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Water Treatment Plant Reflections

S. S. 3. 2. S. 1. S. 4. Q. T. S. m. 1. 5. p. 1. Water Treatment Plant Reflections. Raw Water. Raw Water. Flocculation. Flocculation. Sedimentation. Sedimentation. S. S. S. S. 3. 3. 2. 2. S. S. 1. 1. alum. alum. S. S. 4. 4. Q. Q. T. T. Clearwell. Clean.

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Water Treatment Plant Reflections

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  1. S S 3 2 S 1 S 4 Q T S m 1 5 p 1 Water Treatment Plant Reflections Raw Water Raw Water Flocculation Flocculation Sedimentation Sedimentation S S S S 3 3 2 2 S S 1 1 alum alum S S 4 4 Q Q T T Clearwell Clean m m 1 1 Water p p 1 1

  2. LabVIEW Software • Writing software to control a water treatment plant is too complicated for a first programming assignment! • I will provide fully functional software that allows some flexibility in configuring the plant • You will need to add the code that controls the flow rate of the alum pump

  3. When it doesn’t work! • You are creating a complex system • Any component that fails can lead to failure in the system • What could you do if you assemble the entire system and it doesn’t “work”

  4. Modular approach • Break a system down into its components and test individual pieces • What are the system components that can fail? • Brainstorm!

  5. Scientific Method of Troubleshooting • The Scientific method: • Create hypotheses • Design experiments to test the hypotheses • Draw conclusions based on the data • How can you choose which components to test first? • Intuition? • Ask which component could cause the observed symptoms • Requires a basic understanding of how the system works!

  6. Automated System Hardware • Controls • Power supply • Microproccessor • can loose its program (download program again) • May need to be reset by temporarily unplugging the power • Water damage • Valves • Sensors • Power supply • Pressure sensors (wet, hole in diaphragm, installed backwards) • Data acquisition hardware • Noisy sensors (turbidity sensors are noisy)

  7. Automated System Software • Configuration • voltages measured at a port are converted to physical units • Sensor output is connected to a particular location in the plant for control logic • Software may not do what the author thought it was going to do • Malicious intent to frustrate students… • Unintended programming errors

  8. Hydraulic Challenges (getting the water to go where you want it to go) • Leaks • Connections not sufficiently tight • Overflows • Caused by water not going where you thought it was going • Excessive head loss • tubing size too small • Valve orifice too small

  9. Hydraulic Challenges • Challenges from working at this small scale! • Flow rate into the plant is controlled by the computer • Water surface inside accumulator doesn’t need to be higher than the tank it is delivering water to! • Control the water level in the sedimentation tank • How? • What does the outflow look like? • Large scale (order 1 m) • Tiny scale (order 1 mm) • Our scale (order 5 mm)

  10. 0.080 0.075 0.070 Surface tension (N/m) 0.065 0.060 0.055 0.050 0 20 40 60 80 100 Temperature (C) Surface Tension • Pressure increase in a spherical droplet DppR2 2pRs Surface molecules DppR2 = 2pRs

  11. Example: Surface Tension • Estimate the difference in pressure (in Pa) between the inside and outside of a droplet of water that is forming at the end of a tube of water. The tube is 3 mm in diameter. s = 0.073 N/m R = 1.5 x 10-3 m Water won’t flow from tube until the elevation difference exceeds 1 cm!

  12. Hydraulic Challenges • Flow control to the filter • What is the potential energy difference that causes water to go through the filter? • What happens as the filter head loss changes? • If a water surface is moving, air must be moving too!

  13. Is there anything left to do? • Plant hydraulics • Design for robustness • Think about anything that could happen that would cause a leak • Alum flow control • Graph plant parameters • HMI (human machine interface) • As a plant operator what would you like to know? • How can you present this information in a easy to understand format?

  14. Three Ways to Control Alum Pump • Specify pump rpm • Specify alum dose • ___________________ • ___________________ • ___________________ • Automatic • ___________________ • ___________________ • ___________________ Alum stock concentration Plant flow rate Tubing size Raw water turbidity Plant flow rate Tubing size

  15. Manual rpm

  16. Manual alum dose

  17. Automatic Alum Dose

  18. Automated Alum Dose

  19. Pointers • Stamp module must be on the computer side of the bench divider • No one may operate their plant until both of the stamp modules on their bench are in safe locations • Pressure sensors can fail if one drop of water soaks into the terminals • Use manual valves to make it easy to drain tanks • Include a manual shutoff valve at the plant influent • Make sure your plant won’t cause a spill after you leave!

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