Effects of Thermal Hydrolysis Process on Micropollutants Removal and AD Process

Balasundaram, G., Gahlot, P., Tyagi, V.T., Sahu, A.K., Kazmi, A.A.

18th IWA Conference on Sustainable Sludge Management (IWA2024)

Introduction & Significance

Thermal hydrolysis process (THP) is applied mainly to improve the methane yield in the downstream anaerobic 
digestion (AD) process. However, the potential of THP in pre-treating the high SRT sludges, mitigating the risk of emerging  organic micropollutants and effects on anaerobic microbiome in digester remains unclear. In this study, 160℃- 30 min showed the best efficiency in terms of cumulative methane yield (507 mL CH4/g VSadded) with a VS removal (54%). THP  pretreated sludges showed >80% removal of Trimethoprim, Enrofloxacin, Ciprofloxacin, and Bezafibrate and <50% removal  of Carbamazepine, 17α-ethinylestradiol, and Progesterone. Proteobacteria, Firmicutes and Bacteroidetes were the most abundant phylum in THP digester. The thermal hydrolysis proves to be an efficient pretreatment technique for enhancing  methane generation and volatile solids removal in reduced operation time of 15 days over untreated sludge. Moreover, the  effects of varying HRTs and OLR on the AD of thermally hydrolyzed sewage sludge in comparison with the control sludge  was studied. The semicontinuous studies revealed that the maximum methane yield of 408 L CH4/kgVSadded and VS 
removal 54% were observed for the THP sludge at 10 days HRT and 6 kg VS/m3.day OLR. Hence, the HRT of conventional  anaerobic digesters (25-30 days) can be reduced by almost 3 times (to 10 days) with the implementation of THP integrated 
AD.

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