The reactors on the biolectric kit are too small for what you are trying to get out of it and you are over working it which is causing the foam issue.
What retention rate are you currently working too?
It pumps fresh air into the head space in the tank so that it mixes with the gas. Bacteria in the air react with the H2S and turn it into H and S, the S then drops into the slurry and passes out at the end of the process.
Can't really say what your pumps are doing without seeing them and what they are hooked up to.. but I am sure your plant provider can confirm this. I really cannot see you being at >2000ppm if you are injecting air and adding iron