I might add that grey water ...

I might add that grey water reuse is generally driven by water scarcity and, as you have mentioned, this is becoming a serious issue in South Africa. Prof. Anthony Turton has written extensively on the subject and speaks his (expert) mind rather than adhering to political agendas. I recommend reading some of his papers.

Grey water is already a necessity in parts of SA, and black water recycling for direct potable water use is likely to be implemented soon as has been done in Windhoek and in Singapore for several years. This does, of course, require substantial (and expensive) treatment, but when scarcity becomes critical then economics don't matter.