METHOD AND SYSTEM FOR TREATING PLANT WASTEWATER

摘要

A method for treating a plant wastewater which contains a nitrogen component and a phosphorus component in an amount insufficient for biotreatments or does not contain the components is provided in which the wastewater is subjected to anaerobic and aerobic biotreatments at a reduced cost. The method is characterized by comprising: a pretreatment step in which a plant wastewater (11) discharged from a chemical plant, petroleum plant, or petrochemical plant and containing organic compounds is introduced into an anoxic tank (1), and compounds (12) comprising a nitrogen component and a phosphorus component are added to conduct an anaerobic biotreatment; a primary treatment step in which the treated wastewater is introduced into an anaerobic biotreatment tank (2) to conduct an anaerobic biotreatment; a secondary treatment step in which the wastewater is introduced into an aerobic biotreatment tank (3) to conduct an aerobic biotreatment, and the treated water is passed through a solid-liquid separation means and discharged as secondary treated water; and a tertiary treatment step in which the secondary treated water is introduced into a reverse osmosis membrane separator (4) and separated into RO filtrate water (16) and RO concentrate water (17), at least some of the RO concentrate water (17) being returned to the anoxic tank (1).