Enhancing Anaerobic Digestion of Pharmaceutical Industries Wastewater with the Composite Addition of Zero Valent Iron (ZVI) and Granular Activated Carbon (GAC)

Abstract

Anaerobic digestion of pharmaceutical wastewater is challenged by its contained toxic compounds which limits the stability and efficiency of methane production and organic degradation. In this study, zero valent iron (ZVI) and granular activated carbon (GAC) were added with different strategies to improve anaerobic digestion of pharmaceutical wastewater. The results confirmed a synergy effect of ZVI+GAC for both COD removal (increased by 13.4%) and methane production (increased by 11.0%). Furthermore, ZVI+GAC improved the removal of pharmaceutical intermediates, in particular, dehydroepiandrosterone (DHEA) degradation increased by 69.52%, leading to a significant reduction of biotoxicity by 88.43%. The promoted results were attributed to the establishment of direct interspecies electron transfer (DIET). Microbial community analysis revealed that ZVI+GAC could increase the bacterial richness index and archaeal diversity index. The relative abundance of acetotrophic methanogens decreased but hydrogenotrophic and methylotrophic methanogens increased, which broadening the pathway of methane production.

Keywords: anaerobic digestion, zero valent iron, granular activated carbon, degradation mechanisms, pharmaceutical wastewater