Nitrous oxide emissions treating hypersaline wastewater in suspended and attached partial nitritation - anammox...

Nitrous oxide (N₂O) emissions from partial nitritation- anammox (PN/A) processes for deammonification has become an important issue as the technology has become more widespread, however, N₂O emissions from PN/A treating hypersaline wastewater has been little reported. Here, N₂O emissions from completely mixed suspended and attached single-stage PN/A reactors treating hypersaline (4 % salinity; 40 g/kg) wastewater for ammonium removal were first investigated without the addition of organics. Results show that N₂O emissions in fixed bed and suspended PN/A reactors without organic addition ranged from 0.08 % to 1.0 % and 0.09 % to 1.5 % of ammonium removed, respectively. Bulk ammonium and nitrite concentrations were shown to be the main controlling factors for N₂O emissions. The presence of influent organics was subsequently studied to see its effect on nitrogen removal and N₂O emissions. The addition of acetate to both fixed bed and suspended reactors reduced N₂O emissions by 52.5 % and 72.4 %, respectively. Quantitative PCR results showed an increase in the functional genes related to denitrification with the addition of acetate, however, deammoniafication was not significantly affected.