Effect of TiO₂ nanoparticles on UASB biomass activity and dewatered sludge

The accumulation of the nanowastes in the wastewater treatment plants has raised several concerns; therefore, it is an utmost priority to study the nanoparticle (NP) toxicity in such systems. In this work, the effect of TiO₂ NPs on up-flow anaerobic sludge blanket (UASB) microflora and their photocatalytic effect on dewatered sludge were studied. We observed 99.98% removal of TiO₂ NPs by sludge biomass within 24 h, though negligible toxicity was found up to 100 mg/L TiO₂ concentration on extracellular polymeric substances (EPS), volatile fatty acid and biogas generation. The low toxicity corresponds to the agglomeration of TiO₂ NPs in UASB sludge. Alterations in dewatered sludge biochemical composition and increase in cell damage were observed upon exposure to sunlight as evidenced by FTIR and fluorescent microscopy, respectively. Results suggest the negligible toxicity of TiO₂ NPs on UASB biomass activity; however, once exposed to open environment and sunlight, they may exert detrimental effects.