Method of controlling an anaerobic treatment process

US4659471A · kind A · utility

Assignee

• Purac Aktiebolag · SE

Inventors

• Nils Molin
• Thomas Welander · Furulund, SE
• Bengt G. Hansson · Hörby, SE
• Per Andersson · Montréal, CA
• Goran E. Annergren · Sundsvall, SE

Key dates

• Filing date: Aug 6, 1984
• Grant date: Apr 21, 1987
• Expiry date: Aug 6, 2004

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S210/928
• WIPO field: Biotechnology
• WIPO sector: Chemistry

Abstract

The invention relates to a method of treating wastewater from the manufacture of peroxide bleached mechanical or chemi-mechanical pulp. The method comprises a hydrolysis step, a methane fermentation steps and an aerobic step. After the hydrolysis and methane fermentation steps, sludge is separated from the wastewater and partially recycled to the hydrolysis step. The redox potential of the outgoing water from the hydrolysis step is continuously measured and controlled to a value between -400 and -260 mV by regulating the amount of sludge recycled or by passing ingoing wastewater directly to the aerobic treating step.