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Nitrogen removal efficiency was investigated in three subsurface flow constructed wetlands (CWs) with and without reed. Root bag made of nylon sieve with 300 mesh was used to enwrap the reed root in one of reed CWs to distinguish reed rhizosphere from non-rhizosphere. The CWs with root bag enwrapped reed root (hereinafter called as mesh CWs) and other CWs were fed with artificial ammonium-rich wastewater. The results indicated that the COD and N removal occurred mainly in the front of CWs, and C and nitrogen removal occurred concurrently along the stream way. When C/N ratio of influent was 5, the removal efficiencies of NH4+ -N in control CWs, reed CWs and mesh CWs were 66.2%, 94.2% and 82.2%, respectively. TN removal efficiencies were 67.2%, 90.7% and 76.1% respectively. Simultaneous nitrification and denitrification phenomenon in this study was also observed. The removal efficiency of organic carbon was different from nitrogen removal efficiency, mesh CWs showed the highest COD removal efficiency with 80.9%, while control CWs and reed CWs were 72.2% and 56.2%, respectively. C/N ratio of wastewater throughout the bed was more than 5 in three CWs, which indicated carbon source supply was enough for denitrification. The oxidation-reduction position (ORP) and concentration of total organic carbon in rhizosphere and non-rhizosphere were detected. The ORP in the front of mesh CWs's rhizosphere was much higher than that in control CWs and non-rhizosphere in mesh CWs, which were 11-311 mV and 62-261 mV, respectively. Root exudates also showed the difference between rhizosphere and non-rhizosphere in mesh CWs, the TOC of them were 21.3-54.6 mg x L(-1) and 6.65-12.0 mg x L(-1). Due to the higher ORP and concentration of TOC, the nitrogen removal efficiency in plant CWs was much higher than that in control CWs.
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PMID:[Effect of reed rhizosphere on nitrogen and COD removal efficiency in subsurface flow constructed wetlands]. 1925 73

The electrochemical treatment of wastewaters from textile industry is a promising treatment technique for substances which are resistant to biodegradation. This paper presents the results of the electrochemical decolourisation and degradation of C.I. Reactive Orange 4 synthetic solutions (commercially known as Procion Orange MX2R). Electrolyses were carried out under galvanostatic conditions in a divided or undivided electrolytic cell. Therefore, oxidation, reduction or oxido-reduction experiences were tested. Ti/SnO(2)-Sb-Pt and stainless steel electrodes were used as anode and cathode, respectively. Degradation of the dye was followed by TOC, total nitrogen, COD and BOD(5) analyses. TOC removal after an oxidation process was higher than after oxido-reduction while COD removal after this last process was about 90%. Besides, the biodegradability of final samples after oxido-reduction process was studied and an improvement was observed. UV-Visible spectra revealed the presence of aromatic structures in solution when an electro-reduction was carried out while oxido-reduction process degraded both azo group and aromatic structures. HPLC analyses indicated the presence of a main intermediate after the reduction process with a chemical structure closely similar to 2-amine-1, 5-naphthalenedisulfonic acid. The lowest decolourisation rate corresponded to electrochemical oxidation. In these experiences a higher number of intermediates were generated as HPLC analysis demonstrated. The decolourisation process for the three electrochemical processes studied presented a pseudo-first order kinetics.
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PMID:Influence of electrochemical reduction and oxidation processes on the decolourisation and degradation of C.I. Reactive Orange 4 solutions. 1934 78

A full-scale pre-denitrification process treating cokes wastewater containing toxic compounds such as phenols, cyanides and thiocyanate has shown good performance in carbon and nitrogen removal. However, field operators have been having trouble with its instability without being able to identify the causes. To clarify the main cause of these sudden failures of the process, comprehensive studies were conducted on the pre-denitrification process using a lab-scale reactor system with real cokes wastewater. First, the shock loading effects of three major pollutants were investigated individually. As the loading amount of phenol increased to 600 mg/L, more COD, TOC and phenol itself were flowed into the aerobic reactor, but phenol itself did not inhibit nitrification and denitrification, owing to the effect of dilution and its rapid biodegradation. Higher loading of ammonia or thiocyanate slightly enhanced the removal efficiency of organic matter, but caused the final discharge concentration of total nitrogen to be above its legal limit of 60 mg-N/L. Meanwhile, continuous inflow of abnormal wastewater collected during unstable operation of the full-scale pre-denitrification process, caused a sudden failure of nitrogen removal in the lab-scale process, like the removal pattern of the full-scale one. This was discovered to be due to the lack of inorganic carbon in the aerobic reactor where autotrophic nitrification occurs.
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PMID:Sudden failure of biological nitrogen and carbon removal in the full-scale pre-denitrification process treating cokes wastewater. 1942 99

The membrane bioreactor (MBR), a combination of activated sludge process and the membrane separation system, has been widely used in wastewater treatment. However, 90% of MBR reported were employing polymeric membranes. The usage of ceramic membranes in MBR is quite rare. Four submerged ceramic membrane bioreactors (SCMBRs) with different membrane pore size were used in this study to treat sewage. The results showed that the desirable carbonaceous removal of 95% and ammonia nitrogen removal of 98% were obtained for all the SCMBRs. It was also showed that the ceramic membranes were able to reject some portions of the protein and carbohydrate, whereby the carbohydrate rejection rate was much higher than that of protein. Membrane pore size did not significantly affect the COD and TOC removal efficiencies, the composition of EPS and SMP or the membrane rejection rate, although slight differences were observed. The SCMBR with the biggest membrane pore size fouled fastest, and membrane pore size was a main contributor for the different fouling potential observed.
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PMID:Performance and fouling characteristics of different pore-sized submerged ceramic membrane bioreactors (SCMBR). 1949 61

A 4-aminobenzenesulphonate-degrading strain W1 was isolated from the activated sludge of Dalian municipal wastewater treatment plant. Strain W1 was able to utilize 4-ABS as sole carbon and energy source under aerobic condition. It was identified as Pannonibacter sp. according to its morphological, physiological and biochemical characteristics and the analysis of its 16S rDNA gene. The optimum conditions for 4-ABS biodegradation in the shaking flasks were 10% inoculum, 30 degrees C, pH 7.0 and were rotated at speed 150 r/min, respectively. Strain W1 could keep high degrading ability even in the presence of extra carbon source. Release of ammonia and sulfate were around 77.6% and 91.5% of theoretic concentration according to 4-ABS degradation, for 4-ABS could serve as the nitrogen and sulfur source. Strain W1 showed efficient biodegradability even at 2,500 mg/L, and 90% 4-ABS removal was achieved in 32 h. The 84.4% TOC removal was achieved after 94.7% consumption of 4-ABS, and no aromatic intermediates were detected, referring the complete mineralization of 4-ABS by strain W1.
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PMID:[Isolation and identification of a 4-aminobenzenesulphonate biodegrading strain and its degradation characteristics]. 1954 28

The electrooxidation of high strength leachate from an industrial solid waste landfill site was carried out in a three-dimensional carbon bed electrode reactor (TDR). This paper discusses the kinetics and mechanism of electrooxidation on the basis of time course variation of COD, TOC and TKN (total Kjeldahl nitrogen) from the raw leachate. The batch experiments were run at different applied currents (1-3 A) for a period of 6h. A two-stage pseudo-first order reaction kinetics model was developed based on the initial rapid removal of pollutants (Phase I) followed by slow oxidation kinetics (Phase II). About 60-64% COD was removed within 1h with a rate constant 5.83 x 10(-3) min(-1) in Phase I, which was near 5-7 times greater than that of Phase II (0.81-1.03 x 10(-3)min(-1)). The mineralization efficiency was found to be significant in the range 0.83-0.84. The apparent faradic efficiency and specific energy consumption for COD removal were also estimated. The mechanism of electrooxidation was discussed with the help of adsorption, kinetic and SEM results.
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PMID:Kinetics of electrooxidation of landfill leachate in a three-dimensional carbon bed electrochemical reactor. 1956 36

A reef system in the southwestern Gulf of Mexico is affected by anthropogenic activities, sourced by urban, fluvial, and sewage waters. Dissolved metals have higher concentrations during the rainy season. V and Pb, were derived from an industrial source and transported to the study area by rain water. On the other hand, Jamapa River is the main source for Cu and Ni, which carries dissolved elements from adjacent volcanic rocks. Principal Component Analysis shows a common source for dissolved nitrogen, phosphates, TOC, and suspended matters probably derived from a sewage treatment plant, which is situated near to the study area.
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PMID:Distribution of dissolved trace metals around the Sacrificos coral reef island, in the southwestern Gulf of Mexico. 1959 44

Electrochemical oxidation is a promising technology to treatment of bio-refractory wastewater. Coking wastewater contains high concentration of refractory and toxic compounds and the water quality usually cannot meet the discharge standards after conventional biological treatment processes. This paper initially investigated the electrochemical oxidation using boron-doped diamond (BDD) anode for advanced treatment of coking wastewater. Under the experimental conditions (current density 20-60mAcm(-2), pH 3-11, and temperature 20-60 degrees C) using BDD anode, complete mineralization of organic pollutants was almost achieved, and surplus ammonia-nitrogen (NH(3)-N) was further removed thoroughly when pH was not adjusted or at alkaline value. Moreover, the TOC and NH(3)-N removal rates in BDD anode cell were much greater than those in other common anode systems such as SnO(2) and PbO(2) anodes cells. Given the same target to meet the National Discharge Standard of China, the energy consumption of 64kWhkgCOD(-1) observed in BDD anode system was only about 60% as much as those observed in SnO(2) and PbO(2) anode systems. Further investigation revealed that, in BDD anode cell, organic pollutants were mainly degraded by reaction with free hydroxyl radicals and electrogenerated oxidants (S(2)O(8)(2-), H(2)O(2), and other oxidants) played a less important role, while direct electrochemical oxidation and indirect electrochemical oxidation mediated by active chlorine can be negligible. These results showed great potential of BDD anode system in engineering application as a final treatment of coking wastewater.
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PMID:Advanced treatment of biologically pretreated coking wastewater by electrochemical oxidation using boron-doped diamond electrodes. 1959 22

The results of an investigation characterizing the nutrients and suspended solids contained in stormwater from Kranji Catchment in Singapore are reported in this paper. Stormwater samples were collected from 4 locations and analyzed for the following eleven analytes: TOC, DOC, TN, TDN, NH(4)(+), NO(2)(-)+NO(3)(-) (NO(x)), TP, TDP, OP, SiO(2) and TSS. Stormwater was sampled from catchments with various proportions of rural and urban land use, including forested areas, grassed areas, agricultural and residential and commercial areas. The event mean concentrations (EMCs) of nutrients and TSS from sampling stations which have agricultural land use activities upstream were found to be higher. Comparison of site EMCs (SMCs) with published data showed that the SMCs of the nutrients and TSS are generally higher than SMCs reported for forested areas but lower than published SMCs for urban areas. Positive correlations (p<5%) were found between loading and peak flow at locations most impacted by ubanisation or agricultural activities. Correlation between loading and rainfall variables was less distinct. EMC was found to correlate less with rainfall and flow variables compared to pollutant loading. Unlike loading, no consistent pattern exists linking EMC to any particular storm or flow variable in any of the catchments. Lastly, positive correlations were obtained between the particulate forms of nitrogen and phosphorus and TSS.
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PMID:Nutrients and suspended solids in dry weather and storm flows from a tropical catchment with various proportions of rural and urban land use. 1966 Aug 49

The performances of A/O-MBR/RO system for the removal of nitrogen and COD were investigated. Result indicated that most organic was removed in the A/O-MBR and the average removal efficiency was 95.6%. The water quality of RO effluent which in terms of TOC < 0.9 mg x L(-1), TN < 12.65 mg x L(-1), total rigidity < 0.038 mol x L(-1), total alkalinity < 14.6 mg x L(-1) could meet the water quality requirements for the town wastewater reuse. The average removal efficiency of organic was almost unaffected by COD/N, but the process of TN removal was affected by COD/N. TN removal was primarily based on simultaneous nitrification and denitrification (SND) process occurred in the aerobic zone and the average removal efficiency of TN was 89.4% with average COD/N of 10.2. Both aerobic SND and conventional biological nitrification/denitrification contributed to nitrogen removal, the average removal efficiency of TN was 72%, 74% with average COD/N of 7.1 and 5.6. The fouling cake layer formed on the RO membrane surface was observed by scanning electric microscopy. The membrane fouling was characterized by Fourier transform infrared spectroscopy technique which showed that the major components of the foulants were soluble microbe products.
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PMID:[Combined MBR-RO process treating high strength wastewater]. 1966 50


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