Formation of biofilms from new pipelines at both ends of the drinking water distribution system and comparison of disinfection by-products formation potential.

The gradual updating of the water supply network is one of the crucial ways to ensure the safety of drinking water all over the world. The phenomenon and regularity of the biological risk and chemical risk of biofilms of the new pipes in drinking water distribution system (DWDS) is inadequate researched by now. In order to explore the biochemical risks of biofilms after new pipes are used, this paper studied the growth of biofilms, the content of disinfection by-products (DBPs) and the potential for disinfection by-products (DBPsFP) after 2-year use by establishing a pilot test platform at both ends of the DWDS in City S. The results showed that the total bacterial count in new pipelines was between 1.38 × 108-9.97 × 108/cm2; the DBPsFP at the front end and at the back end was subtly different. The overall DBPsFP of biofilms was the highest, followed by the ductile cast iron pipe and the galvanized pipe whereas the stainless steel pipe was the lowest. The HPC content of the 2-year-old pipe (1.68 × 105-7.09 × 106 CFU/cm2) was remarkably higher than that of the 1-year-old pipe (1.04 × 105-8.76 × 105 CFU/cm2), and the generation DBPsFP was about 50% higher. When a new pipeline was put into use in the urban drinking water distribution system, biofilms with certain biological hazards and risks of DBPs disinfection by-products would form in a short period of time.

Photocatalytic performance of TiO2 catalysts modified by H3PW12O40, ZrO2 and CeO2.

The binary composite photo-catalysts CeO2/TiO2, ZrO2/TiO2 and the ternary composite photo-catalysts H3PW12O40-CeO2/TiO2, H3PW12O40-ZrO2/TiO2 were prepared by sol-gel method. The catalysts were characterized by thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photocatalytic elimination of methanol was used as model reaction to evaluate the photocatalytic activity of the composite catalysts under ultraviolet light irradiation. The effects of doped content, activation temperature, time, initial concentration of methanol and gas flow rate on the catalytic activity were investigated. The results showed that after doping a certain amount of CeO2 and ZrO2, crystallization process of TiO2 was restrained, particles of catalysts are smaller and more uniform. Doping ZrO2 not only significantly improved the catalytic activity, but also increased thermal stability. Doping H3PW12O40 also enhanced the catalytic activity. The catalytic activities of binary and ternary composite photocatalysts were significantly higher than un-doped TiO2. The dynamics law of photocatalytic reaction over the binary CeO2/TiO2 and ZrO2/TiO2 catalysts has been studied. The activation energy 15.627 and 15.631 kJ/mol and pre-exponential factors 0.5176 and 0.9899 s(-1) over each corresponding catalyst were obtained. This reaction accords to the first order dynamics law.

The spatial distribution of pollutants in pipe-scale of large-diameter pipelines in a drinking water distribution system.

In large-diameter drinking water pipelines, spatial differences in hydraulic and physiochemical conditions may also result in spatial variations in pipe corrosion, biofilm growth and pollutant accumulation. In this article, the spatial distributions of various metals and organic contaminants in two 19-year-old grey cast iron pipes which had an internal diameter of 600mm (DN600), were investigated and analyzed by Atomic Absorption Spectrometry, Gas Chromatography-Mass Spectrometry, Energy Dispersive Spectrometer, X-ray Diffraction, etc. The spatial distribution of heavy metals varied significantly across the pipe section, and iron, manganese, lead, copper, and chromium were highest in concentration in the upper portion pipe-scales. However, the highest aluminum and zinc content was detected in the lower portion pipe-scales. Apart from some common types of hydrocarbons formed by microbial metabolites, there were also some microalgae metabolites and exogenous contaminants accumulated in pipe-scale, which also exhibited high diversity between different spatial locations. The spatial distributions of the physical and chemical properties of pipe-scale and contaminants were quite different in large-diameter pipes. The finding put forward higher requirements on the research method about drinking water distribution system chemical safety. And the scientific community need understand trend and dynamics of drinking water pipe systems better.