Environmental Biotechnology Group (EBiTG), Department of Civil Engineering, Indian Institute of Technology, Roorkee 247667, India.
Department of Environmental Science, Gurukul Kangri University, Haridwar, India.
Sci Total Environ. 2022 Jul 10;829:154621. doi: 10.1016/j.scitotenv.2022.154621. Epub 2022 Mar 17.
Thermal-chemical pre-treatment has proven to facilitate the solubilization of organics and improvement in biogas generation from the organic fraction of municipal solid waste (OFMSW). However, the production of recalcitrant is inevitable when OFMSW is pretreated at high temperatures and alkali dosage. This study develops a strategy to use Fe to reduce the formation of recalcitrant compounds, i.e., 5-HydroxyMethyl Furfural (5-HMF), furfurals, and humic acids (HA) during thermal-alkali pre-treatment. It was postulated that the formation of the recalcitrant compound during pre-treatment can be reduced by Fe dosing to oxidize intermediates of Maillard reactions. A decrease in 5-HMF (45-49%) and furfurals (54-66%) was observed during Fe (optimum dose: 10 mg/L) mediated thermal-alkali pre-treatment owing to the Lewis acid behavior of FeCl. The Fe mediated assays show a substantial improvement in VS removal (28%) and biogas yield, i.e., 31% (292 mL/gVS) in 150 °C + 3 g/L NaOH, 34% (316 mL/gVS) in 175 °C + 3 g/L NaOH, and 36% (205 mL/gVS) in 200 °C + 3 g/L NaOH assays, over their respective controls (no Fe dosing). The reducing property of Fe rendered a low ORP (-345 mV) in the system than control, which is beneficial to the anaerobic microbiome. Electrical conductivity (EC) also shows a three-fold increase in Fe mediated assays over control, promoting direct interspecies electron transfer (DIET) amongst microbes involved in the electrical syntrophy. The score plot and loading plots from principal component analysis (PCA) showed that the results obtained by supplementing 10 mg/L Fe at 150, 175, and 200 °C were significantly different. The correlation of the operational parameters was also mutually correlated. This work provides a techno-economically and environmentally feasible option to mitigate the formation of recalcitrant compounds and enhance biogas production in downstream AD by improving the degradability of pretreated substrate.
热化学预处理已被证明可以促进有机物的溶解，并提高城市固体废物有机部分（OFMSW）的沼气生成。然而，当 OFMSW 在高温和高碱剂量下预处理时，不可避免地会产生难降解物质。本研究开发了一种策略，即在热碱预处理过程中使用 Fe 还原 5-羟甲基糠醛（5-HMF）、糠醛和腐殖酸（HA）等难降解化合物的形成。据推测，通过 Fe 投加氧化美拉德反应中间体，可以减少预处理过程中难降解化合物的形成。在 Fe（最佳剂量：10mg/L）介导的热碱预处理过程中，观察到 5-HMF（45-49%）和糠醛（54-66%）的减少，这是由于 FeCl 的路易斯酸行为。Fe 介导的试验表明，VS 去除率（28%）和沼气产量有了显著提高，即在 150°C+3g/LNaOH 条件下，沼气产量为 31%（292mL/gVS），在 175°C+3g/LNaOH 条件下，沼气产量为 34%（316mL/gVS），在 200°C+3g/LNaOH 条件下，沼气产量为 36%（205mL/gVS），分别比各自的对照组（无 Fe 投加）高。Fe 的还原性能使系统中的 ORP（-345mV）低于对照组，有利于厌氧微生物群落。与对照组相比，Fe 介导的试验中电导率（EC）也增加了三倍，促进了参与电共生的微生物之间的直接种间电子转移（DIET）。主成分分析（PCA）的得分图和加载图显示，在 150°C、175°C 和 200°C 补充 10mg/LFe 时，得到的结果有显著差异。操作参数的相关性也相互关联。这项工作提供了一种在技术、经济和环境上可行的选择，通过提高预处理底物的可降解性，减轻难降解化合物的形成并提高下游 AD 中的沼气产量。
