Methods for Controlling Catalase in a De-Ink Pulp Mill, 1995 Pulping Conference Proceedings

Bobby Ng

Newstech Recycling

Dan Davies

Degussa Canada Ltd.

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. Catalase is an enzyme capable of being produced by all living cells to protect themselves against naturally occurring peroxides. In a mill whitewater environment, sufficient catalase can be generated to hamper or even disable an H2 O2 treatment stage. The mill tested different options available to combat either the catalase itself or the bacteria generating the enzyme. Some of the options tried included biocide treatments, peracetic acid treatment, use of high H2 O2 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°C). The various options will be discussed, examining their effectiveness, impact on the pulp or process, and practical aspects of their implementation in the mill. The successful solution was the use of an elevated H2 O2 dosage in the pulper to both circumvent the problem and eliminate catalase.