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Abstract Background The composition of anaerobically digested sludge is inherently complex, enriched with structurally complex organic compounds and nitrogenous constituents, which are refractory to biodegradation. These characteristics limit the subsequent rational utilization of resources from anaerobically digested sludge. White-rot fungi (WRF) have garnered significant research interest due to their exceptional capacity to degrade complex and recalcitrant organic pollutants. However, the exploration of WRF in the context of sludge treatment remains an under-investigated area within the scientific community. The present investigation explores the application of WRF in the treatment of anaerobically digested sludge, offering a novel approach for the valorization of sludge resources. Results In this study, WRF enzymes, manganese peroxidase (MnP) and lignin peroxidase (LiP), exhibited sustained high activities of approximately 102 U/L and 26 U/L, respectively, within the anaerobically digested sludge under a controlled pH of 5.5 within the growth system. These conditions were found to significantly enhance the treatment efficacy of the anaerobic sludge. The removal of soluble chemical oxygen demand (COD) and Total COD by Trametes versicolor powder was better than that of Phanerochaete chrysosporium powder. The treatment of sludge samples with WRF, specifically Phanerochaete chrysosporium powder, resulted in a significant reduction of ultraviolet radiation (UV254). Fourier-transform infrared spectroscopy (FTIR) analysis revealed that the application of Trametes versicolor powder exerted a notably pronounced impact on the functional groups present in sludge samples. Specifically, there was a significant decrease in the peak intensities corresponding to the C-O bonds, indicative of saccharide degradation, alongside an observable increase in the intensities of amide peaks, which is suggestive of protein synthesis enhancement. Microbial community analysis demonstrated that Phanerochaete chrysosporium was the predominant fungal species, exerting a significant regulatory role within the sludge ecosystem. Conclusion In conclusion, this research furnishes a robust scientific foundation for the utilization of WRF in the treatment of anaerobic digestion sludge. It elucidates the fungi’s capacity to ameliorate the physicochemical attributes and microbial community composition within the sludge. Furthermore, the study offers a certain reference for the subsequent use of WRF in the treatment of other types of sludge.

Hydrogen production from mixed microalgae biomass, predominantly containing Scendesmus and chlorella species, was investigated with a focus on enhancement strategies, in particular (i) pH control (at 5.5) and (ii) methanogenic inhibitor (BESA) addition along with pH control at 5.5. The results obtained showed that the later condition remarkably increased the performances. This was mainly ascribed to the occurrence of a suitable environment for the hydrogen producers to perform actively. Hydrogen production under these conditions (i.e., both pH 5.5 and pH5.5+BESA) was significantly higher than that of the control experiment. Using the pH control at 5.5 and BESA addition, peak hydrogen production rate (HPR) and hydrogen yield (HY) were attained as 210 mL/L/d and 29.5 mL/g VSadded, respectively. This improvement was nearly 3-folds higher compared with the control experiment with an HPR of 62 mL/L/d and an HY of 9.5 mL/g VSadded.

To investigate the influence of lipid concentration (of total solids, w/w) on anaerobic treatment of food waste under thermophilic condition, a siphon-driven self-agitated anaerobic reactor was operated for 220 days. The average lipid concentration was changed from 12.8% to 59.3% (w/w) step by step. The gas production rate increased from 1.97 to 2.31 L/L/d with lipid concentration increased from 12.8% to 19.7% (w/w), whereas decreased sharply to 0.78 L/L/d when the concentration further increased to 59.3% (w/w). The COD recovery from output at different lipid concentration was analyzed in this study. With the concentration increased from 12.8% to 59.3% (w/w), the percentage of COD recovered as methane gas decreased from 80.9% to 35.4%, while the percentage of COD remained in the effluent was also decreased significantly from 15.5% to 2.60%. The lipid concentration under 40% (w/w) was recommended in the co-digestion of food waste and grease trap waste. Keywords: Siphon-driven self-agitated anaerobic reactor (SDSAR), Lipid concentration, Thermophilic, Co-digestion, Methane