For our toilets on the farm we use a bucket system with sawdust as a biological blanket. The entire contents are composted in a separate heap, the pathogens are killed in the thermophilic phase and the minerals returned to the soil. We use this finished compost as food for our poorest sand soils where we grow our wood lot.
Human feaces can also contain large amounts of oestrogen, steroids, anti-biotics, other drugs and a myriad of things people consume in their diet. The composting process breaks all this down into the original components. We ensure that the portion of bad stuff will never be more than what the micro-organisms can manage.
All toilet systems contaminate the ground and the groundwater at some stage of the process. We have chosen composting toilets as our way of keeping the groundwater uncontaminated, save water and enrich our soils. Further reading: The Humanure Handbook