Characterization and anaerobic treatability study of pre-hydrolysis liquor (PHL) from dissolving pulp mill

Abstract

Anaerobic degradation showed potential as the disposal solution for pre-hydrolysis liquor (PHL) from the dissolving pulp industries. This PHL contained pentose and hexose carbohydrates as monomeric (14.5 g/L) and oligomeric (39.7 g/L) forms along with acetic acid (10.38 g/L), furfural (1.14 g/L) and lignin (11.08 g/L). The average chemical oxygen demand (COD) value of the PHL was around 100 g/L with a biochemical oxygen demand (BOD5) value of 55 g/L. Respirometric studies at 35 °C showed a decrease in methane production with increasing concentration of PHL in the feed. Presence of slowly biodegradable substrates (furfural and lignin) in the feed was suspected to cause such behavior. Therefore, PHL was introduced to a master culture reactor to acclimatize the seed sludge to PHL as substrate. The seed microbes were able to adapt to furfural, but not to the entire lignin present in PHL feed. Lignin concentration going over a threshold value (approximately 7 g/L) was suspected to cause reactor failure. This anaerobic treatability study reflects on the potential of applying anaerobic digestion for PHL waste stream disposal and biogas production.