Biomass segregation between biofilm and flocs improves the control of nitrite-oxidizing bacteria in mainstream partial nitritation and anammox processes
Biomass segregation between biofilm and flocs improves the control of nitrite-oxidizing bacteria in mainstream partial nitritation and anammox processes
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DOI：
10.1101/480780
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发表时间：
2018-11
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通讯作者：
M. Laureni;D. Weissbrodt;K. Villez;O. Robin;N. de Jonge;A. Rosenthal;G. Wells;J. Nielsen;E. Morgenroth;A. Joss
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文献类型：
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作者：
M. Laureni;D. Weissbrodt;K. Villez;O. Robin;N. de Jonge;A. Rosenthal;G. Wells;J. Nielsen;E. Morgenroth;A. Joss
亚硝酸盐氧化细菌(NOB)的控制对在主流条件下实施部分亚硝化和厌氧氨氧化(PN/A)工艺提出了挑战。本研究的目的是了解在生物膜和絮体共存的混合PN/A系统中，操作条件如何影响微生物竞争和对NOB的控制。采用复合式PN/A移动床生物膜反应器(MBBR；又称一体化固定膜活性污泥法或IFAS)，在15℃下对经过好氧处理的城市污水(23mgNH4-N·L−1)进行处理。絮体中主要富含氨氧化细菌(AOB)和非氨氧化细菌(NOB)，生物膜中主要富含厌氧氨氧化细菌(AMX)。在所有其他操作条件不变的情况下，将溶解氧浓度(DO)从1.2mgO2·L降至0.17mgO2·−-1后，观察到NOB从絮体中洗出。在低DO条件下，生物膜中残留的少量NOB组分的活性受到抑制。结果表明，在好氧脱氮效率(80mGN·L−·d−1)与常规处理厂相当的情况下，出水NO3−浓度(0.5mgN·L−1)始终保持在较低水平。一个简单的动态数学模型，假设AOB和NOB在絮体中完全分离，AMX在生物膜中，能够定性地再现絮体中NOB的选择性洗脱响应于DO设定点的下降。同样，数值模拟表明，絮体去除是实现NOB选择性洗脱的有效操作策略。模型认为，NOB和AMX对−的直接竞争是导致AOB和NOB(即絮体中的μNOB<；μAOB)实际生长速率不同的关键机制，并允许选择性地清洗NOB。实验结果和模型预测表明，与主流PN/A应用中控制NOB的单一生物膜系统相比，混合系统提供了更高的操作灵活性，因为操作员可以很容易地控制这些变量。亮点混合PN/A系统为NOB控制提供了更大的操作灵活性，AOB和NOB主要在絮体中浓缩，而AMX在生物膜(亚硝酸盐-汇)中使用AMX使用NO2−，允许区分AOB和NOB的生长速率DO的减少或絮体去除的增加导致选择性NOB从絮体中洗脱。在限制DO时，生物膜中少量NOB的活性受到抑制
The control of nitrite-oxidizing bacteria (NOB) challenges the implementation of partial nitritation and anammox (PN/A) processes under mainstream conditions. The aim of the present study was to understand how operating conditions impact microbial competition and the control of NOB in hybrid PN/A systems, where biofilm and flocs coexist. A hybrid PN/A moving-bed biofilm reactor (MBBR; also referred to as integrated fixed film activated sludge or IFAS) was operated at 15 °C on aerobically pre-treated municipal wastewater (23 mgNH4-N·L−1). Ammonium-oxidizing bacteria (AOB) and NOB were enriched primarily in the flocs, and anammox bacteria (AMX) in the biofilm. After decreasing the dissolved oxygen concentration (DO) from 1.2 to 0.17 mgO2·L−1 - with all other operating conditions unchanged - washout of NOB from the flocs was observed. The activity of the minor NOB fraction remaining in the biofilm was suppressed at low DO. As a result, low effluent NO3− concentrations (0.5 mgN·L−1) were consistently achieved at aerobic nitrogen removal rates (80 mgN·L−1·d−1) comparable to those of conventional treatment plants. A simple dynamic mathematical model, assuming perfect biomass segregation with AOB and NOB in the flocs and AMX in the biofilm, was able to qualitatively reproduce the selective washout of NOB from the flocs in response to the decrease in DO-setpoint. Similarly, numerical simulations indicated that flocs removal is an effective operational strategy to achieve the selective washout of NOB. The direct competition for NO2− between NOB and AMX - the latter retained in the biofilm and acting as a “NO2-sink” - was identified by the model as key mechanism leading to a difference in the actual growth rates of AOB and NOB (i.e., μNOB < μAOB in flocs) and allowing for the selective NOB washout. Experimental results and model predictions demonstrate the increased operational flexibility, in terms of variables that can be easily controlled by operators, offered by hybrid systems as compared to solely biofilm systems for the control of NOB in mainstream PN/A applications. Highlights Hybrid PN/A systems provide increased operational flexibility for NOB control AOB and NOB enrich primarily in the flocs, and AMX in the biofilm (“NO2-sink”) AMX use NO2− allowing to differentiate AOB and NOB growth rates A decrease in DO or an increase in floc removal leads to selective NOB washout from flocs The activity of the minor NOB fraction in the biofilm is suppressed at limiting DO