A process for treating sulphate containing effluent, which includes reducing sulphate contained in said sulphate containing effluent to sulphide in a biological sulphate reducing reactor, wherein sulphate is reduced to sulphide through sulphate reducing bacteria; (ii) receiving the effluent from the biological sulphate reducing reactor into a two-phase fluidised bed reactor containing limestone particles and low density plastic floating media; precipitating calcium carbonate from the received effluent on the limestone particles in the two-phase fluidised bed reactor; aerating the received effluent in the two-phase fluidised bed reactor to remove CO 2 produced in the biological sulphate reducing process, thereby to increase the pH of the received effluent in the two-phase fluidised bed reactor; producing elemental sulphur on the plastic floating media through biological sulphide oxidation of the received effluent by sulphide oxidizing bacteria on the low density plastic floating media; recycling, within the fluidised bed reactor, the contents of the fluidised bed reactor at a sufficient rate to effect abrasion, wherein recycling removes elemental sulphur from the plastic floating media; recycling, within the two-phase fluidised bed reactor, hydroxyl ions produced by the sulphide oxidation process, wherein recycling hydroxyl ions produced by the sulphide oxidation process comprises further increasing the pH of the solution and increasing the pH of the solution comprises enhancing calcium carbonate precipitation, and (iii) harvesting the elemental sulphur from below the low density plastic floating media in a top portion of the two-phase fluidised bed reactor. reducing sulphate contained in said sulphate containing effluent to sulphide in a biological sulphate reducing reactor, wherein sulphate is reduced to sulphide through sulphate reducing bacteria; (ii) receiving the effluent from the biological sulphate reducing reactor into a two-phase fluidised bed reactor containing limestone particles and low density plastic floating media; precipitating calcium carbonate from the received effluent on the limestone particles in the two-phase fluidised bed reactor; aerating the received effluent in the two-phase fluidised bed reactor to remove CO 2 produced in the biological sulphate reducing process, thereby to increase the pH of the received effluent in the two-phase fluidised bed reactor; producing elemental sulphur on the plastic floating media through biological sulphide oxidation of the received effluent by sulphide oxidizing bacteria on the low density plastic floating media; recycling, within the fluidised bed reactor, the contents of the fluidised bed reactor at a sufficient rate to effect abrasion, wherein recycling removes elemental sulphur from the plastic floating media; recycling, within the two-phase fluidised bed reactor, hydroxyl ions produced by the sulphide oxidation process, wherein recycling hydroxyl ions produced by the sulphide oxidation process comprises further increasing the pH of the solution and increasing the pH of the solution comprises enhancing calcium carbonate precipitation, and precipitating calcium carbonate from the received effluent on the limestone particles in the two-phase fluidised bed reactor; aerating the received effluent in the two-phase fluidised bed reactor to remove CO 2 produced in the biological sulphate reducing process, thereby to increase the pH of the received effluent in the two-phase fluidised bed reactor; producing elemental sulphur on the plastic floating media through biological sulphide oxidation of the received effluent by sulphide oxidizing bacteria on the low density plastic floating media; recycling, within the fluidised bed reactor, the contents of the fluidised bed reactor at a sufficient rate to effect abrasion, wherein recycling removes elemental sulphur from the plastic floating media; recycling, within the two-phase fluidised bed reactor, hydroxyl ions produced by the sulphide oxidation process, wherein recycling hydroxyl ions produced by the sulphide oxidation process comprises further increasing the pH of the solution and increasing the pH of the solution comprises enhancing calcium carbonate precipitation, and (iii) harvesting the elemental sulphur from below the low density plastic floating media in a top portion of the two-phase fluidised bed reactor.