Apparatus and method for treating wastewater

A method for treating wastewater comprising:

• a pre-treatment step of removing impurities contained in high concentration wastewater and crushing the impurities using a crusher;
• a first aerobic treatment step of supplying wastewater containing organic acids to a first aerobic tank and injecting air to the first aerobic tank to be aerobically treated;
• an anaerobic treatment step of supplying the wastewater, from which excess organic acids are removed by the aerobic treatment, to an anaerobic tank to be anaerobically treated;
• a degassing step of supplying the wastewater treated in the aerobic and anaerobic treatment steps to a degassing tank to remove air and gas;
• and
• a post-treatment step of precipitating the wastewater aerobically treated using a solid-liquid separation tank, a pressure floatation tank or a precipitation tank;
• and
• a second aerobic treatment step of repeatedly treating the degassed wastewater in a second aerobic tank after the degassing step.