| 摘要 |
PROBLEM TO BE SOLVED: To efficiently reduce a nitrate group concentration by neutralizing acid waste nitrogen compound and waste alkaline substance discharged at a manufacturing stage, and then adding the nitrogen compound to a step of biologically denitrogenating by using denitrifying bacteria, thereby recycling waste solvent. SOLUTION: In the step of surface treating a printing plate, a washing step is executed in each of an alkali etching step, a desmutting step, a nitrate electrolyzing step, a nitrifying step and the like, and large quantities of acid waste and alkaline waste are discharged. The waste liquid is divided into aluminum hydroxide sludge and neutral drain in a neutralizing step and an aggregating step. A supernatant in the aggregating step is sent to a denitrifying tank as waste liquid. As a denitrogenating step, a biologically denitrifying method is adopted to treat the waste nitrogen compound. Thus, a concentration of the nitrogen oxide is remarkably reduced, and the waste acid and the waste alkaline substances can be efficiently industrially treated.
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