After waste goes into the holding tank, can the system be plumbed to
then treat the waste with the treatment device, and discharge the waste
when the vessel leaves the no discharge zone, or is a pump-out the only
option to empty the holding tank?

Peggie Hall wrote:
However, any boat equipped with a treatment device only needs to have a
holding tank too--and use it of course--while in "no discharge" waters.
In fact, almost all boats fitted with treatment devices also have a tank
for use if/when they visit a "no discharge" harbor or marina.
--
Peggie