A novel treatment technique for DMSO wastewater

We have developed an efficient treatment technique for wastewater containing dimethyl sulfoxide [DMSO, (CH₃)₂SO], a compound used as a photoresist stripping solvent in semiconductor manufacturing processes. Generally, wastewater containing organic compounds can be treated biologically, but with DMSO wastewater, biological treatment is not available because noxious compounds are produced that harm the environment. Here, we present an effective DMSO wastewater treatment technique in which we add an oxidizing agent and irradiate the wastewater with ultraviolet light to prevent damage to the environment. The use of hydrogen peroxide (H₂O₂) as an oxidizing agent in combination with ultraviolet irradiation causes DMSO to decompose promptly into methanesulfonic acid (MSA, CH₃SO₂OH). With continued treatment, the resultant MSA decomposes gradually into the inorganic compound sulfuric acid (H ₂SO₄). In this reactive route, no noxious compounds are generated. We confirmed that MSA can be biologically treated comparatively easily, and that by combining the initial ultraviolet irradiation/H₂O₂ addition treatment to rapidly produce MSA with a biological treatment to convert the MSA to H ₂SO₄, the total processing can be treated at very low cost. These treatment techniques make use of the characteristically high reactivity of DMSO and are very effective as a means of treating DMSO wastewater