Enhanced efficiency of industrial-scale anaerobic digestion by the addition of glycosidic enzymes

Abstract

The results of the action of two glycosidic enzymes added to an anaerobic digester processing mixed wastewater sludge are reported in this paper. The experiment was performed at a continuously operating full-scale wastewater treatment plant during a 6-month period. The addition of the enzyme mixture resulted in improved gas production and dewatering properties. Dewatering experiments, both on enzyme-treated and reference sludge on the local centrifuges, indicated that the carbonaceous matter was decreased by 7% in enzyme-treated sludge, and the average dry solids increased from 27% (reference) to 31% in enzyme-treated sludge. The polymer dosage was decreased from 8 to 5 kg/t dry solids. Additionally, practical experiences were gathered concerning the transformation from static laboratory-scale batch experiments to a dynamic continuous industrial scale setup. Preliminary cost calculations showed beneficial aspects and economical feasibility of enzyme addition to an anaerobic sludge digestion process.

Keywords:

• Anaerobic digestion
• biosolids
• enzyme addition
• sludge
• full-scale

Acknowledgments

The authors wish to thank the wastewater treatment plant M⊘lleåværket in Lundtofte (Denmark) and Novozymes for their support.

Notes

∗ Depending on the treatment process.

∗∗ Tax by the Danish State on dry solids to incineration of 330 DKK (approx. 45 EUR).