Color, dye and DOC removal, and acid generation during fenton oxidation of dyes.

The removal of color, dye and dissolved organic carbon by Fenton discoloration was investigated using the synthetic dye wastewaters containing various dyes (reactive blue 19, Eriochrome Black T or Fast Green FCF). The results indicated that discoloration of dyes was very rapid but mineralization of dyes was insignificant based on the removal of dissolved organic carbon. The rates of color, dye and dissolved organic carbon removal were in the order of reactive blue 19 > Fast Green FCF > Eriochrome Black T. The generation of SO(2-)4, and N(O-)3, increased with the progress of the Fenton reaction. The concentrations of SO(-2)4 and N(O-)3, generated are in the order of reactive blue 19 > Fast Green FCF> Eriochrome Black T. A mathematic model was proposed to formulate the formation of SO(2-)4 and N(O-)3 during dye degradation. Results indicated that one S-containing and two N-containing functional groups are involved in the oxidation reaction, and that S-containing groups are involved in the oxidation reaction earlier than N-containing functional groups.

Removal of dissolved natural organic matter from source water with alum coagulation.

In this study, the effectiveness of enhanced alum coagulation for removal of natural organic matter (NOM) at various alum dosages and pH conditions was assessed for three source waters. Results from the laboratory jar tests at various conditions were compared. Tested pH ranged from 5.0 to 8.0, with alum dosages ranging from 60-120 mg l(-1) for removal of dissolved NOM with various concentration of dissolved organic carbon (DOC) and alkalinity. Alum coagulation profiles of the three source waters were also compared. For Cheng-Kung Water Treatment Plant (high DOC, high alkalinity), laboratory tests showed 50% DOC removal with alum dosage of 70-110 mg (-1). after acidifying the raw water to pH = 6. For Tai Lake Water Treatment Plant (high DOC, low alkalinity), laboratory tests showed that the highest DOC removal (approximately 50%) was achieved at an alum dosage of 80 mg l(-1) at pH = 8 (natural condition). However, alum coagulation showed little DOC removal for source water from Kee-Lung River (low DOC, low alkalinity). Higher alkalinity in Cheng-Kung Reservoir accounts for the necessity to acidify the raw water before enhanced coagulation for optimum DOC removal.

Suppressed gene expression of adipocyte resistin in an insulin-resistant rat model probably by elevated free fatty acids.

Resistin, the peptide specifically secreted from adipocytes, is a hormone antagonistic to insulin action and, thus, may serve as a link between human obesity due to adiposity and insulin resistance associated with type 2 diabetes. To test this hypothesis, we studied the gene expression of resistin in adipocytes isolated from rats fed with a fructose diet which induced insulin resistance. Compared to the control rats (C) on a normal chow diet, the fructose-fed rats (F) developed hyperinsulinemia, glucose intolerance, hypertriglyceridemia and hypertension, a profile reminiscent of the syndrome X of patients with non-insulin-dependent diabetes mellitus (NIDDM). The F rats had significantly elevated plasma free fatty acids (FFA), enlarged epididymal fat pads, and increased adipocyte size compared with the C rats. We examined the glucose transport and the relative quantity of resistin mRNA produced in the adipocytes of these two groups of rats. Compared to the C rats, the F rats had a clearly reduced insulin-stimulated glucose transport. The gene expression of resistin and other adipocyte peptides was measured on the mRNA by semiquantitative RT-PCR; the validity of this technique was established in advance with a rat-fasting and then refeeding experiment. The F rats showed a decreased expression of the resistin gene, whereas gene expression of leptin and angiotensinogen in contrast increased. Free fatty acids were found to suppress the expression of resistin gene in normal rat adipocytes. These results demonstrate that an insulin-resistant instance in the fructose diet rat model exists with the decreased gene expression of resistin.

Catalyzed UV oxidation of organic pollutants in biologically treated wastewater effluents.

A batch reactor was used to evaluate the efficiency of advanced oxidation process of the organic pollutants in biologically treated wastewater effluents with UV/H2O2. A 450-W high-pressure mercury vapor lamp was used as the light source. During the degradation process, the concentration of the dissolved organic compounds could be increased by more than twofold due to the decomposition of microorganisms. This increase of the dissolved organic compounds was eliminated if the water was filtered before the photodegradation experiments. It is observed that the UV alone could play a role for the oxidation of the organic pollutants; however, the addition of a small amount of hydrogen peroxide promotes the degradation efficiency of organic compounds in wastewater. The best oxidation efficiency was obtained when the water samples were under acidic conditions (pH 5), and the rate of degradation was not enhanced with the increasing H2O2 dosages. The optimum H2O2 dose was between 0.01% and 0.1% for the oxidation processes in this study. The presence of the carbonate/bicarbonate ions in water inhibits the degradation of the organic compounds.

Hydroxyl radical scavenging role of chloride and bicarbonate ions in the H2O2/UV process.

Simultaneous effect of inorganic anions, such as chloride and bicarbonate ions, on the scavenging of hydroxyl radicals (HO*) in the H2O2/UV process is the focus of this paper. The model compound of n-chlorobutane (BuCl) was used as the probe of HO*. By changing the pH conditions (2-9) and the concentrations of NaCl (0.25-2500 mM) and NaHCO3 (25 mM), the variation of HO* concentrations and the rate of H2O2 decomposition were compared. In general, the BuCl and H2O2 follow closely the first-order reaction within the first 10 and 40 min, respectively. In the presence of chloride alone at the pH range of 2-6, the HO* concentration in the reaction mixture increases with the increase of pH, and the HO* concentration at pH = 6 is 100 times of that at pH = 2. Including bicarbonate species in the solution, the peak HO* concentration was found at a certain pH, which shifts from 4, 5, to 5-7, as the molar ratios of chloride/bicarbonate species increase from 1 to 100. In addition, without bicarbonate species HO* concentration decreases significantly with increasing chloride concentration but remained rather unchanged beyond 1250 mM. In contrast, the HO* scavenging in the presence of bicarbonate species became relatively significant only when the chloride concentration reached beyond 250 mM. Throughout all experiments of different water quality conditions, the H2O2 decomposition rate remains rather unchanged.

Decolorization of textile wastewater by photo-fenton oxidation technology.

This paper describes the use of photo-fenton process for color removal from textile wastewater stream. The wastewater sample to be treated was simulated by using colorless polyvinyl alcohol (PVA) and reactive dyestuff of R94H. As a result, the hydroxyl radical (HO*) oxidation can effectively remove color, but the chemical oxygen demand (COD) was removed in a slight degree. The color removal is markedly related with the amount of HO* formed. The optimum pH for both the OH* formation and color removal occurs at pH 3-5. Up to 96% of color can be removed within 30 min under the studied conditions. Due to the photoreduction of ferric ion into ferrous ion, color resurgence was observed after 30 min. The ferrous dosage and UV power affect the color removal in a positive way, however, the marginal benefit is less significant in the higher range of both. PVA as the major background COD of a textile wastewater stream inhibits the color removal insignificantly as its concentration increases.