Effect of recirculated-inoculation and straw supplement on biogas production of municipal sludge

Anaerobic fermentation of sludge was studied under different inoculation and straw content,as well as the changes of sludge properties before and after anaerobic fermentation.The biogas production efficiency of sludge with 10%(volume ratio,the same below) biogas slurry inoculation reflux(C/N was6.16) was better than that with 20%(C/N was 5.99); the biogas production efficiency of sludge was improved by adding straw.Biogas production of sludge with 20% biogas slurry(1 600 m L sludge) and20 g straw(C/N was 7.53) was 783 m L more than that with 20% biogas slurry and 15 g straw(C/N was 7.15),C/N of sludge with 10% biogas slurry and 15 g straw was 7.94 which was the highest,and its total gas production and methane volume percentage were also higher than others.Meanwhile,the physicochemical properties of sludge was changed through anaerobic fermentation,the organic matter(does not include straw) of sludge reduced 2.4%(mass ratio) on average after anaerobic fermentation.