Greenhouse gases from membrane bioreactors: New perspectives on monitoring and mathematical modeling

Abstract The awareness that the wastewater sector represents a significant source of greenhouse gas emission has increased, and is the awareness is evident based on the numerous research papers published in technical literature in the last 10 years. This chapter is aimed at providing a timely overview on greenhouse gas production and emission from membrane bioreactors. Specifically, this chapter dedicates particular attention to nitrous oxide (N2O), considering both experimental and mathematical modeling approaches. Referring to the experimental data, the observed results highlighted the significant contribution of the aerated compartments toward nitrous oxide emission as well as the importance of specific wastewater features (i.e., carbon to nitrogen ratio or presence of recalcitrant compounds, like hydrocarbons), showing at the same time high emissions variability. In terms of mathematical modeling, the results highlighted that models combining the N2O formation contribution due to autotrophic (as nitrifiers and denitrifiers) and heterotrophic provide excellent results in terms of predicting the N2O emission from membrane bioreactors. Results have also demonstrated that these mathematical models represent excellent tools for predicting the MBR behavior under different operational conditions with the aim to reduce effluent pollutants (solid, liquid, and gaseous).