Reusability performance of green zinc oxide nanoparticles for photocatalysis of bathroom greywater

Abstract

Abstract This study aims to investigate the potential of green zinc oxide nanoparticles (ZnO NPs) in reusability performance for photocatalysis of bathroom greywater. It was found that ZnO NPs photocatalytic treatment of real bathroom greywater (RBGW) effluent reduces both the COD and BOD5 concentrations by 72.01, 62.75 and 57.79% (COD) and 70.18, 60.32 and 57.56% (BOD5) respectively for the first, second and third cycle. Meanwhile for the photocatalysis of ABGW, it was observed that COD and BOD5 were removed by 82.27, 68.27 and 60.96% (COD) and 82.91, 74.37 and 60.39% (BOD5) for the first, second and third cycle respectively. Besides, TSS and turbidity were reduced by 52.34, 46.85 and 37.98% (TSS) and 80.38, 67.65 and 56.81% (turbidity) respectively in RBGW and for ABGW, TSS and turbidity were reduced by 60.94, 52.37 and 41.95% (TSS) and 80.68, 72.63 and 69.91% (turbidity) for the first, second and third experimental run respectively. This designates that green ZnO NPs can be reused multiple times as an effective photocatalyst. However, ZnO NPs were used in the dispersed form, which causes difficulty in the separation of ZnO NPs from the greywater. Thus, further investigation in producing appropriate fixed film should be focused. Moreover, phytotoxicity analysis of V. radiate seeds in the treated ABGW and RBGW was not significantly different from their germination in water. This assured the less lethal nature of the degradation metabolites in greywater effluent. This investigation would be a solution to wastewater treatment plant for reusing photocatalyst in order to achieve the development of advanced and greener technologies.