The occurrence of titanium dioxide nanoparticle (TNP), an emerging contaminant, in Taihu Lake of China was investigated. Ti was present at a concentration of 224 ± 59 μg/L in the water samples collected from a water source in east Taihu Lake. Approximately 0.19% of the Ti-containing matter was at the nano-scale. Scanning Electron Microscope analysis verified the existence of Ti-containing components, such as TiOx and FeTiOx. Furthermore, Ti K-edge X-ray absorption near-edge structure spectroscopy was used to detect the phase composition of nano-scaled Ti-containing matter. The spectra showed the three characteristic peaks of TiO₂ in the samples, suggesting the occurrence of TNP in Taihu Lake. A least-squares linear combination fitting analysis indicated that the TNP concentration in the water source was ~0.77 μg/L in water and ~0.85 μg/g-dry in sediment. The removal performance of the TNP at a full-scale conventional drinking water treatment plant indicated that ~61% of TNP was removed via coagulation/sediment, sand filtration, and disinfection/clear water reservoir. The coagulation/sediment process accounted for approximately 70% of the total removed TNP. The finished water contained ~ 0.30 μg/L TNP. This study is the first that reported the presence and transport of TNP in a full-scale drinking water treatment system.

The occurrence of cyanobacteria in freshwater systems can negatively impact drinking water resources by affecting esthetics, taste, creating odor, and/or causing health concerns due to the release of toxins. To understand and predict cyanobacteria growth, monitoring programs for drinking water reservoirs include the measurement of physical and chemical water quality parameters known to influence cyanobacteria growth. This study was authored to elucidate the factors governing cyanobacteria growth for data captured from a monitoring program implemented from 2011 to 2016 in a raw water reservoir in Waterloo, Ontario, Canada. Total phosphorus (TP), dissolved inorganic nitrogen (DIN), phycocyanin levels (a proxy for cyanobacteria cell counts), and turbidity are the key parameters assessed. Phycocyanin relative fluorescence units (PC- RFU ≥ 1.5) were used as an indicator of elevated growth periods to help predict the onset of elevated growth. The TP concentration during baseline growth (0.029 mg/L, ρ < 0.05) was significantly different from that observed during elevated growth (0.074 mg/L), suggesting TP was involved in promoting growth. Pearson’s correlation coefficient analysis indicated that PC-RFU had a statistically significant, positive and moderately strong relationship with TP: r(84) = 0.56, ρ < 0.01, and turbidity: r(84) = 0.60, ρ < 0.01 suggesting a link between nutrients and elevated growth. This information is useful for implementing future cyanobacteria growth mitigation strategies in raw water reservoirs.