Evaluation of microaeration strategies in the digestion zone of UASB reactors as an alternative for biogas desulfurization

ABSTRACT

This study aimed at evaluating the microaeration as an alternative for hydrogen sulfide removal from biogas of UASB reactors treating sewage. The set-up consisted of two pilot-scale UASB reactors, including a conventional anaerobic and a modified UASB reactor, operated under microaerated conditions. Air was supplied in the digestion zone, at 1 and 3 m from the bottom of the reactor, and three different air flows were investigated: 10, 20, and 30 mL.min^-1, corresponding to 0.003, 0.005 and 0.005 LO₂/L_influent, respectively. The main results showed that the microaeration provided a substantial decrease in hydrogen sulfide concentrations when compared to the concentrations observed in the biogas of the anaerobic UASB reactor. Hydrogen sulfide concentrations remained below 70 ppm_v throughout the experimental period, corresponding to an average removal efficiency of 98%. Although a decrease in methane concentrations in biogas was observed, the feasibility of energy use would not be affected. The effect of microaeration on the overall performance of the reactor was evaluated, however, no significant differences were observed. The feasibility of limiting aeration conditions in the reactor digestion zone as an efficient alternative for hydrogen sulfide removal from biogas was demonstrated.

GRAPHICAL ABSTRACT

KEYWORDS:

• UASB reactors
• biogas
• hydrogen sulfide
• microaeration
• energy use

Acknowledgements

The authors would like to acknowledge the support obtained from the following Brazilian institutions: Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq; Fundação de Amparo à Pesquisa do Estado de Minas Gerais – FAPEMIG; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES; Financiadora de Estudos e Projetos – Finep; Instituto Nacional de Ciência e Tecnologia em Estações Sustentáveis de Tratamento de Esgoto – INCT ETEs Sustentáveis (INCT Sustainable Sewage Treatment Plants). We also acknowledge the support from Companhia de Saneamento de Minas Gerais – COPASA.

Data availability statement

Data available on request from the authors.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) [Grant Number 465746/2014-4]; Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) [Grant Number PPM-00544-17]; Coordenação de Aperfeiçoamento de Pessoal de Ní­vel Superior (CAPES) [Grant Number Finance code 001]; Financiadora de Estudos e Projetos [Grant Number FINEP]; Instituto Nacional de Ciência e Tecnologia em Estações Sustentáveis de Tratamento de Esgoto (INCT) [Grant Number INCT Sustainable Sewage Treatment Plants].