Characteristics Of N₂O Generation In Denitrifying SBR Nitrogen Removal System

Nitrous Oxide?N₂O?is one of the most important greenhouse gases in the world,with an 265 times warming effect of carbon dioxide,9.5 times warming effect of methane,about120 years duration in atmosphere,and wastewater treatment process is viewed as the important sources of N₂O production.With the increasing of sewage treatment plants,it is an crucial issue for researchers in this field to investigate the way of controlling the N₂O production of biological removal.In this study,sequencing batch reactor?SBR?denitrification system was used as a culture condition and fed with artificial water,and the dissolved N₂O and N₂O emission conditions and influence factor were discussed with the variation of active sludge distribution,nitrite concentration and C/N value.The main conclusions are as follows:?1?While the sludge was floc,nitrite concentration has an influence on the production of N₂O and NO.When the C/N value is 3 or 4,the rate between N₂O emission and NO_x^--N removal of denitrification process was gradually increasing,along with nitrite concentration is increased.the rate of N₂O emission to NO_x^--N removal of denitrification process was reducing when the C/N value was 2.The rate between dissolved N₂O and NO_x^--N removal of denitrification process decreased first and then increased with increasing of nitrite concentration.Different C/N ratios and nitrite,bacteria reduces the nitrite,dissolved nitrous oxide and dissolved nitric oxide in turn,respectively.Orthogonal and Synergetic analysis showed that nitrite concentration had greater effect on N₂O generation than C/N,which effect was not significant.?2?While the sludge was floc,The variation of electron acceptor has an influence on the production of N₂O and NO.When the electron acceptor is nitrate nitrogen,many parameters such as the ratio of dissolved N₂O to the denitrification NO_x^--N,the ratio of N₂O emission to the denitrification NO_x^--N and the dissolution rate of N₂O were higher than that of which the electron acceptor was nitrite.When the C/N value is 2,the concentration of electron acceptor is 500 mg/L,the C/N value required for the nitrate nitrogen as the electron acceptor was greater than that of the nitrite of the electron acceptor,which ones are 1.92 and1.63.?3?When the sludge was Granular,the variation of C/N value on has an influence on N₂O production.With the increasing of C/N value,many parameters such as the peak concentration of dissolved N₂O,the ratio of both the peak concentration of dissolved N₂O and denitrification to NO_x^--N,the maximum speed of dissolved N₂O and the the average speed of dissolved N₂O altogether were gradually increasing.The maximum ratio of the denitrification under unit sludge concentration and the average speed of dissolved N₂O of reaching accumulation peak were all increased first and then decreased.The escape rate of N₂O is synchronous with the rate of soluble N₂O formation,and the corresponding value is small.?4?The effect of different C/N on the yield of N₂O was compared,when the sludge was floc and granule.Many parameters such as The degradation rate of nitrite,The maximum ratio of the denitrification under unit sludge concentration,the maximum speed of dissolved N₂O,the the average speed of dissolved N₂O,the average speed of dissolved N₂O of reaching accumulation peak,the peak concentration of dissolved N₂O,the peak of dissolved N₂O to the denitrification NO_x^--N,the ratio of N₂O emission to the denitrification NO_x^--N altogether were higher than that of the sludge was floc.According to the corresponding value of sludge,it can be seen that the amount of N₂O production and escape amount of granular sludge are more than that of the floc sludge,but the degradation rate is also large.In general,the rate of N₂O emission is very little,the granular sludge is more obvious than the floc sludge on the degradation of the sludge,and the same conclusion is obtained through the difference comparison.