Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556, USA; Southern Nevada Water Authority, 1299 Burkholder Blvd., Henderson, NV 89015, USA.
Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556, USA.
Water Res. 2024 Apr 1;253:121272. doi: 10.1016/j.watres.2024.121272. Epub 2024 Feb 7.
Temperature is known to have an important effect on the morphology and removal fluxes of conventional, co-diffusional biofilms. However, much less is known about the effects of temperature on membrane-aerated biofilm reactors (MABRs). Experiments and modeling were used to determine the effects of temperature on the removal fluxes, biofilm thickness and morphology, and biofilm microbial community structure of nitrifying MABRs. Steady state tests were carried out at 10 °C and 30 °C. MABRs grown at 30 °C had higher ammonium removal fluxes (5.5 ± 0.9 g-N/m/day at 20 mgN/L) than those grown at 10 °C (3.4 ± 0.2 g-N/m/day at 20 mgN/L). The 30 °C biofilms were thinner and rougher, with a lower protein to polysaccharides ratio (PN/PS) in their extracellular polymeric substance (EPS) matrix and greater amounts of biofilm detachment. Based on fluorescent in-situ hybridization (FISH), there was a higher relative abundance of nitrifying bacteria at 30 °C than at 10 °C, and the ratio of AOB to total nitrifiers (AOB + NOB) was higher at 30 °C (95.1 ± 2.3%) than at 10 °C (77.2 ± 8.6 %). Anammox bacteria were more abundant at 30 °C (16.6 ± 3.7 %) than at 10 °C (6.5 ± 2.4 %). Modeling suggested that higher temperatures increase ammonium oxidation fluxes when the biofilm is limited by ammonium. However, fluxes decrease when oxygen becomes limited, i.e., when the bulk ammonium concentrations are high, due to decreased oxygen solubility. Consistent with the experimental results, the model predicted that the percentage of AOB to total nitrifiers at 30 °C was higher than at 10 °C. To investigate the effects of temperature on biofilm diffusivity and O solubility, without longer-term changes in the microbial community, MABR biofilms were grown to steady state at 20 °C, then the temperature changed to 10 °C or 30 °C overnight. Higher ammonium oxidation fluxes were obtained at higher temperatures: 1.91 ± 0.24 g-N/m/day at 10 °C and 3.19 ± 0.40 g-N/m/day at 30 °C. Overall, this work provides detailed insights into the effect of temperature on nitrifying MABRs, which can be used to better understand MABR behavior and manage MABR reactors.
温度对传统共扩散生物膜的形态和去除通量有重要影响。然而，对于温度对膜曝气生物膜反应器（MABR）的影响，人们知之甚少。本研究通过实验和建模来确定温度对硝化 MABR 的去除通量、生物膜厚度和形态以及生物膜微生物群落结构的影响。在 10°C 和 30°C 下进行稳态测试。在 20mgN/L 时，30°C 下生长的 MABR 的氨氮去除通量（5.5±0.9g-N/m/d）高于 10°C 下生长的 MABR（3.4±0.2g-N/m/d）。30°C 下的生物膜更薄、更粗糙，其胞外聚合物（EPS）基质中的蛋白质与多糖比（PN/PS）更低，生物膜脱落量更大。基于荧光原位杂交（FISH），30°C 下硝化细菌的相对丰度高于 10°C，氨氧化菌（AOB）与总硝化菌（AOB+NOB）的比值在 30°C（95.1±2.3%）高于 10°C（77.2±8.6%）。在 30°C 时，厌氧氨氧化菌（Anammox）的丰度高于 10°C（16.6±3.7%比 6.5±2.4%）。模型表明，当生物膜受氨限制时，较高的温度会增加氨氧化通量。然而，当氧气成为限制因素时，即当基质中氨氮浓度较高时，由于氧气溶解度降低，通量会下降。与实验结果一致，模型预测 30°C 时 AOB 占总硝化菌的比例高于 10°C。为了在不改变微生物群落的情况下研究温度对生物膜扩散性和氧气溶解度的影响，MABR 生物膜在 20°C 下达到稳态后， overnight 将温度升高至 10°C 或 30°C。较高的温度下获得了更高的氨氮氧化通量：10°C 时为 1.91±0.24g-N/m/d，30°C 时为 3.19±0.40g-N/m/d。总的来说，这项工作提供了温度对硝化 MABR 影响的详细见解，这有助于更好地理解 MABR 的行为和管理 MABR 反应器。
