TiO2-biochar composites as alternative photocatalyst for stormwater disinfection

Abstract

Presence of bacteria/pathogens in urban stormwater constrains its safe reuse and highlights disinfection as essential for its reclamation. The novelty of this study is the preparation of a series of TiO2-biochar composites, which are easily separable from water, with different mass ratio values and testing for bacteria removal in stormwater as an effective disinfection approach. Although TiO2-biochar composites have been investigated in the past, most of the past studies have focused on organic pollutant degradation/removal in wastewater. TiO2-biochar composite application for stormwater treatment is limited, particularly for stormwater disinfection, to ensure safe reuse. In this study, the photocatalytic activity of the composites was tested using transient species scavenging experiments. Hydroxyl radicals (•OH) and electron deficiencies (h+) were found to be the key species promoting photocatalytic disinfection with h+ being identified as exerting the most significant influence on the process. Composites prepared using biochar produced at 500 °C and TiO2/biochar ratio values 1:4 and 1:2 (labeled 500–1:4 and 500–1:2, respectively) showed the best inactivation performance for synthetic (99.2% and 99.4%, respectively) and real stormwater (99.4% and 99.3%, respectively) as well as low bacteria reactivation (51.7% and 54.1%, respectively) after seven days of dark storage. Furthermore, 500–1:4 and 500–1:2 exhibited good durability, showing high disinfection (> 90%) and recovery efficiency (70%–80%) after eleven cycles. The results of this study suggest TiO2-biochar composites as very attractive for effective stormwater disinfection.