Department of Environmental Science and Engineering, Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Fudan University, Shanghai 200438, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China.
Centre for Technology in Water and Wastewater (CTWW), School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia.
Water Res. 2022 Aug 1;221:118744. doi: 10.1016/j.watres.2022.118744. Epub 2022 Jun 14.
Waste activated sludge (WAS) contains high concentrations of microplastics (MPs), which could serve as vectors of various organic pollutants and heavy metals, causing synergistic transportation and pollution. The application of combined hydrothermal pretreatment (HTP) and anaerobic digestion (AD) has raised growing concerns since the low-temperature hydrothermal treatment could enhance the biogas production of WAS. However, the changes in physicochemical properties, adsorption performances, and effects on AD of MPs by HTP have not been studied. The study used three typical MPs in WAS, and it was found that the HTP (170°C & 30min) increased MPs' specific surface area and carbonyl index (CI) while decreasing the relative crystallinity. The adsorption capacity to Cd increased through the carbonylation for polyethylene microplastic (PE-MP) and polystyrene microplastic (PS-MP) while decreasing by the dechlorination for polyvinyl chloride microplastic (PVC-MP). Meanwhile, increased hydrophilicity reduced the adsorption capacities of all three typical MPs for ofloxacin. The above results indicated that the HTP could be worth blocking the adsorption of polar MPs for polar pollutants. For the pristine MPs, only PVC-MP at the highest concentration (0.5 g kg VS) significantly (p < 0.05) reduced methane production by 16.2 ± 3.3% of WAS without the HTP. However, the HTP resulted in significant (p < 0.05) inhibition of methane production of WAS at high concentrations of PE-MP and PVC-MP (e.g., 0.1 and 0.5 g kg VS), which was due to the acceleration of the released toxic plastic additives (dibutyl phthalate, dimethyl phthalate, and bisphenol-A). Microbial analysis showed the abundances of vital anaerobes, such as acid-producing bacteria (Acetoanerrobium and Mesotoga), proteolytic bacteria (Proteiniborus), and methanogens (Methanosaeta) clearly decreased with the PE-MP and PVC-MP after the HTP, which might result in the decreased methane production. The study provided deep-insight of MPs' behaviors during the combined HTP-AD process.
剩余活性污泥（WAS）中含有高浓度的微塑料（MPs），它们可能成为各种有机污染物和重金属的载体，导致协同传输和污染。低温水热处理可以提高 WAS 的沼气产量，因此，联合水热预处理（HTP）和厌氧消化（AD）的应用引起了越来越多的关注。然而，HTP 对 MPs 的物理化学性质、吸附性能以及对 AD 的影响尚未得到研究。本研究使用 WAS 中的三种典型 MPs，发现 170°C 和 30min 的 HTP 增加了 MPs 的比表面积和羰基指数（CI），同时降低了相对结晶度。碳酰化作用使聚乙烯微塑料（PE-MP）和聚苯乙烯微塑料（PS-MP）的吸附能力增加，而脱氯作用使聚氯乙烯微塑料（PVC-MP）的吸附能力降低。同时，亲水性的增加降低了所有三种典型 MPs 对氧氟沙星的吸附能力。上述结果表明，HTP 可以阻止极性 MPs 对极性污染物的吸附。对于原始 MPs，只有在未进行 HTP 的情况下，浓度最高（0.5 g kg VS）的 PVC-MP 才会显著（p < 0.05）降低 WAS 的甲烷产量 16.2±3.3%。然而，高浓度的 PE-MP 和 PVC-MP（例如 0.1 和 0.5 g kg VS）进行 HTP 后，会显著（p < 0.05）抑制 WAS 的甲烷产量，这是由于释放出的有毒塑料添加剂（邻苯二甲酸二丁酯、邻苯二甲酸二甲酯和双酚-A）的加速作用。微生物分析表明，产酸菌（Acetoanerrobium 和 Mesotoga）、蛋白水解菌（Proteiniborus）和产甲烷菌（Methanosaeta）等重要厌氧菌的丰度在 HTP 后明显随 PE-MP 和 PVC-MP 的添加而降低，这可能导致甲烷产量降低。本研究深入了解了 MPs 在联合 HTP-AD 过程中的行为。
