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

A quinoline-degrading bacterium QL2, which utilizes quinoline as sole source of carbon, nitrogen and energy, was isolated from activated sludge in a coke-plant wastewater biological treatment system. According to the morphological characteristics, physiological and biochemical characteristics, and sequence analysis of 16S rRNA, the strain was identified as Rhodococcus sp.. The optimal temperature, initial pH, and shaker rotary speed for strain QL2 utilizing quinoline are 35-42 degrees C, pH 8-9, and 150 r/min, respectively. Extra nitrogen sources stimulate the isolate growth on quinoline, and inorganic nitrogen better than organic nitrogen, NH4+ -N better than NO3(-) -N. The degradation reaction of quinoline by strain QL2 can be described with zero order kinetic equation within the initial quinoline concentrations of 60-680 mg/L. When the initial concentration was 150 mg/L, quinoline was degraded completely in 8 hours and TOC removal efficiency was 70% in 14 hours. This bacterium produced pigmented compounds, and ring nitrogen was released into the growth medium as ammonium. The main intermediate in the degradation pathway was 2-hydroxyquinoline by the analysis of HPLC and GC/MS. With a broad range of substrate utilization, the strain can degrade phenol, naphthalene, pyridine, and some other kinds of aromatic compounds.
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PMID:[Isolation, identification and degradation characteristics of a quinoline-degrading bacterium Rhodococcus sp QL2]. 1861 25

A soil column filled with sandy soil was constructed to investigate changes of terminal electron acceptors (TEA) and TOC in redox zones of landfill leachate pollution plume, and their models were established, respectively. Results indicated that the time of peak-concentration appearance of different reducing products was related to the ability of terminal electron acceptors to compete for terminal electrons. The most competitive ones showed sharp concentration increased earlier. For example, the peak concentration of NO2(-) appeared earlier than that of Fe2+. The concentration of TOC increased in methanogenic zone, iron reduction zone, nitrate reduction zone and oxygen reduction zone, and its rate was 8.27, 8.56, 8.85, 9.06 and 9.11 mg/(L h), respectively. Degradation rate of contaminants by different microbes mainly depended on the amount and availability of terminal electron acceptors. The reaction rate was related to ability of terminal electron acceptors to compete for terminal electron, that is the stronger the ability of terminal electron acceptors to compete for terminal electrons, the easier could be used and consumed by microorganisms and the more sensitive to reflect on environmental pollution.
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PMID:[Terminal electron acceptor process in landfill leachate pollution plume]. 1864 38

The separate effect of protein concentration, nitrate concentration and carbon/nitrogen (C/N) ratio on the rate and efficiency of nitrate reduction was studied in batch reactors fed with a mixture of a synthetic substrate and a saline protein-rich salmon-plant effluent. At a constant nitrate concentration (40 mg L(-1)), the specific rate of nitrate removal decreased by 60% with increasing initial protein concentration (392 to 1900 mg L(-1)) and ammonification prevailed under these conditions; meanwhile at a constant protein concentration (1104 mg L(-1)), the specific rate of nitrate removal increased 58 times with increasing nitrate concentrations (0.5 to 78 mg L(-1)) and denitrification was the main route for nitrate reduction. The C/N ratio had an inverse effect on the specific rate of denitrification; the latter ranged from 227 to 563 [mg NO3(-)-N (g VSS d)(-1)] for a C/N ratio of 163 to 16 [mg TOC (total organic carbon) (mg NO3(-)-N)(-1)], respectively. On the other hand, the ammonia production rate was proportional up to a C/N ratio of 150.
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PMID:Organic and nitrogenous matter effects on the denitrification of saline and protein-rich effluents. 1872 43

A comparative study of the degradation of Acid Orange 7 (AO 7) aqueous solutions in acidic medium of pH 3.0 by electro-Fenton process using Pt or boron-doped diamond (BDD) anode was reported. The oxidative degradation of AO 7 by electrochemically generated hydroxyl radicals follows a pseudo-first order kinetic with a similar rate constant with BDD or Pt anode. The absolute rate constant of the AO 7 hydroxylation reaction was determined as (1.10+/-0.04)x10(10)M(-1)s(-1) by using the competition kinetic method. The comparative study of TOC measurements during electro-Fenton treatment showed a higher mineralization rate with BDD than Pt anode at the first hours of electrolysis because of the higher oxidizing power of this anode. The electro-Fenton degradation of AO 7 was followed by monitoring the formation and evolution of aromatic intermediates which are oxidized to aliphatic carboxylic acids before mineralization (transformation to CO(2) and inorganic ions, i.e. sulphate, nitrate and ammonium). The follow-up of the solution toxicity evolution shows the formation of intermediates more toxic than AO 7 and the connection between toxicity and aromaticity. A mineralization reaction pathway of AO 7 by electro-Fenton degradation involving all the intermediates identified was proposed.
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PMID:Degradation of Acid Orange 7 by electrochemically generated (*)OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: a mechanistic study. 1876 Aug 22

Radiolysis of aqueous solution of thiocyanate by 60Co gamma-rays was studied. In condition of pH = 1 and pH = 3,25 mg/L SCN- was decomposed under the dose of 6 kGy, with decomposition rate of 98.11% (pH = 1) and 95.97% (pH = 3) respectively. 25 mg/L SCN- (pH = 7) was decomposed under the dose of 9 kGy and the decomposition rate is 99.33%. In the alkaline condition, pH = 10 and pH = 12, the dose of 18 kGy was need, and the decomposition rate is 99.64% and 99.93% respectively. High SCN- concentration means that more radiation dose is need. From the comparison of before radiolysis and after radiolysis's TOC (total organic carbon) and TN (total nitrogen) of SCN- solution, little TOC and TN was removed. The determination of SO4(2-) and NO3- concentration indicated that sulfur element was removed and converted to SO4(2-), and nitrogen element rarely converted to NO3-, but converted to other forms of nitrogen.
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PMID:[Radiolysis of aqueous solution of thiocyanate by gamma-rays]. 1876 4

Ethanol and acetate were examined as potential candidates to enhance denitrification at low temperature in soils contaminated by fur farms. Five pilot-scale sand and gravel columns with a top layer of soil from a fur farm were set up and fed with nitrate-containing water (influent concentration of 100 and 200 mg L(-1)) for 459 days at 6+/-2 degrees C. Two of the columns also received acetate and two other ethanol while one received no additional C-substrate. During the experiment, various C:N-ratios were tested to find the most optimal concentration of the added C-substrates, and effluent concentrations of nitrate, nitrite, and TOC were monitored. At the end of the experiments, soils in the columns were unpacked and the soils were used to measure a pattern of enzyme activities and the rates of denitrification in microcosms. The fur farm contaminated soil appeared to harbour a good intrinsic potential for denitrification, which could be greatly enhanced by the introduction of ethanol or acetate. Consequently, in the C-substrate-fed columns, 95-100% of the influent nitrate was removed after an acclimatization period of some weeks. Ethanol with C:N-ratio of ca. 6 at the nitrate level 200 mg L(-1) proved to be the most promising candidate to be used in field trials.
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PMID:Acetate and ethanol as potential enhancers of low temperature denitrification in soil contaminated by fur farms: a pilot-scale study. 1878 79

The extensive use of antibiotics has been a worldwide environmental issue. In this study the fate of oxytetracycline (OTC), under photoirradiation, was investigated. The results showed that OTC photolysis followed first order model kinetics. Direct photolysis rate was found to be dependent on the initial OTC concentration, with k value ranging from 0.0075 to 0.0141 min(-1), in the OTC concentration from 40 to 10 mg/L. OTC photolysis was highly pH-dependent and strongly enhanced at a high pH value, with a k value of 0.0629 min(-1) at pH 9. Enhanced OTC photolysis has also been observed in the presence of nitrate and low concentration of dissolved organic matter. Upon irradiation for 240 min, only 13.5% reduction of TOC occured in spite of a rapid consumption of 90% of OTC. The byproducts from OTC photolysis have been analyzed using high-performance liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS), and the degradation pathway of OTC in the photo process was proposed. By employing luminescent bacterium to assess the adversity of the degradation compounds, an increased effect of toxicity occured in spite of the great consumption of OTC in the photoirradiation process. After irradiation for 240 min, the inhibition rate was 47%, significantly higher than the initial rate of 21% (p < 0.05), revealing a potentially higher adversity risk on the microorganism upon OTC photolysis.
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PMID:Aqueous oxytetracycline degradation and the toxicity change of degradation compounds in photoirradiation process. 1881 75

By decreasing hydraulic retention times to increase substrates loading rates under anoxic conditions, an attached-growth bioreactor packed with porous sponges was started to treat the wastewater contaminated by sulfide, nitrate, nitrite and organic carbon. The influent concentrations of sulfide, nitrate-nitrogen, nitrite-nitrogen and TOC were 200 mg/L, 52.5 mg/L, 20 mg/L, 20 mg/L and relevant removal efficiencies were 99%, 99%, 95.5% and 80% respectively. The simultaneous removal of nitrogenous compounds, sulfide and organic carbon was achieved by the desulfurization and denitrification process. With increasing of the substrate loading rates, the adaptabilities of nitrate and nitrite to the influent shock load decreased. The adaptability of nitrate to the shock load was better than that of nitrite. Compared with the impact on the bioreactor brought by the increasing of the influent shock load, the destruction of anoxic environment had greater influence on the degradation of nitrate and nitrite. 60% of the removed sulfide was converted to sulfur by microorganisms. The dominant reaction of autotrophic denitrification occurred together with the heterotrophic denitrification whose percent was 21.76%.
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PMID:[Simultaneous removal of sulfide, nitrogenous compounds and organic carbon by anoxic attached-growth bioreactor]. 1882 66

A box filled with sandy soil was constructed to investigate dynamitic development and evolution of redox zones in landfill leachate-polluted plume. The results indicated that with time elapsing and pollution aggravating, redox zones moved ahead slowly; Methanogenic zone/ sulfate reduction zone extended gradually, and then inert zone appeared with further pollution. During the whole course of the dynamitic development and evolvement of redox zones, concentrations of TOC, sulfide, NH4(+) -N, HCO3-, CO2 and Fe2+ increased with time and decreased with distance; concentrations of NO3- and DO decreased with time and increased with distance; SO4(2-) concentration decreased first and then increased over time; but decreased with distance. Moreover, with time elapsing and pollution aggravating, the Fe3+ content of sediments was decrease and TOC was increase. Within oxygen reduction zone, nitrate reduction zone, iron reduction zone and methanogenic zone/sulfate reduction zone, Fe3+ content of sediments accounted for 70.5% of OXC decreased to 56.3%, 41%, 28.3% and 15%, and the TOC accounted for 98.7% of RDC increased to 102.0%, 107.0%, 142.9% and 162.1%, respectively; Fe2+ mainly precipitated as FeS and FeCO3, and accounted for 80.6%, 175.6%, 377.7% and 555.1% of total Fe2+, respectively.
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PMID:[Dynamitic development and evolution of redox zones in pollution plume]. 1882 81

A combined strategy of a photo-Fenton pretreatment followed by a Sequencing Batch Biofilm Reactor (SBBR) was evaluated for total C and N removal from a synthetic wastewater containing 200 mg L(-1) of the antibiotic Sulfamethoxazole (SMX). Photo-Fenton reaction was performed with two different H2O2 concentrations (300 and 400 mg L(-1)) and 10 mg L(-1) of Fe2+. The pre-treated effluents with the antibiotic intermediates as sole carbon source, together with a nutrients solution, were used as feed for the biological reactor. The SBBR was operated under aerobic conditions to mineralize the organic carbon and the hydraulic retention time (HRT) was optimized down to 8 hours. Then, an anoxic denitrification stage of 24 hours of HRT was added right after the aerobic stage of the same duration in order to remove the NO3(-) generated along the chemical-biological treatment. TOC, COD and SMX concentrations together with O2 uptake rate (OUR) profiles were monitored in purpose of assessing the performance of the system. NO3(-), NH4+ and total N concentrations were analyzed to find out the fate of N contained in the initial SMX molecule. A start up strategy resulted in the correct formation of a biofilm over the volcanic support. The total TOC removals achieved with the combination of the chemical and the biological processes were 75.7 and 87.7% for the low and the high H2O2 concentration pretreatments respectively. Practically all N present in the SMX solution was eliminated in the SBBR when the aerobic-anoxic strategy was used.
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PMID:Combination of photo-Fenton and biological SBBR processes for sulfamethoxazole remediation. 1902 9


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