Advanced steam-explosion pretreatment mediated anaerobic digestion of municipal sludge: Effects on methane yield, emerging contaminants removal, and microbial community

Gowtham Balasundaram; Pallavi Gahlot; Banafsha Ahmed; Pinakshi Biswas; Vinay Kumar Tyagi; Kine Svensson; Vinod Kumar; A A Kazmi

doi:10.1016/j.envres.2023.117195

Advanced steam-explosion pretreatment mediated anaerobic digestion of municipal sludge: Effects on methane yield, emerging contaminants removal, and microbial community

Environ Res. 2023 Dec 1;238(Pt 2):117195. doi: 10.1016/j.envres.2023.117195. Epub 2023 Sep 26.

Authors

Gowtham Balasundaram¹, Pallavi Gahlot¹, Banafsha Ahmed¹, Pinakshi Biswas¹, Vinay Kumar Tyagi², Kine Svensson³, Vinod Kumar⁴, A A Kazmi¹

Affiliations

¹ Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
² Environmental Hydrology Division, National Institute of Hydrology, Roorkee, 247667, India. Electronic address: vinayiitrp@gmail.com.
³ Cambi AS, Skysstasjon 11A, 1383, Asker, Norway.
⁴ School of Water, Energy and Environment, Cranfield University, Cranfield, MK43 0AL, UK.

PMID: 37758117
DOI: 10.1016/j.envres.2023.117195

Abstract

Advanced steam explosion pretreatment, i.e., the Thermal hydrolysis process (THP) is applied mainly to improve the sludge solubilization and subsequent methane yield in the downstream anaerobic digestion (AD) process. However, the potential of THP in pretreating the high solids retention time (SRT) sludges, mitigating the risk of emerging organic micropollutants and effects on anaerobic microbiome in digester remains unclear. In this study, sludge from a sequencing batch reactor (SBR) system operating at a SRT of 40 days was subjected to THP using a 5 L pilot plant at the temperature ranges of 120-180 °C for 30-120 min. The effect of THP on organics solubilization, methane yield, organic micropollutant removal, and microbial community dynamics was studied. The highest methane yield of 507 mL CH₄/g VS_added and volatile solids (VS) removal of 54% were observed at 160°C- 30min THP condition, i.e., 4.1 and 2.6 times higher than the control (123 mL CH₄/gVS_added, 20.7%), respectively. The experimental values of hydrolysis coefficient and methane yield have been predicted using Modified Gompertz, First order, and Logistics models. The observed values fitted well with all three models showing an R² value between 0.96 and 1.0. THP pretreated sludges showed >80% removal of Trimethoprim, Enrofloxacin, Ciprofloxacin, and Bezafibrate. However, Carbamazepine, 17α-ethinylestradiol, and Progesterone showed recalcitrant behavior, resulting in less than 50% removal. Microbial diversity analysis showed the dominance of Proteobacteria, Firmicutes, Chloroflexi, and Bacteroidetes, collectively accounting for >70-80% of bacterial reads. They are mainly responsible for the fermentation of complex biomolecules like polysaccharides, proteins, and lipids. The THP-mediated anaerobic digestion of sludge shows better performance than the control digestion, improved methane yield, higher VS and micropollutants removal, and a diverse microbiome in the digester.

Keywords: Bio-methane; Micropollutants; Sewage sludge; Thermal hydrolysis process (THP).

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anaerobiosis
Bioreactors
Fermentation
Hydrolysis
Methane
Sewage* / microbiology
Steam*

Substances

Sewage
Steam
Methane