If by waste you mean excrement then this is not a good idea in the slightest. First you have bacteria, viruses, and parasites that must be killed off. If it isn't properly treated, you end up with a situation similar to that of what we saw in the recent North Korean refugee who suffered from parasites. After that, as you mentioned, there are pharmaceuticals which are notoriously hard to filter out. Next on the list is heavy metals that can become concentrated in excrement. Even after addressing these concerns, if the process to treat the waste is too costly, then there goes the benefit.

I would compare some of the challenges this faces to those that are faced when turning salt water into fresh water through desalination (probably not a direct comparison).

I encourage you to do a little more research on this. Bad and good bacteria exists in this world regardless of how Human's try to control it. Waste processing plants use a combination of bacteria and UV to treat wastewater. That process is very similar to what nature does with animal and human waste.

However, moving human waste is a tough problem and requires substantial resources (fossil fuels, infrastructure, electricity, etc...) and the act of moving it is usually the source of contamination.

I think it's completely valid and beneficial to compost human waste, but that needs to be done on a local/individual scale.

DC's water treatment plant does this. Solid waste goes into a biodigester which produces methane which is used to create electricity to help run the plant. The other product is "biosolids" which are rated safe for use on food crops.

https://www.dcwater.com/biosolids

This wouldn't be nearly enough though. The amount of human waste is, however, dwarfed by animal waste.

Lots of sewage sludge is spread on farms in the US.

https://www.epa.gov/biosolids

There was a story about this in Motherboard just the other day. Tl,dr— Metals and drugs are a big problem *edit: spelling https://motherboard.vice.com/en_us/article/8q8xnk/turns-out-...

See also http://www.slate.com/articles/news_and_politics/roads/2016/0...

It is worth noting that not all crops absorb toxic metals in the soil, and some crops/plants sequester certain metals extremely well - (Kale/Thorium, Garlic/Selenium). Possibly we could use certain crops to ameliorate certain metal toxins.

We already do. It's called phytoremediation. Some of us even make a pretty decent living specializing in the field.

Most of the mass in plants comes from the air, and most of the mass of soil loss is from erosion and runoff, so this wouldn't avert loss, just reconnect mass flows for the process for natural soil generation, while not altering the processes that lead to the unnatural rates of loss in the first place.

Or you can just account for not collecting waste of people that take drugs from a list ... you could have people that are part of the program and get some kind of crypto token for truning in their grade-A poo.

Well call them the Elite Shitters

Well I don't think you'd collect waste at the individual level, that seems absurdly arduous. Most developed nations already have an excellent pipeline (literally) for collecting and centralizing human waste. It would probably make more sense to collect it somewhere along the line at sewage treatment facilities. There would still be many other challenges with that.