A blower tripped on a Friday and nobody was on site until Monday. What we found in the tank, why BOD recovers in days and ammonia in weeks, what we did in order, and the design question underneath it.
Your STP can pass BOD and TSS and still fail ammonia, because the bacteria that remove ammonia are slow, alkalinity-hungry, oxygen-hungry and easy to kill. Field notes on the four things that quietly wipe them out, the food processing plant where I created my own nitrification problem with one piping decision, and what I check before anyone orders more bacteria.
