If SAUR/SPANC are signing it off… then all will be well.
As I say, they’ve knocked it on the head around here due to pollution of the ground water … they’re gradually bringing us kicking and screaming into the modern world… 
IIRC the outflow from a correctly installed and working filter bed is non toxic and will not pollute the ground water table - so why not discharge into a ditch? Discharging a fosse directly to a ditch on the other hand… 
Yes, it’s treated water that will go into the ditch.