Anaerobic digestion of wastewater produced in the manufacture of cellulosic pulp from wheat straw in immobilised cell bioreactors

The kinetics of the anaerobic digestion of wastewater produced in the manufacture of cellulosic pulp from wheat straw (COD of 38.8 g/l) were studied. Laboratory experiments were carried out in 1-1 bioreactors containing supports of different chemical composition and features, namely: saponite, montmorillonite, bentogel, sepiolite (pansil) and PVC, to which the microorganisms responsible for the process adhered. The process was simultaneously performed in a control digester with suspended biomass. The bioreactors used were batch fed by incrementing the volume loads from 10 to 200 ml over a period of 5 months. Inhibition phenomena and low biodegradability of the wastewater (29–30%) were observed in the COD range studied (0.4–7.8 g/l) due to the accumulation of lignin and its derivatives. The model used showed a slight influence of the support on the kinetics of the biodegradation.