Department of Chemical and Environmental Engineering, University of Oviedo, c/Julián Clavería 8, 33006, Oviedo, Asturias, Spain.
Department of Chemical and Environmental Engineering, University of Oviedo, c/Julián Clavería 8, 33006, Oviedo, Asturias, Spain.
J Environ Manage. 2024 Jul;363:121315. doi: 10.1016/j.jenvman.2024.121315. Epub 2024 Jun 7.
The rising generation of waste activated sludge (WAS) demands a fundamental shift towards resource reuse and recovery. The conventional methodologies used to manage this by-product derived from wastewater treatment plants are increasingly constrained due to stringent regulatory measures aimed at mitigating its adverse impacts on the environment and public health. Therefore, this work evaluated a promising strategy for the efficient management of WAS, transforming it into a valuable renewable source to produce high-value-added compounds, such as lipids and a slow-release fertilizer (struvite). Wet oxidation (WO) was identified as a suitable technique for solubilising WAS while generating short-chain fatty acids (primarily acetic acid). It was found that conducting WO at 200 °C for 120 min resulted in a 65% reduction of the total suspended solids (TSS) content and 87% of the volatile suspended solids (VSS) content. Additionally, under these conditions, 4440 ± 105 mg/L and 593 ± 21 mg/L of acetic and propionic acid were obtained, respectively, which were assimilated by Yarrowia lipolytica to produce biolipids. Furthermore, the rupture of WAS flocs also led to the solubilisation of 980 ± 8 mg/L of ammonium. During the struvite precipitation stage, a NH:PO:Mg ratio of 1:1.5:1.5 was found to be the most effective for removing soluble ammonium (97.4 ± 0.8%), resulting in a high-purity struvite formation, and enhancing the carbon/nitrogen (C/N) ratio of the oxidised WAS from 3 to 105. This improvement in the C/N ratio raised the lipid content from 36 ± 1% to 49 ± 1% during the cultivation of Y. lipolytica. The application of the sequencing batch culture strategy further increased lipid content to 59 ± 1%, with 6.0 ± 0.3 g/L as the final concentration after the fifth cycle. The lipids produced, mainly monounsaturated fatty acids with 40% of oleic acid, offer potential as biodiesel feedstock. This lipid composition led to biodiesel properties, including cetane number, iodine value, kinematic viscosity and density that met international standards. Therefore, this research presents a promising alternative not only for WAS management but also for harnessing valuable resources, thereby establishing a basis for large-scale studies.
不断增长的废活性污泥（WAS）代际需求，需要向资源再利用和回收方向进行根本性转变。由于旨在减轻其对环境和公共健康负面影响的严格监管措施，传统的污水处理厂副产物管理方法越来越受到限制。因此，本工作评估了一种高效管理 WAS 的有前景的策略，将其转化为有价值的可再生资源，以生产高附加值化合物，如脂质和缓释肥料（鸟粪石）。湿式氧化（WO）被确定为一种合适的技术，可以在产生短链脂肪酸（主要是乙酸）的同时溶解 WAS。结果发现，在 200°C 下进行 120 分钟的 WO 处理，可使总悬浮固体（TSS）含量降低 65%，挥发性悬浮固体（VSS）含量降低 87%。此外，在这些条件下，分别获得了 4440±105mg/L 和 593±21mg/L 的乙酸和丙酸，这些酸被 Yarrowia lipolytica 吸收以生产生物脂质。此外，WAS 絮体的破裂还导致 980±8mg/L 的铵溶解。在鸟粪石沉淀阶段，发现 NH:PO:Mg 比为 1:1.5:1.5 时最有效地去除可溶性铵（97.4±0.8%），形成高纯度的鸟粪石，并将氧化 WAS 的碳/氮（C/N）比从 3 提高到 105。C/N 比的这种提高使 Yarrowia lipolytica 培养过程中的脂质含量从 36±1%提高到 49±1%。应用序批式培养策略进一步将脂质含量提高到 59±1%，第五周期后最终浓度为 6.0±0.3g/L。所生产的脂质主要为单不饱和脂肪酸，其中油酸含量为 40%，可用作生物柴油原料。这种脂质组成导致生物柴油的特性，包括十六烷值、碘值、运动粘度和密度，符合国际标准。因此，本研究不仅为 WAS 管理提供了有前途的替代方案，也为利用有价值的资源提供了一种途径，从而为大规模研究奠定了基础。
