Performance and mechanism of calcium peroxide reducing H2S production from sludge anaerobic fermentation

•0.25 g/g VSS CaO2 reduced by 80.5% of H2S production from anaerobic fermentation.•CaO2 addition destroyed sludge EPS structure and caused cell lysis.•The abundance and activity of S2− producers were reduced by CaO2 addition.•CaO2 addition promoted metal ions release and changed sulfur transformation.•Organic sulfur hydrolysis and inorganic sulfate reduction were inhibited.