Juan Huang

Widespread application of dyes has led to severe threats to water environments, and advanced oxidation processes (AOPs) have been confirmed as an effective solution to dye degradation. Among them, ozonation was one of the most prevalent AOPs. In this study, the effects of using AOPs—mainly based on ozone (O₃)—to treat printing and dyeing wastewater (PDW) were compared. Firstly, ozone carrier active carbon fiber (ACF) was investigated for adsorption performance evaluation on pretreatment. The results showed that ACF treated by ultrasound performed best compared with ACF treated with other four pretreatment methods. Secondly, comparative studies based on individual O₃, ultraviolet (UV), and combined O₃/UV processes on PDW under different pH conditions were conducted. The decolorization rate of reactive brilliant blue X-BR dye under acidic conditions was higher than in alkaline and neutral dyes. In addition, with the utilization of single ozone and O₃/UV under pH = 4 conditions, the decolorization rate could be above 99%. However, individual UV caused few variations in wastewater chromaticity. Thirdly, the effects of pH, UV light intensity, hydraulic retention time (HRT), and ACF filling rate on the performance of the O₃/UV/ACF system were preliminarily screened using a saturated L9 orthogonal design. In terms of the results, the performance of the constructed O₃/UV/ACF AOP system was superior than the conventional oxidation method, in which HRT had the largest apparent main effect on decolorization, followed by pH, ACF filling rate, and UV light intensity. Among the factor levels examined, the best-performing combination was pH 4, a UV power of 48 W, an HRT of 3 h, and an ACF filling rate of 80%. In a subsequent single kinetic experiment conducted using this combination, the final decolorization efficiency was 92.14%, the COD removal was 60%, and the biodegradability increased by 63.08%. This study offered novel insights into an O₃-based AOP system for improving PDW treatment.

Microplastics (MPs) are pervasive in freshwater and may threaten aquatic ecosystem health. We surveyed surface waters of Shijiu Lake and its inflowing tributaries during the dry (January–March) and rainy (May–July) seasons of 2024. MP abundance ranged within 17.54–30.93 items/L, with higher values in the rainy than in the dry season (28.18 ± 6.03 vs. 24.53 ± 5.68 items/L; one-way ANOVA, p < 0.05). Abundance correlated positively with turbidity (r = 0.44; R² = 0.20; p < 0.05), whereas associations with total nitrogen, total phosphorus, and suspended solids were not significant (p > 0.05). Small particles (38–75 μm) dominated and were slightly more prevalent in the dry season, while the fraction of larger particles (>150 μm) was relatively higher in the rainy season. Granules predominated across sites, but their share decreased in the rainy season, accompanied by a notable increase in fibers. The Pollution Load Index (PLI) indicated slight but spatially uneven pollution (PLI = 1.00–1.43), generally higher during the rainy season and consistently elevated at the lake center; the Nongkan River exhibited the lowest levels. Ecologically, the patterns indicate rainfall-driven inputs and hydrodynamic controls (runoff, resuspension, residence time), identifying the lake center and tributary interfaces as priority zones for monitoring and mitigation. These results provide lake-scale evidence to refine seasonal monitoring and inform source-reduction strategies in similar inland waters.

The widespread occurrence of nano-plastics (NPs) in aquatic environments poses emerging challenges to the pollutant removal performance and ecological stability of constructed wetlands (CWs). This study investigates the performance of calcium-modified (Ca-MBF) and manganese-modified basalt fiber (Mn-MBF) bio-nests as novel substrates to mitigate NP-induced inhibition of CWs. Laboratory-scale CWs were operated for 180 days to evaluate substrate-associated enzyme activities, microbial community structure, and functional gene profiles. Results showed that Mn-MBF bio-nests enhanced the activities of dehydrogenase (DHA), urease (UR), ammonia monooxygenase (AMO), nitrite oxidoreductase (NOR), nitrate reductase (NAR), nitrite reductase (NIR), and phosphatase (PST) by 86.2%, 65.5%, 127.0%, 62.8%, 131.5%, 65.3%, and 107.0%, respectively, compared with the control. In contrast, Ca-MBF bio-nests increased these enzyme activities by 48.6%, 53.5%, 67.0%, 30.6%, 95.0%, 45.3%, and 54.6%, respectively. MBF bio-nests also enhanced microbial diversity, enriched denitrifying and phosphorus-removing bacteria (e.g., Thauera, Plasticicumulans), and promoted extracellular polymeric substance secretion. Functional gene prediction indicated elevated abundances of nitrogen cycle-related genes, thereby enhancing nitrification, denitrification, and phosphorus removal processes. These synergistic effects collectively improved nitrification, denitrification, and phosphorus removal efficiency, with Mn-MBF showing superior performance. This study highlights MBF bio-nests as a sustainable strategy to enhance the resilience and long-term operational stability of CWs in environments impacted by nano-plastic pollution.