In this study, a laboratory-scale hybrid biofilm reactor (HBR) was constructed to treat food wastewater (FWW) before it is discharged into the sewer. The chemical oxygen demand (COD) of 29 860 mg L⁻¹ in FWW was degraded to 200–350 mg L⁻¹ using the HBR under the operating parameters of COD load 1.68 kg m⁻³ d⁻¹, hydraulic retention time (HRT) of 426.63 h, dissolved oxygen (DO) of 8–9 mg L⁻¹, and temperature of 22–23 °C. The biomass of biofilm on the surface of filler was 2.64 g L⁻¹ for column A and 0.91 g L⁻¹ for column O. Microbial analysis revealed richer and more diverse microorganisms in filler biofilms compared to those in suspended sludge. The hybrid filler was conducive to the development of functional microbial species, including phyla Firmicutes, Actinobacteriota, and Chloroflexi, and genus level norank_f_JG30-KF-CM45, which will improve FWW treatment efficiency. Moreover, the microorganisms on the filler biofilm had more connections and relationships than those in the suspended sludge. The combination of an up-flow anaerobic sludge bed (UASB) and HBR was demonstrated to be an economical strategy for practical applications as a shorter HRT of 118.34 h could be obtained. Overall, this study provides reliable data and a theoretical basis for the application of HBR and FWW treatments.

The differentiated responses of biological groups to environmental change are central to river ecosystem management; however, the shared and distinct environmental selection processes that shape their spatial patterns remain understudied. We investigated two adjacent rivers with contrasting environmental conditions and applied eDNA metabarcoding to characterize the eukaryotic plankton and fish communities. The alpha diversity showed no significant river-to-river difference for either group, but beta diversity differed strongly, indicating high spatial turnover. Both groups exhibited distance–decay relationships, which were stronger in plankton, whose community assembly was mainly stochastic; in contrast, fish assembly was predominantly deterministic. Community variation in both groups was significantly associated with physical and chemical factors—electrical conductivity (EC), the potential of hydrogen (pH), water temperature (WT), dissolved oxygen (DO), chemical oxygen demand (COD), and biochemical oxygen demand (BOD5)—while plankton also responded to nutrient variables, including total phosphorus (TP), total nitrogen (TN), and ammonium nitrogen (NH4-N). Collectively, our results emphasize differential environmental selection across biological groups and provide a basis for designing targeted river restoration and water quality improvement strategies.

Rural greywater management is a critical global challenge due to the lack of centralized treatment in dispersed communities. This study aimed to characterize the pollution characteristics and bacterial community structure of samples from four greywater collection tanks in eastern China using high-throughput sequencing and absolute quantification of the 16S rRNA gene. Pollution characteristics showed spatial heterogeneity: chemical oxygen demand ranged from 19.8 to 272.5 mg/L, total nitrogen from 8.6 to 16.4 mg/L, and dissolved oxygen from 1.3 to 5.3 mg/L. Dissolved greenhouse gases also varied, with N₂O reaching 103.6 ppmv and CH₄ up to 50.4 ppmv. Based on the estimated absolute abundance of 16S rRNA gene copies, we found that the bacterial communities were dominated by Pseudomonadota, Actinomycetota, Bacteroidota, and Bacillota. Key genera such as Acinetobacter, Pseudomonas, and unclassified Enterobacteriaceae were positively correlated with nitrate, suggesting their potential association with denitrification and potential N₂O production. The methanotrophic genus Methyloparacoccus was enriched in a tank with high dissolved organic carbon. Co-occurrence network analysis revealed that core taxa like unclassified Paracoccaceae and Limnohabitans function as module hubs, maintaining community stability. These findings reveal associations between bacterial taxa, pollutant transformation, and greenhouse gas emissions in rural greywater and provide fundamental insights to support the development of low-carbon, resource-oriented treatment technologies.

Ecological water replenishment is crucial for alleviating ecological degradation of lakes in cold and arid areas. However, especially if high-nitrogen water is used as a water source for replenishment, the water volume in lakes effectively increases, resulting in new environmental pressures, posing potential threats to aquatic ecosystems. Clarifying the response characteristics of plankton communities to high nitrogen replenishment is crucial for lake management. Under high nitrogen replenishment conditions, we focused on the ecological niche characteristics (including niche width and niche overlap), interspecies relationships and interaction networks of dominant phytoplankton and zooplankton species in Ulansuhai Lake in Inner Mongolia, with the aim of exploring the potential associations and response patterns of the plankton community. The results indicated that under high nitrogen replenishment conditions, the structure of plankton communities generally remained stable, with no significant fluctuations in species composition, density, biomass, or diversity indices. The niche width values of the dominant species were mostly above 0.6, suggesting that these species adopted niche-broadening strategies to enhance their environmental adaptability. Within the phytoplankton community, species exhibited a significant positive correlation, reflecting strong co-occurrence and niche differentiation. In contrast, interspecific relationships among zooplankton were not significant, reflecting asynchronous dynamics and different developmental trends under fluctuating environments. Co-occurrence network analysis further indicates that both phytoplankton and zooplankton form complex networks characterized by a high degree of modularity. Nevertheless, the phytoplankton and zooplankton networks in 2024 exhibited a reduction in size, an increase in negative cohesion (indicating heightened competition), and a decline in network robustness compared to 2023. The findings of this study provide a theoretical basis for the scientific implementation of ecological water replenishment and ecosystem management in cold and arid lakes under high-nitrogen conditions.