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The photoelectrochemical degradation of methylene blue in aqueous solution was investigated with three-dimensional electrode-photocatalytic reactor. It was found that the methylene blue could be degraded more efficiently by photoelectrochemical process than by photocatalytic oxidation or electrochemical oxidation alone. The decolorization efficiency and COD reduction were 95% and 87% for a photoelectrochemical process, respectively, while they were only 78% and 68% for a single electrochemical process and 89% and 71% for a single photochemical process. The TOC reduction of the former also reached as high as about 81% within a reaction time of 30.0 min. And these degradation reactions conformed to pseudo-first-order kinetics.
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PMID:Feasibility study of photoelectrochemical degradation of methylene blue with three-dimensional electrode-photocatalytic reactor. 1192 70

This paper examines the correlations between some water quality parameters and fluorescence intensities and spectra in filtered wastewater using a 280 nm excitation wavelength. We did not obtain satisfying linear relationships between fluorescence and COD or TOC (r2 approximately 0.4) for any of the emission wavelengths used between 320 and 400 nm (especially at 355 nm, the average emission lambda(max.)). The relationships with NK were better (r2 approximately 0.7); leading us to suggest that one evaluates mainly the organic nitrogen content at lambda(ex.) = 280 nm. Whole spectra processing did not improve the correlations. Gel permeation chromatography yielded markedly different TOC and fluorescence chromatograms, which explains the difficulty of correlating organic content and fluorescence. Other investigations are necessary before spectrofluorimetry can be used as a reliable technique for on-line wastewater pollution estimation.
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PMID:On the use of fluorescence measurements to characterize wastewater. 1193 23

To obtain a further appreciable reduction of discharges in the area of sewage disposal, besides waste water purification at our treatment plants, discharge of wastewater through the sewer system has to be taken into account. Today, control strategies pursuing this aim are mainly based on hydraulic conditions like level or flow rate. They all neglect the wastewater organic load as an essential parameter. The main reasons are the expensive methods used to continuously measure traditional organic sum parameters like COD or TOC. A meaningful alternative to those parameters is the spectral absorption coefficient at lambda = 254 nm (SAC), defined in DIN 38402 by the German Institute for Standardisation. As a purely physical parameter, the SAC shows a good correlation to organic sum parameters like COD and TOC, especially if municipal wastewater is considered. By using an UV-process probe, it is possible to measure the SAC and infer the organic load of raw wastewater continuously without any sample pre-treatment. By the use of this instrument numerous possibilities arise, in order to control the sewers discharge load depend.
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PMID:Online load measurement in combined sewer systems--possibilities of an integrated management of waste water transportation and treatment. 1193 62

Landfill leachate characterization is a critical factor in establishing a corresponding effective management strategy or treatment process. However, it is often difficult to forecast leachate quality because of a variety of influencing factors such as waste composition and landfill operations. This paper describes leachate formation mechanisms, summarizes leachate quality indicators, and investigates the temporal variation of leachate quality from pre-sorted and baled municipal solid waste characterized with high organic and moisture content. The purpose of the study is to evaluate the potential effects of waste composition and site-specific operational procedures on biodegradation processes and leachate quality at a field-scale landfill that receives in excess of 1800 tonnes per day of refuse. For this purpose, waste disposal and leachate generation rates were monitored and leachate samples were collected for a period of 18 months during the early stages of refuse deposition. Chemical analysis was performed on the samples and the temporal variation of several parameters were monitored including pH, COD, TOC, TDS, chlorides, sulfates, orthophosphates, nitrates, ammonia nitrogen, hardness, and heavy metals. Chemical concentration levels were related to biological activity within the landfill and the results indicated that: (1) pre-sorting and baling of the waste did not hinder waste stabilization; and (2) the high organic and moisture contents resulted in an extremely strong leachate, particularly at the onset of biodegradation processes, which can affect the leachate treatment facility.
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PMID:Temporal variation of leachate quality from pre-sorted and baled municipal solid waste with high organic and moisture content. 1195 74

The combination of chemical and biological water treatment processes is a promising technique to reduce recalcitrant wastewater loads. The key to the efficiency of such a system is a better understanding of the mechanisms involved during the degradation processes. Ozonation has been applied to many fields in water and wastewater treatment. Especially for effluents of textile finishing industry ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the COD. However, little is known about the reaction intermediates and products formed during ozonation. This work focuses on the oxidative degradation of purified (>90%), hydrolyzed Reactive Red 120 (Color Index), a widely used azo dye in the textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the dye in ultra pure water was performed in a laboratory scale cylindrical batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (535 nm), was almost complete after 150 min with an ozone concentration of 12.8 mg/l. The TOC/TOC0 ratio was about 74% and the COD was diminished to 46% of the initial value. The BOD5/COD ratio increased from 0.01 to 0.14. To obtain detailed information on the reaction processes during ozonation and the resulting oxidation products organic and inorganic anions were analyzed. Oxidation and cleavage of the azo group yielded nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused an increase in the amount of sulfate. Formic acid and oxalic acid were identified as main oxidation products by high performance ion chromatography (HPIC). The concentrations of these major products were monitored at defined time intervals during ozonation.
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PMID:Ozonation of the purified hydrolyzed azo dye Reactive Red 120 (CI). 1204 67

A hybrid two-phase system, consisting of a solid waste reactor as the acidification reactor and a wastewater reactor, i.e. an upflow anaerobic sludge blanket (UASB) reactor, as the methanogenic reactor, for anaerobic digestion of food waste was investigated. After the pre-acidification stage, COD and total VFA removals in the methanogenic phase were in the ranges of 74-93% and 77-100%, respectively, while leachate COD and total VFA concentrations in the acidification phase decreased by 95% and 97-99%, respectively. Some 99% of the total CH4 generated was from the methanogenic phase with the CH4 content of 68-70%. About 77-79% of TOC, 57-60% of volatile solids and 79-80% of total COD were removed. The results of this laboratory-scale study show that the hybrid two-phase anaerobic batch reactor system is suitable for effective conversion of food waste into CH4 and CO2. The hybrid two-phase system can be further developed into an effective and efficient way to enhance waste stabilization in operating bioreactor landfills.
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PMID:A hybrid two-phase system for anaerobic digestion of food waste. 1220 Oct 98

Advanced chemical oxidation of raw and biologically pretreated wastewater by ozonation, H2O2/UV-C treatment and the successive combination of ozonation and H2O2/UV-C oxidation was investigated. For the raw textile wastewater, the application of successive O3 + H2O2/UV-C oxidation enhanced the COD and TOC removal efficiency of the H2O2 (50 mM)/UV-C process by a factor of 13 and 4, respectively. In case of the biotreated textile wastewater, the preliminary ozonation step increased COD removal of the H2O2 (10 mM)/UV-C treatment system from 15% to 62%, and TOC removal from 0% to 34%, but did not appear to be more effective than applying a single ozonation process in terms of TOC abatement rates. Enhancement of the biodegradability was more pronounced for the biologically pre-treated wastewater with a two fold average increase in the BOD5/COD ratio for the studied chemical oxidation systems.
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PMID:The effect of pre-ozonation on the H2O2/UV-C treatment of raw and biologically pre-treated textile industry wastewater. 1220 Nov 15

Nearly 91% of organic pollutants in Hong Kong leachate could be effectively removed by the UASB (upflow anaerobic sludge blanket) process followed by the fenton coagulation. The COD (chemical oxygen demand) of leachate was lowered from an average of 5620 mg/L to 1910 mg/L after the UASB treatment at 37 degrees C, and was further lowered to 513 mg/L after fenton coagulation. The remaining refractory residues could be further removed by photochemical oxidation with the addition of H2O2. The BOD/COD ratio was greatly increased from 0.062 to 0.142, indicating the biodegradability of organic residues was improved. The photochemical oxidation for the fenton-coagulation supernatant was most effective at pH 3-4, with the addition of 800 mg/L of H2O2, and UV radiation time of 30 minutes. The final effluent contained only 148 mg/L of COD, 21 mg/L of BOD (biochemical oxygen demand) and 56 mg/L of TOC (total organic carbon).
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PMID:Photo-assisted fenton oxidation of refractory organics in UASB-pretreated leachate. 1221 91

One of the major problems encountered in the textile industry is production of highly colored large volumes of wastewater. It is often not possible to predict the characteristics of textile wastewaters by using reported values in the literature because every textile industry is unique with respect to the type of production and the technology and chemicals used in production. Furthermore, the concentrations of pollutants in textile wastewaters vary according to the wastewater management practices and amount of water used in the production. In the first part of this study, wastewater characteristics of a cotton mill textile industry were determined by using the normal and log-normal II distribution functions for flow, COD, TOC, pH and colour. These parameters were measured in the effluent of the equalization tank and the statistical fits were evaluated by using the chi-Square test. It was found that flow and TOC values fitted normal distribution; COD values fitted log-normal II distribution. On the other hand, pH and colour did not fit in to aforementioned distributions. In the second part of this study, the treatment of textile wastewater by coagulation/flocculation/precipitation (CFP) was investigated. Lime, iron and aluminum salts with anionic polielectrolite combination were used as coagulants. Aluminum salts and the combination FeSO4 + lime + polielectrolite were used to remove the colour from mixed textile wastewaters, successfully. On the other hand, FeSO4 + lime + polielectrolite was more effective than aluminum salts to remove the colour from wastewater of indigo dyeing process. In the third part of this work, the removal of sulfide arising from indigo dyeing was investigated. Sulfide removal was accomplished by chemical oxidation and catalyzed air oxidation and removal efficiencies up to ninety percent were found. Chemical oxidation using sodium hypochlorite resulted in color removal too; however, dosages of hypochlorite have to be carefully monitored in order to avoid toxic effects of excess chlorine in water.
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PMID:Chemical treatment of textile wastewaters: statistical characterization, colour and sulfide removal. 1239 14

Phosphate is generally analyzed by color intensity of phosphoantimonylmolybdenum blue (PAMB): especially by a spot test based on spectrophotometric or visual determination. Visual determination is one of the simplest and most inexpensive methods; however, it is believed to be of low precision. In this work, we have developed an alternative phosphate spot test, where phosphate concentration is measured by the color band length of PAMB formed in a detection tube similar to a gas detection tube. The color band is formed by the entrapment of the hydrophobic ion pair of PAMB and quaternary ammonium ions in the column; we demonstrated that this color band length correlates quantitatively with the phosphate concentration. In order to optimize the measurement performance, systematic investigations have been carried out for various experimental parameters such as phosphate concentration, preparation conditions of the column packing material, the type of support material (either silica-gel or PVC), the solution feeding conditions (filtration or penetration), and volume of the sample solution. The effects from some co-existing components were also studied for the measurement of real samples. Determination of phosphate concentrations in actual wastewaters was successfully carried out by this method, indicating that the quantification range achievable was of 3-18 mg PO(4) L(-1) without dilution prior to the analysis. No interference was observed from suspended solid (SS) and organic pollutants (COD, TOC) during the wastewater analysis. Because of the simplicity and rapid processing of the samples (not requiring any special instruments) this newly developed method can be applied to the on-site analysis of wastewater.
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PMID:A spot test for aqueous phosphate by color band formation. 1247 87


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