You can design the process ...

You can design the process with or without, usually the inflow characteristics will influence the decision as you may want to reduce organic load going to aeration to reduce oxygen demand and subsequent energy demand

also can use primary settling to increase volatiles that can be concentrated up as a fermented feed to help with process requirements

and of course primary settlers present an opportunity to digest sludge that can produce biogas for beneficiation

but commitment should be made at design stage as process needs to be operated accordingly

hope this helps