The gard guide is a good start.

I can recall reading something about the "eMalahleni Water Reclamation Plant" in South Africa, but I imagine you already know it.

It’s a references on sustainability and more importantly applies concept of ZERO WASTE DISPOSAL (the gypsum produced is used in construction of houses and the RO system produces drinking water) regarding the costs...I imagine that it must be very expensive...but I don't have a clue.
Best of luck, if you find something interesting please share it with all of us.

The type of technology and the likely treatment quality relates to the acidity loading and the chemistry of the AMD. So there are a number of options but typically if you have more than 100 - 150kg/d of acidity then passive is unlikely to be viable in the long term. Happy to look at the data and let you know my thoughts.

The conventional AMD I have experience on involves the following: Softening multi step UF pressurised, RO as polisher step. The gypsum is recovered with final thickening process and filter press.

For the past few years I have been developing an alternative to lime based on hydrotalcite formation that offers many potential advantages.

Try: http://www.gardguide.com/index.php/Chapter_7

Our efforts are focused in AMD alkaline typical treatment followed by an acidification and modification with nutrients in order to produce irrigation water. All of our projects have as main goal the biomass production (energetic crops). We use knowledge and expertise in agronomic process, and in the soil-water-plants system.