SuPaP: Enables resource recycling and sustainable wastewater treatment

This study investigated how wastewater from a Swedish pulp mill can be treated using a technology that not only improves water quality but also generates renewable energy. The mill uses two processes – CTMP and SGW – which produce wastewater rich in organic material and sulphate, which is difficult to treat.

Researchers tested an anaerobic biofilm reactor with mobile bed material (AnMBBR), in which microorganisms grow on small carriers and break down pollutants without oxygen. It was compared with an established technology, the EGSB (expanded granular sludge bed) reactor.

Results from AnMBBR:

• Eliminated 31–36% of organic pollutants (measured as dissolved COD).
• Reduced 65–71% of sulphate, which otherwise inhibits methane-producing microorganisms.
• Produced biogas with up to 81% methane content.

Despite overload and pH drops that temporarily impaired performance, the system recovered without needing to be re-inoculated, only by pH adjustment and reduced flow rate. This resilience is important for industrial use.

EGSB showed better results for organic removal (up to 52%) and slightly higher methane production, but the microgranules deteriorated over time.

An important conclusion was that the balance between organic content and sulphate affects the efficiency of microorganisms. Lower ratios favoured sulphate reduction while maintaining methane production.

Summary:
AnMBBR is a robust and energy-efficient method for treating wastewater from pulp production, with the potential to contribute to a more sustainable pulp and paper industry. With further optimisation, such as increased surface area for microbes and improved pH control, the technology could become a valuable tool for the future.