Dosing and Instrumentation Construction and Modification

Spring 2007

Assembly and installation of the turbidimeters, tube settlers, and alum feed pump was completed in the same day.

Summer 2008 Modifications

When the temperatures dropped this winter the sampling set-up started to have problems reporting viable results. One hypothesis was that the half submerged tube settlers, acting as sedimentation tanks, were not settling as well because of temperature change between the submerged portion and the portion at room temperature. It is believed that the water was flowing faster at the edges of the tubes than in the center, and because of this the residence time in the tube was made shorter. This issue was corrected by submerging the entire settling tube.

A suspension system (Submerged Settling Tube) was created to submerge the tubes and still keep it hanging at the correct angle. After implementing this set-up on one of the setting tubes in the tank it found that the upper baffle spacer got in the way of the string holding the lower end of the tube at the correct angle. Thus the set-up was altered to so that the tube was placed, still at 60 degrees and submerged, but instead of being suspended the bottom was supported by one of the lower baffle spacers and the top rested against the side of the tank. This was the same method of tube settler placement that was done previously just further down in the tank.

The temperature difference between the air temperature at the plant and the water temperature (close to freezing) is causing air to bubble out of solution in the turbidimeters and it is believed that this might be causing false readings. The air doesn't stay in solution because the water is less soluble. To correct this problem the plan is to raise the pressure on this system (new schematic) to a point that will keep the air in solution. The configuration of how water is drawn from the settling tubes to the turbiditimeters and then discarded was rearranged. Water flows from the tubes, through the pump then into the meters. From the meters the water travels up and drops into an exit tube about a meter above the tank. The outlet tube was extended as close to the ceiling as possible in order to allow increased pressure in the system, this height ended up being about 8 feet above the top of the tank.

Spring 2009

In order to mimic the dosing of the Cornell University Water Filtration Plant, which uses polyaluminum chloride, the pilot plant has switched from using alum as a flocculant to polyaluminum chloride (although it could easily be switched back as necessary).