Experimental Methods
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Two ACD experimental set ups ([the lab prototype] and [the robust ACD]) were used in identical experiments to collect data sets relating change in float height to dosing in Fall 2008. First the chemical doser was positioned at 5 cm intervals along the lever arm. The water level in the grit chamber bucket was varied while readings were taken of the changing water height in the collection column (explained below).
The 7 kPa pressure sensor at the base of the bucket was calibrated to read in centimeters of water and it was zeroed for the condition when the float just became buoyant and was no longer resting on the bottom of the bucket. The lever arm was made horizontal at the point by adjusting the length of fishing line tied to its end. This was checked with a level. By zeroing the pressure sensor at a lever arm height of zero all readings from the bucket pressure sensor were then equivalent to change in float height, which was also equal to negative change in the height of the end of the lever arm because of the fishing line connecting the float to the end of the lever arm.
A flow controller (flow control module-FCM) was connected to the chemical dosing tube at the T as is described in the [ACD experimental set up]. The FCM was fed from a bucket of water less than 1 m above it at all times, ensuring that there were not significant changes in water level within the FCM. The FCM was positioned at a level even with the lever arm such that it dosed no water when the lever arm was zeroed. The FCM began to dose with a change in driving head of 1mm from that zero.
To measure flowrate from the FCM through the ACD a 7kPa pressure sensor was used at the bottom of the collection column. Water flowed from the FCM through the T into the chemical dosing tube and then into the column. The pressure sensor at the base of the collection column was calibrated to read in centimeters of water, and it was zeroed after the valve at the base of the column had been opened and the water completely drained out. As water was dosed from the FCM into the column, the pressure sensor transmitted data to a computer running the program Easy Data, which recorded both water level and time lapse in 1 second steps. Since the column dimensions are known, these variables can then be used to solve for a flowrate.
Concurrent data from the pressure sensor at the base of the bucket can be used to show the exact height of the float relative to the apparatus for each flowrate. Data was collected at several float heights for each distance the chemical dosing tube was attached along the lever arm or 10 cm, 15 cm, 20 cm, and 25 cm.
Experimental Results
This data has not been fully analyzed as of 10/20/08