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!