MBR Plant, Performance of Sludge

I plan to add a bit of flocculant to improve the filterability of the sludge in our MBR sewage treatment plant.

What is the best unit to dose flocculants into? The Aeration tank or the MBR tank?

Are there any impacts of flocculant on the Membranes or on the process? In this case, am planning to use aluminium chlorohydrate.