生物炭和铁添加对低温条件下厌氧氨氧化脱氮的影响OA

To address the current challenges in anaerobic ammonium oxidation(Anammox)processes—Specifically,the accumulation of nitrate byproducts limiting total nitrogen(TN)removal efficiency and the inhibition of nitrogen removal performance at low temperatures—An iron and biochar synergistic strategy for low-temperature enhancement of Anammox coupled with denitrification was proposed in this study.An experiment was conducted using an up-flow Anammox sludge bed.It was operated continuously at room temperature for 159 days.As the temperature decreased,the reactor's nitrogen removal performance was observed to decline continuously.In the 126th day,biochar was introduced into the reactor.Following an adaptation period,the total nitrogen removal rate was gradually increased.To further accelerate the nitrogen removal efficiency,Fe0,Fe2+,and Fe3+were introduced into the reactor in the 144th day.Consequently,the nitrogen removal efficiency was sharply increased from(38.76±3.48)%to(90.81±2.17)%.Concurrently,the nitrate accumulation was reduced from(9.07±1.17)mg/L to(1.79±1.99)mg/L,and the effluent total nitrogen was maintained at(8.78±2.11)mg/L.Based on comprehensive analyses,including SEM,XRD,XPS,microbial sequencing,and metagenomic sequencing,the following conclusions were drawn.The introduction of biochar and iron resulted in the formation of denser and more stable granular sludge.Not only was the enzymatic activity enhanced,but the introduction of iron also led to an increase in the relative abundance of Azospira—A nitrate-dependent ferrous iron-oxidizing bacterium—From 7.71%to 10.81%.This enrichment introduced iron-autotrophic denitrification.The iron-autotrophic denitrification process removed the nitrate byproduct generated by the Anammox reaction.Sufficient nitrite was supplied by this coupled process to support the anammox reaction,the nitrogen removal performance of the Anammox process was maintained under low-temperature stress.