Efecto inhibitorio del sulfuro sobre un proceso respiratorio nitrificante
Water pollution is a serious problem affecting Mexico and the world. This contamination is given by high concentrations of carbon, nitrogen and sulfur compounds, among others. Sewage can come from industries or households. This water is dropped in receiving aquifers without being treated, causing eu...
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2010 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:nc580m827 |
| Acceso en línea: | https://doi.org/10.24275/uami.nc580m827 |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Nitrification info:eu-repo/classification/LEM/Ingeniería bioquímica info:eu-repo/classification/LEM/Desnitrificación info:eu-repo/classification/LEM/Sulfuros info:eu-repo/classification/LEM/Amonio info:eu-repo/classification/LEM/Denitrification info:eu-repo/classification/LEM/Biochemical engineering info:eu-repo/classification/LEM/Nitrificación info:eu-repo/classification/LEM/Sewage -- Purification info:eu-repo/classification/LEM/Aguas residuales -- Purificación info:eu-repo/classification/LEM/Sulfides info:eu-repo/classification/LEM/Ammonium info:eu-repo/classification/cti/6 |
| Sumario: | Water pollution is a serious problem affecting Mexico and the world. This contamination is given by high concentrations of carbon, nitrogen and sulfur compounds, among others. Sewage can come from industries or households. This water is dropped in receiving aquifers without being treated, causing eutrophication pollution phenomena as well as serious damage to human health and the environment. The main nitrogen pollutant is ammonia and sulfide in the case of sulfur compounds, as this compound is highly toxic and corrosive. Ammonia and sulfide can be found in a large amount of industrial effluents such as petrochemical, food processing, paper, just to name a few, observing high concentrations of these two pollutants. One possible way of treating water contaminated by ammonium is nitrification-denitrification. Nitrification is a chemolithoautotrophic respiratory process where ammonium is oxidized to nitrite and subsequently to nitrate. Nitrate is then reduced to nitrogen gas by denitrification. Little is known about the effect of sulfide on the nitrifying respiratory process. Some authors mention that sulfide causes inhibitory effects on nitrification, but these studies do not show kinetic data or response variables as evidences to these assumptions, so it is not known whether sulfide causes inhibition or its toxicity affects the respiratory nitrifying process. For these reasons the aim of this study was to extend the information on the effect of sulfide on nitrification by using response variables such as efficiency of ammonium consumption and yields of nitrite and nitrate formation, and kinetic variables such as specific rates for ammonium consumption and nitrate formation, which determine the effect of sulfide on nitrification. This study was conducted in batch cultures inoculated with the nitrifying sludge from a continuous stirred tank reactor at steady state. In this reactor the efficiency of ammonium consumption (E-NH₄⁺ ) was of 100% ± 3.4 and the yield of nitrate production (YNO3-) of 0.96 ± 0.09. In batch cultures without sulfide, the nitrifying process was carried out successfully under the experimental conditions used, obtaining that after 24h, the E-NH₄⁺ was 100% ± 2.3 and YNO3- of 0.88 ± 0.04. The specific rates of NH₄⁺ -N consumption and NO3 - -N production were 0.095 ± 0.01 and 0.088 ± 0.009 mg N/mg protein h, respectively. By adding sulfide to nitrifying cultures at initial concentrations of 112 ± 2.5, 58 ± 2.5 and 13 ± 0.7 mg HS- -S/L the specific speeds decreased by 92%, 92% and 73.7% respectively for the consumption of ammonium and 96.5 %, 95% and 88.6% respectively for the production of nitrate. The results evidence the inhibitory effect of sulfide on nitrification and that sulfide inhibited the whole breathing nitrifying process. After 60h, the E-NH₄⁺ was 11.1%, 29.7% and 100% respectively, while the YNO3- was 0.3, 0.65 and 0.47, showing that sulfide affected mainly the nitrite oxidizing process. Moreover, it was found that the removal of sulfide during the tests was due to chemical oxidation and not biochemical oxidation, since in all cases the rate of sulfide removal was close to the velocity obtained in the abiotic control (38.0 ± 2.1 mg HS- -S/Lh), with sulfate (SO₄²⁻ ) as the main product and a transient formation of thiosulfate (S₂O₃²⁻ ). Test was also performed under the same experimental conditions, but now with an initial sulfate concentration of 83.2 ± 2.6 mg SO₄²⁻ -S/L, observing that sulfate had no significant effect on nitrification, showing that sulfide was the responsible for the nitrification inhibition and not the product of its oxidation. During all tests the pH was monitored, obtaining an average value of 8.6 ± 0.3. It has been previously reported that at such pH value nitrification is performed favorably. Another point discussed was the oxygen availability during the tests. Prior to carrying out the kinetics, it was verified that the amount of oxygen present in the serological bottles was sufficient, calculating with the highest concentrations of ammonium and sulfide used in this study. Therefore, neither the sulfate present during the kinetics at different concentrations of sulfide (from the oxidation of sulfide) or the increase in the pH value, nor the lack of oxygen availability, were the causes of the negative effect observed on the nitrifying respiratory process. |
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