Basic ​​calculations ​​for MBBR ​​technology for ​​domestic water

Dear Colleagues.
I am currently ​trying to ​create basic ​calculations ​for MBBR ​technology for ​domestic water. ​The technological ​scheme I have ​chosen is:​
1. mechanical treatment
2.Anoxic tank
3.Aeration tank (MBBR)
4.Secondary ​settlement tank ​with lamellas.​
SALR - 95%
I think to use ​recirculating ​nitrate flow ​from aeration ​tank and ​recirculation ​of activated ​sludge from ​secondary ​settlement. ​
In these ​technological ​scheme will ​there be a ​change in the ​size of bio ​media ? what ​media surface ​area (m2 / m2) ​to use ? ​
Thank you in advance
Best regards