SM^2og

ri---^gt^r

2 5 2 laquo

76 LA bull bull (

r

KM -J-XUK(U vlgt1 ^bullbullVOHif Ailiamp-

bullI Report Wo 028-02-76 bullbull

r

y i

A LABORATORY STUDY OK TUBE SETTUiUCs bull o

DR M NAWAZ TARIQ Director end Professor of Public Health Engineering

DR KUAN Mil YAO WHO Professor of Sanitary Engineoriiig j

7970 j

J

lur Conmunliv Thaler Supply j

j A i r bullbullbull

bullbullbullbullvnn-^--- 1

15z^lS^zoj

bull 1

bull LIBRARY INTERNATIONAL REFERENCE bull czmr rc-r-rbull - bull vji Y VVATE- SUPPLY I A0 Si-T- bull -] j PO iVjraquo gt ^ A D The Hague bull I s IC70 C j i i fct 141142

bull o raquo 2-S2 T^L f l

A LABORATORY STUDY ON TUBE SETTLING

INTRODUCTION

The term tube settling used herein refers to the use of shallow settling devices with a detention period a fraction of that of conventional settling tanks to achieving comparable settling efficiencies The settling device can be short pieces of pipes closely spaced plafcs cr tubes of any convenient shapes The application of tube settling in water treatment so far is mostly for coagulated

bull raw water (1 2) Very little appears to have been done in exploring the potential of the use of tube settlers for plain sedimentation of raw water as a possible economical pretreatrnent process especially for applications in developing countries

laquo

i i

O

OBJECTIVE

The objective of the study is to investigate the settling efficiency of a small-scale tube settling device using natural raw water from vn irrigation canal as well as synthetic raw water both without coagulation The use of canal water is significant since many small communities in Pakistan rely on such a source for their drinking water supplies In other words the results obtained should be relevant to practical conditions

DESCRIITION OF APPARATUS

The schematic sketch of Uie experimental set up is shewn in Figure I It consisted of a raw water reservoir a constant head tank a raw water recirshyculation system including an electric centrifugal pump the tube settling lank (high rate settlers) and a rotameter for flow control The suspended particles were kept in suspension in the raw water reservoir by an electric stirrer

The constant head lank had a main section and an overflow section The main section measured 15 cm by 15 cm and 12-8 cm deep to the over flow level Tnc raw water was first pumped from the reservoir into the main section

VCb H3^3

Intern v fer Cor

bull4 raquo y w raquoI^raquoTlaquo raquomdashbullraquo

i ^ _ ^ V i ^ c C V l ^ V - raquo ^ gt V j Y o u v ^ l i i ^ w ~ J ^ ^

of the constant head lank in such a way that the incoming jet would provide substantial stirring to prevent sediment in thcconsiant head tank The supply lo the tube settling tank was led oil near the bottom of the inlet side ofthc main section of the constant head tank The excess water in the constant head tank (lowed over the top of its partition into the overflow section for return by gravity to the raw water reservoir The pumping rate was kept greater than the flow to the tube settling tank

The tube settling tank rectangular in plan was made of No 22 galvanized iron sheet The tank was 895 cm long and 185 cm wide with an overflow depth of 105 cm It had an inlet comparuneiu and in outlet compartment Both compartments extended to the full width of the tank and were f 8 cm wide A perforated baffle was provided at the inlet side f and an overflow weir at the outlet side The lube settlers were formed by [ fourteen No 22 galvanized iron sheet plates each 61 cm long and 185 cm wide spaced at a clearance of 63 mm by glass tubing along the two sides of the tank |

The rotameter was inserted in the feedline between the constant head | tank and the tube settling tank -

METHODOLOGY

The canal water was normally taken fresh from a nearby irrigation canal in the morning of the day a run was to be made in plastic containers of approxishymately 5 and 10 liters The use of small containers was lo facilitate agitation A before feeding the raw walcr into the raw water reservoir

Synthetic raw water was prepared with tapwater and Chinese Fullers earth at the rate of 50 grains per 10 liters on the day a run was to be made

Flow rale control was obtained by setting the float in the rotameter at a given reading The actual flow was checked by a stopwatch and a plastic 1-litre measuring cylinder Water temperature was measured by a mercury thermo- n meter every hour Hourly raw water samples were taken from the raw water i reservoir for turbidity determinations on a Hach Turbidimeter Model 2100A i(

during a run

Effluent samples were taken at 15-minutc intervals from 7cro hour for turbidity measurements Effluent sampling continued until a steady turbidity reading was reached f

The settling tank was filled to overflow level with tapwater and settled I water from the previous run before each run

0

bullricca^u laquoraquogtraquoSlaquor^tt tgt^rrflaquopoundM

gt^-ltwMSrflaquoraquoJ raquo-raquoi^sywlti^Cirraquoraquoraquo^laquorfj

CD

0 D

l

UJ to

LU

cc LU a X LU

O

r L) r -LU

o

lt

r o CO

u

1 TIE

CO

7

Ti i- j T T T

LO

f k

rgt

CM

c laquo

O)

c

to

3

a E a

ltsgt

o

gt O

o

t laquo

CC

TO

(0 CC

a E TO

C O

c o

co en

k

6gt bullbull

laquo E ltn bull-

O CC

ra CO

TJ (D lt0 o raquobullmdash t ~

ltlgt u

in lto

c TO

bull a

X

c

m C O

O

~ c4 co

o

nif

bull

7 i

I

M

u

bulli r

V l i I - ^

bull1 1

EXPERIMENTAL RESULTS

(a) Synthetic raw water

Ten runs were made in January and February 1975 using synthetic raw water Table I presents the results The efficiency achieved was quite encoushyraging ft was therefore decided to proceed to the second stage using natural nncoagulated canal water as the influent Notice that the raw water turbicity varies even though the same dosage of Fullers earth was used in each run

TABLE 1

Tube Settling of Synthetic Raw Water

Run

1

2

3

4

5

6

7

8

9

10

Water Temp

Flow Rate

mlmin

Raw Water Turbidity

JTU

Effluent Turbidity

JTU

Efficiency

56

555

555

56

575

55

545

575

60

605

279

430

725

216

182

116

79

965

101

221

100

150

180

125

160

130

105

175

130

130

13

19

23

12

15

9

69

7

8

102

907

864

836

914

893

946

951

95

963

927

(b) Canal raw water

Ten runs were made from May to June 1975 using raw water from the canal The experiment was interrupted due to he^vy flood-damages of the canal

Z-nrWSUraquoiW+aCyaVn ampltjmmdash4raquo-mjwim

7 it l l l W I I ll i ugtj^itpoundraquopoundgtlaquolaquo

intake in the fall the sen son of high turbiciiiy for canal water Hence the results were somewhat inadequate for highly turbid raw water Table 2 presents the results indicated as Run 1 to Run 10 for May to June 1975 Runs 11 to 15 were made from September to November 1974 when the canal water Ind a turbidity level of less than 100 JTU (bull

TABLE 2

Tube Settling of Canal Raw Water

Run

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Water Temp degF

78

82

87

74

825

75

81

83

74

74

SI

71

695

64

62

Flow Rate

nilmin

76

90

95

96

109

116

157

154

164

203

635

684

61

120

J 23

Raw Water Turbidity

JTU

10

110

175

160

175

160

170

280

250

280

70

24

23

20

14

Effluent Turbidity

JTU

22

25

26

30

30

33

45

90

80

102

75

57

43

42

37

Efficiency

i

78

773

851

814

829

794

735

679

68

635

893

762

814

79

754

1 bull

i

bull

bull

kx--

bull

bull bull bull

bull_

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

bull 1

bull LIBRARY INTERNATIONAL REFERENCE bull czmr rc-r-rbull - bull vji Y VVATE- SUPPLY I A0 Si-T- bull -] j PO iVjraquo gt ^ A D The Hague bull I s IC70 C j i i fct 141142

bull o raquo 2-S2 T^L f l

A LABORATORY STUDY ON TUBE SETTLING

INTRODUCTION

The term tube settling used herein refers to the use of shallow settling devices with a detention period a fraction of that of conventional settling tanks to achieving comparable settling efficiencies The settling device can be short pieces of pipes closely spaced plafcs cr tubes of any convenient shapes The application of tube settling in water treatment so far is mostly for coagulated

bull raw water (1 2) Very little appears to have been done in exploring the potential of the use of tube settlers for plain sedimentation of raw water as a possible economical pretreatrnent process especially for applications in developing countries

laquo

i i

O

OBJECTIVE

The objective of the study is to investigate the settling efficiency of a small-scale tube settling device using natural raw water from vn irrigation canal as well as synthetic raw water both without coagulation The use of canal water is significant since many small communities in Pakistan rely on such a source for their drinking water supplies In other words the results obtained should be relevant to practical conditions

DESCRIITION OF APPARATUS

The schematic sketch of Uie experimental set up is shewn in Figure I It consisted of a raw water reservoir a constant head tank a raw water recirshyculation system including an electric centrifugal pump the tube settling lank (high rate settlers) and a rotameter for flow control The suspended particles were kept in suspension in the raw water reservoir by an electric stirrer

The constant head lank had a main section and an overflow section The main section measured 15 cm by 15 cm and 12-8 cm deep to the over flow level Tnc raw water was first pumped from the reservoir into the main section

VCb H3^3

Intern v fer Cor

bull4 raquo y w raquoI^raquoTlaquo raquomdashbullraquo

i ^ _ ^ V i ^ c C V l ^ V - raquo ^ gt V j Y o u v ^ l i i ^ w ~ J ^ ^

of the constant head lank in such a way that the incoming jet would provide substantial stirring to prevent sediment in thcconsiant head tank The supply lo the tube settling tank was led oil near the bottom of the inlet side ofthc main section of the constant head tank The excess water in the constant head tank (lowed over the top of its partition into the overflow section for return by gravity to the raw water reservoir The pumping rate was kept greater than the flow to the tube settling tank

The tube settling tank rectangular in plan was made of No 22 galvanized iron sheet The tank was 895 cm long and 185 cm wide with an overflow depth of 105 cm It had an inlet comparuneiu and in outlet compartment Both compartments extended to the full width of the tank and were f 8 cm wide A perforated baffle was provided at the inlet side f and an overflow weir at the outlet side The lube settlers were formed by [ fourteen No 22 galvanized iron sheet plates each 61 cm long and 185 cm wide spaced at a clearance of 63 mm by glass tubing along the two sides of the tank |

The rotameter was inserted in the feedline between the constant head | tank and the tube settling tank -

METHODOLOGY

The canal water was normally taken fresh from a nearby irrigation canal in the morning of the day a run was to be made in plastic containers of approxishymately 5 and 10 liters The use of small containers was lo facilitate agitation A before feeding the raw walcr into the raw water reservoir

Synthetic raw water was prepared with tapwater and Chinese Fullers earth at the rate of 50 grains per 10 liters on the day a run was to be made

Flow rale control was obtained by setting the float in the rotameter at a given reading The actual flow was checked by a stopwatch and a plastic 1-litre measuring cylinder Water temperature was measured by a mercury thermo- n meter every hour Hourly raw water samples were taken from the raw water i reservoir for turbidity determinations on a Hach Turbidimeter Model 2100A i(

during a run

Effluent samples were taken at 15-minutc intervals from 7cro hour for turbidity measurements Effluent sampling continued until a steady turbidity reading was reached f

The settling tank was filled to overflow level with tapwater and settled I water from the previous run before each run

0

bullricca^u laquoraquogtraquoSlaquor^tt tgt^rrflaquopoundM

gt^-ltwMSrflaquoraquoJ raquo-raquoi^sywlti^Cirraquoraquoraquo^laquorfj

CD

0 D

l

UJ to

LU

cc LU a X LU

O

r L) r -LU

o

lt

r o CO

u

1 TIE

CO

7

Ti i- j T T T

LO

f k

rgt

CM

c laquo

O)

c

to

3

a E a

ltsgt

o

gt O

o

t laquo

CC

TO

(0 CC

a E TO

C O

c o

co en

k

6gt bullbull

laquo E ltn bull-

O CC

ra CO

TJ (D lt0 o raquobullmdash t ~

ltlgt u

in lto

c TO

bull a

X

c

m C O

O

~ c4 co

o

nif

bull

7 i

I

M

u

bulli r

V l i I - ^

bull1 1

EXPERIMENTAL RESULTS

(a) Synthetic raw water

Ten runs were made in January and February 1975 using synthetic raw water Table I presents the results The efficiency achieved was quite encoushyraging ft was therefore decided to proceed to the second stage using natural nncoagulated canal water as the influent Notice that the raw water turbicity varies even though the same dosage of Fullers earth was used in each run

TABLE 1

Tube Settling of Synthetic Raw Water

Run

1

2

3

4

5

6

7

8

9

10

Water Temp

Flow Rate

mlmin

Raw Water Turbidity

JTU

Effluent Turbidity

JTU

Efficiency

56

555

555

56

575

55

545

575

60

605

279

430

725

216

182

116

79

965

101

221

100

150

180

125

160

130

105

175

130

130

13

19

23

12

15

9

69

7

8

102

907

864

836

914

893

946

951

95

963

927

(b) Canal raw water

Ten runs were made from May to June 1975 using raw water from the canal The experiment was interrupted due to he^vy flood-damages of the canal

Z-nrWSUraquoiW+aCyaVn ampltjmmdash4raquo-mjwim

7 it l l l W I I ll i ugtj^itpoundraquopoundgtlaquolaquo

intake in the fall the sen son of high turbiciiiy for canal water Hence the results were somewhat inadequate for highly turbid raw water Table 2 presents the results indicated as Run 1 to Run 10 for May to June 1975 Runs 11 to 15 were made from September to November 1974 when the canal water Ind a turbidity level of less than 100 JTU (bull

TABLE 2

Tube Settling of Canal Raw Water

Run

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Water Temp degF

78

82

87

74

825

75

81

83

74

74

SI

71

695

64

62

Flow Rate

nilmin

76

90

95

96

109

116

157

154

164

203

635

684

61

120

J 23

Raw Water Turbidity

JTU

10

110

175

160

175

160

170

280

250

280

70

24

23

20

14

Effluent Turbidity

JTU

22

25

26

30

30

33

45

90

80

102

75

57

43

42

37

Efficiency

i

78

773

851

814

829

794

735

679

68

635

893

762

814

79

754

1 bull

i

bull

bull

kx--

bull

bull bull bull

bull_

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

i ^ _ ^ V i ^ c C V l ^ V - raquo ^ gt V j Y o u v ^ l i i ^ w ~ J ^ ^

of the constant head lank in such a way that the incoming jet would provide substantial stirring to prevent sediment in thcconsiant head tank The supply lo the tube settling tank was led oil near the bottom of the inlet side ofthc main section of the constant head tank The excess water in the constant head tank (lowed over the top of its partition into the overflow section for return by gravity to the raw water reservoir The pumping rate was kept greater than the flow to the tube settling tank

The tube settling tank rectangular in plan was made of No 22 galvanized iron sheet The tank was 895 cm long and 185 cm wide with an overflow depth of 105 cm It had an inlet comparuneiu and in outlet compartment Both compartments extended to the full width of the tank and were f 8 cm wide A perforated baffle was provided at the inlet side f and an overflow weir at the outlet side The lube settlers were formed by [ fourteen No 22 galvanized iron sheet plates each 61 cm long and 185 cm wide spaced at a clearance of 63 mm by glass tubing along the two sides of the tank |

The rotameter was inserted in the feedline between the constant head | tank and the tube settling tank -

METHODOLOGY

The canal water was normally taken fresh from a nearby irrigation canal in the morning of the day a run was to be made in plastic containers of approxishymately 5 and 10 liters The use of small containers was lo facilitate agitation A before feeding the raw walcr into the raw water reservoir

Synthetic raw water was prepared with tapwater and Chinese Fullers earth at the rate of 50 grains per 10 liters on the day a run was to be made

Flow rale control was obtained by setting the float in the rotameter at a given reading The actual flow was checked by a stopwatch and a plastic 1-litre measuring cylinder Water temperature was measured by a mercury thermo- n meter every hour Hourly raw water samples were taken from the raw water i reservoir for turbidity determinations on a Hach Turbidimeter Model 2100A i(

during a run

Effluent samples were taken at 15-minutc intervals from 7cro hour for turbidity measurements Effluent sampling continued until a steady turbidity reading was reached f

The settling tank was filled to overflow level with tapwater and settled I water from the previous run before each run

0

bullricca^u laquoraquogtraquoSlaquor^tt tgt^rrflaquopoundM

gt^-ltwMSrflaquoraquoJ raquo-raquoi^sywlti^Cirraquoraquoraquo^laquorfj

CD

0 D

l

UJ to

LU

cc LU a X LU

O

r L) r -LU

o

lt

r o CO

u

1 TIE

CO

7

Ti i- j T T T

LO

f k

rgt

CM

c laquo

O)

c

to

3

a E a

ltsgt

o

gt O

o

t laquo

CC

TO

(0 CC

a E TO

C O

c o

co en

k

6gt bullbull

laquo E ltn bull-

O CC

ra CO

TJ (D lt0 o raquobullmdash t ~

ltlgt u

in lto

c TO

bull a

X

c

m C O

O

~ c4 co

o

nif

bull

7 i

I

M

u

bulli r

V l i I - ^

bull1 1

EXPERIMENTAL RESULTS

(a) Synthetic raw water

Ten runs were made in January and February 1975 using synthetic raw water Table I presents the results The efficiency achieved was quite encoushyraging ft was therefore decided to proceed to the second stage using natural nncoagulated canal water as the influent Notice that the raw water turbicity varies even though the same dosage of Fullers earth was used in each run

TABLE 1

Tube Settling of Synthetic Raw Water

Run

1

2

3

4

5

6

7

8

9

10

Water Temp

Flow Rate

mlmin

Raw Water Turbidity

JTU

Effluent Turbidity

JTU

Efficiency

56

555

555

56

575

55

545

575

60

605

279

430

725

216

182

116

79

965

101

221

100

150

180

125

160

130

105

175

130

130

13

19

23

12

15

9

69

7

8

102

907

864

836

914

893

946

951

95

963

927

(b) Canal raw water

Ten runs were made from May to June 1975 using raw water from the canal The experiment was interrupted due to he^vy flood-damages of the canal

Z-nrWSUraquoiW+aCyaVn ampltjmmdash4raquo-mjwim

7 it l l l W I I ll i ugtj^itpoundraquopoundgtlaquolaquo

intake in the fall the sen son of high turbiciiiy for canal water Hence the results were somewhat inadequate for highly turbid raw water Table 2 presents the results indicated as Run 1 to Run 10 for May to June 1975 Runs 11 to 15 were made from September to November 1974 when the canal water Ind a turbidity level of less than 100 JTU (bull

TABLE 2

Tube Settling of Canal Raw Water

Run

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Water Temp degF

78

82

87

74

825

75

81

83

74

74

SI

71

695

64

62

Flow Rate

nilmin

76

90

95

96

109

116

157

154

164

203

635

684

61

120

J 23

Raw Water Turbidity

JTU

10

110

175

160

175

160

170

280

250

280

70

24

23

20

14

Effluent Turbidity

JTU

22

25

26

30

30

33

45

90

80

102

75

57

43

42

37

Efficiency

i

78

773

851

814

829

794

735

679

68

635

893

762

814

79

754

1 bull

i

bull

bull

kx--

bull

bull bull bull

bull_

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

gt^-ltwMSrflaquoraquoJ raquo-raquoi^sywlti^Cirraquoraquoraquo^laquorfj

CD

0 D

l

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bull a

X

c

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~ c4 co

o

nif

bull

7 i

I

M

u

bulli r

V l i I - ^

bull1 1

EXPERIMENTAL RESULTS

(a) Synthetic raw water

Ten runs were made in January and February 1975 using synthetic raw water Table I presents the results The efficiency achieved was quite encoushyraging ft was therefore decided to proceed to the second stage using natural nncoagulated canal water as the influent Notice that the raw water turbicity varies even though the same dosage of Fullers earth was used in each run

TABLE 1

Tube Settling of Synthetic Raw Water

Run

1

2

3

4

5

6

7

8

9

10

Water Temp

Flow Rate

mlmin

Raw Water Turbidity

JTU

Effluent Turbidity

JTU

Efficiency

56

555

555

56

575

55

545

575

60

605

279

430

725

216

182

116

79

965

101

221

100

150

180

125

160

130

105

175

130

130

13

19

23

12

15

9

69

7

8

102

907

864

836

914

893

946

951

95

963

927

(b) Canal raw water

Ten runs were made from May to June 1975 using raw water from the canal The experiment was interrupted due to he^vy flood-damages of the canal

Z-nrWSUraquoiW+aCyaVn ampltjmmdash4raquo-mjwim

7 it l l l W I I ll i ugtj^itpoundraquopoundgtlaquolaquo

intake in the fall the sen son of high turbiciiiy for canal water Hence the results were somewhat inadequate for highly turbid raw water Table 2 presents the results indicated as Run 1 to Run 10 for May to June 1975 Runs 11 to 15 were made from September to November 1974 when the canal water Ind a turbidity level of less than 100 JTU (bull

TABLE 2

Tube Settling of Canal Raw Water

Run

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Water Temp degF

78

82

87

74

825

75

81

83

74

74

SI

71

695

64

62

Flow Rate

nilmin

76

90

95

96

109

116

157

154

164

203

635

684

61

120

J 23

Raw Water Turbidity

JTU

10

110

175

160

175

160

170

280

250

280

70

24

23

20

14

Effluent Turbidity

JTU

22

25

26

30

30

33

45

90

80

102

75

57

43

42

37

Efficiency

i

78

773

851

814

829

794

735

679

68

635

893

762

814

79

754

1 bull

i

bull

bull

kx--

bull

bull bull bull

bull_

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

7 i

I

M

u

bulli r

V l i I - ^

bull1 1

EXPERIMENTAL RESULTS

(a) Synthetic raw water

Ten runs were made in January and February 1975 using synthetic raw water Table I presents the results The efficiency achieved was quite encoushyraging ft was therefore decided to proceed to the second stage using natural nncoagulated canal water as the influent Notice that the raw water turbicity varies even though the same dosage of Fullers earth was used in each run

TABLE 1

Tube Settling of Synthetic Raw Water

Run

1

2

3

4

5

6

7

8

9

10

Water Temp

Flow Rate

mlmin

Raw Water Turbidity

JTU

Effluent Turbidity

JTU

Efficiency

56

555

555

56

575

55

545

575

60

605

279

430

725

216

182

116

79

965

101

221

100

150

180

125

160

130

105

175

130

130

13

19

23

12

15

9

69

7

8

102

907

864

836

914

893

946

951

95

963

927

(b) Canal raw water

Ten runs were made from May to June 1975 using raw water from the canal The experiment was interrupted due to he^vy flood-damages of the canal

Z-nrWSUraquoiW+aCyaVn ampltjmmdash4raquo-mjwim

7 it l l l W I I ll i ugtj^itpoundraquopoundgtlaquolaquo

intake in the fall the sen son of high turbiciiiy for canal water Hence the results were somewhat inadequate for highly turbid raw water Table 2 presents the results indicated as Run 1 to Run 10 for May to June 1975 Runs 11 to 15 were made from September to November 1974 when the canal water Ind a turbidity level of less than 100 JTU (bull

TABLE 2

Tube Settling of Canal Raw Water

Run

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Water Temp degF

78

82

87

74

825

75

81

83

74

74

SI

71

695

64

62

Flow Rate

nilmin

76

90

95

96

109

116

157

154

164

203

635

684

61

120

J 23

Raw Water Turbidity

JTU

10

110

175

160

175

160

170

280

250

280

70

24

23

20

14

Effluent Turbidity

JTU

22

25

26

30

30

33

45

90

80

102

75

57

43

42

37

Efficiency

i

78

773

851

814

829

794

735

679

68

635

893

762

814

79

754

1 bull

i

bull

bull

kx--

bull

bull bull bull

bull_

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

7 it l l l W I I ll i ugtj^itpoundraquopoundgtlaquolaquo

intake in the fall the sen son of high turbiciiiy for canal water Hence the results were somewhat inadequate for highly turbid raw water Table 2 presents the results indicated as Run 1 to Run 10 for May to June 1975 Runs 11 to 15 were made from September to November 1974 when the canal water Ind a turbidity level of less than 100 JTU (bull

TABLE 2

Tube Settling of Canal Raw Water

Run

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Water Temp degF

78

82

87

74

825

75

81

83

74

74

SI

71

695

64

62

Flow Rate

nilmin

76

90

95

96

109

116

157

154

164

203

635

684

61

120

J 23

Raw Water Turbidity

JTU

10

110

175

160

175

160

170

280

250

280

70

24

23

20

14

Effluent Turbidity

JTU

22

25

26

30

30

33

45

90

80

102

75

57

43

42

37

Efficiency

i

78

773

851

814

829

794

735

679

68

635

893

762

814

79

754

1 bull

i

bull

bull

kx--

bull

bull bull bull

bull_

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

ilMampAMrtti

i euro0

lt

XJ

lt gt o

cc

gt

co cr

100 - 1 0 -

EFFECT OF PLATES ON SETTLING EFFICIENCY (SYNTHETIC RAW WATER)

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

--- -1laquo-ltuplusmnuk-

(c) Effect of Plates on Settling Efficiency

Six runs were made with the plates removed from the settling tank to observe the cfEct of the presence of plates on settling These runs used synshythetic raw water prcpUvcJ from Chinese Fullers earth as in (a) and were made during the same period as for the runs in (a) to minimize Ihc temperature effect Fig 2 presents the comparison of the results of the two sets of runs one with plates and the other without plates Notice that the set with plates is the same one presented in Table 1

DISCUSSION AND CONCLUSIONS

It is easy to see that settling efficiency of a given tube settling system varies substantially with the characteristics of raw water I

For the canal water studied the tube settling device can provide good j pretrealmcnt without coagulation at moderate level of raw water turbidity [bull Performance tends to deteriorate as raw water turbidity reaches the level of ( 250-280 JTU In view of the limited results on highly turbid water further j study is necessary before definite conclusions can be made (

The presence of plates docs improve the settling efficiency especially at higher flow rales Since the experimental settling lank without plates is still a j shallow settler the improvement of efficiency due to the plates compared with that of conventional settling tanks of say 3 meters deep would be more subshystantial than that indicated in Fig 2

Acknowledgement

The study was in a way inspired by tiie global programme of the WHO International Reference Center en Community Water Supply for slow sand filtration systems and was intended as the contribution from the Institute of Public Health Engineering and Research Lahore Pakistan to the Programme The opinions expressed do not necessarily represent the views of the World Health Organization

The help renderd by Arshad Mahmud Rana and Jamshad Qureshi Research Assistants and Mohammad Rafiquc and Aslam Khan Stenographers is gratefully acknowledged

References

J HANSEN S P and CVLP G L (1967) Applying Shallow Depth Sedishymentation Thcoy J Am Water Works Assoc 59 pp 1134-48

2 YAO K M (1973) Design of High-Rate Settlers J Environmental Eng Div ASCE 99 EE 5 pp 621-37

- bull

I

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h^ dirty narfaio Ic^eP lf3 c^ynpri off the cattd boi Krji i s

bull bull bull bull - bull bull -

now OftraquocS o v e r y c-tx woi i thc No s r r d u a d u r l o urelti os- provldocS

Gh lo r tn t t i e n ig clone by duuv-^nf a c n i c u l a t o d rngtlt-

laquogt b l o n c h i raquo c powdor Jntogt tlJo saaraquoliltyiQ o f t h e a l e u F vrtoi tr^uk fox

tiwcci a daFo^o c h e c k v-olaquo iapcitgt o t o t i i e rigtituampl e h l o s r i o o lr thlt

apatozsi d u r i n g t h o e u y p l y pcrtuclUo-iitlgt e t o t amp e t i G reg apoundcopy poundiot

oVfiilatflo l o c a l l y t o Juc-e t h e c-pound t o a t i v e n o s o opound lictC CpornSAcsi

i n C e n r o l l i n c Vatoi-OnxiJO dlfsooeffs

ko T r e a t R t T t 11 art fc pevrfomraquoanccopy

F o l l o w i n g CcjK^ieti K-copyrta SQUOSV d u r i n g t h e violsect

0nnrpl o lo Kampw Va te fo

2 | laquo c-ttiraquoraquoU Water f rom S e t t l i n g TcopyraquoU Nolaquoiraquo ( f ro ing f i l l e d )raquo

3laquo i iott lr t tf vattgtY fi-ou S e t t l i n g Tilik No 2

gtbull F i l t e r e d t t i i t^r

T u r b i d i t y aaa twreKon t io wcro CJRlaquoO eft tfccopy Xnofc^tu^c-

trifch a Hicl i Turbidiiotir by t h e w i l t o r ftiujampeir find tlia weZltn

culaquo ia f a l l o w s 8raquo

Sample FttrbidifcyciTAUcopy

I 1 6 0

5o G e n e r a l UewionCeo

I t vfa n e t t h o aisa of t h o v i ^ i t amppound t o oiTftr laquo d v i c

lta r-oy 3poundjfCtpoundi o f t h e t r laquo 3 t n r e n t l -gtn t c Iti o t i m e wujj ato ohos-S j

t o blaquo jibl o t o pako o thorupoundh chr-ok on t h laquo prpoundciraquolt acficit t i e n s oj

t h e Hy^ttWoTno f o l l o w i n g yrc t h o r o f o r e ampororcl cocrrueiitfl tgtpoundampcv1 est

bull i ox-ipt ebtiUi-vtJcraquoiiG raquond l i m i t e d l a b o r a t o r y draquoteltraquo

I

I t bpvcxXa t h a t p r e pound r o i t t i w t isi jor-foris ing 1

GampfciefaefcrriJy Oa t h laquo o t h e r raquosnltpoundetfcc T i l terra affcopy ampcopy6 ltioisQ t o o

vftll $UCJG1Ipound rot6 t h e ouiul l t u r b i d i t y r e d u c t i o n j

The Dyetow provi-d^a m ciiopix raquonfe tippcurtixiHiy fox

fu r thes rjt-scitsflo cr in^tnncftotho inji rev orient of tho vithOrav- iae

oporafclwi uiay reltiuco tho t u r M d i t y of se t t lo r v o t e r ntr-scJuGcK3

i n t o tho f i l t e r i laquo vLlaquow ci t h e lour t u r b i d i t y isi the Scnfc bming

f i l l -G--iraquoXt voulc bltraquo l s o laquoif in t e r c j ^ telt boe tho jgtlaquooolbio

d i f JVrcfteo in perforwvncc i f tte ewttling fclaquofiamps aso copypointed ea

6 C6iir6ampQijolaquoa flow b a laquo i 5

Tho laquo-jverlt-itiampn bull cf tfcic- fiifcatfe raquolaquoltbullpound tcopy noert coro

fitulaquoJAerlaquoeTho flow e e a t r o l i3 tic-no by v a r y i n g he Water- d e p t h l a

the iampXzampSvihia l a i iut too cu-itoa i n eschar eotuatrio0raquoJtlcraquovfcvaz-a

thiis approach -ices tivo a icucJi aiuipioi ti2siampruingtin-2 a c lo o

s tudy w o r t h v h i l o C r i t i c a l studio a e r o a l 00 tacsccoofry 40 cXft jrJSO

tho Tac t s t h ^ t only cue out of Ihxaa i i i t c ro it In uao nt -sm^

tjKicraquo tijcopy f i l t e r ru-i i s oucl too t-hort lyto t h e fiXteiampHkt nu-icr

cjutsliCy ftppoars n o t os poundltgtGd os i t ahould bo uncles tho

copylycumatjinooso

Tho t ros i tuont r laquo o i l i t i laquo e orcopy ueofis2JLe t o Q c e r t n

ex ten t^ fo i - He5C rlaquotucXiraquoS8 tltlaquo cboorvo tho wamprkin^ cr epoundOw tu^cS

f i l t r a t i o n ^laKto

now OftraquocS o v e r y c-tx woi i thc No s r r d u a d u r l o urelti os- provldocS

Gh lo r tn t t i e n ig clone by duuv-^nf a c n i c u l a t o d rngtlt-

laquogt b l o n c h i raquo c powdor Jntogt tlJo saaraquoliltyiQ o f t h e a l e u F vrtoi tr^uk fox

tiwcci a daFo^o c h e c k v-olaquo iapcitgt o t o t i i e rigtituampl e h l o s r i o o lr thlt

apatozsi d u r i n g t h o e u y p l y pcrtuclUo-iitlgt e t o t amp e t i G reg apoundcopy poundiot

oVfiilatflo l o c a l l y t o Juc-e t h e c-pound t o a t i v e n o s o opound lictC CpornSAcsi

i n C e n r o l l i n c Vatoi-OnxiJO dlfsooeffs

ko T r e a t R t T t 11 art fc pevrfomraquoanccopy

F o l l o w i n g CcjK^ieti K-copyrta SQUOSV d u r i n g t h e violsect

0nnrpl o lo Kampw Va te fo

2 | laquo c-ttiraquoraquoU Water f rom S e t t l i n g TcopyraquoU Nolaquoiraquo ( f ro ing f i l l e d )raquo

3laquo i iott lr t tf vattgtY fi-ou S e t t l i n g Tilik No 2

gtbull F i l t e r e d t t i i t^r

T u r b i d i t y aaa twreKon t io wcro CJRlaquoO eft tfccopy Xnofc^tu^c-

trifch a Hicl i Turbidiiotir by t h e w i l t o r ftiujampeir find tlia weZltn

culaquo ia f a l l o w s 8raquo

Sample FttrbidifcyciTAUcopy

I 1 6 0

5o G e n e r a l UewionCeo

I t vfa n e t t h o aisa of t h o v i ^ i t amppound t o oiTftr laquo d v i c

lta r-oy 3poundjfCtpoundi o f t h e t r laquo 3 t n r e n t l -gtn t c Iti o t i m e wujj ato ohos-S j

t o blaquo jibl o t o pako o thorupoundh chr-ok on t h laquo prpoundciraquolt acficit t i e n s oj

t h e Hy^ttWoTno f o l l o w i n g yrc t h o r o f o r e ampororcl cocrrueiitfl tgtpoundampcv1 est

bull i ox-ipt ebtiUi-vtJcraquoiiG raquond l i m i t e d l a b o r a t o r y draquoteltraquo

I

I t bpvcxXa t h a t p r e pound r o i t t i w t isi jor-foris ing 1

GampfciefaefcrriJy Oa t h laquo o t h e r raquosnltpoundetfcc T i l terra affcopy ampcopy6 ltioisQ t o o

vftll $UCJG1Ipound rot6 t h e ouiul l t u r b i d i t y r e d u c t i o n j

The Dyetow provi-d^a m ciiopix raquonfe tippcurtixiHiy fox

fu r thes rjt-scitsflo cr in^tnncftotho inji rev orient of tho vithOrav- iae

oporafclwi uiay reltiuco tho t u r M d i t y of se t t lo r v o t e r ntr-scJuGcK3

i n t o tho f i l t e r i laquo vLlaquow ci t h e lour t u r b i d i t y isi the Scnfc bming

f i l l -G--iraquoXt voulc bltraquo l s o laquoif in t e r c j ^ telt boe tho jgtlaquooolbio

d i f JVrcfteo in perforwvncc i f tte ewttling fclaquofiamps aso copypointed ea

6 C6iir6ampQijolaquoa flow b a laquo i 5

Tho laquo-jverlt-itiampn bull cf tfcic- fiifcatfe raquolaquoltbullpound tcopy noert coro

fitulaquoJAerlaquoeTho flow e e a t r o l i3 tic-no by v a r y i n g he Water- d e p t h l a

the iampXzampSvihia l a i iut too cu-itoa i n eschar eotuatrio0raquoJtlcraquovfcvaz-a

thiis approach -ices tivo a icucJi aiuipioi ti2siampruingtin-2 a c lo o

s tudy w o r t h v h i l o C r i t i c a l studio a e r o a l 00 tacsccoofry 40 cXft jrJSO

tho Tac t s t h ^ t only cue out of Ihxaa i i i t c ro it In uao nt -sm^

tjKicraquo tijcopy f i l t e r ru-i i s oucl too t-hort lyto t h e fiXteiampHkt nu-icr

cjutsliCy ftppoars n o t os poundltgtGd os i t ahould bo uncles tho

copylycumatjinooso

Tho t ros i tuont r laquo o i l i t i laquo e orcopy ueofis2JLe t o Q c e r t n

ex ten t^ fo i - He5C rlaquotucXiraquoS8 tltlaquo cboorvo tho wamprkin^ cr epoundOw tu^cS

f i l t r a t i o n ^laKto

The Dyetow provi-d^a m ciiopix raquonfe tippcurtixiHiy fox

fu r thes rjt-scitsflo cr in^tnncftotho inji rev orient of tho vithOrav- iae

oporafclwi uiay reltiuco tho t u r M d i t y of se t t lo r v o t e r ntr-scJuGcK3

i n t o tho f i l t e r i laquo vLlaquow ci t h e lour t u r b i d i t y isi the Scnfc bming

f i l l -G--iraquoXt voulc bltraquo l s o laquoif in t e r c j ^ telt boe tho jgtlaquooolbio

d i f JVrcfteo in perforwvncc i f tte ewttling fclaquofiamps aso copypointed ea

6 C6iir6ampQijolaquoa flow b a laquo i 5

Tho laquo-jverlt-itiampn bull cf tfcic- fiifcatfe raquolaquoltbullpound tcopy noert coro

fitulaquoJAerlaquoeTho flow e e a t r o l i3 tic-no by v a r y i n g he Water- d e p t h l a

the iampXzampSvihia l a i iut too cu-itoa i n eschar eotuatrio0raquoJtlcraquovfcvaz-a

thiis approach -ices tivo a icucJi aiuipioi ti2siampruingtin-2 a c lo o

s tudy w o r t h v h i l o C r i t i c a l studio a e r o a l 00 tacsccoofry 40 cXft jrJSO

tho Tac t s t h ^ t only cue out of Ihxaa i i i t c ro it In uao nt -sm^

tjKicraquo tijcopy f i l t e r ru-i i s oucl too t-hort lyto t h e fiXteiampHkt nu-icr

cjutsliCy ftppoars n o t os poundltgtGd os i t ahould bo uncles tho

copylycumatjinooso

Tho t ros i tuont r laquo o i l i t i laquo e orcopy ueofis2JLe t o Q c e r t n

ex ten t^ fo i - He5C rlaquotucXiraquoS8 tltlaquo cboorvo tho wamprkin^ cr epoundOw tu^cS

f i l t r a t i o n ^laKto