You should really consider ...
Published by Farid Turan
You should really consider the 'hybrid' treatment processes of combining adsorption with AOP processes along with enhanced biological treatment, once the recalcitrant COD is made more biodegradable. Since they already have MBR it may be that this can be done as a "side-stream"?
Once approach that I see great future opportunities is nano-bubbles to provide very efficient AOP with O2 and/or ozone (see NABAS technolgy). They provide lots of OH- free-radicals very efficiently. feel free to contact me for further support (Farid Turan at MBR Solutions Ltd. UK).