Acclimatizing waste activated sludge in a thermophilic anaerobic fixed-bed biofilm reactor to maximize biogas production for food waste treatment at high organic loading rates

Chuansheng Wang; Sumire Nakakoji; Tze Chiang Albert Ng; Peilin Zhu; Ryohei Tsukada; Masahiro Tatara; How Yong Ng

doi:10.1016/j.watres.2023.120299

Acclimatizing waste activated sludge in a thermophilic anaerobic fixed-bed biofilm reactor to maximize biogas production for food waste treatment at high organic loading rates

Water Res. 2023 Aug 15:242:120299. doi: 10.1016/j.watres.2023.120299. Epub 2023 Jul 2.

Authors

Chuansheng Wang¹, Sumire Nakakoji², Tze Chiang Albert Ng³, Peilin Zhu¹, Ryohei Tsukada², Masahiro Tatara², How Yong Ng⁴

Affiliations

¹ Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 117576, Singapore.
² Kajima Technical Research Institute, 2-19-1 Tobitakyu, Chofushi, Tokyo 182-0036, Japan.
³ National University of Singapore Environmental Research Institute, 5A Engineering Drive 1, 117411, Singapore.
⁴ Center for Water Research, Advanced Institute of Natural Sciences, Beijing Normal University at Zhuhai, 519087, China; Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 117576, Singapore. Electronic address: huanghy@bnu.edu.cn.

PMID: 37441869
DOI: 10.1016/j.watres.2023.120299

Abstract

Thermophilic anaerobic digestion (TAD) provides a promising solution for sustainable high-strength waste treatment due to its enhanced methane-rich biogas recovery. However, high organic loading rates (OLR) exceeding 3.0 kgCOD/m³/day and short hydraulic retention times (HRT) below 10 days pose challenges in waste-to-energy conversion during TAD, stemming from volatile fatty acids (VFAs) accumulation and methanogenesis failure. In this study, we implemented a stepwise strategy for acclimatizing waste activated sludge (WAS) in a thermophilic anaerobic fixed-bed biofilm reactor (TA-FBBR) to optimize methanogen populations, thereby enhancing waste-to-energy efficiencies under elevated OLRs in food waste treatment. Results showed that following stepwise acclimatization, the TA-FBBR achieved stable methane production of approximately 5.8 L/L-reactor/day at an ultrahigh OLR of ∼20 kgCOD/m³/day and ∼15 kgVS/m³/day at 6-day HRT in food waste treatment. The average methane yield reached 0.45 m³/kgCOD_removal, attaining the theoretical production in TAD. Moreover, VFA concentrations were stabilized below 1000 mg/L at the ultrahigh OLR under 6-day HRT, while maintaining an acetate/propionate ratio of > 1.8 and a VFA/TAK ratio of < 0.3 serving as effective indicators of system stability and methane yield potential. The microbial community analysis revealed that the WAS acclimatization strategy fostered the microbial diversity and abundance of Methanothermobacter and Methanosarcina. Methanosarcina in the biofilm were observed to be twice as abundant as Methanothermobacter, indicating a potential preference for biofilm existence among methanogens. The findings demonstrated an effective strategy, specifically the stepwise acclimatization of WAS in a thermophilic fixed-bed biofilm reactor, to enhance the food waste treatment performance at high OLRs, contributing valuable mechanistic and technical insights for future sustainable high-strength waste management.

Keywords: Fixed-bed biofilm reactor; Food waste; High organic loadings; Methane production; Stepwise acclimatization; Thermophilic anaerobic digestion (TAD).

MeSH terms

Anaerobiosis
Biofilms
Biofuels
Bioreactors
Food
Methane
Refuse Disposal*
Sewage*

Substances

Sewage
Biofuels
Methane