Alleviating the membrane fouling potential of the denitrification filter effluent by regulating the COD/N ratio and carbon source in the process of wastewater reclamation

•Higher COD/N ratio in DNF operation led to more aggravated membrane fouling.•Fouling of DNF effluent: glucose > methanol > ethanol > sodium acetate-fed HOA and HON fractions in DNF effluent dominated subsequent UF membrane fouling.•DNF operation could alleviate UF fouling by regulating external carbon addition.•DNF-UF process should be optimized as an integrated system rather than separate units.