Biomethane production improvement by hydrothermal pretreatment of thickened waste activated sludge

This study evaluated the impact of hydrothermal pretreatment on thickened waste activated sludge (TWAS) for solubilization enhancement and biomethane production improvement through the mesophilic anaerobic digestion process. In order to assess the effect of temperature, retention time and severity index (SI) of the hydrothermal pretreatment, TWAS was exposed to fifteen different pretreatment conditions within a combination of 10 different pretreatment temperature range (150-240 degrees C), five different retention times (5-30 min) and five different severity indexes (SI = 3, 3.5, 4, 4.5 and 5). The solubilization enhancement was observed in all hydrothermally pretreated samples with the highest solubilization efficiency of 49% in pretreatment conditions of 200 degrees C and 10 min retention time within the corresponding SI = 4. Biomethane production was not improved in all fifteen pretreatment conditions, pretreatment with SI beyond 4 decreased the biodegradability of TWAS. The highest biomethane production was observed in the pretreatment condition of 170 degrees C and 10 min with a 40% increase compared to non-pretreated TWAS.

Automated summary

The study found that hydrothermal pretreatment can enhance solubilization of thickened waste activated sludge but did not improve biomethane production. The optimal selection of temperature and retention time for hydrothermal pretreatment significantly impacts the outcomes.