Pilot surface water treatment plant Hoa An, Vietnam

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Pilot surface water treatment plant Hoa An, Vietnam

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At Hoa An research station - belonging to Can Tho University - a student dormitory and other research facilities are under construction. The existing ground water supply will not meet the prospective fresh water demands of about 300 people in the nearest future.

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  1. Part Project 2: Improvement of the Rural Water Supply Pilot Surface Water Treatment Plant Hoa An, Vietnam Manual & Documentation (Version from the 27.09.2007) Funded by the Federal Ministry of Research and Education, Germany (Project ID 02WD0621)
  2. SANSED II Part Project 2: Water Supply The Pilot Surface Water Treatment Plant Hoa An was developed within the Project – Part Project 2: Improvement of the Rural Water Supply funded by the German Federal Ministry of Research and Education (BMBF) Project ID 02WD0621 Authors Dipl.-Ing. Thomas Nuber, Environmental Engineering and Ecology, Ruhr-University Bo- chum, Germany Frank Benstoem, Environmental Engineering and Ecology, Ruhr-University Bochum, Ger- many Dipl.-Geoökol. Thilo Herrmann, Ingenieurbüro Technische Hydrologie, Bayreuth, Germany M.Eng. Le Anh Tuan, Department of Environmental and Water Resources Engineering, Col- lege of Technology, Can Tho University, Vietnam II
  3. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION Contents 1. Introduction...................................................................................................................1 1.1. Idea of the pilot surface water treatment plant..........................................................1 1.2. Purpose of the manual .............................................................................................1 1.3. Contact .....................................................................................................................1 2. Treatment Concept.......................................................................................................3 2.1. Treatment Capacity ..................................................................................................4 2.2. Water Catchment......................................................................................................4 2.3. Flocculation ..............................................................................................................4 2.4. Sedimentation...........................................................................................................5 2.5. Rapid Sand Filtration ................................................................................................5 2.6. Slow Sand Filtration..................................................................................................6 2.7. Disinfection UV-Lamp ...............................................................................................6 2.8. Disinfection with Chlorine .........................................................................................6 3. Dimensioning................................................................................................................7 3.1. Sedimentation Tanks ................................................................................................7 3.1.1. Sedimenation Area ...............................................................................................7 3.1.2. Flow Rate..............................................................................................................7 3.1.3. Flow Velocity.........................................................................................................7 3.1.4. Retention time.......................................................................................................8 3.2. Tube Reactors ..........................................................................................................8 3.2.1. Equations for the dimensioning of the Tube Reactors..........................................8 3.2.2. Dimensioning of the Micro Flocculation Reactor R-1a and R-2a:.........................9 3.2.3. Dimensioning of the Macro Flocculation Reactor R-1b and R-2b.......................10 3.3. Rapid-Sand-Filter ...................................................................................................11 3.3.1. Diameter of the filter ...........................................................................................11 3.3.2. Filter Height ........................................................................................................11 4. Electrical Set-up .........................................................................................................12 4.1. Operating Mode ......................................................................................................12 5. How to get the treatment plant started .......................................................................14 III
  4. SANSED II Part Project 2: Water Supply 6. How to shut down the treatment plant ........................................................................18 7. Troubleshooting..........................................................................................................18 8. Maintenance ...............................................................................................................18 9. Literature ....................................................................................................................22 10. Appendix.....................................................................................................................23 IV
  5. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION Symbols, Abbreviations, Dimensions PSWTP Pilot Surface Water Treatment Plant A [m²] Area d [m] Diameter G [ s −1 ] Velocity gradient l [m] Length Q [m 3 / s ] Flow rate Re [−] Reynolds coefficient t [s] Time v [m / s ] Flow velocity λ [−] Loss coefficient υ [m ² / s ] Kinematic viscosity V
  6. SANSED II Part Project 2: Water Supply Figures Fig. 1: Process Overview .........................................................................................................3 Fig. 2: Process Flow Chart 1/3 ...............................................................................................24 Fig. 3: Process Flow Chart 2/3 .............................................................................................25 Fig. 4: Process Flow Chart 3/3 ...............................................................................................26 Fig. 5: Plan View ....................................................................................................................27 Fig. 6: Sedimentation Tanks...................................................................................................28 Fig. 7: Electrical Installation....................................................................................................29 Tables Tab. 1: Electrical components ................................................................................................12 Tab. 2: Parts List ....................................................................................................................30 VI
  7. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION 1. Introduction 1.1. Idea of the pilot surface water treatment plant At Hoa An research station - belonging to Can Tho University - a student dormitory and other research facilities are under construction. The existing ground water supply will not meet the prospective fresh water demands of about 300 people in the nearest future. In the framework of the SANSED-Project a pilot surface water treatment plant (PSWTP) Is being constructed in Hoa An. The PSWTP should be used for scientific purposes but it should also be able to supply the research station with water. For the design of the pilot surface water treatment plant the following conditions had to be reached: • treatment steps are easy to understand • treatment plant can be rebuilt with parts available in Vietnam • low costs and low maintenance but efficient • robust Besides standard treatment components (e.g. sedimentation tanks, disinfection) tube reac- tors where the flocculation takes place and a slow sand filter are applied. The tube reactors provide a reliable formation of settleable flakes even under sub-optimal operating conditions and do not need maintenance. 1.2. Purpose of the manual In this manual treatment steps are explained, the dimensioning of significant components is shown and recommendations for maintenance are given as well as a description how to start up and how to shut down the plant . This manual also contains a documentation of the treatment plant including technical out- lines, part lists and pictures taken during the installation process. Manuals of additional equipment (e.g. dosage pumps, UV-Lamp, etc.) are also enclosed. 1.3. Contact For information, questions and problems please contact: 1
  8. SANSED II Part Project 2: Water Supply Dipl.-Ing. Thomas Nuber Ruhr-University Bochum, Germany Environmental Engineering & Ecology Universitätsstr. 150 44780 Bochum, Germany Tel:: + 49 (0) 234 – 32 28277 email: thomas.nuber@rub.de Or : Le Anh Tuan, M.Eng. Can Tho University College of Technology Department of Environmental and Water Resources Engineering Campus II, 3/2 Street, Can Tho City, Vietnam email: latuan@ctu.edu.vn 2
  9. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION 2. Treatment Concept In the following section the concept of the pilot surface water treatment plant (PSWTP) is described. An overview of the applied purification process of the surface water is given in the Fig. 1. Water Catchment Al3+ Flocculation Sedimentation From Rinsing To Sludge Water Storage Discharge Rapid Sand Filtration Slow Sand Filtration To Rinsing Water Storage UV-Disinfection NaOCl Chlorination To distribution network Legend Qmax [m³/h] = 3,0 1,5 Project: Treatment Plant Hoa Anh, Vietnam Title: Process Flow 1/3 Date: 30.07.2007 Editor: Frank Benstöm Fig. 1: Process Overview For detailed process information see Fig. 2 to Fig. 4 in the appendix. A list of all components of the PSWTP is given with their labelling and technical specifications in Tab. 2 of the ap- pendix. A plain view of the PSWTP is shown in Fig. 5 in the appendix. 3
  10. SANSED II Part Project 2: Water Supply 2.1. Treatment Capacity The PSWTP is designed for a maximum flow rate of 3 m³/h. 2.2. Water Catchment The surface water is abstracted with the submersible water pump (P-1c(I)) from the water reservoir located in the canal next to the PSWTP. Non-return valve V-1c prevents already treated water to flow back to the catchment when the pump is switched off. The water catchment itself consists of a fence surrounding the submersible pump preventing bigger particles (e.g. leaves) of blocking the system (Photo 1). The pressure of raw water is increased by pump P-1a(I) situated inside the treatment plant. The flow rate of raw water is measured by the flow rate meter I-1 and can be adjusted using valve V-1a to the desired flow rate. Water samples of the raw water can be taken at sampling valve V-1b. 2.3. Flocculation The treatment goal of the flocculation is to destabilize non-settleable particles in the raw wa- ter and to agglomerate small particles by forming flocs. For the destabilization and agglomeration Polyaluminiumchloride (PAC) solution is used as flocculant. It is stored in stock solution tank S-1. Stirrer M-1 is used to guarantee a homoge- neous mixture when fresh PAC solution has to be prepared by solving PAC in water. The PAC stock solution is added to the water stream with dosing pump P-1b. The typical “pulsated-dosage-characteristic” of the dosing pump is smoothened with pulsation damper D- 1. This secures a continuously dosage for optimal mixture with the water stream and to maximize accuracy of measuring the flow rate with flow rate meter I-2 (Photo 2). In injection nozzle N-1 the PAC stock solution and the water stream are rapidly mixed by changing the tube diameter. This leads to an instantaneous change in velocity and therefore turbulences are formed within the tube. Water samples can be taken at sample valve V-2b. After that the water stream is split into 2 sub-streams. Every single stream passes one tube reactor (R-1a and R-2a) with small diameter for micro-flocculation. Water samples can be taken after the micro-flocculation at sample valve V-3b and V-4b. 4
  11. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION After forming micro-flakes the water flows through another tube reactor (R-1b and R-2b) for macro-flocculation to accumulate the micro flakes to settleable macro flakes. Both are wound around sedimentation tanks E-1 and E-2 to save space (Photo 3). The water in the tube re- actors can be released to the sludge stream opening valve V-4a in case of maintenance. 2.4. Sedimentation The treatment goal of the sedimentation is to settle down most of the flakes formed in the flocculation to reduce the load on the rapid sand filters. The flakes are settled in sedimentation tanks E-1 and E-2 (Fig. 6). Therefore the water stream coming from the top of the sedimentations tanks is redirected using a deflector. Due to the large diameter of the tanks the velocity of the water stream is slowed down and the flakes can be settled. The clearified water is taken from the top of the sedimentation tanks and is stored in tank E-3 (Photo 4). Water samples can be taken at valve V-6b. The sludge can temporarily be released by valves V-5a and V-6a. Valve V-7a can be used to empty storage tank E-3 in case of maintenance. 2.5. Rapid Sand Filtration The treatment goal of the rapid sand filtration is to remove residue small non-settleable parti- cles. The water is pumped from the storage tank E-3 through two serially connected rapid-sand filters F-1a and F-2a via pump P-2a (Photo 5 and 6). The flow can be adjusted using valve V- 6a. The filters can be backwashed with rinsing pump P-4 which takes water from rinsing water storage tank E-4 (Photo 9). The backwash flow can be measured using flow rate meter I-3. Valves V-9a to V-16a are needed to switch from operating process to backwash process. Valve V-7b is used to take water samples. 5
  12. SANSED II Part Project 2: Water Supply 2.6. Slow Sand Filtration The treatment goal of the slow sand filter consists of aeration, reduction of dissolved organic substances and reduction of germs. The slow sand filter will be designed and built under construction supervision of ITH (Thilo Herrmann) and Le Anh Tuan. 2.7. Disinfection UV-Lamp The treatment goal is the disinfection of the treated water. The water is pumped through the ultraviolet disinfection lamp (UV) by pump P-3a (Photo 7 and 8). After that a sub-stream of the water is used to (re-)fill the rinsing water tank E-4 con- trolled automatically by float valve V-1d (Photo 9). This sub-stream can be adjusted using valve V-18a. The flow rate can be adjusted using valve V-17a. Water samples can be taken before and after UV-treatment (V-8b and V-10b). 2.8. Disinfection with Chlorine The treatment goal is the persistent disinfection of the treated water. Either disinfection with the UV lamp or with chlorine or both can be applied. Sodium hypochlorite solution is added to the treated water by dosing pump P-2b. Pulsation damper D-2 is needed to smoothen the signal for a continuously injection to gain a homoge- nous mixture (Photo 8). Water samples can be taken at valve V-11b. After the chlorination step the treated water (re-)fills the water supply tank of the student dormitory throw an underground pipe. 6
  13. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION 3. Dimensioning In the following section the dimensioning of the treatment componets is described. 3.1. Sedimentation Tanks The technical drawings of the sedimentation tanks and figures can be found in Fig. 6. 3.1.1. Sedimenation Area With a diameter of the sedimentation tank of 1,6 m and diameter of the inflow-pipe of 0,11 m the sedimentation area Ased is:. Ased = (π ⋅ (1,6 m)² / 4) − (π ⋅ (0,11 m)² / 4) = 2,00 m² (1) 3.1.2. Flow Rate The total capacity of the treatment plant is Q=3 m³/h. There are two sedimentation tanks with a maximum flow rate Q = 1,5 m³/h each. 3.1.3. Flow Velocity For the sedimentation step the flow velocity of the water within the sedimentation tank has to be lower than the velocity of particles which should be settled. According to (HAHN UND HERMANN H. (1981): WASSERTECHNOLOGIE: FÄLLUNG, FLOCKUNG, SEPARATION, SPRINGER VERLAG, BERLIN, 1987) for aluminium flakes a mean sedimentation velocity of v ref = 2,38 m/h can be assumed. The flow velocity can be calculated with the following equation: Q 1,5 m³ / h v= = = 0,75 m / h (2) Ased 2,00 m² Therefore the calculated flow velocity is smaller than the mean sedimentation velocity of v ref = 2,38 m/h according to [HAHN UND HERMANN H. (1981)]: ! v ref > v → 2,38 m / h > 0,75 m / h => Condition fulfilled 7
  14. SANSED II Part Project 2: Water Supply 3.1.4. Retention time The retention time tr withing the sedimentation tanks is calculated according to the following equation: l sed ⋅ Ased tr = (3) Q With the sedimentation length lsed = 0,73 m and the sedimentation area ASed=2,0 m the reten- tion time is: 0,73 m ⋅ 2,00 m tr = = 0,97 h ≅ 1 h (4) m³ 1,5 h 3.2. Tube Reactors In the following sections the dimensioning of the tube reactors will be described. 3.2.1. Equations for the dimensioning of the Tube Reactors According to [GROHMANN, A. (1981)] the velocity gradient G of a tube reactor can be de- scribed as: λ ⋅ v3 G= (5) 2 ⋅ d ⋅υ whereas: 1 − v⋅d Q λ = 0,3164 ⋅ Re 4 with Re = and v= υ A According to equation (5) the diameter of a tube reactor can be calculated with 8 11 3 11 − − − d = 1,339 ⋅ G 27 ⋅ Q 27 ⋅ υ 30°C 27 ⋅π 27 (6) The length of a tube reactor can be calculated according to the following equation: 4⋅Q ⋅tr l = v ⋅t r = π ⋅d ² 8
  15. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION 3.2.2. Dimensioning of the Micro Flocculation Reactor R-1a and R-2a: According to GROHMANN (1981) the velocity gradient G and the retention time tr for the mi- cro flocculation can be set to: G = 500 s −1 and t r = 30 s 3.2.2.1. Diameter According to equation 5 and the above given numbers the required diameter is calculated as: 8 11 3 11 − − − d =1,339 ⋅ 500 27 − 4 27 −7 ⋅[4,17 ⋅ 10 ] ⋅[8,06 ⋅ 10 ] 27 ⋅π 27 = 0,0266 m For the installation d = 0,025 m is chosen. 3.2.2.2. Length According to equation 6 and the above calculated figures the length of the tube reactor can be calculated as follows: 4 ⋅ Q ⋅ t r 4 ⋅ 4,17 ⋅10 −4 ⋅ 30 l = v ⋅t = = = 22,51 m π ⋅d² π ⋅ 0,025² For the installation l = 25 m is chosen. 3.2.2.3. Verification of Minimum Flow Velocity To avoid sedimentation within the tube reactor the velocity has to be higher than 0,1 m / s , [see GROHMANN (1981)]. The flow velocity can be calculated according to the following equation 4 ⋅ Q 4 ⋅ 4,17 ⋅10 −4 v= = = 0,85 m / s > 0,1 m / s π ⋅d ² π ⋅ 0,025² With the calculated flow velocity the condition according to GROHMANN (1981) is fulfilled. 9
  16. SANSED II Part Project 2: Water Supply 3.2.3. Dimensioning of the Macro Flocculation Reactor R-1b and R-2b According to GROHMANN (1981) the velocity gradient and the retention time for the macro flocculation can be set to: G = 20 s −1 t r = 100 s 3.2.3.1. Diameter According to equation 5 and the above given numbers the required diameter is calculated as: 8 11 3 11 − − − d =1,339 ⋅ 20 27 − 4 27 −7 ⋅[4,17 ⋅ 10 ] ⋅[8,06 ⋅ 10 ] 27 ⋅π 27 = 0,0669 m For the installation a diameter d = 0,070 m is chosen. 3.2.3.2. Length According to equation 6 and the above calculated figures the length of the tube reactor can be calculated as follows: 4 ⋅ Q ⋅ t r 4 ⋅ 4,17 ⋅10 −4 ⋅100 l = v ⋅t = = =10,84 m π ⋅d ² π ⋅ 0,070² For the installation a length l = 15 m is chosen. 3.2.3.3. Verification of Minimum Flow Velocity To avoid sedimentation within the tube reactor the velocity has to be higher than 0,1 m / s [GROHMANN (1981)]. The flow velocity can be calculated according to equation 4 ⋅ 4,17 ⋅10 −4 v= = 0,11 m / s > 0,1 m / s π ⋅ 0,070² With the calculated flow velocity the condition is fulfilled. 10
  17. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION 3.3. Rapid-Sand-Filter For the rapid-sand-filter the following boundary condtions are given: Flow: Q = 3m³ / h Filter velocity: v f = 12m / h 3.3.1. Diameter of the filter The required filter area Amin is calculated according to the equation Q Amin = vF Therefore, with the given Q and vf the required Area is 3m³ / h Amin = = 0.25m² 12m / h With the required area the required diameter is: 4 ⋅ Amin 4 ⋅ 0,25m² d min = = = 0,56m π π The chosen diameter is 0,6 m 3.3.2. Filter Height According to HANCKE (2000) the minimum filter height is h = 2,0 m. A height of h=2,4 m is chosen. 11
  18. SANSED II Part Project 2: Water Supply 4. Electrical Set-up In the following section the electrical set up is described. It ensures the power supply of each component of the PSWTP and is responsible for the semi-automatic control. See especially Fig. 7 and Tab. 1 for the electrical installation and Tab. 2 for further explanations of con- nected consumer loads (e. g. pumps). Tab. 1: Electrical components Item Labelling Properties Switch ES-1 … ES-17 230 V Operation Control Lamp EL-1 … EL-16 230 V; 25 W Contactor, triple ER-1, ER-2 230 V; 5 A Maximum Current Contactor, double ER-4 230 V; 5 A Maximum Current Contactor, single ER-3 230 V; 5 A Maximum Current Level Control Switch ESS-1 … ESS-4 230 V; 7 A Maximum Current Pump P-1a(I), P-1a(II), P-2a, P-3a 230 V; 370 W Rinsing Pump P-4a 230 V; 740 W Submerged Pump P-1c(I), P-1c(II) 230 V; 750 W Dosing Pump P-1b, P-2b 230 V; 100 W UV-Disinfection Lamp UV 230 V; 200 W Extensions LL-1 … LL-3 230 V; 750 W Air Compressor K-1 230 V; 300 W Stirring Device R-1, R-2 230 V; 750 W Σ Entire Maximum Load = 8,2 kW 4.1. Operating Mode The voltage is smoothened by a voltage stabilizer with a maximum capacity of 10 kVA. A main switch is installed to shut down the electric supply in case of maintenance. A main Cir- 12
  19. Pilot Surface Water Treatment Plant Hoa An, Vietnam MANUAL & DOCUMENTATION cuit breaker is used to prevent the installations from over-current. Furthermore a ground fault circuit interrupter connected with a grounding behind the PSWTP is used to reduce the risk of accidents for the operating staff. All switches, control lamps and contactors are assembled in a control panel (Photo 10). The treatment plant is operated with level control switches which are installed in significant spots within the process. The level control switches are operating contactors which are con- trolling the consumer loads (e.g. pumps). The consumer loads can be switched on/off by the manually operated switches ES-1 to ES- 17. The operating status is displayed by lamps EL-1 to EL-16. When level control switch ESS-1 is switched on the contactor ER-1 supplies the pumps P-1c (I), P-1a (I) and P-1b with electricity. When level control switch ESS-3 is switched on contactor ER-3 supplies pump P-2a with electricity. When level control switch ESS-4 is switched on contactor ER-4 supplies the pump P-3a and P-2b with electricity. UV-Lamp, rinsing pump P-4a and stirring devices M-1 and M-2 are controlled manually by switches. Switches ES-1 to ES-17, contactors ER-1 to ER-4 and operation control lamps EL-1 to EL-16 are built in a control panel for central control of the PSWTP. The electrical set-up described in the following can be used as an option for further exten- sions of the PSWTP. Consumer loads are not connected yet. - When level control switch ESS-2 is switched on contactor ER-2 supplies pumps P-1c (II), P-1a (II) and P-1b with electricity. This circuit works simultaneously to consumer loads P-1c (I), P-1a (I) and P-1b described above and may be used for tapping an- other water resource. 13
  20. SANSED II Part Project 2: Water Supply 5. How to get the treatment plant started In order to get the treatment plant started the following steps have to be done. Please read this chapter first before you are starting the treatment plant. Options for the Operational Mode - If the treatment plant is running without the purpose to (test modus) the valve V 19 -a has to be closed. - If the student dormitory is to be supplied with the treated water (regular modus) the valve V19-a has to be opened. For the operational mode check if the floating switch is in position. Step 1: Release of the remaining water - If the treatment plant was not running for a long time it is recommended to release the remaining water from the sedimentation tanks E-1 and E- 2 and also from the storage tank E-3 by opening the valves V5a, V6a and V7a. - After the remaining water is released close the valves V5a, V6a and V7a. Step 2: Turn on the Power Supply - Open the “Electrical Installation Box” - Check the voltage stabilizor - Switch on the main circuit breaker - Switch on the main switch - Switch on the ground fault circuit interupter 14

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