Abstract: A process (10) for treating sulphate-containing water (28) includes feeding the water into a biological sulphate reduction stage (12) containing a complex carbon source (18). The water is subjected to biological sulphate reduction in the presence of an electron donor source, thereby to reduce sulphates in the water to sulphides and to produce alkalinity. The complex carbon source is contacted with water containing higher sulphide and alkalinity concentrations or levels than the sulphate-containing feed water, thereby converting complex carbon molecules to electron donors. The, or another, electron donor source is regularly added to the biological sulphate reduction stage (12).

Abstract: A process for treating sulphide-containing water includes maintaining a steep redox potential gradient in an interface zone of the sulphide-containing water. The water is exposed to an oxygen-containing environment, and the interface zone is located immediately below the surface of the water. Sulphide in the water is biologically oxidized, in the interface zone, to sulphur. The sulphur may be removed by settling, thereby achieving a final removal of sulphur compounds.

Abstract: A process (10) for treating sulphate-containing water (28) includes feeding the water into a biological sulphate reduction stage (12) containing a complex carbon source (18). The water is subjected to biological sulphate reduction in the presence of an electron donor source, thereby to reduce sulphates in the water to sulphides and to produce alkalinity. The complex carbon source is contacted with water containing higher sulphide and alkalinity concentrations or levels than the sulphate-containing feed water, thereby converting complex carbon molecules to electron donors. The, or another, electron donor source is regularly added to the biological sulphate reduction stage (12).

Abstract: A process for treating which contains carbonaceous solids, includes subjecting the water to hydrolysis in a biological hydrolysis reaction stage, in the presence of sulfate ions, thereby to produce treated water, a slurry component, and a sulfur-containing component. Treated water, the slurry component, and the sulfur-containing component are withdrawn from the reaction stage.

Abstract: A process for treating sulphate-containing waste water comprises introducing a feedstock comprising sulphate-containing waste water, into a pond. The sulphate-containing waste water is subjected to biological sulphate reduction in the pond, thereby to convert dissolved sulphate anions to dissolved sulphide anions. Treated waste water, containing the dissolved sulphide anions, is withdrawn from the pond.

Abstract: A process for treating sulphate- and metal-containing waste water, includes subjecting, in a reaction stage, the sulphate- and metal-containing waste water to biological sulphate reduction in which sulphates in the waste water are converted to sulphides, with metals present in the waste water precipitating out and treated waste water being obtained. The precipitated metals are withdrawn from the reaction stage, while treated waste water is withdrawn from the reaction stage. The treated waste water is subjected to polishing and/or to nutrient removal.

Abstract: A process for treating metal-containing acid water comprises adding an alkaline aqueous component to metal-containing acid water, thereby to raise the pH of the acid water and to cause metals therein to precipitate. The precipitated metals are separated from the water in a separation stage. The water is then passed to a biological alkalinity generating stage wherein the alkalinity of the water is increased biologically. The alkaline aqueous component, which is added to the metal-containing acid water, is withdrawn from the alkalinity generating stage. Treated water is also withdrawn from the alkalinity generating stage.

Abstract: A process for treating sulphate- and metal-containing waste water comprises adding a sulphide compound to the waste water. The sulphide compound reacts with a metal in the waste water to form a corresponding metal sulphide, which precipitates from the waste water. The precipitated metal sulphide is separated from the waste water, to obtain sulphate-containing waste water, which is subjected to biological sulphate reduction in which sulphates in the waste water are converted to sulphides.

Abstract: A process for treating acid water process comprises raising the alkalinity of an aqueous component by means of algae, and separating algae from the aqueous component, thereby to obtain a purified alkaline aqueous component. The purified alkaline aqueous component is added to acid water, thereby raising the pH of the acid water.

Abstract: A method of producing a secondary metabolites comprises providing a porous substratum which has a biofilm of micro-organism attached thereto, and causing a nutrient solution to flow through the substratum, at a rate which is sufficiently low for a nutrient gradient to be established across the biofilm, such that the nutrient concentration at a high level along the gradient is sufficiently high to support primary growth of the micro-organism, and the nutrient concentration at low level along the gradient being sufficiently low to induce secondary growth of the micro-organism, thereby to produce secondary metabolite. The substrate is in the form of a hollow fibre membrane having a relatively thin, porous skin on the inside, and a relatively thick, finger-like, externally unskinned void structure radiating outwardly from the skin.