Greenhouse gases from sequential batch membrane bioreactors: A pilot plant case study

• The N2O production in a Sequential Batch MBR under salinity variation was studied.
• Salinity increase induced higher N2O emission from both anoxic and aerobic tanks;.
• The decrease of autotrophic activity promoted higher N2O emissions.
• High DO concentration in the anoxic tank suggested N2O increase via denitrification.

The paper reports the results of nitrous oxide (N2O) emissions from aerobic and anoxic tank of a Sequential Batch Membrane Bioreactor (SB-MBR) pilot plant. The influence of salinity variation on N2O emission was analyzed by gradually increasing the inlet salt concentration from 0 to 10 g NaCl L−1.The observed results showed that the N2O concentration of the gaseous samples was strongly influenced by the salt concentration. This result was likely related to a worsening of the nitrification activity due to the effect of salinity on autotrophic bacteria. Dissolved oxygen concentration and salinity were found to be the key factors affecting N2O concentration in the gaseous samples withdrawn from the anoxic tank. Despite the fact that the N2O concentration in the anoxic tank was higher than in the aerobic one, it was found that the aerobic tank emitted around 25 times more N2O than the anoxic one.

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