Enhanced Biohydrogen Production by Accelerating the Hydrolysis of Macromolecular Components of Waste Activated Sludge Using TiO2 Photocatalysis as a Pretreatment

The effects of TiO2 photocatalysis on the hydrolysis of protein of waste activated sludge (WAS) and its biodegradability were investigated in this study. After 12-h UV irradiation, the removal ratio of protein by TiO2 photocatalysis reached 98.1%. The optimal condition for photocatalytic degradation of protein is TiO2 dosage of 5.0 mg·L under 2.4 w·m UV light irradiation. TiO2 photocatalysis in comparison with other pretreatments obviously accelerated the hydrolysis of WAS and improved the conversion of total COD (tCOD) to soluble COD (sCOD). The sCOD/tCOD ratio of WAS pretreated by TiO2 photocatalysis, UV photolysis and TiO2 adsorption and that of the control were 92.8%, 32.5%, 18.0% and 16.6%, respectively. TiO2 photocatalytic pretreatment accelerated the biohydrogen production from 10-fold diluted WAS. The bioreactors containing UV photolysis and TiO2 adsorption pretreated WASs and the control reactor require 0.5-d, 0.9-d and 0.7-d start-up period for biohydrogen production, respectively. While the bioreactor containing TiO2 photocatalysis pretreated WAS obtained a hydrogen yield of 0.5 mL-H2/g-VS merely after 0.5-d mesophilic fermentation. The cumulative biohydrogen production from TiO2 photocatalysis pretreated WAS during 4-d mesophilic fermentation reached 11.7 mL-H2/g-VS, which was 1.2 times higher than that from the control. TiO2 photocatalytic pretreatment enhanced the biohydrogen production from WAS via accelerating the hydrolysis of its macromolecular components to smaller molecule weight hydrolysates.