Presentation on theme: "WORKSHOP ON DAM OPERATION BY IR CHAN CHIANG HENG ON 10 TH SEPTEMBER 2014 AT THE MALAYSIAN WATER ASSOCIATION (GROUND FLOOR)"— Presentation transcript:
WORKSHOP ON DAM OPERATION BY IR CHAN CHIANG HENG ON 10 TH SEPTEMBER 2014 AT THE MALAYSIAN WATER ASSOCIATION (GROUND FLOOR)
TABLE OF CONTENTS SECTIONDESCRIPTION 1Raw Water Sources 2Operation of Regulating Dam 3Critical Volume Assessment 4Formulation of Contingency Plan 5Effect of Reservoir Storage on Water Quality 6Limnological Survey of Impounded Water 7Treatment Problems and Solutions
b) Underground Source Well c) Impounded Source (Dam) Classification by Function ClassificationExampleDam Owner a)Water Supply Direct Abstraction Dam Release (Regulating Dam) Klang Gates Dam Sungai Tinggi Dam WA b) IrrigationPedu DamMADA c) Flood MitigationSungai Batu DamJPS d) Flood Mitigation and Water Supply Water Supply and Flood Mitigation Sungai Batu Dam Klang Gates Dam JPS WA e) Hydro ElectricTemenggong DamTNB
NOTES: 1) The Dam owner has control over:- Dam level (Volume) Point of Dam release (Water Quality) Quantity of Dam Rele ase
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.
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
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 river In 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 Curve Reservoir Control Curve Estimation of Time of Travel Recession Constant Regulation of Discharge
SG. TINGGI RESERVOIR ELEVATION-STORAGE-AREA CURVE Elevation - metre Storage – cubic metre 1 x 10 6 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 12 70 60 50 40 30 20 10 Storage / Elevation Area / Elevation Availability of surface area at different elevation.
JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC 110 100 90 80 70 60 50 40 30 20 10 0 2020 MLD 1900MLD 1700MLD 1300MLD Total Reservoir Storage (MCM) 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=q o x k t Flow at any time Flow t days later Recession constant applicable to any river reach K t = 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
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 Volume Active volume = Total Volume – Dead Volume Dead volume is defined as the volume of water below the lowest outlet or drawoff level.
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 DEPTHS TABULATIONS FOR SUNGAI TINGGI DAM Dam Level (M)IntervalVolumeComments 57.00 to 53.000.01M15.40MGTWL is at 57.00M (70.01ML) 53.00 to 49.000.01M12.65MG 49.00M is the 1st (57.51ML) Drawoff Level 49.00 to 45.000.01M9.62 MG (43.73ML) 45.00 to 41.000.01M7.70MG 41.00M is the 2nd (35.00ML)Drawoff Level 41.00 to 36.000.02M9.24MG (42.01ML) 36.00 to 32.000.025M7.56MG 32.00M is the 3rd (34.37ML)Drawoff Level
DAM VOLUME AT 0.01M INTERVAL (Sungai Tinggi Dam-Tabulation) Level (M)Volume (MG) 56.9922641.88 56.9822626.48 56.9722611.09 56.9622259.69 56.9522580.29 56.9422564.89 56.9322549.49 56.9222534.09 56.9122518.70 56.9022503.30 56.8922487.90 56.8822472.50 56.8722457.10 56.8622441.70 56.8522426.31 56.8422410.91 56.8322395.51 56.8222380.11 56.8122364.71 56.8022349.32 56.7922333.92 56.7822318.52 56.7722303.12 56.7622287.72 56.7522272.32 56.7422256.93 56.7322241.53 56.7222226.13 56.7122210.73 56.7022195.33 56.6922179.93 56.6822164.54 56.6722149.14 56.6622133.74 56.6522118.34 56.6422102.94 56.6322087.54 56.6222072.15 56.6122056.75 56.6022041.35 Level 57.00M to 53.00M Depth Interval 0.01M Total Depth Difference 4.00 M Vol. at this Depth Interval 15.40MG Tot. Volume Difference 6159.30MG
Between Critical Dept h Definition: Elevation or level of water in reservoir coinciding with the selected critical volume.
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 Plan a) Status of available vol. in dam as on 5/7/2002:- Dam level = 53.32M Tot. 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 level 1 st critical level of 49.00M 2 nd critical level of 47.00M Dam Level (m) Active Volume At Specific Level (ML) Volume Between Specific (ML) Percentage To Total Active Volume 53.3274,140 75.26 26.640 49.0047,500 48.22 8,750 47.0038,750 39.34 Critical Volume
b) Sustaining period Available Volume (ML) Rate of Dam Release (MLD) 800700600500400300 Sustaining Period In Days 1 st Critical Level (53.32M to 49.00M) 26,640 2 nd Critical Level (49.00M to 47.00M) 8,750 33 11 38 13 47 15 53 18 67 22 89 29 Total4451597189118
SECTION 5 EFFECT OF RESERVOIR STORAGE ON WATER QUALITY
WATER QUALITY IN DEEP RESERVOIRS Introduction 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) 30 oC 28.5 oC 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
SECTION 6 LIMNOLOGICAL 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 a) pH b) Colour c) Turbidity d) Iron (Soluble and Insoluble Form) e) Manganese (Soluble and Insoluble Form) f) Dissolved oxygen g) Alkalinity h) 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 Quality Siting of the reservoir Depth of reservoir - depth of reservoir< 6.0M shallow - depth of reservoir> 6.0M deep stratify thermally Detrimental effects:- a) Thermal and chemical stratification b) Algae problems c) Insufficient or minimal mixing of inflowing raw water with stored water
Parameter EpilimnionHypolimnion 1.0 Physical Changes a) pH b) Colour (HU) c) Turbidity (NTU) 6.5 to 7.2 Higher value due to algae action (photosynthesis) 35 to 150 3 to 28 Sedimentation 6.0 to 6.5 Lower value due to Stratification. 375 to 625 Decay of vegetation and leaching of organic matter from the soil. 6 to 66 Result of suspended matter. d) Temperature C 30 to 32 Subject to sunlight and wind action. 28 to 29 Shielded by the thermocline. WATER QUALITY - SUNGAI TINGGI DAM
Parameter EpilimnionHypolimnion 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 CaCO 3 (mg/l) 5 to 7 Exposed to atmosphere and wind action. 0.40 to 1.50 High dissolved oxygen content (aerobic condition resulting in precipitation). 0.03 to 0.07 High dissolved Oxygen content. 0.10 to 0.13 Nitrification can bring about a reduction in ammonical Nitrogen in the aerated surface waters. 4.4 to 6.9 Algae remove calcium carbonate and CO 2 by photosynthesis. The result is an increase in pH and decrease in calcium carbonate. 2 to 5 Shielded from atmosphere and wind action. 7 to 20 Low dissolved oxygen Content (anaerobic condition, Metal remain in soluble state). 0.07 to 0.30 Low dissolved oxygen content. 0.54 to 1.73 Increase in the cold anaerobic stagnant zone. 8.9 to 17.2
TREATMENT CHANGING FORM OF METAL Aeration Use 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 ) SourceNatural (a)Found in most natural waters - dissolution of rocks and minerals. (b)The hypolimnion of dam - the dark, cold and anaerobic. Man-madeIndustrial discharge. TypeIron (Fe), Manganese (Mn). FormSoluble 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 FormOxidation 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 At Scour - Sg. Semenyih Dam
61 Quality Surveillance of Sg. Semenyih Dam to Intake (Year 1994) IRON (ppm) 06 Jan 20 Jan 03 Feb 17 Feb 03 Mac 24 Mac 14 Apr 28 Apr 12 May 26 May 16 Jun 30 Jun \ 14 Jul 28 Jul 11 Aug 25 Aug 08 Sep 22 Sep 06 Oct 27 Oct 10 Nov 24 Nov 15 Dec 29 Dec 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
(a) Use of Potassium Permanganate USE OF CHEMICALS (CHEMICAL MEANS) AdvantageBesides 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 (KMn0 4 ) To determine KMnO 4 Dosage and Reaction Time Table 1 : Raw Water Quality Date06/10/03 pH6.21 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 TOC3.90 (a) Use of Potassium Permanganate
Date of Test24/09/03 Beaker No123456 Pre-lime (mg/L)222222 Potassium Permanganate (mg/L)0.000.100.200.300.400.50 Liquid Alum Dosage (as mg/L product)24 Flocculant AN910 (mg/L)0.10 Floc Sized3d3 d3d3 d3d3 d3d3 d3d3 d3d3 Table 2 : Jar Test Data Settled water quality SW pH188.8.131.52.106.086.11 SW Turbidity (NTU)3.763.823.583.553.683.65 SW Colour (Pt-Co)24 21 22 SW Fe (mg/L)0.12-0.110.120.13- SW Al (mg/L)0.098-0.0730.0610.054- SW Mn (mg/L)0.0960.0910.0820.0660.0780.085 SW TOC (mg/L)2.7-184.108.40.206-
Date of Test24/09/03 Beaker No123456 Pre-lime (mg/L)222222 Potassium Permanganate (mg/L)0.30 Retention time for KMnO 4 Dosing (mm)1197531 Liquid Alum Dosage (as mg/L product)24 Flocculant AN910 (mg/L)0.10 Floc Sized3d3 d3d3 d3d3 d3d3 d3d3 d3d3 Table 3 : Jar Test Data
Table 4 : Jar Test Data Filtered water quality FW Turbidity (NTU)0.3410.3480.3350.3290.3890.350 FW Colour (Pt-Co)666566 FW Fe (mg/L)-0.01 -- FW Al (mg/L)-0.08 0.07-- FW Mn (mg/L)0.0090.0100.0120.0140.0230.028 FW TOC (mg/L)-220.127.116.11-- Settled water quality Beaker No. 123456 SW pH6.106.096.116.086.056.07 SW Turbidity (NTU)3.082.852.722.752.732.71 SW Colour (Pt-Co)201918 19 SW Fe (mg/L)-0.11 0.12-- SW Al (mg/L)-0.0560.0550.057-- SW Mn (mg/L)0.016 0.0170.0200.0320.046 SW TOC (mg/L)-1.92.02.1--