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.​ 5.desinfection 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