Nitrogen ratios

The target nitrogen level at the outfall of the water treatment plant should be 1 ppm N. This varies with environmental regulations, because some places in this country have a Nitrogen limit placed by EPA of 1 ppm (i.e. cannot be any higher than 1 ppm) in which case they will target 0.5 ppm. However, the optimum for waste plant performance is 1 ppm at the furthest end of the facility, or at outfall (where it enters natural ground waters).
As for addition of nitrogen to the aeration basin the ratio to target is 100/5/1 (BOD/N/P). So for every 100 ppm of BOD in the waste stream, you should add 5 ppm of nitrogen and 1 ppm of phosphorus. Of course you get N from the ultra biocid addition so it becomes harder to figure how much additional N (if any) will be needed. That is why I say it is best to target 1 ppm residual at the outfall. Have them check the outfall for N level. If it is 1 ppm or more they are golden. If it is less than 1 ppm then they need to add a little nitrogen until they get 1 ppm at the outfall.