An organic wastewater treatment apparatus includes: a first treatment device configured to perform methane fermentation on organic wastewater containing a floating substance, an organic substance, and a nitrogen component under an anaerobic condition and perform membrane filtration to obtain membrane-filtered water; a second treatment device provided downstream of the first treatment device and including a vacuum degassing device that removes and recovers a part of dissolved methane in the membrane-filtered water; and a third treatment device provided downstream of the second treatment device and configured to perform post-treatment.

A semiconductor process wastewater treatment system and a method for treating semiconductor process wastewater using the system are disclosed. The disclosed semiconductor process wastewater treatment system comprises: an advanced oxidation reaction tank for advanced oxidation of a semiconductor process wastewater comprising tetramethyl ammonium hydroxide (TMAH) using a UV/PDS process that activates peroxydisulfate (PDS) with ultraviolet light (UV ray); an anaerobic biological reaction tank for biologically treating the semiconductor process wastewater that has passed through the advanced oxidation reactor, the anaerobic biological reaction tank configured to treat the semiconductor process wastewater with microorganisms comprising sulfate reducing bacteria (SRB) under anaerobic conditions, and configured to react sulfate generated in the advanced oxidation reactor with the sulfate reducing bacteria to generate H.sub.2S; and a gas separator for separating the H.sub.2S from gas generated in the anaerobic biological reactor.