Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice, Via Torino 155, 30170 Mestre-Venice, Italy.
Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padua, Italy.
Chemosphere. 2023 Oct;338:139468. doi: 10.1016/j.chemosphere.2023.139468. Epub 2023 Jul 11.
The present study describes the microbial production of polyhydroxyalkanoates (PHA) from thermally pre-treated sewage sludge at pilot scale level, investigating for the first time the effect of the organic loading rate (OLR) under oxygen limitation on biomass storage properties and kinetics. Polymer characteristics have been also evaluated. The selection/enrichment of PHA-storing biomass was successfully achieved in a Sequencing Batch Reactor (SBR) under short hydraulic retention time (HRT; 2 days). Low OLR (2.05 g COD/L d) was ideal for the selection of an efficient PHA-producing consortium cultivated under limited oxygen availability. In the fed-batch accumulation conducted under high DO regime, such biomass was characterized by 51% of PHA content on cell dry weight, with a related storage yield (Y) of 0.61 COD/COD. On the contrary, medium OLR (4.56 g COD/L d) was not technically feasible to sustain the required consortium's selection under low DO regime. The PHA produced by biomass cultivated under low DO regime was characterized higher thermal stability and crystalline domain compared to PHA traditionally produced under high DO regime. The mass balance assessment highlighted a global yield of 51 g PHA/kg VS (volatile solids of thickened sludge), which was 9% lower than yield obtained under high DO regime, in the face of a realistic reduction of the energy cost of the process.
本研究描述了在中试规模下，利用热预处理污水污泥生产聚羟基烷酸酯（PHA）的情况，首次研究了在缺氧条件下有机负荷率（OLR）对生物量储存特性和动力学的影响。还评估了聚合物的特性。在短水力停留时间（HRT；2 天）下，在序批式反应器（SBR）中成功地实现了 PHA 储存生物量的选择/富集。低 OLR（2.05 g COD/L d）有利于在有限氧气供应下选择高效的 PHA 生产菌丛。在高 DO 条件下进行的分批进料积累中，这种生物量的细胞干重中 PHA 含量为 51%，相关储存产率（Y）为 0.61 COD/COD。相反，中 OLR（4.56 g COD/L d）在低 DO 条件下无法从技术上维持所需菌丛的选择。在低 DO 条件下培养的生物量产生的 PHA 与在高 DO 条件下传统生产的 PHA 相比，具有更高的热稳定性和结晶区。质量平衡评估突出了全球 51 g PHA/kg VS（浓缩污泥的挥发性固体）的产率，与高 DO 条件下的产率相比，降低了 9%，同时降低了工艺的能源成本。
