MLSS Performance Problem

Hello team,

I am running MBR system constituting Mbr module, Aeartion module and Aanoxic module. This is an 8 train system.

The challenge is that one of the trains has literally got no MLSS, reads about 100-500 mg/l against a target of 7000 mg/l.

What could be the problem? What established way exists for improving MLSS in activated sludge systems?