Photocatalytic degradation of waste activated sludge using a circulating bed photocatalytic reactor for improving biohydrogen production

In this study, a sloping trough circulating bed photocatalytic reactor (STCBPR) was developed to degrade waste activated sludge (WAS). Effects of the four factors (shape of trough, circulating speed, TiO2 dosage and dilution multiple of WAS) on the photocatalytic degradation of WAS were examined. Under the optimum conditions, 45% of the chemical oxygen demand (COD) removal and 47% of the volatile solids (VS) removal were achieved in 7.5-fold dilution after reaction for 8 h. Moreover, the WAS was pretreated by STCBPR and then fermented to produce hydrogen. The result showed that the cumulative hydrogen production from photocatalysis pretreated WAS was 3.6 times higher than that from UV-light pretreated WAS, and 17 times higher than that from raw WAS. Therefore, it could be confirmed that the STCBPR has higher photocatalytic degradation efficiency for WAS, and photocatalytic pretreatment could enhance the biohydrogen production.