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)

TiO2-mediated photocatalytic degradation process was employed to treat aqueous 2-, 3- and 4-NT (nitrotoluene) pollutants. The NT disappearance and TOC removal rates for three isomers showed no significant differences. Three hydroxylated aromatic intermediates resulting from the photocatalytic degradation of 4-NT were identified; this suggested two (initial) degradation pathways. Formation of acetic acid, formic acid, and formaldehyde was also noted. The mineralization products included NH4+, NO3- and CO2. N2 bubbling or the presence of a positive hole acceptor during 4-NT degradation resulted in a high 4-aminotoluene formation. This indicated an effective reduction of 4-NT's nitro group to amino moiety. Generally, Pt-loaded TiO2 (Pt-TiO2) had no influence on the disappearance rate of 4-NT. However, the use of Pt-TiO2 along with a higher light intensity source resulted in an accelerated TOC removal.
 ...
PMID:Photocatalytic degradation of nitrotoluene in aqueous TiO2 suspension. 1176 18

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 textile mill effluents ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the chemical oxygen demand (COD). However, little is known about the reaction intermediates and products formed during ozonation. This work deals with the degradation of hydrolyzed Reactive Yellow 84 (Color Index), a widely used azo dye in textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the hydrolyzed dye in ultra pure water was performed in a laboratory scale cylindric batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (400 nm), was almost complete after 60 and 90 min with an ozone concentration of 18.5 and 9.1 mg/l, respectively. The TOC/TOC0 ratio after ozonation was about 30%, the COD was diminished to 50% of the initial value. The BOD5/COD ratio increased from 0.01 to about 0.8. Oxidation and cleavage of the azo group yield nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused increases 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.
 ...
PMID:Ozonation of hydrolyzed azo dye reactive yellow 84 (CI). 1180 21

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.
 ...
PMID:Ozonation of the purified hydrolyzed azo dye Reactive Red 120 (CI). 1204 67

Simultaneous removals of dye and nitrate by photo-dependent denitryfying sludge(PDDS) have been demonstrated in a continuous-flow bench-scale reactor. The best C/N for the degradation of azo dyes by PDDS was 1.5. The specific removal rate of azo dye AB92 decreased with a decrease in hydraulic retention time and increased with a decrease in solids retention time. The degradation rate of TOC decreased with a decrease in hydraulic retention time. AB92, which has nitro and hydroxyl substitutions in non-para positions, was uniquely degraded. During continuous flow treatment experiments using PDDS, complete degradation of azo dyes AB92 and AO20 at influent concentrations of 40 mg/L and 30 mg/L, respectively, was achieved with an HRT of 16.
 ...
PMID:Continuous treatment of azo acid dyes by photo-dependent denitrifying sludge. 1221 77

Simultaneous biological phosphorus and nitrogen removal with enhanced anoxic phosphate uptake was investigated in an anaerobic-aerobic-anoxic-aerobic sequencing batch reactor ((AO)2 SBR). Significant amounts of phosphorus-accumulation organisms (PAOs) capable of denitrification could be accumulated in a single sludge system coexisting with nitrifiers. The ratio of the anoxic phosphate uptake to the aerobic phosphate uptake capacity was increased from 11% to 64% by introducing an anoxic phase in an anaerobic aerobic SBR. The (AO)2 SBR system showed stable phosphorus and nitrogen removal performance. Average removal efficiencies of TOC, total nitrogen, and phosphorus were 92%, 88%, and 100%, respectively. It was found that nitrite (up to 10 mg NO2(-)-N/l) was not detrimental to the anoxic phosphate uptake and could serve as an electron acceptor like nitrate. In fact, the phosphate uptake rate was even faster in the presence of nitrite as an electron acceptor compared to the presence of nitrate. It was found that on-line sensor values of pH, ORP, and DO were somehow related with the dynamic behaviours of nutrient concentrations (NH4+, NO3-, and PO4(3-)) in the SBR. These on-line sensor values were used as real-time control parameters to adjust the duration of each operational phase in the (AO)2 SBR. The real-time controlled SBR exhibited better performance in the removal of phosphorus and nitrogen than the SBR with fixed-time operation.
 ...
PMID:Biological nitrogen removal with enhanced phosphate uptake in a sequencing batch reactor using single sludge system. 1223 Jan 80

The effect of ditching of boreal forest land (W. Finland) on P and N dynamics and export was assessed using a paired catchment approach (response stream + control stream) for a 4-year study period. After the ditching operations, there was a small but significant increase in the NH4+ export, but no significant changes in the concentrations and loads of total reactive P, total non-reactive P, total organic N and NO3-. In both streams, the reactive P fraction largely followed the Fe concentrations. High input to output ratios, and thus, high retention was a typical feature of the inorganic N compounds. Total organic N and the TOC/TON ratio were positively correlated with the total organic carbon.
 ...
PMID:Impact of forest ditching on nutrient loadings of a small stream--a paired catchment study in Kronoby, W. Finland. 1238 85

The performance of the submerged membrane separation activated sludge process with intermittent aeration was investigated in a laboratory scale experiment by changing organic loading rate and intermittent aeration cycle. A rectangular PVC tank was used as an aeration tank, in which a flat-sheet type Micro-Filtration membrane made of poly-olefin with a pore size of 0.2 microm was submerged. Organic loading rate to the reactor was set at 0.3 and 0.8 g-TOC/L/day. C/N ratio in the feed was set at around 5.0 for every condition. Aeration cycle was changed from 10 min-10 min (aeration-stop) to 120 min-120 min in different organic loading conditions. Flux through the membrane was set at 0.25 m/day. Membrane fouling proceeded rapidly in 0.8 g-TOC/L/day conditions. However, when organic loading rate was 0.3 g-TOC/L/day, bacterial metabolic substances were degraded rapidly compared to the production, thereby decreasing viscosity in mixed liquor. Nitrogen removal rate was between 60% and 80% for 0.8 g-TOC/L/day loading, and between 50% and 65% for 0.3 g-TOC/L/day loading. And the nitrogen removal was highest in 40 min to 60 min aeration cycle conditions. Too short aeration cycle did not result in sufficiently long anoxic periods for denitrification while too long a cycle resulted in unnecessary anaerobic periods after depletion of nitrate. Intermittent aeration was effective also for decreasing viscosity in mixed liquor.
 ...
PMID:Effect of loading rate and intermittent aeration cycle on nitrogen removal in membrane separation activated sludge process. 1242 Sep 74

This study was undertaken to examine the degradation of TNT, RDX and HMX in a circular photocatalytic reactor with TiO2 as a photocatalyst. We examined the impact of parameters such as the initial concentration, initial pH of solution on rates of photocatalized transformation, and the mineralization. The results showed that photocatalysis is an effective process for the degradation of TNT, RDX and HMX. They could be comoletely degraded in 150 min with 1.0 g/L TiO2 at pH 7. An increase in the photocatalytic degradation of HMX was noticed with decreasing initial HMX. The rates of RDX and HMX degradation were greater in neutral pH than in acidic and alkaline conditions. In case of TNT degradation, the rate of degradation was the fastest at pH 11. Approximately 82% TOC decrease in the TNT degradation was achieved after 150 min, whereas TOC decrease in RDX and HMX was 24% and 59%, respectively. Nitrate, nitrite, and ammonium ions were detected as the nitrogen byproducts from the photocatalysis, and more than 50% of the total nitrogen was recovered as nitrate ion in every explosives.
 ...
PMID:Photocatalytic degradation of explosives contaminated water. 1252 45

Recently, use of low levels of medium- and low-pressure ultraviolet light for successful inactivation of Cryptosporidium parvum oocysts has generated tremendous excitement in the water industry. Accurate delivery of the target dose, lamp performance, sensor stability and impact of water characteristics are some factors that could impact disinfection efficacy, in turn influencing decisions on application of this technology. To this end, American Water Systems, the largest investor owned water utility in the US, has responded to some of these challenges by ascertaining the long-term feasibility of applying UV for treatment of finished water. A 4 x 1 UV reactor with a 12 inch (0.3 m) diameter was installed after granular activated carbon filtration and was operated with a finished water flow rate of 600 gpm (2,700 L/min). Over a 12-month period, various chemical (THM, HAA, UV254, DOC, TOC, metals, nitrate, nitrites) and physical measurements (lamp voltage, current, sensor measurements) were monitored to define their impact (if any) on the operation of the reactor. MS2 bacteriophage challenge studies were conducted with various lamp configurations and lamp age. These inactivation data demonstrated high levels of correlation with controlled bench scale inactivation data. For C. parvum oocysts, bench scale studies were performed with a modified in vitro infectivity assay using HCT-8 cells, an enhanced infectivity protocol and with either immunofluorescence or quantitative PCR based detection. While both assays indicated increasing infections levels of HCT-8 cells with increasing oocyst inocula, UV treatment of oocysts produced markedly different infectivity responses. Based on the data generated in this study, one in vitro infectivity assay was selected to demonstrate > 3 logs inactivation with low UV doses (5 mJ/cm(20-10 mJ/cm2).
 ...
PMID:Assessing UV reactor performance for treatment of finished water. 1263 26

The effect of combining the photocatalytic processes using TiO2 and the photo-Fenton reaction with Fe3+ or ferrioxalate as a source of Fe2+ was investigated in the degradation of 4-chlorophenol (4CP) and dichloroacetic acid (DCA) using solar irradiation. Multivariate analysis was used to evaluate the role of three variables: iron, H2O2 and TiO2 concentrations. The results show that TiO2 plays a minor role when compared to iron and H2O2 in the solar degradation of 4CP and DCA in the studied conditions. However, its presence can improve TOC removal when H2O2 is totally consumed. Iron and peroxide play major roles, especially when Fe(NO3)3 is used in the degradation of 4CP. No significant synergistic effect was observed by the addition of TiO2 in this process. On the other hand, synergistic effects were observed between FeOx and TiO2 and between H2O2 and TiO2 in the degradation of DCA.
 ...
PMID:Evaluation of the combined solar TiO2/photo-Fenton process using multivariate analysis. 1507 71


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