[Impact of Salinity on Leachate Treatment and N2O Releases from Semi-aerobic Aged-refuse Bioreactor].

Semi-aerobic Aged-refuse Bioreactor (SAARB) has a good effect on nitrogen removal in leachate, but a strong greenhouse gas (N2O) was generated during the nitrification and denitrification process. The effect of salinity (7-30 g x L(-1)) on the leachate treatment and the N2O production from SAARB system was investigated. Experimental results showed that salinity ranging from 7 to 30 g x L(-1) had no significant effect on COD removal, and the removal efficiency was always more than 85%. On the contrary, it had a strong influence on the removal of nitrogen. The removal efficiencies of NH4+ -N and TN decreased from 98. 23% and 91.48% at 7 g x L(-1) salt to 31.75% and 34.24% at 30 g x L(-1) salt, respectively. Moreover, there was significant nitrite (NO2- -N) accumulation in the presence of 30 g x L(-1) salt. Meanwhile, salinity had different inhibition strength on nitrification and denitrification bacteria, and the order of inhibition strength was as follows: nitrification bacteria > denitrification bacteria. In addition, the N2O production increased with salinity concentration, and the highest N2O accumulation (1397 microg +/- 369.88 microg) was observed with addition of 30 g x L(-1) salt, which accounted for 8.87%o of the total nitrogen removal. Meanwhile, it was 6-117 times higher in the presence of 30 g x L(-1) salt than that in low salinity conditions (7-20 g x L(-1)). And the peak time of the N2O production showed a delayed trend. These results indicated that salinity recirculation in leachate had a negative effect on the nitrogen removal and N2O production. Overall, salinity seemed to be a key parameter during leachate recirculation.