THIOPAQ® technology for the mining and metallurgical industries
THIOPAQ® technology, developed and marketed by PAQUES Bio Systems B.V. in Balk, Netherlands, was first applied commercially in 1992 for the treatment of contaminated groundwater at the Budelco zinc refinery in the Netherlands. In its most basic form, a THIOPAQ® system essentially consists of two biological process stages in series: (i) sulfate reduction to sulfide (anaerobic stage), and (ii) sulfide oxidation to elemental sulfur (aerobic stage). In practice, many process variants exist and the THIOPAQ® process can be tailored to a host of applications in the mining and metallurgical industries, ranging from the treatment of acid mine drainage to acid plant blowdown. Sulfate may be (partially) replaced by sulfite ion in scrubber solution obtained by washing SO2-containing gases of insufficient strength for processing in a sulfuric acid plant. The biogenic sulfide produced can be employed for the chemical precipitation of metals in solution either inside the anaerobic bioreactor or in a separate vessel.
Since the solubilities of most metal sulfides are much lower than of their respective hydroxides, considerably lower effluent metal concentrations can be achieved with THIOPAQ® systems than in neutralization processes which immobilize metals predominantly by hydrolytic precipitation. Moreover, the compact metal sulfide precipitate formed may be reprocessed at an appropriate stage in the flowsheet of a smelter or a refinery.
In recent years, PAQUES has made significant advances in the design, construction and operation of aerobic and anaerobic bioreactors for aqueous metal-sulfur systems. In addition, the company has diversified its technology portfolio in order to be able to treat more complex solutions and to allow the development of process oriented applications of THIOPAQ® technology. A new PAQUES designed plant at Budelco treating acidic sulfate bleed streams and process water will be commissioned this year. In the new THIOPAQ® installation at Budelco, sulfate reduction will be carried out in a 500 m3 reactor to which hydrogen will be added as the electron donor