Septage - or the liquid from septic tanks - is untreated. That is not the same thing. Biosolids have been through a wastewater treatment facility suitable for land application - not food crops, though. It doesn’t smell great, but in theory, shouldn’t be harmful. Lots of folks question whether the pathogens can survive the process and would be harmful to animals and humans. Other folks question whether the regulation process is sound - in other words, are there more heavy metals - like molybdenum for one - that kinda stuff being put back in too high a concentration.
google up “The Case for Caution” and Cornell and you’ll see a whole list of issues of concern. Yes, it’s good that the bad stuff is out of the water and put in the sludge, but putting it on cropland can be problematic. EPA bureaucrats (under both D and R administrations) tried to push one-size- fits-all regulations for the whole country, and laid into anyone (inside or outside EPA) who differed with them.