Long-term Effects Of Acetylene On N₂O Production Of Activated Sludge:Biomass Performance And Microbial Community

In recent years,the recovery of nitrous oxide(N2O)from nitrogen contaminated wastewater has become a research focus of environmental engineering.Microbial denitrification in the wastewater treatment process is the main source of N2O.Acetylene is often used as an inhibitor of N2O reductase,however,there are few researches on the N2O production performance of activated sludge and the dynamics of microbial community under long-term acclimation of acetylene currently.This study found that after long-term acclimation(>100 days),the activated sludge(S0)cultured in the SBR without acetylene didn’t produce N2O during the nitrite denitrification process.The N2O production ratio of activated sludge(S10)cultured with 10%acetylene(V/V)was 6.3-56.2%.The N2O production ratio of activated sludge(S40)cultured with 40%acetylene(V/V)could be stable over 94.0%.However,batch experiments in series without acetylene found that the ability of S40 to produce N2O continued to decrease during the denitrification process,and there was no N2O production after about 6 hours.High-throughput 16S rRNA gene sequencing analysis showed that Saprospiraceae became the dominant bacteria in S40 at the end of cultivation,and its abundance was as high as 42.2%,which was 10.8 times the corresponding abundance in S0 at the same period.Metagenomics analysis showed that long-term acclimation with 40%acetylene didn’t significantly change the total relative abundance of nosZ in activated sludge,but the ratio of nosZⅡ/nosZⅠ in S40 was 2.0 times of the corresponding value in S0,indicating that denitrifiers harboring nosZⅡ dominates the community of S40.Metatranscriptomics analysis showed that the expression activity of nosZⅡ in S40 was comparable to that in S0 and S10,indicating that the high N2O production of S40 wasn’t caused by the inhibition of functional genes transcription.This study explores the N2O production performance of activated sludge under long-term exposure of acetylene,and reveals the key bacterial community,the abundance and expression of functional genes during the cultivation process.