I would assume that acid disposal is the least of the concerns (since acids are neutralised in A/B and not used in STBs) plus the majority of acids used are pretty much compatible with life. Citric acid, phosphoric acid, hydrochloric acid acetic acid etc are totally fine.
Bases on the other hand are also pretty safe. Ammonia is volatile and a very minor component of earth's atmosphere. Most importantly, it is a by-product of many biological processes, so it is abundant in the ecosystem. It is toxic to organisms however but on the other hand organisms know how to deal with it pretty well.
Other weak bases like sodium carbonate are easily buffered and neutralised in natural ecosystems and I do not feel there is an environmental thread from their use. (at least in those small scale projects some people may partake)
NaOH and KOH might be slightly more harmful, but there are no strong evidence for that. NaOH is used as a drain cleaner as burnt wrote.
Solvents is my biggest concern. Some of them can be pretty nasty. I am not aware how they can be metabolised or cleared by the ecosystems or how they affect them. I feel that people should try and use them as little as possible or reuse them. I really freak out when I see people writing about doing 4x 500ml naphtha pulls, then evaporating the whole thing or even half of it!
I like the FASA not only because xylene can be reused many times, but because minimal amounts of it are necessary since it is such an excellent solvent. And acetone is practically safe for the environment. Its volatility means that it does not accumulate on earth for too long. It evaporates very fast in the atmosphere where it is degraded by the sun's UV.
