A review on the removal of nitrogen oxides from polluted flow by bioreactors

Nitric oxide (NO) and nitrogen dioxide (NO2) are the main pollutants of nitrogen oxides (NOx) released during a combustion process. They induce harmful effects both to the environment and human health, such as the formation of acid rain, an increase of the tropospheric ozone, global warming, etc. Selective catalytic reduction, selective non-catalytic reduction, adsorption and scrubbing (absorption) are the conventional technologies used to control NOxemission from exhaust gas. The bioreactor appears superior to conventional technologies in terms of simplicity and economy in operation, low process energy requirements, and easy treatment of residual products. This paper reviews two biologically-based NOxremoval theories, i.e., nitrification and denitrification. The use of bacteria, fungi and microalgae are discussed and compared. The study indicates that the bioreactor is a promising technology that can be used to control NOxemitted during combustion processes.