Journal of Water Supply Research and Technology-aqua 

Abstract: Granular ferric hydroxide (GFH) is an adsorbent, developed for arsenic removal from natural water. It can be applied in simple fixed bed reactors, similar to those for activated alumina or activated carbon. GFH has a high adsorption capacity in model systems and in natural waters. The application of GFH in test adsorbers showed a high treatment capacity of 30 000–40 000 bed volumes, until the new German and WHO drinking water standard for arsenic of 10 μg/L was exceeded. The residue of this technique is a solid waste, enriched with arsenic. The typical residual mass is in the range of 5–25 g/m 3 treated water. This new technique for arsenic removal provides a simple and effective method, particularly for small water facilities.

Abstract: Nanocomposites of silica incorporated with carbon nanotubes (silica/CNT) and activated carbon (silica/AC) were synthesized and characterized by scanning electron microscopy (SEM), element mapping, energy dispersive X-ray spectroscopy (EDX), thermogravimetric analyzer (TGA) and Fourier transform infrared spectroscopy (FTIR). Silica/CNT and silica/AC were investigated for efficient removal of mercury ions from aqueous solutions. The adsorbents have been analyzed on the basis of adsorption capacity, reusability, and their application in packed columns. The effects of experimental parameters, like pH, contact time and initial concentrations on the adsorption of mercury ions, were optimized. The kinetic data for the adsorption process obeyed a pseudo-second-order kinetic model with R2 of 0.999. Fitting the data to an intraparticle diffusion model indicated that surface adsorption and intraparticle diffusion were concurrently operating. In addition, this study used the Langmuir, Freundlich and Temkin isotherms to describe the behaviour of equilibrium adsorption. The equilibrium adsorption of the studied mercury ions is best fitted using the Freundlich isotherm, with silica/CNT of higher capacity than silica/AC. The silica/CNT showed better performance than silica/AC indicating silica/CNT has better efficiency.

Abstract: Dissolved organic nitrogen (DON) is an issue for the water field primarily due to the formation of disinfection by-products of health concern, and its potential role in membrane fouling. This article reviews the following DON issues: (1) analytical measurement, (2) occurrence, (3) structural composition, and (4) treatability during potable water treatment. There is no direct measurement for DON, rather DON is calculated by the difference between total dissolved nitrogen and inorganic nitrogen ions. DON concentrations range from 10 mg N/l with a median value of ∼0.3 mg N/l in surface waters. DON sources include wastewater discharges, agricultural fertilizers, algae, forest litter and soils. DON is comprised of a broad spectrum of molecular weight compounds encompassing multiple N-containing functional groups. Carbon to nitrogen ratios (C/N or DOC/DON) range between 5 and 100 mg C/mg N (median ∼15 mg C/mg N), and may be a good indicator of organic matter sources. During chlorination higher org-N content leads to (1) increasing chlorine demand, (2) production of di-HAA>tri-HAA, (3) production of HAA>THM, and (4) production of higher levels for halogenated (nitromethanes, HANs) and non-halogenated (NDMA) org-N DBPs. Information on DON removal during potable water treatment is lacking and should be a focus of future research.

Abstract: Perfluorinated compounds such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are emerging environmental pollutants. From the available literature, tap and surface water samples in several countries were found to be contaminated with PFOS and PFOA. These compounds were detected globally in the tissues of fish, bird and marine mammals, but their concentrations in animals from relatively more industrialized areas were greater than those from the less populated and remote locations. The bioconcentration factors (BCFs) of PFOS in fish were in the range of 10,000 or above, while the BCF of PFOA in fish was below 200. Blood samples of occupationally exposed people and the general population in various countries were found to contain PFOS and PFOA which suggested a possibility of atmospheric transport of these compounds. There is still a dearth of information about the environmental pathways of PFOS and PFOA. Some advanced oxidation methods, photocatalysis, adsorption, and reverse osmosis membrane filtration were found effective in degrading or removing PFOS and PFOA from the water environment. The presence of these compounds in the tap water, surface water and animal and human tissues indicates their global contamination and bioaccumulative phenomena in the ecosystems.