In a method for removing sulphate and heavy metals from waste water: a) in a first treatment step (I) hydrogen sulphide is guided through the waste water, heavy metals that are present in the waste water are precipitated as sulphide, and are removed from the waste water, b) in a second treatment step (II), calcium sulphate is precipitated from the waste water by adding a precipitation auxiliary agent, c) the calcium sulphate is removed in the second treatment step (II) and one part thereof is guided to a third treatment step (III) in which sulphate is converted into hydrogen sulphide with the aid of sulphate-reducing bacteria, d) hydrogen sulphide formed in the third treatment step (III) is guided back to the first treatment step (I).