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Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pH), current density ( j), conductivity ( k) and treatment time ( t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal ( Y ) and specific energy consumption ( Y ) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m, k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV-visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole. [ABSTRACT FROM AUTHOR]

Water quality standards of raw water resources are getting more stringent in Taiwan. This is due to the higher number of potential contaminants released to the water bodies leading to the potential risks to the human health. Raw water resources, including one river and three reservoirs representative of the major raw water resources in northern and central Taiwan, at four locations were selected to measure turbidity, electrical conductivity (EC), oxidation and reduction potential (ORP), pH, alkalinity, total organic compounds (TOC), zeta potential, particle size, Al, Fe and heavy metal contents. Natural organic matter (NOM) was also examined using high-performance size-exclusion chromatography to distinguish the different molecular weight distribution of organic compounds, such as humic acids, that might affect the subsequent raw water treatment. TOC is highly related to NOM, biochemical oxygen demand (BOD5) and chemical oxygen demand, and the influent standard is 4 mg/L in Taiwan. EC, ORP, pH, alkalinity, TOC and zeta potential had values of 231.68-350.60 µS/cm, 210.5-271.55 mV, 8.17-8.58, 65.65-86.25 mg/L, 1.54-2.73 mg/L and -16.58 to -22.60 mV, respectively. However, average turbidity (128.24 NTU) and average particle size at the Daiji River (5,067.56 nm) were higher than those at the Shimen, Yongheshan and Liyutan Reservoirs (2.20-6.39 NTU and 1,105.12-1,627.26 nm, respectively). These measured data and metal contents (the latest three years' data, at least two seasons including summer and autumn) met the regulatory standards in Taiwan. Water quality index (WQI) containing dissolved oxygen solubility, faecal coliforms, pH, BOD5, nitrates, total phosphates, temperature deviation, turbidity and total solids indicated good conditions for three reservoirs and medium condition for Daiji River. NOM, which might produce potential disinfectant by-products, had similar patterns and contained humic acids and low molecular weight acids (LMWs), with the intensity order of Yongheshan Reservoir > Shimen Reservoir > Liyutan Reservoir > Daiji River. The Carlson trophic state index and field-emission scanning electron microscope plot of filtered solid of raw water showed the potential risk of algae to drinking water safety. [ABSTRACT FROM AUTHOR]

This research studied how the air pollutants of urban areas affect a neighboring reservoir and its water quality. Through the atmospheric dispersion process, air pollutants move from the Taipei metropolitan to the Feitsui reservoir and enter the water body through dry and wet depositions. ISCST3 (Industrial Source Complex Short Term Model), an air quality model, was used to simulate dispersion, dry deposition and wet deposition of the air pollutants. Then the nitrogen loadings to the Feitsui Reservoir were evaluated. The results indicate that wet deposition places a greater burden than dry deposition does on the water body. Wet and dry deposition of NH4+ together make up a rather large proportion of the total pollution. The ratio ranged from 21.9 to 25.2%. Those of nitrate make up a smaller proportion, ranged from 2.0 to 2.3%. If we take indirect deposition into account and calculate the NO3- and NH4- together, the proportion is 1 5.9-1 7.6%. [ABSTRACT FROM AUTHOR]

Both surface treatments, H2-reducing pretreatment at 400 °C and the deposition of copper as a catalyst, were attempted to enhance the removal of nitrate (40 (mg N) L-1) using zerovalent iron in a HEPES buffered solution at a pH of between 6.5 and 7.5. After the iron surface was pretreated with hydrogen gas, the removal of the passive oxide layers that covered the iron was indicated by the decline in the oxygen fraction (energy dispersive X-ray analysis) and the overlap of the cyclic polarization curves. The reaction rate was doubled, and the lag of the early period disappeared. Then, the deposition of copper onto freshly pretreated iron promoted nitrate degradation more effectively than that onto a nonpretreated iron surface, because of the high dispersion and small size of the copper particles. An optimum of 0.25-0.5% (w/w) Cu/Fe accelerated the rate by more than six times that of the nonpretreated iron. The aged 0.5% (w/w) Cu/Fe with continual dipping in nitrate solution for 20 days completely restored its reactivity by a regeneration process with H2 reduction. Hence, these two iron surface treatments considerably promoted the removal of nitrate from near-neutral water; the reactivity of Cu/Fe was effectively recovered. [ABSTRACT FROM AUTHOR]

The surface and bulk properties of Al(III)/SiO2 and Fe(III)/SiO2 suspensions were determined as a function of prepared pH. The TEM results showed that Al(III) tends to form Al(OH)3 coatings on the surface of SiO2 while Fe(III) tends to form the discrete Fe(OH)3 phase in bulk solution with system pH increase. The charge reversals (CR) observed in the Al(III)/SiO2 system represent, in order of increasing pH, the point-of-zero charge (PZC) on the SiO2 substrate (CR1), the pH of surface nucleation of Al(OH)3 (CR2), and, at high pH, the PZC of the Al(OH)3 coating (CR3). The observed electrophoresis mobility of Fe(III)/SiO2 is the overall result contributed by negatively charged SiO2 and positively charged Fe(OH)3. [ABSTRACT FROM AUTHOR]