Creating and Saving Data Sets

Now that you have a good idea of how to change the parameters of the program, you can use this model to study some different situations you might encounter. For example, you might want to see how different concentrations of a certain substrate in the feed stream affects the heterotrophic biomass. The program allows you to store your data in a file and then plot your results. Unfortunately the procedure can lead to a little confusion at first. This might be where this guide can be the most helpful.

The first thing to do is set up a new directory to store your data. This is done by selecting option 9 from the main menu. This will give you a screen like this:

To create a new directory, type in the new name at the first prompt. Then move the cursor to File Options: and type 6. If you want to set up a new directory on your disk, just type:

(1) Enter filename/directory: A:\[Directory]
(2) File Options: 6

The main purpose of setting up data sets is to help you visualize different situations. We'll try a simple example:

Let's say you want to observe how the growth of the heterotrophic organisms vary for different solids retention time. The best way to do this is create a data set and then make a plot. This is the tricky part of this program so let's see how it's done.

Create a Data File

From the main menu, go to option 10 STORE Process Variables. Enter your new filename. Then you have to select which tank you will be monitoring. For this problem we'll select the last tank #3. Options 3 & 4 ask for X and Y coordinates. For this problem we are going to examine the effect of different SRTs on Heterotrophs. If you hit the F1 key, you will receive a listing of the variables you can use for X and Y coordinates on a graph. In this problem we will manually change SRT and watch the effect on heterotrophs. So I select (6) SRT for the X coordinate and (14) Heterotrophs for the Y. Finally, enter y (yes) for save automatically. This means every time the program computes a solution, it will automatically save the SRT and heterotroph biomass to this file.

Generating the Data Set

Now we can generate a data set that records heterotrophic biomass for different SRTs. Here I'll use SRTs of 5, 10, 15, and 20 days. Option 4 from the main menu allows me to change the SRT. I change SRT to 5, go back to the main menu, and solve the steady-state equation (option 5). This generates the first point in my data set. For a good plot, however, we need more sets. So I go back and change the SRT to 10, 15 and 20. Make sure that you select option 5 each time to generate a data point.

We now have a new data set, so let's make a graph.