Using anammox biofilms for rapid start-up of partial nitritation-anammox in integrated fixed-film activated sludge for autotrophic nitrogen removal. Suspended sludge and biofilms in PNA-IFAS reactors

This study aims to develop a new seeding and start-up strategy to assist the start-up and improve the nitrogen removal of a PNA-IFAS reactor. Two bioreactors, including a reactor that was started conventionally with the pre-acclimated suspended PNA sludge and bare biocarriers (PA-S) and a reactor that used the new seeding method with anammox biofilms pre-acclimated on biocarriers in a packed bed biofilm reactor and ammonia-oxidizing bacteria (AOB) sludge in the suspension (PA-B), were used in the experiments. Abstract Integrated fixed-film activated sludge (IFAS) reactors are suitable for partial nitritation-anammox (PNA) for autotrophic nitrogen removal; however, its start-up and biofilm formation are slow and difficult. In this study, a new sludge seeding strategy was developed for the start-up of PNA-IFAS by using the pre-cultivated anammox biofilms.Two bioreactors were used in the experimental study, including a reactor that was started conventionally with the pre-acclimated suspended PNA sludge and bare biocarriers (PA-S) and a reactor that used the new seeding method with anammox biofilms pre-acclimated on biocarriers and ammonia-oxidizing bacteria (AOB) sludge in the suspension (PA-B). The use of anammox biofilms as the seed biomass greatly shortened the start-up period of the PNA-IFAS reactor to one month or so. Moreover, reactor PA-B achieved a higher nitrogen removal rate (707.3 mg N/(L*d)), better nitrogen removal efficiency (86.8%), and lower nitrate yield (9.4%) than reactor PA-S. The biofilm development in PA-B was accelerated and its biofilm content was nearly 10 times higher than that of PA-S. The initial segregation of anammox in the biofilm and AOB in the suspended sludge provided an environment that not only accelerated the start-up of PNA-IFAS but also helped suppress the enrichment of unwanted nitrite-oxidizing bacteria (NOB) in the bioreactor, as evidenced by the lower NOB abundance in PA-B (2.2%) according to microbial community analysis.

本研究旨在开发一种新型接种启动策略，以辅助短程硝化-厌氧氨氧化一体化固定膜活性污泥（Partial Nitritation-Anammox-Integrated Fixed-film Activated Sludge, PNA-IFAS）反应器的启动过程，并提升其脱氮性能。本实验设置两组生物反应器：一组采用传统启动方式，以预驯化的悬浮态PNA污泥与裸生物载体为接种物，记为PA-S；另一组采用新型接种方法，以填充床生物膜反应器中预驯化的载体附着型厌氧氨氧化（Anammox）生物膜，以及悬浮态氨氧化细菌（Ammonia-oxidizing bacteria, AOB）污泥为接种物，记为PA-B。
摘要：一体化固定膜活性污泥（Integrated Fixed-film Activated Sludge, IFAS）反应器适用于短程硝化-厌氧氨氧化（Partial Nitritation-Anammox, PNA）自养脱氮工艺；然而其启动过程与生物膜形成速度缓慢且难度较高。本研究通过预培养厌氧氨氧化生物膜，开发了一种适用于PNA-IFAS工艺启动的新型污泥接种策略。本实验设置两组生物反应器：一组采用传统启动方式，以预驯化的悬浮态PNA污泥与裸生物载体为接种物，记为PA-S；另一组采用新型接种方法，以预驯化的载体附着型厌氧氨氧化生物膜及悬浮态氨氧化细菌污泥为接种物，记为PA-B。
以厌氧氨氧化生物膜作为接种生物质，可将PNA-IFAS反应器的启动周期大幅缩短至1个月左右。此外，相较于PA-S反应器，PA-B反应器的氮去除速率更高（707.3 mg N/(L·d)），脱氮效率更优（86.8%），且硝酸盐产率更低（9.4%）。PA-B反应器的生物膜发育进程显著加快，其生物膜量较PA-S反应器提升近10倍。生物膜内厌氧氨氧化菌与悬浮污泥内氨氧化细菌的初始空间分异，不仅加速了PNA-IFAS工艺的启动，还有助于抑制反应器内有害亚硝酸盐氧化细菌（Nitrite-oxidizing bacteria, NOB）的富集；微生物群落分析结果显示，PA-B反应器内的NOB丰度仅为2.2%，可佐证上述结论。