Method for treating acidic wastewater

A method for treating acidic wastewater is provided to effectively treat metal included in wastewater and minimize an amount of sludge causing secondary environmental pollution. An acidic wastewater containing plenty of heavy metals is put into neutralizing tanks(10,20). The acidic wastewater is neutralized into pH 6-8.5 by adding magnesium hydroxide and air oxidation. The neutralized acidic wastewater is transferred to a reactor(40) to treat the acidic wastewater with alkaline lime and air oxidation so that pH of the wastewater becomes higher than 9.5. The wastewater is transferred to a sediment and final discharge tank(50) to be reversely neutralized.