Impact of alkali and heat pretreatment on the pathway of hydrogen production from sewage sludge

Due to the presence of various types of hydrogen-producing bacteria and numerous organics such as protein and carbohydrate, sewage sludge is a potential material for biological hydrogen production. In this study, two batch tests were carried out to investigate the impact of alkali and heat pretreatment on the pathway of hydrogen production from sewage sludge. The results showed that the heat treatment had a stronger lethal effect on bacteria than the alkali treatment, and could effectively kill hydrogen-consuming bacteria. The heat treatment was more suitable for enriching acidophilic hydrogen-producing bacteria, while the alkali treatment was more suitable for enriching basophilic hydrogen-producing bacteria. A maximum hydrogen production of 10.32 mL/g-COD from alkali pretreated sludge was obtained at an initial pH of 11; while a maximum hydrogen production of 8.94 mL/g-COD from heat pretreated sludge was obtained at an initial pH of 5. Hydrogen production in alkali conditions (pH>9) from alkali pretreated sludge mainly depended on the fermentation of protein by protein-utilizing bacteria; whereas hydrogen production in acidic conditions (pH<6) from heat pretreated sludge mainly depended on the fermentation of carbohydrate by glucose-utilizing bacteria.