Reduction of Nitrous Oxide Emissions from Biological Nutrient Removal Processes by Thermal Decomposition

The potential to mitigate nitrous oxide (N2O) emissions from biological nutrient removal (BNR) processes by means of thermal decomposition was demonstrated through computer modeling. Different N2O concentrations, as a percentage of the wastewater influent ammonia nitrogen (NH3-N), were input to a combustion process as part of the oxidant air stream and for all influent concentrations, were shown to be decomposed to negligible concentrations. In addition to N2O, the fate of: CO2, hydrogen sulfide (H2S) and ten commonly occurring volatile organic compounds (VOCs); all of which may be contained in the fugitive gas emissions from a biological process at a wastewater treatment facility was examined. The CO2 was shown to reduce the production of thermal nitrogen oxides (NOx). The sulfur released from the H2S formed sulfur dioxide (SO2) and eight of the ten VOCs were destroyed while an increase in chloroform and methylene chloride was observed. Although, H2S and most of the VOCs may not be emitted from a BNR process, but earlier in the treatment train; their fate through the combustion process was examined. The computer simulations indicate that the thermal destruction of N2O has the potential of mitigating fugitive N2O emissions and warrants further investigation.