I suspect that the BOD is ...

Published April 24, 2017 00:50 by Kumar Packiakumar, Senior Design Engineer at Tweed Shire Council NSW Australia

I suspect that the BOD is very high. The effluent has to undergo anaerobic treatment before subjecting it to aeration. The anaerobic treatment can be accomplished in deep pits. Alternatively subject the effluent to advanced oxidation process to reduce the BOD.