The effect of recirculation in increasing organic loading rate (OLR) anddecreasing hydraulic retention time (HRT) in a semi-continuous two-stage anaerobicdigestion system using stirred tank reactor (CSTR) and an upflow anaerobic sludge bed(UASB) was evaluated. Two-parallel processes were in operation for 100 days, one withrecirculation (closed system) and the other without recirculation (open system). For thispurpose, two structurally different carbohydrate-based substrates were used; starch andcotton. The digestion of starch and cotton in the closed system resulted in production of91% and 80% of the theoretical methane yield during the first 60 days. In contrast, in theopen system the methane yield was decreased to 82% and 56% of the theoretical value, forstarch and cotton, respectively. The OLR could successfully be increased to 4 gVS/L/dayfor cotton and 10 gVS/L/day for starch. It is concluded that the recirculation supports themicroorganisms for effective hydrolysis of polyhydrocarbons in CSTR and to preserve thenutrients in the system at higher OLRs, thereby improving the overall performance andstability of the process.
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机译：在使用搅拌釜反应器（CSTR）和上流厌氧污泥床（UASB）的半连续两级厌氧消化系统中，评估了再循环对增加有机负荷率（OLR）和减少水力停留时间（HRT）的影响。两个平行的流程运行了100天，一个流程进行了再循环（封闭系统），另一流程没有进行了再循环（开放系统）。为了这个目的，使用了两种结构上不同的基于碳水化合物的底物。淀粉和棉。在封闭的系统中，淀粉和棉花的消化在开始的60天内产生了理论甲烷产量的91％和80％。相反，在开放系统中，甲烷的收率分别为淀粉和棉花的理论值的82％和56％。棉花的OLR可以成功提高到4 gVS / L /天，淀粉的成功提高到10 gVS / L /天。结论是，再循环支持微生物有效地水解了CSTR中的多烃，并在较高的OLR值下保留了系统中的营养，从而提高了工艺的整体性能和稳定性。
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