Bilge

[Bellman]

OKO:-

I know waste ejection is a complex process on our subs, to avoid any sign of the sub presence

Bill:-

The sanitary tanks are periodically emptied by pumping the waste to sea

Seriously this is a real issue. It seems that the French have the answer by clearing it from the sub possibly in
bio-degradable containers. But this entails the risk in surfacing (?) so may not be as secure as other possible solutions.
The weight reduction must impinge on 'future' performance as whilst equilibrium is maintained by its replacement
with water, this can be discharged for greater bouyancy. So your performance potential has improved.

On a long patrol in Cold War like conditions its an issue which will require carefull route planning.