If you simply used the default values, your solution set should look something like this:
By now you should have a pretty good idea of how this program works and what exactly it does. Notice how we can monitor the growth of microorganisms and determine the substrates being used. You can now go back and change the substrate concentrations in the feed stream, or the SRT, maybe even the recycle rates. If you're wondering what are some interesting things to try, check out this help file created by Suzanne Link. Regardless, you should see that this program is capable of modeling some fairly complex biological transformations occuring in an activated sludge.