Alkalization as a method of preliminary hydrolysis of waste activated sludge before the anaerobic digestion process

The aim of the research work was to determine the possibility of initial hydrolysis of the waste activated sludge with the use of the alkalization process. On the basis of the tests performed, it was found that the obtained pH value drops quite quickly after adding NaOH. In practice, after a period of 30 minutes, a further decrease in the pH value takes place, but at a lower rate. Therefore, 30 minutes was considered as a technically valid reaction time. After this reaction time, the COD (soluble COD; S-COD) values were recorded. They represented the release of organic matter into the liquid phase. In addition, a second disintegration method was carried out, on the alkalized earlier waste activated sludge, based on the phenomenon of hydrodynamic cavitation. Carrying out such a hybrid method of destroying activated sludge flocs and microorganisms contributed to the achievement of much greater hydrolysis effects. On the basis of the conducted research, it can be concluded that the use of such hydrolysis processes lead to good results in relation to further sludge processing, e.g. anaerobic digestion, which may result in a significant improvement in biogas production and an increase in biogas yield. Pol. J. Mater. Environ. Eng. June 2021, vol. 1(21), 16–25