Pilot Plant Maintenance, Troubleshooting, and Tips

I. Sedimentation Tank Maintenance

Tank Drainage Manifold

A tank drain system was designed to drain in 30 minutes (Q ~drain~ = 20 L/min. The design is similar to the effluent launder except this manifold is located at the bottom of the tank.

By the same method as was used for the tank effluent manifold the manifold diameter was determined to be 1.905cm (0.75") and the orifice diameter is 0.3572cm (9/64").
* The available head for the sludge ports is the total water depth (84.455cm or 33.25") minus the head loss in the manifold and minus the velocity head at the end of the manifold.
* Kminor was assumed to be 0 in the manifold and 1.0 for the pipe entrances and exits.
* The constant for the determining orifice diameter was found to be 0.63
*Qratio = 0.90
* 15 orifices were assumed to provide a similar layout to the effluent manifold.
The hole size in the drain manifold was increased to 1/4" to allow for faster tank drainage.

Cleaning the Sed Tanks

II. Troubleshooting

This section includes some minor issues the team has come across.

Note that there is always at least one operator at the treatment plant during regular hours. The operators are generally willing (and usually able) to help solve problems, so don't hesitate to ask if they're free to help out.

Starting the pilot plant

• Check with the operators to see if it is permissible to run the pilot plant.
• Check that all the cords, including the power strips, are plugged in.
• Check with the plant operators to make sure they haven't turned off parts of the Filtration Plant for maintenance. The operators are also very helpful in figuring out what might be unplugged or turned off.

Starting the alum pump

If the alum pump has been switched on, but no alum is flowing (i.e., the corresponding box in the process controller reads "0" mg/L):

• Go to configuration in the process controller.
• In the top left corner there are methods, files, etc. buttons, and an icon that looks like an open folder. Click on the folder.
• Open the Fall 2008 folder (or a newer folder).
• Open Sept 9 2008 (or any configuration that may have been saved later).

If there is a leak

Determine the source of the leak.

If it is a pipe:

• If the pipe connects the flocculator to the sed tank, plug the inlets with the screw caps already created. The benefit to this over just turning off the plant is that the flocculator can continue to run, since the water can leave through the weir in the flocculator which usually just handles excess flow.
• Dry off the pipe to the best of your ability with a towel.
• When the pipe is completely dry - this is pretty essential, since the caulk will not set properly if it is wet. Wait at least a few hours or a day to ensure that the surface is dry, then caulk the pipe, paying special attention to the bottom of the seal. The cure time is usually 24-48 hours, so leave the pipes plugged for this duration of time.
• If water continues to leak, make sure that the leak is not coming from another location, and repeat the above steps if necessary.

If it is the plant leveling tank:

• Try to determine which component is causing the issue.
• Plug the pipes connecting the flocculator and the sedimentation tanks so that water stops flowing into the plant leveling tank.
• Ask Tom or one of the other nice plant operators if they could show you how to tighten the flanges of the connecting pieces.

Peristalic Pumps

It can be hard to tell which way to set the switch on a pump. If you're unsure, let a little air into part of the tubing and see which direction it goes. (That's the direction water is being pumped.)

*It likely that a pump isn't running if

• the power light is off,
• the motor isn't turning (i.e., the circle on the front of the unit isn't turning),
• water in the tubes doesn't seem to be going anywhere.

If the pump is plugged in and switched on, but still isn't running, try turning the dial or pressing the up arrow to increase the pump speed. If it still isn't working, the motor may be the problem. An immediate solution is to use one of the other pumps at the pilot plant if no one else is using it. (If the pump has more than one tube running through, you might need to label the tubes before taking them out so they can put back in the right order.) To take a tube out of a pump, lift the lever near the front of the pump and gently pull the beige tube out of the pump. You probably will not need to disconnect any tubes from one another.

If the flocs look funny

If the flocs are white in color and float,

• First check the flow rate into the pilot plant by looking at the digital monitor, located next to the wall facing Cornell University's Flocculator. If it is much lower than 23 gal/min:
  • Toggle the pump on and off. If this doesn't work:
  • The pump that drives the water through the plant is not operating properly. There may be objects caught in the screen (e.g. leaves) or there may be electrical issues.
• The alum dose is too high for the turbidity of the incoming water. Lower the alum dose slightly:
  • Open process controller.
  • Go to the Configuration tab.
  • Click "Edit Rules."
  • In the menu on the left-and side, go to "alum dose not increment" and change the value.

If the effluent water is turbid and does not contain large flocs, but the water is not unsually white, the alum dose probably is not high enough. Increase the alum dose in Process Controller to account for the increased turbidity. (This is likely to occur if there has been a lot of rain.)

III. Tips

Determining the height of the sludge blanket

As of early November '08, there's no set way to check the height of the sludge blanket. ("Height" refers to the top of the mass of sludge in the tank.) One way to find the top of the sludge blanket is to shine a flashlight into the tank from the top. Let the beam hit one of the walls and check where it's visible from the outside. Move the beam down and watch the spot of light move down until it stops moving even when you're moving the flashlight. This spot is the top of the sludge blanket. (Since the sludge blocks light, the spot of light is visible only until the beam hits the top of the sludge blanket.)

Draining the sed tank on the left

As of November '08, the sed tank on the left (lamella tank) drains very messily. To keep water from spraying on the floor, hold a 90 degree elbow over the opening of the drain so that water flows through the elbow. This allows to direct the water flow. If you need to be able to see the effluent, hold the elbow so that the other end is facing up. Water will flow part of the way up and back down. (If you hold it right, you won't be splashed.)

Lowering the Sludge Blanket with Lamella in the Tank

This can take a while. The sed tank must be carefully drained in intervals when trying to lower the sludge blanket.

1. Open the valve a little. Very dirty water should flow out.
2. Let water flow until the water is more clear than brown.
3. Open the valve a little more and do the same.
4. Repeat 1-3 carefully until the water opening the valve further would seem to make the velocity too high. (Pulling sludge out of the tank too fast could disturb the blanket a little. Just use your judgment.)
5. Repeat this process every few minutes. If the water coming out is very clear as soon as you open the valve, wait longer between draining periods. (Waiting some time between drainings seems to allow more sludge to flow into the outflow pipe at the bottom of the tank.)