Study On The Release Of N₂O In Partial Nitrification Process With High Ammonia-nitrogen Wastewater

Because the global warming is speeding up, how to control the emissions of greenhousegas has become an important problem. N₂O is a kind of important greenhouse gas, althoughits concentration is lower than CO₂in the atmosphere, the greenhouse effect of that is more200times than CO₂. In addition, N₂O can cause ozone hole, acid rain and photochemicalsmog. So N₂O has become an important issue that effects the global climate and threatshuman health. In so many sources of N₂O, the contribution of the biological denitrificationprocess cannot be ignored, especially the SHARON-ANAMMOX combined process can savemuch energy and work efficiently, but the release of N₂O limits its development, and thepartial nitrification process produced most of N₂O. It is crucial to study the release of N₂O inthe partial nitrification process as the front process before anaerobic ammonium oxidationreaction, so that has an important realistic significance.This study’s object is a SBBR reactor which combined the advantages of SBR reactorand biofilm reactor. The reactor started and run stably the partial nitrification process withhigh ammonia-nitrogen wastewater in intermittent aeration conditions, then was studied in thedifferent conditions （such as different ammonia concentration or salinity） to find the factorsthat effect the release of N₂O. This paper also used molecular biology techniques to study thechange of the structure of the microbial community in this system.The mainly researchcontents and results are as follows:（1） The SBBR reactor achieved and operated stably the partial nitrification process whenit run more than30days sludge treatment. The process was divided into start-up phase （1-31days） and stable operation stage （32-133days）, and the ratio of nitrite and ammonia in theeffluent could keep1:1and nitrate also maintained at a low level. We found that NH4+-Nreduced and NO2--N accumulated gradually in the typical cycle of the partial nitrificationprocess in the107days. The accumulation release of N₂O was22.08mg which accounted for1.36%of the nitrogen load in the whole cycle. The change of N₂O could be described by amodel as y=0.0333x-0.4298（R²=0.9941）. In the long operation of the partial nitrification process in the SBBR reator, the release of N₂O was （26.63±4.99,n=5） mg, in other word, itwas about （1.50±0.22,n=5）%of total nitrogen load.（2） The paper studied the microbial community structure in the biofilm by PCR-DGGEand cloning sequencing. The results showed that the microbial community structure hadchanged as the continuous operation, and the dominant species such as Acidobacteria，Cytophagales and Hyphomicrobiaceae was riched,while Arcobacter and Nitrospira wasscreened out gradually because of high temperature and aeration.（3） The experiment studied the influence of different technical conditions （differentammonia nitrogen concentration and salinity） on the release of N₂O in the partial nitrificationreaction. The study found that the release of N₂O increased gradually with the increasing ofthe concentration of ammonia nitrogen and salinity, separately.