The answers provided already ...
Published by Gary Brown, Water Practitioner at Dikubu Water
The answers provided already cover most aspects, one thing additional you may want to consider, depending on the nature of the incoming wastewater, is pre-screening as this should remove some of the suspended material, depending again on inflow characteristics and screen size, budget etc.
You should also share more on the incoming and what the target water quality requirement is? Lamella settling may not be the best option??
Regards