Data Fluctuation Experiment
Objectives
Last semester, our team recorded a lot of data, not knowing how the effluent turbidity data might vary greatly even if the same experiment were to be run twice. This is due to the fact that flocs and floc formation is not an exact science, and that flocs that form during one time in one experiment will not be exactly the same as flocs formed at another time using the same experiment setup with all the same variable values. In order to get a better picture of the noise or random data fluctuations in our past data, we wanted to design a simple experiment to quantify how much of this fluctuation we are seeing and if it is affected by the time, turbidimeter position, and the experiment location within a large number of experiment runs.
Experiment Procedurs
Our team ran a typical experiment multiple times repeatedly to see how the effluent turbidity data fluctuated during the settling state in each experiments and to compare the data fluctuation between experiments. The experiment set up was an influent turbidity of 50 NTU, a flocculator length of 25 feet, and a G of 3.1 1/s. We repeated this experiment at least ten times in a row. We extrapolated the data from just the settling state (600 seconds), we found the average and standard deviation of the influent turbidity and the effluent turbidity separately at each second interval. We conducted this experiment for the typical position of the turbidimeter at the top of the settling column and at a new position of the turbidimeter at the bottom of the settling column.
Results
Figure 1: Standard Deviations of the Influent and Effluent Settling Turbidities from 10 consecutive experiments using the same position of the settling column (top).
Figure 2: Standard Deviations of the Influent and Effluent Settling Turbidities from 10 consecutive experiments using a new position of the settling column (bottom).
Figure 3: Time Averaged data over 60s of the Effluent Settling Turbidities from 10 consecutive experiments using a 25ft Flocculator and turbidimeter position at the top.
Figure 4:Time Averaged data over 60s of the Effluent Settling Turbidities from 10 consecutive experiments using a 25ft Flocculator and turbidimeter position at the bottom.
Figure 5: Time Averaged data over 60s of the Effluent Settling Turbidities from 10 consecutive experiments using a 50ft Flocculator and turbidimeter position at the top.
Discussion
The effluent turbidity standard deviations in both positions have a large range(Figure 1 and 2), and there is a trend of increasing standard deviations as the settling state time increases. The max standard deviation for the effluent turbidity when the turbidimeter was in its standard position (top) is 12.4. The max standard deviation for the effluent turbidity when the turbidimeter was in its new position (bottom) is 14.2. The influent turbidity standard deviations in both positions are generally lower than the effluent turbidity standard deviations, and maintain at low values.
These results definately show us some insights into our data. We see that the settling data in one experiment will not be the same as in the next experiment (when all variables of the experiment remain the same). From the data, it appears that there is no significant difference from having the turbidimeter position at the top or at the bottom of the column, except for the slight increase in the max standard deviation of the effluent settling turbidity, and the increase in range of effluent turbidity standard deviation values. For example, the standard deviation values at the end of the settling time in the top position experiment ranges from 2 to 12, whereas the range of the standard deviation values at the end of the settling time in the bottom position experiment ranges from 5 to 15. This difference in standard deviation is