W.P.F. Barber

Anaerobic digestion is one of the effective technologies for the treatment and recycling of waste activated sludge (WAS). Nonetheless, hindered by the hydrolysis phase of WAS, the actual methane yield falls far below the theoretical value. To overcome this issue, various pretreatment methods have been employed before the anaerobic digestion of WAS [1], [2], [3].

Section snippets Source and pre-treatment of sewage sludge The sewage sludge was taken from the thickening tank of a city sewage treatment plant in Xi'an, China. The sludge indicators were as follows: VSS 18.55 ± 0.97 g/L, TSS 23.20 ± 2.33 g/L, free amino acids 0.01 ± 0.0002 mmol/L, peptides 24.56 ± 1.75 mg/L, polysaccharides 10.57 ± 0.84 mg/L, protein 80.54 ± 0.83 mg/L and free sulfhydryl groups 0.04 ± 0.0005 µg/L in the sludge supernatant.