An Mpumalanga coal mine is on the point of entering into an agreement before year-end to have its acid mine drainage water curse turned into potable water at no cost, Mining Weekly can today report. Recovered potassium nitrate, which retails at about R15 000/t and which is marketed at about R11 000/t to R11 500/t, pays for everything – and a return on investment of about 30% is achieved.