METHODS FOR CONTROLLING CATALASE IN A DEINK PULP-MILL

From June 1993 to August 1994, Newstech Recycling Limited Partnership, with assistance from several vendors, used various measures to combat or circumvent a problem of catalase contamination. In a mill whitewat er environment, sufficient catalase can be generated to hamper or even disable an H2O2 treatment stage. The mill tested different options av ailable to combat either the catalase itself or the bacteria generatin g the enzyme. Some of the options tried included biocide treatments, p eracetic acid treatment, use of high H2O2 dosages, and steep bleaching . Others considered and tried on the laboratory scale without reaching mill-scale trial were very high doses of peracetic acid, alternative biocides, boilouts, and high operating temperatures (70-90 degrees C). The successful solution was the use of an elevated H2O2 dosage in the pulper to both circumvent the problem and eliminate catalase.