دانلود رایگان مقاله گازهای گلخانه ای بیوراکتورهای غشایی بسته توالی

Abstract

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oxygen concentration and salinity were found to be the key factors affecting N2O concentration in the gaseous samples withdrawn from the anoxic tank.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.

4. Conclusions

The N2O concentration in the gaseous phase was significantly influenced by the salinity increase, which depressed the activity of autotrophic biomass within the aerobic tank, with the lowest ammonia removal efficiency (63%) obtained at the highest salinity concentration (10 g NaCl L−1). Samples from the anoxic tank showed even higher concentrations of N2O, likely due to the combined effect of salinity and high DO concentrations, that enhanced incomplete denitrification thus promoting the production of N2O. In terms of N2O flux, the emission from the aerobic tank was 25 times higher than the anoxic one. The salinity increase was crucial for the production of dissolved N2O. Therefore, in order to minimize the N2O production/emission from anoxic-oxic processes it is crucial to limit the salinity fluctuations as well as to maintain the salt concentration below 10 g NaCl L−1.