Construction of the Tapered Baffles Configuration

Fall 2007

The tapered baffles set-up that was the result of new research about velocity gradients in the tank was done during the Fall 2007 semester. The baffle set-up was made using the same materials and with the basic construction design as the previous set-up. Caps and piping were used as the connection holding the baffles a set distance apart. These caps and the pipe were made of CPVC material. The caps were attached to the baffles by #6-32 stainless steel ½ inch screws and nuts. These screws placed through a ¼ inch hole that was drilled in one cap and then through a hole in the baffle and then through another cap. The hole in the baffle what about ¾" wide but this was an error in construction the hole should be the same size as the holes drilled in the caps, ¼". The nut was screwed on to the other end of the screw to keep the structure and ensure that the caps stayed firmly attached to either side of the baffles. Each baffle contained four connections. It was thought that four places of support on the baffle should give the material enough structural support to hold each baffle perpendicular to flow.

The baffles were made out of blue transparent corrugated plastic roofing material. The size of the baffles was determined based on the water level and necessary baffle spacing at the end of the tank. The distance between the water level and the top of the bottom baffle or the height between the bottom of the tank and the top baffle was kept the same through out the tank. This distance was taken as the spacing in the last section times 1.5, resulting in a turnaround of 15.1 cm.

The 20 upper baffles were cut to be 31cm wide by 88 cm long. The 19 lower baffles were cut to be 31cm wide by 62cm long. The values for the baffle spacing and number of baffles per section can be seen in the table below.

Table 1: The above table contains the exact values for the baffle spacings, number of baffles and length of the pipes connecting the baffles for each individual section.

The main difference between the previous set-up and the current set-up is that instead of having the spacing be uniform across the entire flocculator, a tapered spacing that was found above was used. The baffles were also cut ½ cm wider than for the previous set-up. This was done to help create a better seal so that less short circuiting will occur through out the flocculator. The wider baffles also help stabilize the slightly flexible section dividers. Although the wider baffle did help these issues upon observation the section support structure that was put in place over this past summer was still necessary to provided added support.

The design described above produced a flocculator that was two thirds the size of the previous flocculator, taking up two sections of the divided flocculator. The flocculator was set-up so that the baffle structure was placed in the first two sections of the flocculator and data was only collected from these sections. The final section was left with the old set-up in it just to fill the space and help keep the dividers from bowing. This section was not tested, and was just used to fill the tank until the water reaches the exit pipe at the end of the third section. In future set-ups it is hoped that this third section can remain empty and then can be used as sort of sedimentation tank to perform further research on this project.

Summer 2008

In the Summer of 2008 the spacing of the final section of the flocculator was altered to reduce the Gaverage value in that section. The previous Gavg value was 23/s at 10.5cm spacing between baffles. The G value was adjusted to 15/s and the corresponding spacing was 15cm. This change resulted in a noticeable visual change in floc size. Previously flocs were not growing in size in the final section of the floccualtor. After the change flocs started growing in the final section. After more observation of floc size almost doubling in the turn through the final port hole, the last baffle of the final section was removed to reduce G even further to see if the floc size increased noticed though the port hole could be achieved in the flocculator sections. After changing to final baffle spacing to 30cm flocs which lowered the Gavg value for that section to 4/s.

After all of these changes were made the large floc formation seen through the port hole and in the empty third flocculator section were witnessed in the final section of the flocculator. Schematic of the proposed Suspension System to hold tube settlers under water but still allowing it to collect at an angle of 60 degrees.