Water Treatment Plant Reflections
Water Treatment Plant Reflections
S1
Raw Water
alum
Q T
S2
S4
m1
S3
FlocculationSedimentation
p1S5
Clearwell CleanWater
S1S1
Raw Water
alum
QQ TT
S2S2
S4S4
m1m1
S3S3
FlocculationSedimentation
p1p1
LabVIEW SoftwareLabVIEW 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
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
When it doesn’t work!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”
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”
Modular approachModular approach
Break a system down into its components and test individual pieces
What are the system components that can fail? Brainstorm!
Break a system down into its components and test individual pieces
What are the system components that can fail? Brainstorm!
Scientific Method of Troubleshooting
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!
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!
Automated System HardwareAutomated 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)
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)
Automated System SoftwareAutomated 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
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
Hydraulic Challenges (getting the water to go where you want it to go)
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
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
Hydraulic ChallengesHydraulic 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)
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)
pR2 = 2R
Surface TensionSurface Tension
Pressure increase in a spherical droplet
Pressure increase in a spherical droplet
Rp
2R
p2
pR2
2R
Surface moleculesSurface molecules
0.0500.0550.0600.0650.0700.0750.080
0 20 40 60 80 100
Temperature (C)
Sur
face
tens
ion
(N/m
)
Example: Surface TensionExample: 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.
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.
Rp
2R
p2 R = 1.5 x 10-3 mR = 1.5 x 10-3 m
= 0.073 N/m = 0.073 N/m
( )3
2 0.073 /
1.5 10
N mp
x m-=( )
3
2 0.073 /
1.5 10
N mp
x m-=
97 Pap =97 Pap =
hp hp 3
970.01 m water
9806 /p Pa
hN mg
= = =3
970.01 m water
9806 /p Pa
hN mg
= = =
Water won’t flow from tube until the elevation difference exceeds 1 cm!
Hydraulic Challenges 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!
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!
Is there anything left to do?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?
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?
Three Ways to Control Alum Pump
Three Ways to Control Alum Pump
Specify pump rpm Specify alum dose
___________________ ___________________ ___________________
Automatic ___________________ ___________________ ___________________
Specify pump rpm Specify alum dose
___________________ ___________________ ___________________
Automatic ___________________ ___________________ ___________________
Alum stock concentration
Plant flow rate
Tubing size
Raw water turbidity
Plant flow rate
Tubing size
Manual rpmManual rpm
Manual alum doseManual alum dose
Automatic Alum DoseAutomatic Alum Dose
Automated Alum DoseAutomated Alum Dose
1
10
100
0 5 10 15 20Alum Dose (mg/L)
Res
idua
l Tur
bidi
ty (
NT
U) 140 NTU
14 NTU
PointersPointers
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!
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!