Design Parameters
•• DD9090/D/D1010 ratios for dual media filtersratios for dual media filters
• 3 for anthracite / sand media
• 5 for GAC / sand media
•• Low DLow D9090/D/D1010 ratio ratio -- media layeringmedia layering
•• High DHigh D9090/D/D1010 ratio ratio -- mixed mediamixed media
5252
Media Design ParametersMedia Design Parameters
MEDIA DEPTH TO EFFECTIVE SIZE RATIO (L/D10 Ratio)
COARSE TO FINE MEDIA RATIO (D90/D10 RATIO)
ANTHRACITE SAND GAC
Media depth, inches 12 18 12
Media depth, mm 304.8 457.2 304.8
L/D10 Ratio 358.6 1016.0
D90 anthracite, mm 1.49
D90/D10 Ratio (3:1 or 4:1) 3.31
Total L/D10 Ratio >=1,000 1,375
5353
Mud BallsMud Balls
•• Ineffective backwash/surface washIneffective backwash/surface wash
•• Accumulated floc material in mediaAccumulated floc material in media
•• 1/81/8”” to basket ball size mud balls have to basket ball size mud balls have
been observedbeen observed
•• Deteriorate filter bed quicklyDeteriorate filter bed quickly
• Washing wand can break up mud balls
• Raking can break up mud balls