Abstract Two-stage anaerobic system (S1: R1 (acidogenic phase) + R2 (methanogenic phase)) and the one-stage control (S0) were established to investigate the effect of phase separation on the removal of an azo dye orange II, i.e., Acid Orange 7 (AO7), with starch as the primary co-substrate. Although final AO7 removal from two systems showed no statistical differences, the first-order rate constants for AO7 removal (kAO7­) and sulfanilic acid (SA) formation (kSA) were higher in S1. Kinetic analysis showed that kAO7­ and kSA in S1 were 2.7-fold and 1.7-fold of those in S0, respectively, indicating the benefit of phase separation to the AO7 reduction. However, this benefit only appeared in the period with influent AO7 concentrations higher than 2.14 mM. Otherwise, this advantage would be hidden due to the longer HRT (5 d) and sufficient electron donor (1.0 g starch L−1). Within S1, R1 only contributed about 10% of the entire AO7 removal, and kAO7­ in R1 (0.172 h−1) was much lower than in R2 (0.503 h−1). The methanogenic phase rather than acidogenic phase was the main contribution to AO7 removal, because the influent of R2 had more available electron donors and suitable pH condition (pH 6.5–7.0) for the bio-reduction process.

中文翻译：

---

两阶段厌氧工艺有利于以淀粉为主要共底物去除偶氮染料 Orange II

摘要建立两级厌氧系统（S1：R1（产酸相）+R2（产甲烷相））和一级控制（S0），研究相分离对偶氮染料橙II去除的影响，即酸性橙 7 (AO7)，以淀粉为主要辅助底物。尽管两个系统的最终 AO7 去除率没有显示出统计差异，但 S1 中 AO7 去除率 (kAO7) 和磺胺酸 (SA) 形成 (kSA) 的一级速率常数较高。动力学分析表明，S1 中的 kAO7 和 kSA 分别是 S0 中的 2.7 倍和 1.7 倍，表明相分离有利于 AO7 的还原。然而，这种益处仅出现在进水 AO7 浓度高于 2.14 mM 的时期。否则，由于较长的 HRT（5 d）和足够的电子供体（1.0 g 淀粉 L−1），这一优势将被隐藏。在S1内，R1仅贡献了全部AO7去除量的约10%，并且R1中的kAO7 (0.172 h−1)远低于R2中的kAO7 (0.503 h−1)。产甲烷阶段而不是产酸阶段是去除 AO7 的主要贡献者，因为 R2 的进水有更多可用的电子供体和适合生物还原过程的 pH 条件（pH 6.5-7.0）。