The potential effect of different Ca2+ additions (150, 300, 450, 600 and 1000 mg/L) on microbial activity and aggregation, during anaerobic digestion at moderate (8 g/L Na+) and high salinity (20 g/L Na+) has been investigated. Batch tests were carried out in duplicate serum bottles and operated for 30 days at 37 °C. At 8 g/L Na+, methanogenic activity and protein degradation were comparable from 150 to 450 mg/L Ca2+, and a significant inhibition was only observed at a Ca2+concentration of 1000 mg/L. In contrast, at 20 g/L Na+, 150 to 300 mg/L were the only Ca2+ concentrations to maintain chemical oxygen demand (COD) removal, protein hydrolysis and methane production. Overall, increasing Ca2+ concentrations had a larger impact on acetotrophic methanogenesis at 20 g/L than at 8 g/L Na+. Increasing Ca2+ had a negative effect on the aggregation behaviour of the dominant methanogen Methanosaeta when working at 8 g/L Na+. At 20 g/L Na+ the aggregation of Methanosaeta was less affected by addition of Ca2+ than at 8 g/L Na+. The negative effect appeared to be connected with Ca2+ precipitation and its impact on cell-to cell communication. The results highlight the importance of ionic balance for microbial aggregation at high salinity, bringing to the forefront the effect on Methanosaeta cells, known to be important to obtain anaerobic granules.

中文翻译：

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高盐度厌氧消化过程中钙对微生物活性和生物量聚集的影响

在中度 (8 g/L Na+) 和高盐度 (20 g/L Na+) 厌氧消化过程中，不同 Ca2+ 添加量（150、300、450、600 和 1000 mg/L）对微生物活性和聚集的潜在影响具有被调查。批量测试在重复的血清瓶中进行，并在 37°C 下运行 30 天。在 8 g/L Na+ 下，产甲烷活性和蛋白质降解在 150 到 450 mg/L Ca2+ 范围内相当，并且仅在 Ca2+ 浓度为 1000 mg/L 时观察到显着抑制。相比之下，在 20 g/L Na+ 下，150 至 300 mg/L 是唯一能维持化学需氧量 (COD) 去除、蛋白质水解和甲烷生成的 Ca2+ 浓度。总体而言，与 8 g/L Na+ 相比，增加 Ca2+ 浓度对 20 g/L 乙酸营养型产甲烷的影响更大。在 8 g/L Na+ 下工作时，增加 Ca2+ 对主要产甲烷菌 Methanosaeta 的聚集行为有负面影响。在 20 g/L Na+ 时，与 8 g/L Na+ 相比，添加 Ca2+ 对甲烷菌聚集的影响更小。负面影响似乎与 Ca2+ 沉淀及其对细胞间通讯的影响有关。结果强调了离子平衡对高盐度微生物聚集的重要性，将甲烷菌细胞的影响带到了最前沿，已知对获得厌氧颗粒很重要。