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Query: UMLS:C1835664 (TOC)
 2,763 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The efficiencies of chemical oxidation of organic matter in genuine secondary-treated municipal wastewater by using O3, O3/UV, O3/TiO2, UV/TiO2 and O3/UV/TiO2 methods were compared experimentally. Effects of carbonates on these efficiencies were also investigated. Elimination of carbonates from the water increased TOC reduction efficiency of all the methods. The effect of the carbonates on the O3 method was less significant than that on the other methods. The O3/UV method was the most effective for reducing TOC under both carbonate-present and decarbonated conditions. The catalytic ozone process (O3/TiO2) showed a tendency to increase the ozonation efficiency at the beginning of the reaction under the decarbonated condition, but the addition of the TiO2 catalyst inhibited the ozonation under the carbonate-present condition. The photocatalytic oxidation process (UV/TiO2) did not reduce TOC as much as the other methods, but it could reduce TOC over a long time. And the O3/UV/TiO2 method did not show a synergistic effect of ozonation and photocatalytic oxidation. Furthermore, zonation prior to coagulation increased TOC reduction efficiency of coagulation, but this effect was also affected by the carbonates in water.
Water Sci Technol 2001
PMID:Chemical oxidation of organic matter in secondary-treated municipal wastewater by using methods involving ozone, ultraviolet radiation and TiO2 catalyst. 1143 94

A continuous two step O3/H2O2 oxidation system, in which the waste gas from the former reactor was reused in the latter step with an ejector, was established for the purpose of wastewater reclamation in electronics industries. ORP monitor was combined into the system to obtain the optimum ratio of H2O2 to O3 by automatically adjusting the dosage of H2O2, and ion exchange resin was used for removing organic acids formed during oxidation. The effectiveness of the O3/H2O2 oxidation system for TOC removal was investigated under various conditions by using IPA, DMSO, and NMP as model substances. The optimum H2O2/O3 for oxidizing IPA was in a range above 0.15, and it increased with the increase of O3 dose. A sudden drop of ORP from ca. 800 mV to a little more than 200 mV was observed when H2O2/O3 was approaching the optimum point from the lower end. An ORP between 250 mV and 300 mV or 800 mV and 900 mV was proper for H2O2/O3 control. The treatability of the model substances was in an order of IPA << DMSO < NMP, being consistent with the magnitude of the energy of the highest occupied molecular orbital (epsilon HOMO). The two step treatment system developed in this study was found to be more efficient than the conventional single step system. With the help of H2O2 dosing control and two step treatment using waste O3, the system could save about 40% O3 in comparison with the conventional O3/H2O2 oxidation process.
Water Sci Technol 2001
PMID:Improved O3/H2O2 oxidation process for wastewater reclamation. 1143 96

This study aims to remove the color substances, which normally cause difficulties in membrane filtration processes due to fouling using heterogeneous UV/TiO2/H2O2 reactor. It is confirmed that the technique used in this study was effective to remove TOC at 38% and color400 at 89% within 150-min irradiation. The experiment results showed that low concentrations of hydrogen peroxide dosage (less than 0.016 M) to UV/TiO2 system accelerated the TOC and Color400 removal rate from 9% to 38% and 40% to 89% respectively, while over-dosage made this positive effect decline. The humic acid solution treated by photo catalytic oxidation in UV/TiO2/H2O2 reactor did not change the zeta potential on membrane surface and membrane rejection rate.
Water Sci Technol 2001
PMID:Removal of color substances using photocatalytic oxidation for membrane filtration processes. 1143 97

Biological powdered activated carbon (BPAC) was incorporated with a microfiltration (MF, 0.2 micron pore size) system to remove the refractory organic matter contained in secondary sewage effluent. A synthetic secondary sewage effluent was used as influent in this study, containing both non-biodegradable organic substances (such as humic acid, lignin sulfonate, tannic acid and arabic gum powder) and biodegradable ones. These refractory organic materials were possibly degraded in contact with microorganisms for 20-27 days. Although humic acid and arabic gum were weakly adsorbed on the activated carbon, they could be effectively removed in the BPAC reactor. The TOC removal at a powdered activated carbon (PAC) concentration of 20 g/L was higher than at 0.5-2 g PAC/L (83% and 66-68%, respectively). The higher removal efficiency was due to the increased rejection at the membrane module in which most of the PAC was accumulated. More than 90% of non-biodegradable compounds removal (detected as E280, UV absorption at 280 nm) occurred in the BPAC reactor. The biological growth parameter b/Y, used in system design, was estimated to be 0.017 d-1. Relatively high permeate flux of 1.88 m/d could be obtained even at higher PAC concentration of 20 g/L.
Water Sci Technol 2001
PMID:Evaluation of refractory organic removal in combined biological powdered activated carbon--microfiltration for advanced wastewater treatment. 1144 88

Our research aimed to evaluate intermittent soil infiltration of treated sewage for reuse in the north of Chile. Aerated lagoon effluent was infiltrated in columns packed with native soils (sandy-lime, lime-gravel and limey-sand). Columns were operated for more than a year under different cycles of filling and drying, depths and load pressures depending on soil characteristics. The efficiency of the system was determined through influent-effluent microbiological indicators level (faecal coliforms, E. coli, Salmonella spp, MS2 phage, and protozoan cysts), physicochemical characterisation (TOC, COD, BOD, nitrogen), and hydraulic flow measurement. Results showed: (a) high reduction of enteric bacteria (5-7 log10), some inactivation of phage (2-4 log10) and complete removal of intestinal cyst; (b) stable removal of organic matter (80-90% reduction of TOC, COD, BOD); and (c) partial ammonia reduction through adsorption and nitrification with denitrification mainly occurring in sandy soil. Preliminary data from pilot plant working in the field showed better results that those obtained in the laboratory especially removal of microbiological indicators. Microbiological quality of effluent met Class A regulations for agricultural reuse (WHO, 1989) and the system looks like an attractive alternative to cope with water shortage in the region.
Water Sci Technol 2001
PMID:Water quality improvement of treated wastewater by intermittent soil percolation. 1146 52

The present investigation compared the capacity of greenhouse pot-cultivation systems under two salinity conditions (freshwater and saline water) with two mangrove species (Bruguiera gymnorrhiza and Kandelia candel) to remove nutrients from livestock wastewater. During the whole treatment period there were relatively stable leachate TOC concentrations for wastewater-treated pots. Leachate NH4(+)-N concentration of B. gymnorrhiza pots was generally lower than that of K. candel pots. Leachate PO4(3-)-P concentration of pots receiving wastewater under freshwater condition was higher than that under saline water condition. Soil inorganic N content was more than two times higher for the wastewater treatments than that for the controls under low salinity condition and slower rate of increase under saline water condition. Soil P nutrients of both total and extractable inorganic forms significantly increased for both systems due to the discharges of livestock wastewater under both salinity conditions. The rate of increase in P contents for plants receiving livestock wastewater was 1-4 times that of the controls, much more than that in N contents (0.04-1.30 times). N nutrient removal efficiencies were 84.3% (65.6% by soil and 18.7% by plant) and 95.5% (32.2% by soil and 63.4% by plant), respectively by Kandelia candel and B. gymnorrhiza pot-cultivation systems under freshwater condition. Under saline water condition, N nutrient removal efficiencies by K. candel and B. gymnorrhiza pot-cultivation systems were 92.7% (80.7% by soil and 12.0% by plant) and 98.0% (67.6% by soil and 30.3% by plant), respectively. P nutrient removal efficiencies by K. candel and B. gymnorrhiza systems under freshwater condition were 79.2% (76.6% by soil and 2.6% by plant) and 91.8% (88.2% by soil and 3.6% by plant), respectively. The corresponding values were 88.0% (84.2% by soil and 3.8% by plant) and 97.8% (95.9% by soil and 1.9% by plant) under saline water condition.
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PMID:Livestock wastewater treatment by a mangrove pot-cultivation system and the effect of salinity on the nutrient removal efficiency. 1146 29

In this article, the wastewater treatment by UV oxidation with and without preceding desalination is compared. The influence of different chloride concentrations on the TOC degradation and AOX concentration is analyzed. Nanofiltration membrane dialysis is used to separate the chloride ions from wastewater. It is demonstrated that a reduction of the chloride concentration leads to a faster TOC degradation compared to the treatment of non-desalinated wastewater. Furthermore, the additional formation of AOX during the process could be avoided in effect leading to a significant degradation of native AOX.
Water Res 2001 Sep
PMID:Improved AOX degradation in UV oxidative waste water treatment by dialysis with nanofiltration membrane. 1148 22

The principle, structure and function of the regeneration system for urine and waste water treatment were introduced. The experimental results demonstrated that, the treatment capacity was 1.2-1.9 kg/h, and the regeneration efficiency exceeded 92%. The quality of the treated water were: TOC < 20 g/m3, (NH3 + NH4+) < 10 g/m3, electric conductivity < 100 micro s/cm, pH= 6-8.
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PMID:[An experimental study on regeneration device for urine and waste water in space station]. 1154 Mar 82

The focus of resource recovery research at the KSC-CELSS Breadboard Project has been the evaluation of microbiologically mediated biodegradation of crop residues by manipulation of bioreactor process and environmental variables. We will present results from over 3 years of studies that used laboratory- and breadboard-scale (8 and 120 L working volumes, respectively) aerobic, fed-batch, continuous stirred tank reactors (CSTR) for recovery of carbon and minerals from breadboard grown wheat and white potato residues. The paper will focus on the effects of a key process variable--bioreactor retention time--on response variables indicative of bioreactor performance. The goal is to determine the shortest retention time that is feasible for processing CELSS crop residues, thereby reducing bioreactor volume and weight requirements. Pushing the lower limits of bioreactor retention times will provide useful data for engineers who need to compare biological and physicochemical components. Bioreactor retention times were manipulated to range between 0.25 and 48 days. Results indicate that increases in retention time lead to a 4-fold increase in crop residue biodegradation, as measured by both dry weight losses and CO2 production. A similar overall trend was also observed for crop residue fiber (cellulose and hemicellulose), with a noticeable jump in cellulose degradation between the 5.3 day and 10.7 day retention times. Water-soluble organic compounds (measured as soluble TOC) were appreciably reduced by more than 4-fold at all retention times tested. Results from a study of even shorter retention times (down to 0.25 days), in progress, will also be presented.
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PMID:Effects of bioreactor retention time on aerobic microbial decomposition of CELSS crop residues. 1154 85

This paper discusses the development of mixtures with silica fume as a stabilization/solidification agent and binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (Unconfined Compressive Strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC and chromium decreased as more OPC was substituted with silica fume. When the mix had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76 mg-Cr/g-Cr in acidic solution. Also, microstructural studies on the solidified wastes through the scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contribute to setting, but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and contaminant leachability.
Water Sci Technol 2001
PMID:Chemical characteristics and leachability of organically contaminated heavy metal sludge solidified by silica fume and cement. 1154 12


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