Department of Chemical Engineering and Applied Chemistry, University of Toronto, Ontario, Canada.
Water Environ Res. 2011 Mar;83(3):220-32. doi: 10.2175/106143010x12780288628255.
The effect of calcium concentration on the biofilm structure, microbiology, and treatment performance was evaluated in a moving-bed biofilm reactor. Three experiments were conducted in replicate laboratory-scale reactors to determine if wastewater calcium is an important variable for the design and optimization of these reactors. Biofilm structural properties, such as thickness, oxygen microprofiles, and the composition of extracellular polymeric substances (EPS) were affected by increasing calcium concentrations. Above a threshold concentration of calcium between 1 and 50 mg/L, biofilms became thicker and denser, with a shift toward increasingly proteinaceous EPS at higher calcium concentrations up to 200 mgCa2+/L. At 300 mgCa2+/L, biofilms were found to become primarily composed of inorganic calcium precipitates. Microbiology was assessed through microscopy, denaturing grade gel electrophoresis, and enumeration of higher organisms. Higher calcium concentrations were found to change the bacterial community and promote the abundant growth of filamentous organisms and various protazoa and metazoan populations. The chemical oxygen demand removal efficiency was improved for reactors at calcium concentrations of 50 mg/L and above. Reactor effluents for the lowest calcium concentration (1 mgCa2+/L) were found to be turbid (>50 NTU), as a result of the detachment of small and poorly settling planktonic biomass, whereas higher concentrations promoted settling of the suspended phase. In general, calcium was found to be an important variable causing significant changes in biofilm structure and reactor function.
在移动床生物膜反应器中评估了钙离子浓度对生物膜结构、微生物学和处理性能的影响。在重复的实验室规模的反应器中进行了三个实验，以确定废水中的钙是否是这些反应器的设计和优化的重要变量。生物膜结构特性，如厚度、氧微分布和胞外聚合物物质 (EPS) 的组成，受到钙离子浓度增加的影响。在 1 至 50mg/L 之间的阈值浓度之上，生物膜变得更厚、更密集，随着钙离子浓度的增加，EPS 中的蛋白质含量逐渐增加，在 200mgCa2+/L 时达到最高。在 300mgCa2+/L 时，生物膜被发现主要由无机钙沉淀物组成。通过显微镜、变性梯度凝胶电泳和高等生物的计数评估微生物学。发现较高的钙离子浓度改变了细菌群落，并促进了丝状生物和各种原生动物和后生动物种群的大量生长。在钙离子浓度为 50mg/L 及以上时，化学需氧量去除效率得到提高。在最低钙离子浓度（1mgCa2+/L）的反应器中，由于小型和难以沉淀的浮游生物生物量的脱落，导致流出物浑浊（>50NTU），而较高的浓度促进了悬浮相的沉淀。总的来说，钙被发现是一个重要的变量，它会导致生物膜结构和反应器功能发生显著变化。
