Johannesburg — JOHANNESBURG Water was concerned about the possibility of acid mine drainage flooding the city's central business district, but there were potential solutions, the utility's chairman said yesterday.

Last week the parliamentary portfolio committee on water and environmental affairs was warned that the central basin of the Witwatersrand - a geological area situated below Johannesburg - could flood within 18 months, raising the possibility of polluted mine water flooding the city.

Water from mining activities, known as acid mine drainage, contains high levels of heavy metals and sulphates and is also highly acidic.

Government departments and mining companies have been locked in negotiations for the past few months on how best to tackle acid mine drainage and who should pay.

Speaking at a conference on sustainable water use, Johannesburg Water chairman Martie Janse van Rensburg said: "We have been approached and asked if we would buy acid mine drainage treated to raw water levels. The answer is yes, we would, but only if it meets all quality standards and if that price is not more expensive than the water we already buy."

Ms Janse van Rensburg said 20% of Johannesburg's population was "extremely poor". Higher prices for raw water had a knock-on effect throughout the system, and the city's poverty levels meant that affordability was a concern.

Environmental activist Mariette Liefferink, CEO for the Federation for a Sustainable Environment, which campaigns for the treatment of acid mine drainage, said that without urgent intervention, the central basin was likely to flood within 18 months.

Should this occur, buildings would be put at risk, as acid mine drainage corrodes steel and depletes concrete.

She said the US's Environmental Protection Agency had described mining waste, including acid mine drainage, as the second greatest environmental risk, after climate change. Much of this water was also polluted with radioactive uranium, she said.