You can plug the ‘waste water outlet’ where you see fit. We use our washer’s, which in our city, is the waste water system, thats goes into the waste water recycling plant which doesnt mix with the ‘clean water’ cycle. In any case, it is WAY more filtering that if we were using classical litter granule that would be then send to a landfill where those same bacterias and viruses would fest and infiltrate the soil.

It is an interesting debate to have though. It probably depends how your waste water is processed.