Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C1835664 (TOC)
 2,763 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibition of the organic matter consumption rate of a saline and rich proteic effluent by free ammonia was assessed in anaerobic filters at 37 degrees C. Inhibition of substrate (total organic carbon, TOC) consumption rate by ammonia was fitted by the Luong and noncompetitive models. Calculated kinetic parameters using the Luong model were maximum specific growth rate, micromax = 0.28 day(-1); average saturation constant, Ks = 568 mg TOC/L; Luong inhibition parameter, KNH3 = 1707mg ammonia-nitrogen (NH3-N)/L; and Luong exponent, gamma = 0.283 and the noncompetitive calculated parameters were umax= 0.26 day(-1), Ks = 703 mg TOC/L, and inhibition parameter, INH3 = 325 mg NH3-N/L. The Luong and noncompetitive models predicted 50% inhibition of the substrate consumption rate at ammonia concentrations of 147 and 325 mg NH3-N/L, respectively, suggesting biomass adaptation to the ammonia concentration (80 mg NH3-N/L as average) at which the anaerobic filters were previously operating. Ammonia formation by anaerobic digestion of fishing effluent would produce a maximum of 65.1 and 58.6% inhibition of the efficiency, predicted by the Luong and noncompetitive models, respectively. Ammonia influence on the digestion steps was determined by comparing fishing effluent with volatile fatty acids as substrates. The noncompetitive model predicted a 50% inhibition of methane production rate at ammonia concentrations of 196.6 and 188.6 mg NH3-N/L for fishing effluent and volatile fatty acids, respectively, suggesting that the methanogenic step is the one most affected by ammonia.
Water Environ Res
PMID:Ammonia inhibition in the anaerobic treatment of fishery effluents. 1156 75

Cutting oils are emulsionable fluids widely used in metalworking processes. Their composition is normally oil, water, and additives (fatty acids, surfactants, biocides, etc.) generating a toxic waste after a long use. Generally, it is a waste too dilute to be incinerated and it is difficult to treat biologically. Other conventional treatment methods currently used are not satisfactory from the environmental point of view. Wet air oxidation (WAO) and supercritical water oxidation (SCWO) are two forms of hydrothermal oxidation that have been proved to be effective processes to treat a wide variety of industrial wastes, but hardly tested for oily wastes. In the case of refractory wastes, WAO process is not efficient enough due to the moderate temperatures used. SCWO is a more powerful process since operating temperatures are usually around 600 degrees C, but the use of severe conditions leads to major disadvantages in the commercialization of the technology. In order to enhance WAO and SCWO efficiency at mild conditions, the use of free radical promoters has been studied in this work. Both normal and promoted hydrothermal oxidation have been tested to treat cutting oil wastes in a continuous flow system operating at 300-500 degrees C. Hydrogen peroxide has been used both as a source of oxygen and as a source of free radicals by introducing it into the reactor with or without previous thermal decomposition, respectively. Organic material is easily oxidized in both cases, obtaining more than 90% TOC reduction in less than 10s at 500 degrees C. At lower temperatures, the use of promoters clearly enhances the oxidation process. Activation energies have been estimated for normal and promoted oxidation processes.
 ...
PMID:Elimination of cutting oil wastes by promoted hydrothermal oxidation. 1160 43

The organic fraction of a sludge from a wastewater biological treatment plant is characterized by the total organic carbon, TOC, content, cyclohexane and toluene extractions, and thermal desorptions in nitrogen and air flow at different temperatures. The inorganic fraction is characterized by water extraction, FT-IR spectroscopy, thermogravimetric analysis, and scanning electron microscopy/energy dispersion X-ray analysis. The thermal degradation rate of organic carbon is studied in batch experiments in air, in the 250-500 degrees C temperature range. The sample TOC is used to measure the decrease of reagent concentration with time. The TOC vs time data are well fitted by a generalized kinetic model, previously proposed for the MSWIs fly ash thermal degradation. The rate constants of the immediate carbon gasification, k2, and of the dissociative oxygen chemisorption, k1, followed by C(O) intermediate gasification, k3, together with activation and thermodynamic parameters are calculated. The rate determining step is the C(O) oxidation. The influence of desorbed or extracted organic compounds on kinetics and the role of the C(O) formation in explaining the reaction mechanism as well as the comparison with fly ash kinetics are discussed.
 ...
PMID:Thermal oxidation kinetics and mechanism of sludge from a wastewater treatment plant. 1164 66

Catalytic wet peroxide oxidation (CWPO) of diluted aqueous solutions of phenol has been studied over a series of heterogeneous catalysts at 100 degrees C under 1 MPa air pressure. Several catalysts were prepared and tested including zeolitic materials exchanged with metallic ions such as Fe and Cu and different mixed oxides. Likewise, a Fe-TS-1 zeolite was synthesised by isomorphous substitution of Si atoms by Fe and Ti into the MFI zeolitic framework through hydrothermal synthesis of wetness-impregnated Fe2O3-TiO2-SiO2 xerogels. This material showed a complete phenol removal and TOC reduction of up to 68% under the reaction conditions, with a low leaching of iron species as compared to Fe-exchanged zeolitic materials. Perovskite of type LaTi(0.45)Cu(0.55)O3 was also tested, showing copper leaching of 22%, with a TOC conversion of 93% and total phenol removal. The capacity of Fe and Cu containing catalysts to promote free radicals in the presence of H2O2 as well as the thermal decomposition of the oxidant under the reaction conditions have also been studied. In the absence of hydrogen peroxide, Fe and Cu catalysts were not effective in order to decrease TOC content.
Water Sci Technol 2001
PMID:Novel heterogeneous catalysts in the wet peroxide oxidation of phenol. 1169 54

A complete study on the photocatalytic degradation of ethylenediaminetetraacetic acid (EDTA) over TiO2 has been initiated, to establish the influence of several parameters on the reaction rate, the nature of the intermediates and the kinetic regime. TiO2 (Degussa P25) suspensions containing EDTA at pH 3 at different concentrations were irradiated under near UV light. A Langmuirian behavior was observed, from which kinetic constants have been obtained. Experiments with 5.0 mM EDTA (zero order kinetic regime) were performed for 3 hours irradiation under different conditions. Under N2 bubbling, depletion of EDTA was very low. Under O2 bubbling, the concentration of EDTA decreased around 90%. However, the corresponding decrease of TOC ranged only between 4.5% and 9%. A higher TOC reduction (22% or more) was obtained by keeping the pH constant by HClO4 addition, or by hydrogen peroxide addition. Addition of 0.5 mM Fe(III) caused a dramatic increase on the initial rate of EDTA depletion and approximately a 32% TOC decrease. Analysis of the filtered solution was performed by ion chromatography and capillary electrophoresis to monitor the disappearance of EDTA and the formation of degradation products after different irradiation times. So far, glycine, ethylenediamine, formic acid, ammonium, iminodiacetic acid, oxalic acid and glyoxylic acid have been identified.
Water Sci Technol 2001
PMID:Kinetics and mechanisms of EDTA photocatalytic degradation with TiO2. 1169 57

The photocatalytic degradation of three reactive azo dyes (yellow-2, orange-16 and red-2) and one anthraquinone reactive dye (blue-19) was studied. The reactions were carried out in a reactor with recirculation using TiO2 immobilised on glass Raschig rings (system A) and compared with a batch system using the catalyst in aqueous suspension (system B). Both reaction systems were irradiated with a 125 W, lambda > 254 nm lamp. The suspended TiO2 system was also studied using a 125 W 360 nm lamp (system C). Kinetic studies indicated a rapid colour removal, following the order B > A > C. The same trend was observed in COD and TOC removal profiles. The energy consumption per order of magnitude of catalytic degradation of the dyes was lower in the batch reactor (system B) than in the reactor with recirculation and immobilised TiO2 (system A).
Water Sci Technol 2001
PMID:Reactive dyes decolouration by TiO2 photo-assisted catalysis. 1169 59

Photolytic and photocatalytic interactions of hypochlorite ion and humic acid are investigated under various conditions. Humic acid oxidation by aqueous chlorine under dark conditions are expressed in terms of first order reaction kinetics. Upon irradiation (300 nm < lambda < 400 nm), photolysis of aqueous chlorine affect the removal efficiency of humic acid via oxidation. TiO2 sensitised photocatalytic oxidation conditions reveal an increase in the TOC removal rate of humic acid in the presence of aqueous chlorine. Under the specified conditions, increasing the photocatalyst loading up to 1.0 mg/mL markedly increase the TOC removal rate.
Water Sci Technol 2001
PMID:Interactions of hypochlorite ion and humic acid: photolytic and photocatalytic pathways. 1169 60

The photocatalytic oxidation of the non-biodegradable p-nitrotoluene-o-sulfonic acid (p-NTS) in homogeneous (photo-Fenton reactions) and heterogeneous (with TiO2) solutions has been studied at a pilot-scale under solar irradiation at the Plataforma Solar de Almeria (PSA). In this study two different reactors were tested: a medium concentrating radiation system (Heliomans, HM) and a non-concentrating radiation system (CPC). Their advantages and disadvantages for p-NTS degradation have been compared and discussed. The degradation rates obtained in the CPC collector are around three times more efficient than in the HM collectors. However, in both systems, 100% of the initial concentration of p-NTS was removed. Kinetic experiments were performed in both systems using TiO2 suspensions. During the photodegradation, the disappearance of p-NTS was followed by HPLC, the mineralization of the solution by the TOC technique, the evolution of NO3-, NO2-, and SO4(2-) concentration by ionic chromatography, the toxicity by the standard Microtox test, and the biodegradability by BOD5 and COD measurements. The obtained results demonstrated the utility of the heterogeneous catalysis (using TiO2 as catalyst) as a pretreatment method that can be followed by a biological process.
Water Sci Technol 2001
PMID:Concentrating versus non-concentrating reactors for solar photocatalytic degradation of p-nitrotoluene-o-sulfonic acid. 1169 62

Diglyme (CAS No. 111-96-6), a biorefractive ether with teratogenic properties is of considerable importance as a solvent in the synthetic chemical industry. Results of lab-scale investigations into the optimal conditions for the oxidative mineralisation of 0.05 to 1 g/L of diglyme in synthetic process waters by hydrogen peroxide and ozone based advanced oxidation processes are presented. Fenton, photo-assisted Fenton and UV/H2O2 oxidation processes show acceptable TOC removals. At 50 degrees C the initial TOC removal rates varies between 0.07 and 6g TOC/L*h. The rates increase with the initial diglyme and hydrogen peroxide concentration as well as with the UV irradiation energy intensity. For example at a 1 g/l diglyme concentration a stoichiometric H2O2 addition resulted in TOC degradation of 60% to 70% after 30 minutes under the investigated conditions. Treatment with ozone/H2O2 at a pH of 8 and 25 degrees C required at least 100 minutes to achieve comparable mineralisation results. Biodegradability can be reached in far shorter times. Ozone on its own cannot be recommended for diglyme treatment. If complete mineralisation of diglyme is the objective, the UV/H2O2 oxidation process should be favoured. The ozone/H2O2 process might offer a viable alternative in cases where the oxidation step is followed by biological wastewater treatment, so that biodegradability is aimed at.
Water Sci Technol 2001
PMID:Treatment of diglyme containing wastewater by advanced oxidation--process design and optimisation. 1169 72

Abstract The degradation of nitrobenzene using some advanced oxidation processes (O3/UV, O3/UV/H2O2 and O3/UV/Fe(III)) has been investigated. In the combined O3/UV process, the effect of pH and ozone was studied. In the other combinations, the influence of the amount of hydrogen peroxide and ferric ion in the degradation rate and TOC evolution, has been studied. Under our conditions, the combination O3/UV did not improve the degradation rate obtained by ozonation. The best TOC decrease was obtained when the O3/UV process was carried out at low ferric ion concentrations.
Water Sci Technol 2001
PMID:Oxidation of nitrobenzene by O3/UV: the influence of H2O2 and Fe(ll). Experiences in a pilot plant. 1169 81


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>