The Slow Sand Filter Mystery Major Events in Slow Sand Filtration HistoryResearch at CornellParticle Removal MechanismsSearch for the Mystery CompoundSSF research by CEE 453

An old technology that is poorly understoodParticle removal improves with time!Until recently no one knew how particles were removed by slow sand filtersThe mystery is not yet solvedPotential for new useful knowledge

A.Valve for raw water inlet and regulation of filtration rateB.Valve for draining unfiltered waterC.Valve for back-filling the filter bed with clean waterD.Valve for draining filter bed and outlet chamberE.Valve for delivering treated water to wasteF.Valve for delivering treated water to the clear-water reservoirABCDEFFilter CakeSandGravelUnderdrains

1790 - SSF used in Lancashire, England to provide clean water for textile industry1829 - SSF used to filter municipal water (London)1850: John Snow established the link between drinking water (from a contaminated well) and Cholera1885- SSF shown to remove bacteria1892 - Cholera outbreak in Hamburg, Altoona saved by slow sand filters1980s - Giardia shown to be removed by SSF1990s - Cryptosporidium not always removed by SSF

In 1885 Percy F. Frankland used the recently devised 'gelatin process' of Robert Koch to enumerate bacteria in raw and filtered waterFrankland showed that filtration reduced the average bacteria concentration from Thames water 97.9%It is most remarkable, perhaps, that these hygienically satisfactory results have been obtained without any knowledge on the part of those who construct these filters, as to the conditions necessary for the attainment of such results. (Percy F. Frankland)

Large outbreak of Cholera in Hamburg17,000 cases; 8,600 deathsVery few cases in neighborhoods served by Altoona's filtered water supplyHamburg's sewers were upstream from Altoona's intake!Hamburg'swater intakeAltoona'swater intakeand filter bedsHamburg's seweroutfallsHamburgAltoonaElbe River

Milwaukee (March 1 to April 10 1993): an estimated 370,000 city residents suffered from diarrhea, nausea, and stomach cramps caused by CryptosporidiosisEvidence suggests that a substantial proportion of non-outbreak-related diarrheal illness may be associated with consumption of water that meets all current water quality standardsSlow sand filters shown to remove less than 50% of Cryptosporidium oocysts at an operating plant in British Columbia

How do slow sand filters remove particles including bacteria, Giardia cysts, and Cryptosporidium oocysts from water?Why dont SSF always remove Cryptosporidium oocysts?Is it a biological or a physical/chemical mechanism?Would it be possible to improve the performance of slow sand filters if we understood the mechanism?

Sampling tubeLower to collect sampleManifold/valve blockPeristaltic pumpsManometer/surge tubeCayuga Lake water(99% or 99.5% of the flow)Auxiliary feeds(each 0.5% of the flow)1 liter E. coli feed1 liter sodium azideTo wasteFilter cell with 18 cm of mediumSampling Chamber

Continuously mixed Cayuga Lake water0.050.11012345Time (days)Fraction of influent E. coli remaining in the effluent

Fraction of influent E. coli remaining in the effluent

Effluent particle count (Dnumber/l/Dparticle diameter)

long flagellum used for locomotion and to provide feeding currentshort flagellumstalk used to attach to substrate (not actually seen in present study)1 m

Mechanisms

The biological activity of microorganisms being removed in the filter column was not significant The biological activity of the filter biopopulation was only significant for removal of particles smaller than 2 m.Biofilms were expected to increase removal of particles larger than 2 m as well by increasing the attachment efficiency. The lack of biologically enhanced removal of particles larger than 2 m suggested that sticky biofilms did not contribute significantly to particle removal.

The immediate and reversible response of slow sand filters to sodium azide was consistent with bacterivory and inconsistent with particle removal by biofilms. Biologically mediated mechanisms together with physical-chemical mechanisms accounted for removal of particles smaller than about 2 m in diameter. In this research bacterivory was the only significant biologically mediated particle removal mechanism.Mechanisms

Day 5

Day 5

Physical-chemical particle removal mechanisms are significant in slow sand filters. Physical-chemical particle removal efficiency was greatest when particles previously had been retained by the filter (within the bed or in the filter cake) and was considered to be caused by attachment of particles to retained particles. Further work is necessary to determine what types of particles are most effective for filter ripening.

Mechanisms

Chart2

0.00521739130.00292682930.00426299050.00090354610.00001611770.00073826330.00001316930.00050686730.00000904160.00214209970.00037096810.0000066174

0.00235418880.00392364790.00347826090.00040769760.00000727260.00060236410.00001074510.0006794960.0000121210.00235418880.00040769760.0000072726

0.00150583240.00205726410.00209968190.00026077960.00000465190.00036362220.00000648640.00035627630.00000635530.00267232240.00046279190.0000082554

0.00201484620.01946977730.01790031810.00034893040.00000622430.00309997110.00005529810.00337176950.00006014650.04262990460.00738263260.0001316933

0.0103499470.03902439020.04475079530.00179240030.00003197330.00774992770.00013824520.00675823080.00012055510.2547189820.04411214790.0007868838

0.01215270410.0466595970.04750795330.00210460120.00003754240.00822741140.00014676270.00808049340.00014414190.34570519620.059869110.0010679605

0.01136797450.05047720040.04856839870.0019687020.00003511820.0084110590.00015003860.00874162460.00015593530.39236479320.06794960330.0012121025

0.0107953340.05090137860.05132555670.00186953230.00003334920.00888854270.00015855610.00881508370.00015724570.38812301170.0672150130.0011989987

0.01041357370.05005302230.04835630970.00180341920.00003216990.00837432950.00014938340.00866816560.0001546250.41569459170.071989850.0012841734

0.00948038180.0494167550.04899257690.00164180930.0000292870.0084845180.0001513490.00855797710.00015265940.4135737010.07162255490.0012776215

0.00909862140.04793213150.04856839870.00157569620.00002810770.0084110590.00015003860.00830087050.00014807310.43054082710.07456091610.0013300368

0.0089713680.04559915160.04814422060.00155365850.00002771460.00833760.00014872820.00789684580.0001408660.42841993640.07419362090.0013234848

Completely Mixed

2 cm layer

Top Layer

Control

Time (min)

fraction remaining

Sheet1

in turb47.15NTU

in turb 238.2NTU

Control ColumnCompletely Mixed2 cm DepthTop Layer

ErrorErrorErrorError

Time (min)raw dataFraction Remainingpositivenegativeraw dataFraction Remainingpositivenegativeraw dataFraction Remainingpositivenegativeraw dataFraction Remainingpositivenegative

00.1010.002140.000370.000010.2460.005220.000900.000020.1380.002930.000510.000010.2010.004260.000740.00001

50.1110.002350.000410.000010.1110.002350.000410.000010.1850.003920.000680.000010.1640.003480.000600.00001

100.1260.002670.000460.000010.0710.001510.000260.000000.0970.002060.000360.000010.0990.002100.000360.00001

152.0100.042630.007380.000130.0950.002010.000350.000010.9180.019470.003370.000060.8440.017900.003100.00006

2012.0100.254720.044110.000790.4880.010350.001790.000031.8400.039020.006760.000122.1100.044750.007750.00014

2516.3000.345710.059870.001070.5730.012150.002100.000042.2000.046660.008080.000142.2400.047510.008230.00015

3018.5000.392360.067950.001210.5360.011370.001970.000042.3800.050480.008740.000162.2900.048570.008410.00015

3518.3000.388120.067220.001200.5090.010800.001870.000032.4000.050900.008820.000162.4200.051330.008890.00016

4019.6000.415690.071990.001280.4910.010410.001800.000032.3600.050050.008670.000152.2800.048360.008370.00015

4519.5000.413570.071620.001280.4470.009480.001640.000032.3300.049420.008560.000152.3100.048990.008480.00015

5020.3000.430540.074560.001330.4290.009100.001580.000032.2600.047930.008300.000152.2900.048570.008410.00015

5520.2000.428420.074190.001320.4230.008970.001550.000032.1500.045600.007900.000142.2700.048140.008340.00015

Averages18.9570.402060.069630.001240.4870.010330.001790.000032.2970.048720.008440.000152.3000.048780.008450.00015

Error

depth of column (cm)steady state removalpositivenegative

00.0490.0080.000

20.0490.0080.000

200.0100.0020.000

Control ColumnCompletely Mixed2 cm DepthTop Layer

ErrorErrorErrorError

Time (min)raw dataFraction Remainingpositivenegativeraw dataFraction Remainingpositivenegativeraw dataFraction Remainingpositivenegativeraw dataFraction Remainingpositivenegative

00.1030.002700.000470.000010.0610.001600.000280.000010.0720.001880.000330.000010.0790.002070.000360.00001

50.2310.006050.001050.000020.0690.001810.000310.000010.0560.001470.000250.000010.0880.002300.000400.00001

100.2000.005240.000910.000020.0510.001340.000230.000010.0500.001310.000230.000000.0540.001410.000240.00001

150.3270.008560.001480.000030.0690.001810.000310.000010.1130.002960.000510.000010.1690.004420.000770.00002

204.2600.111520.019310.000430.1810.004740.000820.000020.1120.002930.000510.000010.4710.012330.002140.00005

2515.1000.395290.068460.001510.1700.004450.000770.000020.1350.003530.000610.000010.7180.018800.003260.00007

3017.6000.460730.079790.001760.2790.007300.001260.000030.1400.003660.000630.000010.8130.021280.003690.00008

3516.1000.421470.072990.001610.1730.004530.000780.000020.1360.003560.000620.000010.8700.022770.003940.00009

4017.2000.450260.077980.001720.1700.004450.000770.000020.1300.003400.000590.000010.9380.024550.004250.00009

6016.7000.437170.075710.001670.1910.005000.000870.000020.1500.003930.000680.000011.1300.029580.005120.00011

8016.7000.437170.075710.001670.2240.005860.001020.000020.1420.003720.000640.000011.3100.034290.005940.00013

10017.0000.445030.077070.001700.1770.004630.000800.000020.1800.004710.000820.000021.3300.034820.006030.00013

Averages16.6290.435300.075390.001660.1980.005180.000900.000020.1450.003790.000660.000011.0160.026590.004600.00010

Error

depth of column (cm)steady state removalpositivenegative

00.0270.0050.00010

20.0040.0010.00001

200.0050.0010.00002

Turbidity Readings

Trial #Distilled WaterHigh Clay ConcentrationLow Clay Concentration

10.06424.20.846

20.05725.50.945

30.05924.90.81

40.0625.20.88

50.05625.80.77

60.05627.10.855

70.05728.50.903

80.05722.40.854

90.06124.70.893

100.056210.757

110.06822.70.992

120.0550.833

130.0620.781

140.0580.814

150.0590.851

160.0580.915

170.0560.82

180.0630.823

190.060.885

200.0560.945

Std Dev0.0033424.727270.85860

Average0.058902.134520.06174

% error0.056690.086320.07191

depth of column20cm

Determination of k

BPP Concentration (mg/cm^3)CinCoutdk

Control047.1518.95714200.04556

Long_Term038.2016.62857200.04159

Comp Mixed0.3578747.150.48686200.22866

Long-Term0.3578738.200.19771200.26319

2 cm3.5786547.155.2158621.10081

Long-Term3.5786538.200.3059122.41364

Top Layer71.5730347.155.694530.210.56914

Long-Term71.5730338.202.323340.213.99915

Weight of 50 mL of BPP50.377g

Weight of Organics0.437g

Weight of Inorganics0.519g

Total Weight of Dry Solids0.956g

Weight of Dry Solids in 30 mL0.573g

Sheet1

0.00090354610.00001611770.00073826330.00001316930.00050686730.00000904160.00037096810.0000066174

0.00040769760.00000727260.00060236410.00001074510.0006794960.0000121210.00040769760.0000072726

0.00026077960.00000465190.00036362220.00000648640.00035627630.00000635530.00046279190.0000082554

0.00034893040.00000622430.00309997110.00005529810.00337176950.00006014650.00738263260.0001316933

0.00179240030.00003197330.00774992770.00013824520.00675823080.00012055510.04411214790.0007868838

0.00210460120.00003754240.00822741140.00014676270.00808049340.00014414190.059869110.0010679605

0.0019687020.00003511820.0084110590.00015003860.00874162460.00015593530.06794960330.0012121025

0.00186953230.00003334920.00888854270.00015855610.00881508370.00015724570.0672150130.0011989987

0.00180341920.00003216990.00837432950.00014938340.00866816560.0001546250.071989850.0012841734

0.00164180930.0000292870.0084845180.0001513490.00855797710.00015265940.07162255490.0012776215

0.00157569620.00002810770.0084110590.00015003860.00830087050.00014807310.07456091610.0013300368

0.00155365850.00002771460.00833760.00014872820.00789684580.0001408660.07419362090.0013234848

&A

Page &P

Completely Mixed

2 cm layer

Top Layer

Control

Time (min)

fraction remaining

Sheet2

0000.00035814640.00000788550.00027654340.00000608880.00032641190.000007186800.00046695040.0000102811

0000.00039894790.00000878390.00031281140.00000688740.00025387590.000005589700.00104723830.0000230577

0000.0002448090.00000539010.00023120850.00000509070.0002266750.000004990800.00090669980.0000199634

0000.00076616130.00001686910.00031281140.00000688740.00051228540.000011279300.00148245420.0000326401

0000.00213527810.00004701380.00082056330.00001806690.00050775190.000011179500.01931270610.0004252202

0000.00325505230.00007166860.00077069480.00001696890.00061202240.000013475300.06845583610.0015072359

0000.00368573470.00008115120.00126484620.00002784890.00063468990.000013974400.07978958370.0017567782

0000.00394414420.00008684070.00078429530.00001726830.00061655590.000013575100.07298933510.0016070528

0000.00425242210.00009362830.00077069480.00001696890.00058935490.000012976200.07797618410.0017168515

0000.0051228540.00011279310.00086589830.0000190650.00068002490.000014972500.07570943460.001666943

0000.00593888380.00013076020.00101550380.0000223590.00064375690.00001417400.07570943460.001666943

0000.00602955380.00013275650.00080242930.00001766760.00081602980.000017967100.07706948430.0016968881

&A

Page &P

Completely Mixed

2 cm layer

Top Layer

Control

Time (min)

fraction remaining

Sheet3

00.00844778850.0001506938

00.00843729440.0001505066

00.00178820270.0000318984

&A

Page &P

depth of column (cm)

fraction remaining

Sheet4

00.00460409210.0001013712

00.00065606210.0000144449

00.00089633750.0000197352

&A

Page &P

depth of column (cm)

fraction remaining

Sheet5

0.00844778850.00015069380.00460409210.0001013712

Scaling Measurements

Alison Humphries, Michael Steiger, David KeyserSlow Sand Filtration Research Project for Cee 453

&A

Page &P

Control

Control Long-Term

fraction remaining

0.0696286669

0.001242054

0.0753856132

0.0016598132

&A

Page &P

Top Layer

Top Layer Long-Term

fraction remaining

Sheet6

0.00178820270.00003189840.00089633750.0000197352

&A

Page &P

Completely Mixed

Completely Mixed Long-Term

fraction remaining

Sheet7

00.00843729440.000150506600.00065606210.0000144449

&A

Page &P

2 cm

2 cm Long-Term

fraction remaining

Sheet8

0

0

0

0

0

0

&A

Page &P

Concentration of BPP (mg/cm3)

k (1/cm)

Sheet9

&A

Page &P

Sheet10

&A

Page &P

Sheet11

&A

Page &P

Sheet12

&A

Page &P

Sheet13

&A

Page &P

Sheet14

&A

Page &P

Sheet15

&A

Page &P

Sheet16

&A

Page &P

&A

Page &P

&A

Page &P

&A

Page &P

&A

Page &P

&A

Page &P

&A

Page &P

&A

Page &P

C/CoTime (minutes)?

Chart3

0.10.03278688520.02014423080.020952381

0.03485714290.00928961750.031250.0256709957

0.01714285710.00928961750.07163461540.0761904762

0.01485714290.01147540980.07884615380.0883116883

0.020.00765027320.09567307690.0956709957

0.02171428570.00874316940.10384615380.1004329004

0.02228571430.00983606560.16298076920.1064935065

0.02114285710.01803278690.43221153850.1173160173

0.0240.02295081970.56250.1995670996

0.02914285710.03661202190.71634615380.4588744589

0.03714285710.0497267760.70673076920.70995671

0.05314285710.09453551910.70192307690.7186147186

0.07942857140.22404371580.77403846150.8311688312

slurry

Alum

distilled control

tap water control

David, Edwin

Edwin HuhCEE 453

David SausenLab 11

Slow Sand Filter 1

1 g alum in 100 mL distilled water titrated to pH = 7.50

This ripening agent was added to the filter and thoroughly mixed prior to starting the pump.

Slow Sand Filter 2

50 mL sludge

This ripening agent was added to the filter and thoroughly mixed prior to starting the pump.

AlumSludge

Influent Turbidity (NTU)3139

Effluent Turbidity (NTU)

Time (min)

03.444.6

51.351.59

100.461.07

150.230.42

200.160.37

250.580.16

300.170.25

350.40.21

400.480.09

450.110.15

500.070.13

550.380.07

average NTU after 20min:0.293750.17875

Fractional Removal:0.99052419350.9954166667

% Removal:99.052%99.542%

Steve, Kevin

Steven Kundrot and Kevin Lapus

Thursday Lab Section

Overview: We used the bolton point sludge water to for to rippening agents. The first

rippening agent was to be the alum from the sludge and the second was to be the sludge

itself without the alum. The alum was extracted using .1N HCl acid. Then both agents

were neutralized to pH 7. The alum solution was added to column #1 and the sludge slurry

was added to column #2.

Initial Turbidity:12.8Initial Turbidity:14.4

Sand Column #1Sand Column #2

Alum SupernatantSludge w/o Alum

Time (min)TurbidityFraction RemainingTime (min)TurbidityFraction Remaining

52.270.18513.70.95

101.70.13108.220.57

151.840.14158.880.62

200.8490.07204.970.35

250.3690.03252.70.19

300.2580.02302.230.15

350.310.02352.060.14

400.1760.01402.130.15

450.1490.01452.080.14

500.2590.02502.090.15

550.1970.02552.470.17

600.180.01603.530.25

Avg. Frac. Removed:0.056Avg. Frac. Removed:0.319

Amy, Yin

Slow Sand Filtration Lab DataThursday Lab - Anne & Yin

This is similar to David and Edwin's experiment (with distilled water instead of tap water and bacteria instead of clay)

SlurryAlum Floc

InfluentTimeTurbidityInfluentTimeTurbidity

014.8014.5

7017.57018.3

Time (min)Distilled water turbidity (NTU)Tap water turbidity (NTU)

EffluentTimeTurbidityFraction RemainingEffluentTimeTurbidityFraction RemainingInfluent20.823.1

51.7510.00%50.63.28%50.4190.484

100.613.49%100.170.93%100.650.593

150.31.71%150.170.93%151.491.76

200.261.49%200.211.15%201.642.04

250.352.00%250.140.77%251.992.21

300.382.17%300.160.87%302.162.32

350.392.23%350.180.98%353.392.46

400.372.11%400.331.80%408.992.71

450.422.40%450.422.30%4511.74.61

500.512.91%500.673.66%5014.910.6

550.653.71%550.914.97%5514.716.4

600.935.31%601.739.45%6014.616.6

651.397.94%654.122.40%6516.119.2

distilleddistilled

influent17.518.320.823.1

TimeslurryAlumdistilled controltap water control

50.10.03278688520.02014423080.020952381

100.03485714290.00928961750.031250.0256709957

150.01714285710.00928961750.07163461540.0761904762

200.01485714290.01147540980.07884615380.0883116883

250.020.00765027320.09567307690.0956709957

300.02171428570.00874316940.10384615380.1004329004

350.02228571430.00983606560.16298076920.1064935065

400.02114285710.01803278690.43221153850.1173160173

450.0240.02295081970.56250.1995670996

500.02914285710.03661202190.71634615380.4588744589

550.03714285710.0497267760.70673076920.70995671

600.05314285710.09453551910.70192307690.7186147186

650.07942857140.22404371580.77403846150.8311688312

Amy, Yin

slurry

Alum

distilled control

tap water control

Todd, Mark

Todd and Mark's DataThey extracted polymer from sludge that had been treated with acid to remove the alum.

#3 - polymer extraction from residual sludge w/ 100mL 0.1 NaOH

Influent14.9NTU

NTUNTU

timeYellowBlue (sludge)

547.511.1

1039.87.37

15175.06

207.182.3

25.53.771.51

32.52.321.43

382.111.44

452.11.5

501.921.52

Danusha, Cynthia

Tuesday's lab

I think the sludge had been treated with base and then with acid in an attempt to extract both alum and polymer.

The polymer was extracted with acid.

timeturbidity fraction remaining of sludgeturbidity fraction remaining of polymer

200.0820.053

250.10.044

300.0770.049

350.0990.077

400.0680.055

450.0630.047

500.0550.046

Analysis #2: since steady state is hard to define. Simply compare the

turbidity data for one time.

Analysis #3:

L (cm)=16

filtercoefficient (1/cm)

with sludge0.0249616289

without sludge0.0088531573

Erik, Nader

We ran the controls using no ripening agents, just one control with tap water, and one with distilled water.

Thursday Lab

Time (min)Distilled water turbidity (NTU)Tap water turbidity (NTU)

Influent20.823.1

50.4190.484

100.650.593

151.491.76

201.642.04

251.992.21

302.162.32

353.392.46

408.992.71

4511.74.61

5014.910.6

5514.716.4

6014.616.6

6516.119.2

Tuhina, Masako, Steven

Tuhina Ghosh, Masako Iwata, Steven Kao

April 13, 1998

Description:

Ripening Agent Preparation:

Treatment A:

Centifuge 200 mL of Cayuga Lake sludge solution.

Pour off supernatant and add about 100 mL of 1 N NaOH.

Mix thoroughly and centrifuge again.

Remove and save alum-rich supernatant for treatment A.

Treatment B:

Take remaining sludge and add about 100 mL of NaOH again.

Mix thoroughly and centrifuge again.

Pour off supernatant and save remaining sludge for treatment B.

Treatment A is alum extract using NaOH and neutralized to pH of 7.

Treatment B is sludge without alum.

Time (min)Treatment A turbidity (NTU)Treatment B turbidity (NTU)

0129310

55.71.9

102.030.93

151.30.05*

200.180.05

250.070.11

300.070.06* = bad data?

350.070.05

400.060.06

450.1*0.04

500.25*0.06

Influent turbidity23.929.8

Joye, Travis

Joye Thaller

Travis Kluegel

CEE 453

Slow Sand Filtration Lab

We received sludge which had already been washed with acid and centerfuged

twice. We washed it a third time with acid and removed the supernatent.

The sludge was then washed with a base and centerfuged. The supernatent

is the polymer which we tested in the slow sand filter. After washing the sludge a

second time with a base, we removed the supernatant and used the remaining

sludge in the second slow sand filter.

The stir bar was not initially in use during the first 35 min. of the experiment but

was turned on before the 40 min. reading. Also, we did not shake the slow sand

filters to mix the polymer and sludge until after 40 minutes had elapsed.

TimePolymer (NTU)Sludge (NTU)

Influent36.6031.00

50.510.67

103.751.32

153.720.39

200.450.49

250.380.37

300.390.37

35*0.420.38

400.423.77

After Shaking

5:003.503.65

5:042.680.86

5:091.760.68

5:191.460.60

5:301.440.50

*Stir bar was added to tank

Kathy, Amy

Not yet received

Successfully extracted a coagulant from Cayuga Lake Seston using 1.0 N HClThe CLSE fed filters removed up to 99.9999% of the influent coliforms.Analysis of the CLSENonvolatile solids was 44% of the TSSVolatile solids was 56% of the TSSAluminum was dominant metal

Groups of 4Assemble filter apparatusMeasure head loss, flow rate, turbidityCoat filter with CLSEObserve _______________Challenge filter with kaolinObserve ________and _______Control?increased head lossturbidityhead loss