Moving Bed Biofilm Reactor Medium Calculation

How can I ​calculate ​the ​quantity of ​Moving bed ​biofilm reactor ​(MBBR) ​medium to ​be used in MBBR ​#Technology ?​  ​

How do I ​calculate the ​amount of ​polyethylene ​biofilm ​carriers for ​best performance ​while ​maintaining the ​most economic ​costs? ​

Which ​parameters do I ​need to ​consider for ​the evaluation?​  ​