Integrated UV photodegradation and anaerobic digestion of textile dye for efficient biogas production using zeolite

• UV/TiO2 pre-treatment improved biodegradability of high COD (5200 mg/l) methylene blue.
• Integrated AOP and anaerobic digestion (AD) achieved high COD, BOD and colour reductions.
• UV pre-treatment improved biogas generation by 2.7-fold and enhanced methane yield.
• AOP-AD system is more efficient than AD-AOP system treatment technique.

The efficiency of an integrated ultra-violet (UV) photocatalysis and anaerobic digestion (AD) system in the degradation of methylene blue (MB) dye was studied in up-flow fixed bed reactors. Zeolite was applied as support material for micro-organism and photocatalyst in the bioreactor and photoreactor, respectively. It was established that the application of either UV photodegradation or AD process as a single treatment method was not efficient in colour removal and chemical oxygen demand (COD) reduction. The AD process as a stand-alone process could only remove 32% of the colour and 57% COD while photodegradation as a stand-alone process had a good performance on colour removal (70%) but low COD removal efficiency (54%). However, integration of the two processes led to high COD, biochemical oxygen demand (BOD) and colour reduction efficiencies of above 75%. Results show that UV pre-treatment of MB before the AD step improved the biodegradability of the MB dye by 3-fold, this resulted in a 2.7-fold increase in biogas production as compared to a non-UV pre-treated MB.