Landfill leachate as an additional substance in the Johannesburg-Sulfur autotrophic denitrification system in the treatment of municipal wastewater with low strength and low COD/TN ratio

[Display omitted] •Municipal wastewater and leachate were effectively treated in JHB-SAD system.•Protein-like materials were effectively removed in JHB-SAD system.•Influent characteristics affected the diversity of bacterial communities.•Relationships between the environment and dominant genera were found by PCoA. Johannesburg-Sulfur autotrophic denitrification (JHB-SAD) system was investigated for the combined treatment of leachate and municipal wastewater with low strength and low COD/TN ratio. The average removal efficiencies for chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were 85.2%, 96.2% and 75.8%, respectively. The municipal wastewater and leachate (dosing of 2.1‰, v/v) can be treated via the JHB-SAD system to achieve efficient nutrients removal. The mass balance calculations suggested that 58.1–69.8% TN was removed in JHB unit and 32.9–41.2% TN in SAD unit. Further, the denitrifying phosphorus removal process occurred in the anoxic zone. EEM-PARAFAC analysis found that the protein-like materials were more efficiently removed than fulvic-like materials in JHB-SAD system. The tryptophan-like materials had the most positive linear relationship with the COD concentrations. The bacterial community was difference between JHB and SAD unit. Furthermore, bacteria abundance relating to nitrogen removal increased with additional leachate.