WORKSHOP ON DAM OPERATION BY IR CHAN CHIANG HENG ON 10 TH SEPTEMBER 2014 AT THE MALAYSIAN WATER...

WORKSHOP ON DAM OPERATION

BYIR CHAN CHIANG HENG

ON 10TH SEPTEMBER 2014

ATTHE MALAYSIAN WATER ASSOCIATION

(GROUND FLOOR)

TABLE OF CONTENTS

SECTION DESCRIPTION

1 Raw Water Sources

2 Operation of Regulating Dam

3 Critical Volume Assessment

4 Formulation of Contingency Plan

5 Effect of Reservoir Storage on Water Quality

6 Limnological Survey of Impounded Water

7 Treatment Problems and Solutions

SECTION 1RAW WATER SOURCES

RAW WATER SOURCES

a) Surface Source

RiverRiver with augmentation from dam releaseIrrigation CanalOff River storage River Bank Filtration System

Sg. Selangor Phase 1 (SSP1)- Intake

Sg. Sireh Intake

b) Underground Source• Wellc) Impounded Source (Dam)• Classification by Function

Classification Example Dam Owner

a) Water Supply

• Direct Abstraction• Dam Release

(Regulating Dam)

• Klang Gates Dam• Sungai Tinggi Dam

WA

b) Irrigation Pedu Dam MADA

c) Flood Mitigation Sungai Batu Dam JPS

d) • Flood Mitigation

and Water Supply• Water Supply and

Flood Mitigation

• Sungai Batu Dam

• Klang Gates Dam

JPS

WA

e) Hydro Electric Temenggong Dam TNB

NOTES:1) The Dam owner has control over:-• Dam level (Volume)• Point of Dam release (Water Quality)• Quantity of Dam Release

2) All raw water sources do present some form of treatment problem. The extent of treatment problem or pollution varies from source to source.

3) Most water supply dam function as regulating dam i.e. Releases are made during draught to augment flow in river.

SECTION 2OPERATION OF REGULATING DAM

OPERATION OF REGULATING DAM

A) OPERATION PROTOCOL• DEFINITION – Regulating dam: constructed to store

water during wet spell and dam release during drought to augment low river flow.

Controlled release(from impounded reservoir)

Flow to river at periodicals low river flow

Ensure adequate river level Augment flow in the river at Intake

Sg. Selangor Dam

Dam Release

Overflow

B)ACQUISITION OF DATA & THEIR APPLICATION

a) Catchment Area Upstream of dam

For impounded reservoir volume estimation.

b) Rainfall- In catchment of dam (daily).

For estimation of possible increase in volume of impounded water.

c) Characteristic of Impounded water- Frequent initially.- Thereafter bimonthly or monthly.

For planning the treatment of water released at different levels of the impounded reservoir. Monitoring the water quality by conducting limnological survey.

d) Dam Level (daily)

For trending the decrease or increase in dam level and volume. Documenting the acquired data will indicate a cut back or increase in production.

e) Record of quantity of release at varying times (when required).

This information coupled with base flow in river will enable the likely water quantity at the abstraction point to be predicted.

I) At Dam

(a) Water level in river(i) Under normal flow condition (recording at 12 or 24 hourly will suffice). ii) During drought recording of level at close interval is necessary. 6 to 8 hours is likely the frequency.

For base flow volume and recession constant estimation.

For base flow volume and recession constant estimation.

For river level monitoring, the installation of an automatic level recorder is ideal.

(b) Rainfall In catchment of tributaries. For estimation of flow volume from

tributaries into main riverIn relation to forecast of dam releases

(c) Other users likely are the following:- - Compensation water. - Irrigation. - Water treatment plant upstream.

To note water quantity requirement for estimation of required volume at intake in relation to available volume.

II) At Intake

C) APPLICATION OF RELEVANT DOCUMENTS FOR RESERVOIR OPERATION

Rules for Reservoir Operation

Elevation-Storage-Area CurveReservoir Control CurveEstimation of Time of TravelRecession ConstantRegulation of Discharge

SG. TINGGI RESERVOIR ELEVATION-STORAGE-AREA CURVE

Ele

vatio

n -

met

re

Storage – cubic metre 1 x 106

0 20 40 60 80 100 120 140 160 180 200 220 240

0 1 2 3 4 5 6 7 8 9 10 11 1270

60

50

40

30

20

10

Storage / Elevation

Area / Elevation

Availability of surface

area at different

elevation.

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

110

100

90

80

70

60

50

40

30

20

10

0

2020 MLD 1900MLD 1700MLD 1300MLD

Tota

l Res

ervo

ir S

tora

ge (

MC

M)

Reservoir Control Curves

Abstraction rates of 2020, 1900, 1700 and 1300 MLD were selected at intake for Sg Tinggi Dam

ESTIMATION TIME OF TRAVEL

• Based on the observation of the travel time of the wave generated when water was released from the dam to the intake

• Time observed : 16-17 hours• Factors to be considered:

•Ground Condition along the flow path•Ground terrain along the flow path related to the rate of dam release•Possible abstraction of water by others•Weather at time of study of time travel

RECESSION CONSTANT

• Value obtained from the equation

• Reliable values of k can be derived when it is consistently dry across a river basin for many days

• Total River flow= Spill Over Weir + Abstraction + Dam release• Base River Flow = Total River Flow – Dam Release• Min. Base Flow = Compensation Flow + Abstraction

q=qo x ktFlow at any

time

Flow t days later

Recession constant applicable to any

river reach

Kt = 0.95 of base flow

REGULATION OF DISCHARGE

RESERVOIR (DAM) RELEASE

• Factors to consider:

- River level. - Base River Flow. - Impending Weather Condition. - Available Volume in Dam. - Affordable Quantity of release

SECTION 3CRITICAL VOLUME ASSESSMENT

CRITICAL VOLUME

• Active volume available in dam when the volume of dam release has to be regulated or controlled (restricted) to tie over an impending dry period.

• Water rationing may have to be implemented during controlled dam release period.

ACTIVE VOLUME

Total Volume = Active Volume + Dead VolumeActive volume = Total Volume – Dead

VolumeDead volume is defined as the volume of water below the lowest outlet or drawoff level.

EMPANGAN SG. TERIP DAM DRAWOFF TOWER

Syphon No. 1

106.50M

TWL 103.00M

100.75M 99.65M

95.70M 94.60M 92.50M 91.50M

87.70M 86.60M 84.60M 83.50M

79.70M 78.60M

Syphon No. 2

Syphon No. 3

Crown Level = 100.75MSpill Level = 99.65MInlet Soffit Level = 95.70MInlet Cill Level = 94.60M



LOWEST

SG. TINGGI DAM DRAWOFF TOWER – VALVE ARRANGEMENT

Parallel Face Sluice Valve

Air ValveGuard Valve

Regulating Valve

ADVANCED ASSESSMENT OF CRITICAL VOLUME

• Every dam has its critical volume• The specific critical volume of any specific dam

varies with the weather condition in respect of time and quantity.

• To determine the relevant volume to choose from tabulate available active volume in advance based on the following percentages:• 75%• 60%• 50%• 40%

Tabulation Of Data of Active Volume• Available volume between depths from top water level to

first drawoff outlet and between subsequent drawoff outlet

AVAILABLE VOLUME BETWEEN DEPTHSTABULATIONS FOR SUNGAI TINGGI DAM

Dam Level (M) Interval Volume Comments 57.00 to 53.00 0.01M 15.40MG TWL is at 57.00M

(70.01ML) 53.00 to 49.00 0.01M 12.65MG 49.00M is the 1st

(57.51ML) Drawoff Level

49.00 to 45.00 0.01M 9.62 MG (43.73ML)

45.00 to 41.00 0.01M 7.70MG 41.00M is the 2nd

(35.00ML) Drawoff Level 41.00 to 36.00 0.02M 9.24MG

(42.01ML) 36.00 to 32.00 0.025M 7.56MG

32.00M is the 3rd (34.37ML) Drawoff Level

DAM VOLUME AT 0.01M INTERVAL (Sungai Tinggi Dam-Tabulation)

Level (M) Volume (MG)

56.99 22641.88

56.98 22626.48

56.97 22611.09

56.96 22259.69

56.95 22580.29

56.94 22564.89

56.93 22549.49

56.92 22534.09

56.91 22518.70

56.90 22503.30

56.89 22487.90

56.88 22472.50

56.87 22457.10

56.86 22441.70

56.85 22426.31

56.84 22410.91

56.83 22395.51

56.82 22380.11

56.81 22364.71

56.80 22349.32

56.79 22333.92

56.78 22318.52

56.77 22303.12

56.76 22287.72

56.75 22272.32

56.74 22256.93

56.73 22241.53

56.72 22226.13

56.71 22210.73

56.70 22195.33

56.69 22179.93

56.68 22164.54

56.67 22149.14

56.66 22133.74

56.65 22118.34

56.64 22102.94

56.63 22087.54

56.62 22072.15

56.61 22056.75

56.60 22041.35

Level 57.00M to 53.00M Depth Interval 0.01MTotal Depth Difference 4.00 M Vol. at this Depth Interval 15.40MGTot. Volume Difference 6159.30MG

Between Critical Depth

• Definition: Elevation or level of water in reservoir coinciding with the selected critical volume.

SECTION 4FORMULATION OF CONTIGENCY PLAN

FORMULATION OF CONTIGENCY PLAN

• Contingency plan can be formulated in advance for any active volume in dam and dam level.

• Criteria involved in a plan formulation are as follows:• Volume of dam release

i. A range of volume – Values based on past record related to river flow quantity and current based condition.

ii. Sustaining period selected– related to weather condition and active volume available.

• In contingency plan formulation rainfall is not taken into consideration. Any rainfall occurs during the planned period is considered a bonus.

Example of Formation of Contingency Plana) Status of available vol. in dam as on 5/7/2002:-

Dam level = 53.32MTot. Active Vol. = 74,140 ML or 75.26% of Tot. active vol of

98,503ML• Planning Strategy:-

Consider – Critical level, Critical volume & sustaining period

Critical level1st critical level of 49.00M2nd critical level of 47.00M

Dam Level

(m)

Active VolumeAt Specific Level (ML)

VolumeBetween

Specific (ML)

Percentage To Total

Active Volume

53.32 74,140 75.26

26.640

49.00 47,500 48.22

8,750

47.00 38,750 39.34

Critical Volume

b) Sustaining period

Available Volume (ML)Rate of Dam Release (MLD)

800 700 600 500 400 300

Sustaining Period In Days

1st Critical Level (53.32M to 49.00M) 26,640 2nd Critical Level(49.00M to 47.00M) 8,750

33

11

38

13

47

15

53

18

67

22

89

29

Total 44 51 59 71 89 118

SECTION 5EFFECT OF RESERVO IR STORAGE ON WATER QUAL ITY

WATER QUALITY IN DEEP RESERVOIRSIntroduction

• Seasonal density or thermal stratification varies for shallow (less than 6M) and deep (greater than 6M) lakes and reservoirs.

• In shallow reservoirs, water temperatures and oxygen concentrations will depend on the amount of wind induced mixing.

• At surface, water temperatures rise in relation to bottom waters, stratified density layers will form in the water column.

• An oxygen defiency will result at the sediment – water interface, creating anaerobic conditions that will solubilize nutrients and metals from bottom sediments.

• Deep water bodies experience thermal stratification and form three distinct layers of water below the surface.

Top layer is called epilimnion. Bottom layer is called hypolimnion. The layer between is called metalimnion (thermocline).

WATER QUALITY IN DEEP RESERVOIRS

Epliminion (warm, aerobic, well-mixed)

30oC

28.5oC

Thermal Stratification

Thermocline (sharp change in both temperature & water density)

Hypolimnion (cool, anaerobic, poorly mixed)

Lake

Epilimnion: Upper layer of well-mixed warm water

Thermocline:Intermediate/boundary layer that has sharp change in both temperature and density

Hypolimnion: Lower layer, poorly mixed cool water. Low DO and anaerobic.

CASE STUDIES

1)Demonstration by color intensity-Malut Dam

Raw Water at Varying Depth

Treated Water at Varying Depth

SECTION 6LIMNOLOGICAL SURVEY OF IMPOUNDED WATER

• To determine the raw water quality at varying depth in the impoundment or dam

• For a dam, the survey is conducted at varying depth in the Epilimnion, the Thermocline at the Hypolimnion.

• Knowing the water quality will facilitate treatment of the impounded water.

OBJECTIVE

• At surface and at each drawoff point for a dam provided with a variable drawoff tower.

SAMPLING POINT

PARAMETERS TO RECORDa) pHb) Colourc) Turbidityd) Iron (Soluble and Insoluble Form)e) Manganese (Soluble and Insoluble Form)f) Dissolved oxygen g) Alkalinityh) Hydrogen Sulphide

• Weekly initially, thereafter bimonthly and monthly.

• The frequency is dictated by water level or volume of water in the impoundment.

SAMPLING FREQUENCY

• Soluble manganese and iron are the common treatment problem encounters.

• Aeration of the dam normally overcames this problem.

TREATMENT PROBLEM

QUALITY OF IMPOUNDED WATER

INFLUENTIAL FACTORS

Influent QualitySiting of the reservoirDepth of reservoir - depth of reservoir< 6.0M shallow - depth of reservoir> 6.0M deep

stratify thermally

Detrimental effects:-a) Thermal and chemical stratificationb) Algae problemsc) Insufficient or minimal mixing of inflowing raw water with stored water

Parameter Epilimnion Hypolimnion

1.0 Physical Changes a) pH

b) Colour (HU)

c) Turbidity (NTU)

6.5 to 7.2Higher value due to algae action (photosynthesis)

35 to 150

3 to 28Sedimentation

6.0 to 6.5Lower value due to Stratification.

375 to 625Decay of vegetation and leaching of organic matter from the soil.

6 to 66Result of suspended matter.

d) Temperature C 30 to 32Subject to sunlight and wind action.

28 to 29Shielded by the thermocline.

WATER QUALITY - SUNGAI TINGGI DAM

Parameter Epilimnion Hypolimnion

2.0 Chemical Changes a) Dissolved Oxygen mg/l b) Iron mg/l c) Manganese (mg/l) d) Ammonia as N (mg/l) e) Alkalinity as CaCO3 (mg/l)

5 to 7Exposed to atmosphere and wind action. 0.40 to 1.50High dissolved oxygen content (aerobic condition resulting in precipitation). 0.03 to 0.07High dissolved Oxygen content. 0.10 to 0.13Nitrification can bring about a reduction inammonical Nitrogen in the aerated surface waters.4.4 to 6.9Algae remove calcium carbonate and CO2 by photosynthesis. The result is an increase in pH and decrease in calcium carbonate.

2 to 5Shielded from atmosphere and wind action. 7 to 20Low dissolved oxygen Content (anaerobic condition, Metal remain in soluble state). 0.07 to 0.30Low dissolved oxygen content. 0.54 to 1.73Increase in the cold anaerobic stagnantzone. 8.9 to 17.2

SECTION 7TREATMENT PROBLEMS AND SOLUTIONS

TREATMENT

CHANGING FORM OF METAL

AerationUse of Chemicals

Source – Dam (Jetting, Mechanical pumping, Injection)Treatment Plant – Aerator (Cascading/Trickling Aerator)

Oxidants: Potassium permanganate, chlorine, ozone, chlorine dioxide.

Most favored!

THEORY METALS (GENERAL)

Source Natural (a)

Found in most natural waters- dissolution of rocks and minerals.

(b) The hypolimnion of dam- the dark, cold and anaerobic.

Man-made Industrial discharge.

Type Iron (Fe), Manganese (Mn).

Form Soluble and insoluble (particulate)

Total (Fe) or (Mn) = Soluble + Insoluble Form

Analytical Analysis

Total Metal (Fe or Mn) - Acidify Sample and Boil

Soluble Metal (Fe or Mn) - Filter sample through a 0.45 Ωm filter paper.

THEORY

METALS (GENERAL)

Removal

Insoluble Form

by coagulation and flocculation and filtration

Soluble Form

By first converting from soluble to insoluble followed by coagulation and flocculation and filtration

Thus, it is easier to remove in the insoluble form than in the soluble form.

In general, both iron and manganese invariably occur in both the insoluble and soluble form.

TREATMENT

Conversion of Form Oxidation Process

(1) Aeration (Physical Means)

(2) Use of Chemical (Chemical Means)

(1) Aeration (Physical Means)

The function of aeration To introduce oxygen to the water. To remove carbon dioxide (resulting in increase of pH).

Removal of iron and manganese is pH dependent, more so with manganese.

Nature’s Way

TREATMENT

Oxidation Of Fe & Mn – Sg. Terip Dam

Oxidation Of Fe & Mn At Pedas Lama WTP from Beringin DAM, Negeri Sembilan

Oxidation Of Fe & Mn At Scour - Malut Dam

Oxidation Of Fe & Mn At Scour - Sg. Semenyih Dam

61

Quality Surveillance of

Sg. Semenyih Dam to Intake (Year 1994)

IRO

N (

pp

m)

06 J

an20

Jan

03 F

eb17

Feb

03 M

ac24

Mac

14 A

pr28

Apr

12 M

ay26

May

16 J

un30

Jun

\ 14 J

ul28

Jul

11 A

ug25

Aug

08 S

ep22

Sep

06 O

ct27

Oct

10 N

ov24

Nov

15 D

ec

29 D

ec

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Weir Downstream of The Dam Intake

Dates of Sampling

Treatment of Impounded Water Contaminants, Iron and Manganese

Man-Made

• Aeration at Source

(a) Dam

TREATMENT

View Of Air Diffuser – Sg. Terip Dam

Reinforced rubber nose

Cross Connector

Perforated stainlessSteel pipe

Concrete Sinker

SIDE VIEW OF DIFFUSER

C1

C2

6M

PLAN VIEW OF DIFFUSER

Concrete Sinker Perforated stainlessSteel pipe

Cross Connector

6M

0.75M

0.5M0.5M

Stopper Cap

Stainless Steel pipe(grade 304)

Concrete Sinker

DETAILED C1

20MM X 5 MM

20mm

Cross Connector Stainless Steel pipe

Threaded Ends

DETAILED C2

Stainless Steel pipe (grade 304)

Cross Connector

Renforced Rubber Hose

Source from UTM

6.00

5.50

5.00

4.50

4.00

3.50

3.00

2.50

2.00

1.50

1.00

0.50

0.00

Variation of DO vs Depth After Aeration at Location 2

01-09-02Aeration Hrs: 0.00

15-09-02Aeration Hrs: 118.77

29-09-02Aeration Hrs: 221.39

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

4.7 4.6 4.5 4.5 4.4 4.4 4.3 4.2 4.0 3.9 0.4 0.3 0.3 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.0

4.5 4.3 4.2 3.0 2.7 2.5 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.2 1.9 1.5 0.3 0.2 0.1

5.9 5.8 5.8 5.2 5.0 4.9 4.1 4.0 3.8 3.8 3.9 3.9 3.9 3.7 3.7 3.6 3.6 3.3 2.3 1.2 1.1

1/9/02

15/9/02

29/9/02

Dis

so

lve

d O

xy

ge

n (

mg

/L)

Variation of DO at Different Drawoff Level

6.50

6.00

5.50

5.00

4.50

4.00

3.50

3.00

2.50

2.00

1.50

1.00

0.50

0.00

Dis

solv

ed O

xyg

en (

mg

/L)

1st DrawoffLevel = 73.00m

2nd DrawoffLevel = 66.60m

3rd DrawoffLevel = 60.20m

4th DrawoffLevel = 53.80m

Drawoff Level

DO (01.09.02) DO (15.09.02) DO (29.9.02)

(2) Use of Chemicals (Chemical Means)

Chlorine Chlorine Dioxide Ozone Potassium Permanganate (KMnO4)

TREATMENT

(a) Use of Potassium Permanganate

USE OF CHEMICALS (CHEMICAL MEANS)

Advantage Besides effective in removal of iron and manganese, it also helps in the reduction of TOC (Total Organic Carbon).

Analytical Analysis

The optimum dosage and time of reaction has first to be determined.

Adverse Effect of Over Dosage

Colour, add manganese to water.

JAR TEST ON USE OF POTASSIUM PERMANGANATE (KMn04)To determine KMnO4 Dosage and Reaction Time

Table 1 : Raw Water Quality

Date 06/10/03

pH 6.21

Turbidity (NTU) 97.1

Apparent Colour (Pt.Co)

521

Manganese total (mg/L)

0.224

Manganese soluble (mg/L)

0.128

Iron (mg/L) 0.132

Aluminium (mg/L) 0.038

TOC 3.90

(a) Use of Potassium Permanganate

Date of Test 24/09/03Beaker No 1 2 3 4 5 6Pre-lime (mg/L) 2 2 2 2 2 2Potassium Permanganate (mg/L) 0.00 0.10 0.20 0.30 0.40 0.50Liquid Alum Dosage (as mg/L product) 24 24 24 24 24 24

Flocculant AN910 (mg/L) 0.10 0.10 0.10 0.10 0.10 0.10

Floc Size d3 d3 d3 d3 d3 d3

Table 2 : Jar Test Data

Settled water quality

SW pH 6.13 6.12 6.15 6.10 6.08 6.11

SW Turbidity (NTU) 3.76 3.82 3.58 3.55 3.68 3.65

SW Colour (Pt-Co) 24 24 21 21 22 22

SW Fe (mg/L) 0.12 - 0.11 0.12 0.13 -

SW Al (mg/L) 0.098 - 0.073 0.061 0.054 -

SW Mn (mg/L) 0.096 0.091 0.082 0.066 0.078 0.085

SW TOC (mg/L) 2.7 - 2.1 1.8 2.7 -

Date of Test 24/09/03

Beaker No 1 2 3 4 5 6

Pre-lime (mg/L) 2 2 2 2 2 2

Potassium Permanganate (mg/L) 0.30 0.30 0.30 0.30 0.30 0.30

Retention time for KMnO4 Dosing (mm) 11 9 7 5 3 1

Liquid Alum Dosage (as mg/L product) 24 24 24 24 24 24

Flocculant AN910 (mg/L) 0.10 0.10 0.10 0.10 0.10 0.10

Floc Size d3 d3 d3 d3 d3 d3



Filtered water quality

FW Turbidity (NTU) 0.341 0.348 0.335 0.329 0.389 0.350

FW Colour (Pt-Co) 6 6 6 5 6 6

FW Fe (mg/L) - 0.01 0.01 0.01 - -

FW Al (mg/L) - 0.08 0.08 0.07 - -

FW Mn (mg/L) 0.009 0.010 0.012 0.014 0.023 0.028

FW TOC (mg/L) - 1.7 1.8 2.0 - -

Settled water quality

Beaker No. 1 2 3 4 5 6

SW pH 6.10 6.09 6.11 6.08 6.05 6.07

SW Turbidity (NTU) 3.08 2.85 2.72 2.75 2.73 2.71

SW Colour (Pt-Co) 20 19 18 18 18 19

SW Fe (mg/L) - 0.11 0.11 0.12 - -

SW Al (mg/L) - 0.056 0.055 0.057 - -

SW Mn (mg/L) 0.016 0.016 0.017 0.020 0.032 0.046

SW TOC (mg/L) - 1.9 2.0 2.1 - -

73

Use of Potassium Permanganate - SSP 1

b) Use of chemicals (Coagulant)

• Appropriate Choice of Coagulant

Coagulant PAC – Filter – SSP1

Coagulant Alum – Filter – SSP1

WORKSHOP ON DAM OPERATION BY IR CHAN CHIANG HENG ON 10 TH SEPTEMBER 2014 AT THE MALAYSIAN WATER...

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Transcript of WORKSHOP ON DAM OPERATION BY IR CHAN CHIANG HENG ON 10 TH SEPTEMBER 2014 AT THE MALAYSIAN WATER...