The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City 4.6 Facility Design 4.6.1 Design Criteria (1) Intake Facility (a) Water Level at Intake Site High Water Level: +70.0 m Low Water Level: +61.0 m (b) Design flow (Qi): Qi=1.1 x (daily maximum demand) (2) Water Treatment Plant (a) Detention time of receiving well: 1.5 min of daily maximum flow (b) Overflow rate of sedimentation basin: 30 mm/min (c) Filtration rate of rapid sand filter: 120 m/d (d) Treated Water Reservoir Detention time: 2hours of daily maximum demand (3) Distribution Pipeline All distribution pipelines shall be designed to satisfy peak hourly flow and required residual head. (a) Peak hourly flow Peak hourly flow =1.5 x (daily maximum demand) (b) Velocity Calculation: Hazen-Williams, C=110 (c) Residual Head (Hr) in distribution pipeline Peak hourly flow of daily average: Hr>13 m Peak hourly flow of daily maximum: Hr>5 m In case of firefighting during peak hourly flow of daily maximum: Hr>0 m in a fire hydrant (d) Pipe material 100 to 1350 mm in diameter: Ductile Iron Pipe Less than 100 mm in diameter: High Density Polyethylene Pipe 4.6.2. Expansion of the Existing Water Supply System (1) Concept 1) The faults of existing facilities would be repaired to make use of the potential capacity. 2-180 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City 2) Construction for the expansion would be done for increasing the water supply volume to reduce the present gap between demand and supply of water. 3) The consistency between the existing facilities and the facilities to be expanded would be ensured for their effective operation to operate effectively. (2) Installation of new pumps at BPS1 1) There is adequate space and concrete foundation for future installation of three pumps. The proposed pumps will be installed making good use of them. 2) The capacity of proposed pumps is decided through the analysis of distribution pipeline network to provide minimum pressure head of 10m at every supply point. 3) Specification F400mm x 30 m3 /min x 45m x 400kw -2sets (3) Construction of BPS1 reservoir 1) A new reservoir will be constructed next to the existing BPS1 reservoir. 2) There is one tube well (No.26) with a discharging capacity of 5,000 m3 /day in the same compound for the construction of the proposed reservoir. Therefore a new tube well will be drilled in a area, where is not affected by construction of the reservoir, as the alternative to this tube well. 3) The Water volume of 15,900 m3 /day would be newly conveyed to the BPS1 reservoir from the three proposed production wells. 4) Structure • Reinforced concrete structure • Required Volume : 12,500 m3 . • Shape : Effective Depth 6 m x Length 94m x Width 22.5 m = 12,500 m3 (4) Installation of pumps at BPS2 1) Since an existing pump is deteriorated, and a lot of water leaks from the pump, it would be replaced with a new one of the same specification. 2) Specification : φ200 mm x 7.5 m3 /min x 50 m x 110kW -1set 2-181 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City (5) Installation of disinfection equipment at BPS1 • Chemical : Calcium hypochlorite, Ca(ClO)2 ・2Ca(OH)2 • Specific Gravity in Solid : 0.84 • Effective Density : More than 70% • Design Concentration : 0.5~2.0 mg/l, 1.0 mg/l (Average) • Facilities : Solution tank with a mixer, 4 m3 -2 sets Apparatus for Distribution and Dosing -1 set (6) Installation of distribution pipeline and flow meter at BPS1 1) There is no flow meter in the existing distribution main. Two flow meters will be installed in the distribution main near the BPS1 to measure the amount of supplied water for effective management of the distribution system. The total amount of water supply would be 134,900 m3 /day in daily maximum (119,000 m3 /day from the existing 26 tube wells and 15,900 m3 /day from the three proposed tube wells). 2) Specification : Electromagnetic flow meters for 900mm diameter pipes –2sets (7) Groundwater development plan 1) 5 wells (2 in the north and 3 in the south) will be newly constructed. They would be located in the expanded area of the existing well field. The water from northern 2 wells will be conveyed to the existing ground reservoir at Mandalay Hill, and the water from the southern three wells will be conveyed to BPS1. 2) Well Structure : Considering the results of the hydro-geological studies and the actual depth of existing 28 wells, depth and daily maximum pumpage rate of the proposed wells are decided at 150 m and 5,300 m3 /day respectively. 3) Specification of Production Well • Well Casing diameter : φ300mm • Well depth : 150m • Specification Pump Type : Submersible motor pump North wells 200 mm x 110kW x 4.5 m3 /min x 2sets 2-182 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City South wells 200 mm x 90kW x 4.5 m3 /min x 3sets 4) Water Conveyance: Two pipelines will be laid for conveyance of water from the proposed production wells. Lengths of the lines are shown below. See Fig. 4.6.2.2 and Fig. 4.6.2.3. North line : φ300 mm - L=300 m, φ500 mm - L=2,570 m South line : φ300 mm - L=300 m, φ400 mm - L=300 m, φ500 mm - L=2,670 m • The facility drawings are shown in Fig.4.6.2.1 and Fig. 4.6.2.3. 4.6.3. Proposed Intake & Water Treatment Plant (1) Basic Conditions a) Water Quantity In the Year 2010 m3 /day m3 /hr m3 /min m3 /sec Intake 110,000 4,583 76.39 1.273 Transmission 100,000 4,167 69.44 1.157 In the Year 2020 m3 /day m3 /hr m3 /min m3 /sec Intake 220,000 9,167 152.8 2.546 Transmission 200,000 8,333 138.9 2.315 b) Water Quality Raw Water Treated Water PH 7.3 6.5-8.5 Turbidity (NTU) 100 1.5-2.0 (2) Intake Facilities 1) Facility Plan : Entering Basin, Screens, Pump pit, Pump room, Emergency generator, Buildings, and River bed protection. 2) Structure type : Reinforced concrete 3) Entering Basin 2-183 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City The designed water speed is 0.5 m/sec to prevent entry of big sand particles into the pump pit. The effective water depth at the entering basin is designed to be 1.0m, against the designed LWL, so as to reduce the construction cost. • Designed water level : LWL = 61.0m, HWL = 70.0m • Channel : Effective depth 1.0m x Width 3.0m / line –2lines 4) Screens Both coarse screen and fine screen will be installed. The course screen would remove large matter, like a floating wood or stones from raw water. The fine screen would remove smaller particles. A Jib crane for lifting big obstacles and a lifting device for removing accumulated mud or sand from the basin will be installed. Footsteps will be furnished for descending into the basin. 5) Pump Pit The pump pit is designed with its bottom lowered enough to retain sufficient water depth for pump suction. The pit is also designed to be in two lines so that one line is open when the other is being cleaned. The pit will be partitioned from the screening canal by a wall with three holes at different levels for entry of water. A gate will be installed at the lowest one. In the rainy season, the gate would be closed so that water enters through the upper two holes. Sand sediments would not enter the pump pit by this operation. When river water level lowers below the middle hole in the dry season, the gate should be opened after removing the sediments in front of the gate. 6) Pump Room As the placing level of pumps is 12m below the ground level, the scale of structure required has much influence on the construction cost. Therefore, dry installed submersible pump is recommendable to be installed, because it needs the smallest area among the different types. Besides the small installation space required, the dry installed submersible pump has various advantages as follows. a) High passage ability of solid particles, like sand, gravels or floating matter/stuff b) High water proof performance accepts occasional flood. c) High efficiency of energy consumption by motor unified with pump body. d) Easy maintenance of pump. 2-184 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City The cost of this type of pump does not differ so much from other types.? • Number of pumps: 2 units + 1 spare unit; in 2010, Total pumpage rate is 110,000 m3 /day 4 units + 1 spare unit; in 2020, Total pumpage rate is 220,000 m3 /day A fan for ventilation will be installed to avoid any oxygen shortage. The Operation and Control House will be constructed over the pump room. A traveling crane will be installed for maintenance and repairing of equipment of pumping system. Control panels of pumps, fans and cranes and so on, will be placed in the house. 7) Generator for Emergency Purpose Electricity power failures often occur in Mandalay City. One generator and oil tank, which have a capacity to operate one pump, should be installed for using during emergency of electricity failure. 8) Buildings and Landscaping Operation and Control House Reinforced concrete, One story, 180m2 Electric Room Reinforced concrete, One story, 200m2 Workshop Reinforced concrete, One story, 65m2 Landscaping Roads, Fences 9) River Bed Protection A structure will be constructed in order to protect riverbed surrounding the entrance canal from scouring by the river flow. • Structure : Masonry and concrete block (0.5m x 0.5m x 0.3m) • Area to be covered : Surrounding 10m width (3) Water Treatment Plant 1) System Considering the following conditions in Mandalay City, a system of sedimentation with coagulant and rapid sand filter is proposed. a) The fluctuation of water quality is big, especially with turbidity level varying from some tens to a few hundreds NTU, through the year (see Chapter 4.5.4). b) Since there is no better location, the site of proposed WTP had to be selected in an 2-185 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City area that gets inundated by back water of the Ayayarwaddy River. Therefore, land reclamation for the plant is required to raise the ground elevation up to 73.0 m. 2) Treatment System a) Water ① Grit Chamber ② Raw Water Intake ③Conveyance Pipe ④Receiving Well ⑤ Distribution Chamber ⑥ Chemical Mixing Chamber ⑦ Flocculation Basin ⑧ Sedimentation Basin ⑨Rapid Sand Filter ⑩ Clear Water Reservo ir b) Sludge ① Sludge Drying Bed ② Drainage c) Chemical for Treatment Flocculant; Aluminum Sulfate Disinfection; Chlorine Gas (4) Capacity of Facilities The capacity of facilities is summarized as shown in Table 4.6.1 below. Drawings of facilities are shown in Fig. 4.6.3.1 to Fig. 4.6.3.7. Table 4.6.1Capacities of Treatment Facilities Facility Item Unit Grit Chamber Overflow Rate mm/min 350 Mean Flow Velocity cm/sec 4 Rate of Length / Width Basin Mean Diameter of sand to be removed Capacity Remark 4.0 pcs 4 mm 0.1 Receiving Well Shape Distribution Chamber Detention Period min 1.5 Effective Depth m 4.5 Basin pc 1 Free Board cm 60 Mixing Chamber Rectangular System Mechanical Agitation Basin pcs 8 Detention Period min 1.5 Effective Depth m 4.0 m/sec 1.5 Circumference Speed Flocculation Basin (20 / 5) System Horizontal Flow Basin pcs 2-186 8 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Part II Study for Mandalay City Detention Period Sedimentation Basin min Shape Rectangular Basin pcs Overflow Rate mm/min Rate of Length / Width Mean Flow Velocity Water Collecting Rate at Trough System 4.8 m/min 0.4 m /m/day Self Back Washing pcs Shape (54/12) 500 Gravity 32 Rectangular Area/ 1Basin m Rate of Filtration 2 57.42 m/day 120.0 Thickness of Sand cm 60.0 Diameter of Sand mm 0.6 Back Washing Type 6.6x8.7 Surface & Back washing Back Washing Self Back Washing 3 2 Back Washing Speed m /m /min 0.6 Back Washing Period min 6.0 m 3.0 Back Washing Pressure Surface Washing Pressure Water 3 2 Surface Washing Speed m /m /min Surface Washing Period min 6 m 15 Surface Washing Pressure Clear Water Reservoir 30.0 m 3 Basin Chlorination Chamber 8 4.5 Effective Depth Rapid Sand Filter 30.0 System 0.2 Horizontal Flow Basin pcs 8 Detention Period hr 2.0 Basin Nos 4 Effective Depth m 5.0 Alum % 10.0 Infusion volume mg/l 30.0 Intermediate Chlorination Infusion volume mg/l 2.5 Post Chlorination Infusion volume mg/l 2.5 Chemicals Sludge Drying Bed Density Sludge amount Disposed m3 /day/basin 3 Sludge Load Rate kg/ m /year 2-187 590.0 500.0 The Study on Water Supply Systems in Mandalay City and in the Central Dry Zone Basin Effective Depth Part II Study for Mandalay City pcs 4 m 1.9 m2 /unit Area 2,320 Length m 34.0~38.0 Width m 64.0 Structure Declining Wall Rock Masonry Bottom Drainage Gravel Pavement Overflow & Under Drain 4.6.4 Proposed Distribution Reservoirs Two ground reservoirs will be constructed around Mandalay Hill. (1) The places of newly constructed reservoir are decided as considering the following conditions. • The place should be located in the altitude enable to do the gravity distribution. (Designed water level: HWL= 106 m, LWL= 100 m) • The location should be public space and not to harm the natural and social conditions by the construction. • The ground is recommended to be as flat and in good geological character as possible to reduce the construction cost. (2) Structure l Reinforced concrete l Required Volume : West side, 17,000 m3 (near the existing ground reservoir) East side, 25,000 m3 l Shape : Effective Depth 6m x Length 70m x Width 41m = 17,200 m3 (West) Effective Depth 6m x Length 100m x Width 42m = 25,200 m3 (East) 2-188 N φ300 L=300m φ500 L=2570m Proposed Tube Well Mandalay Hill Reservoir Transmission Pipe Fig.4.6.2.2 Proposed Groundwater Development Plan (North) 2-190 N BPS1 Reservoir φ500 L=2670m L=300m L=300m φ300 φ400 Transmission Pipe Proposed Tube Well Fig.4.6.2.3 Proposed Groundwater Development Plan (South) 2-191 Proposed Water Treatment Plant Proposed Proposed Fig. 4.6.3.1 Proposed Raw Water Conveyance Plan 2-192