Pilot Plant Sedimentation Tank Meeting Minutes

Fall 2008 Minutes

November 21, 2008

Accomplishments

• Upon finding the flow rate at 3gal/min, cleaned the pump with a stick with a long brush on the end, and turned to flow back on. This seemed to have addressed most of the issue, since the plant began to run at 24 gal/min immediately afterward. Repeated again on Thursday evening, because the flow rate was slightly low at 22.8 gal/min; however after cleaning, it leveled out at 24.8 gal/min.
• Finally split up the Spring 2008 report into separate links on our wiki page, and did some further organization.
• Discussed with Tom the issues that we're having, and brainstormed potential solutions:
  • We discussed using a bucket and drilling holes in it to prevent the leaves from clogging the pump; however, I expressed some concern about the long term viability of that solution. We looked on McCaster-Carr to see what type of screens they might have and decided on an aluminum screen. We calculated the size of this screen (36" by 52") to make a cage around the entire pump, and will be ordering that tomorrow for manufacturing on Monday 11/24/08.
  • We also discussed what to do about the trough that is not level in the third column of the flocculator, and came up with a design to clamp it in place. This would attach to the trough itself, but it would be anchored to the top of the flocculator.
  • We discussed the possibility of putting holes in the sed tank with lamella to get a better idea of how/if a sludge blanket is forming and what level it's reaching, since a sludge judge would not be possible on this tank. We could attach quarter turn valves to the holes that we make, which would allow us to collect samples and visually inspect the water (and potentially even connect to a turbidity meter to measure, but this would come later). This would be our third priority out of these issues though.

• Began a beginner's guide to the Pilot Plant on the wiki. Have made pages for a glossary and an FAQ page. Also linked to the Maintenance and Troubleshooting page.
• Attempted experiment 1, testing turbidity with lamella at different heights of a sludge blanket. (See issues for why attempt was not entirely successful and for solutions.)
• Took pictures to replace the ones missing from pilot plant wiki pages.
• Temporary Fixes (placed under Maintenance and Troubleshooting):
  • Determining the height of the floc blanket
  • Draining the sed tank with lamella

Outcomes

• Tom fixed the pump whose motor hasn't been turning. Apparently there was also a problem with the fuse.

Metrics

• Tried to lower sludge in lamella tank to collect data at different heights. Drained tank every 5-10 minutes for 3 hours, for as long as very dirty water came out each time. Sludge blanket did not budge. Took data for both tanks anyway. Measured average turbidity about between 4.8 and 5.5 for all sets of measurements. For lamella tank, took data before trying to lower tanks, and after skimming flocs and dirt off top and trying to lower.
• Noticed that turbidity in non-lamella tank lowered after being left undisturbed. Average after some settling was just under 5.0.
• Skimmed flocs and dirt off the top of the free surface in the lamella tank, after which the turbidity in the tank began to decrease. Since the turbidity was dropping when Shaina left the plant, set up the data log to record the turbidity every 10 minutes until someone else visits the plant.

Issues

• As of Friday: Still no sludge blanket in the non-lamella tank. Will have to construct a down-turned opening to attach to the inflow opening so that flocs can be sucked up.
• Sed tank with lamella is difficult and unnecessarily messy to clean. Have temporary fix, but worked with Tom to design a permanent fixture.
• Sludge blanket in tank with lamella could not be lowered in spite of a substantial effort to do so.

• Kellie got to the plant on Monday, to find that the flow rate was only 3 gal/min. Although the alum was pumping al 20mg/L, it did not appear to be overdosing (no white fluffy flocs). At the Pilot Plant meeting on Thursday, we were notified that the alum has not been pumping, because somehow the tube got dislodged from the pump.
• With the colder weather we are having, the ideal alum dose is uncertain, since Tom says that you're supposed to DECREASE the alum when the temperature decreases (not increase - there has been some confusion).
• The previous data was invalid, since it was discovered that our pump was not be working correctly.
• The trough that is located in the flocculator that helps control the level of water in the tank is slanted and has been that way since we inherited the plant at the beginning of the semester.