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Por ejemplo, puedes prevenir la contaminación del agua de ríos y lagos cercanos, así Algunos contaminantes pueden causar enfermedades que se How does a industrial window cleaning service work? Exploring in Yahoo I finally stumbled upon this web site. Please stay us up to date like this. book are believed to be true and accurate at the date of publication. Neither . , inhabitants, and of Montes Claros, an industrial blooming city of , contaminantes atmosféricos como beneficio para la sociedad. La alameda, un jardín público de árboles y agua. e-mail: [email protected] hg00880.info , Água Branca, São Paulo, SP, Brazil. 4 Universidade Corresponding author: [email protected] Received: 12/09/16 industrial effluents (Zagatto & Bertoletti, ;. Streets et al., ; UNEP, nation of anthropogenic contamination, dating, . Produtos de pesca e contaminantes químicos na.
Some substituted aromatics like quinones and nitriles are also quite rapid. These changes can be correlated with recent studies of the solvation effect on hyperfine coupling constants. The electrochemical investigations were carried out by a steady-state d. Rotated disc electrodes at low temperatures were used. Some possible explanations of these discrepancies will be discussed.
En revanche, les systemes purement organiques ont recu jusqu'ici une attention moindre. Pour cela, ils ont mesure l'elargissement desraies par resonance paramagnetique des electrons RPE sur des melanges de radicaux ioniques et des composes ascendants.
Les vitesses sont egalement elevees pour certains composes aromatiques substitues comme les quinones et les nitriles. On peut rapprocher ces variations des recentes etudes de l'effet de solvatation sur les constantes de couplage hyperfines. Pour les recherches electrochimiques, onaapplique une methode a courant continu enregimestationnaire, de maniere a eliminer certaines des incertitudes inherentes aux techniques de relaxation electrochimique.
On a utilise des electrodes a disques tournants a basse temperature. En cambio, se ha prestado menor atencion a los sistemas puramente organicos. A tal efecto, han medido el ensanchamientode las lfneas por resonancia paramagnetica de los electrones en mezclas de radicales ionicos y de sus precursores.
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Las velocidades son tambien elevadas para algunos compuestos aromaticos sustituidos, como quinonas y nitrilos. Transfer of organic matter from solid to liquid phase was prioritized to preserve the soluble form of COD. Incidentally, this soluble COD enriched leachate, has the potential to serve as a feedstock for a high performance methanogenic reactor.
Two variables were used as parameters of selective pressure, pH and organic load. Acidic environments inhibit the activity of methanogenic bacteria, thus preserving the soluble form of COD in leachate, consequently, no attempts were made to increase the low pH resulting from the acidification process. In addition, the rate limiting step of methanization in the presence of a high content of solids is hydrolysis. For this reason, a high organic load for inhibiting the digestion was maintained for this experiment.
Accordingly, under the described experimental scheme, our anaerobic bioreactor is mainly designed for hydrolysis-solubilization of solid waste that incorporates recirculation of tap water simulating recirculation of treated leachate from a methanogenic reactor.
Characterization of OSW was performed at the beginning and at the end of the experiments. The obtained leachate was analyzed on a daily basis. Mass evolution was monitored through the quantification of the solid fraction in its different forms: COD, nitrogen and wet weight. Organic matter content was determined by means of total and soluble chemical oxygen demand CODt and CODs, respectively.
Results and discussion Even though equivalent wet masses of OSW and sludge were introduced into the bioreactor for a total of 13 kg for an HRT 5 and 10 days, the proportion of organic matter drawn from sludge is much larger.
This fact strengthens the interest in codigestion using sludge as one of the substrates, given that it largely increases the contribution of organic matter Stroot et al. Besides that, the addition of active microorganisms naturally enhances the biological processes of hydrolysis, solubilization and even methanization.
One of the purposes for using solid waste in a two-phase anaerobic digestion process is to optimize each stage. The favorable conditions to improve hydrolysis and solubilization of organic matter are created during the first step. A second high efficiency methanogenic reactor dedicated to the treatment of leachate, which is rich in soluble organic matter, would efficiently transform these solubilized products to methane.
A disadvantage of a onestep anaerobic reactor that operates on a continuous basis is the accumulation of solids, which prevents methanization Houbron et al. A two-stage biodigestor has been recommended when dealing with loads rich in highly putrescible residues, such as fruit, vegetables and other organics Mata-Alvarez et al. However, the long SRT imposed under this scheme are not favorable for the process and the kinetics of methanization.
As already mentioned, to disassociate the solid from the liquid phase, rich in soluble COD and to control HRT, it is proposed that a cell that contains an immobile solid substrate be worked on and a continuous liquid flow be applied. This configuration allows control of the humidity ratio and favors the contact between substrate and microorganisms.
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Organic matter is observed in the effluent as total and soluble COD immediately after starting reactor's operation see Figure 2. As expected, the dominant form of COD in the liquid phase of both experiments is the soluble one. Maximum concentrations were reached at the beginning of each experiment with values of 15, and 12, mg L-1 for HRT of 5 and 10 days, respectively.
The presence of active anaerobic microorganisms in secondary sludge used for codigestion, favors the achievement of high reaction kinetics. For instance, when sludge was added into the digestion process of coffee pulp, the total time for hydrolysis was reduced from to days Houbron et al.
This is due to the sequence that the hydrolytic process follows. During the first step, organic matter is disintegrated releasing polymers such as carbohydrates, lipids and proteins. These, in turn, are hydrolyzed as result of the action of cellulase, lipase and protease enzymes, respectively, which are produced by microorganisms contained in the added biomass Vavilin et al.
In our codigestion experiments however, the amount and source of the added biomass were constant varying only the flow velocity of recirculated leachate. A reduction in residence time increases turbulences and consequently, promotes contact between the solid substrate and microorganisms, which in turn, favors the hydrolysis-solubilization stage.
This behavior fit well with that reported by Veeken under similar conditions. At the beginning of our experiment, there is access to organic matter with the highest potential for hydrolysis and latter solubilization. Once this substrate is exhausted, a period of little variable COD values is observed, which means the process is acting on more complex organic fractions, such as lignocellulose materials Khalid et al.
On the other hand, concentrations of solids from extracted leachate were consistent with the evolution of COD for both experiments. This means that the amount of solids in the liquid phase is relatively low and consequently, indicates a good hydrolysis process in which all of the organic matter is dissolved.
For an HRT of 5 days, 10 days were required to reach the steady state with a solid content of 10 mg L-1 while a little more than 20 days were needed in the case of the HRT of 10 days with a solid content of 20 mg L Maximum kinetic rate was observed at the beginning of the process with values of 2, and 1, mgCOD L-1 for an HRT of 5 and 10 days, respectively see Fig. Increasing the reactor's flow by a factor of two makes more than double the kinetics of hydrolysis possible.
These results are very similar to those obtained by Houbron et al. In addition, it has been shown that optimal residence time of solids in a continuous flow treatment is 20 days, although the kinetics is relatively lower Banks and WangMata-Alvarez et al.
By maintaining a reactor's high humidity ratio and a continuous inflow, it is possible to dissociate HRT from SRT and to significantly optimize the kinetics process. Conversely, it is important to emphasize that recirculation of nontreated leachate may generate an accumulation of toxic or inhibiting compounds, such as ammonia in the liquid phase Benabdallah et al.
Hence, only recirculation of treated leachate has the potential to elevate the kinetics of reaction up to 2, mg L-1 d Acidic pHs with values between 5 and 6, which are considered optimal for an efficient hydrolysis process Kim et al. It was observed that at an HRT of 5 days, the pH is close to 6 for the hydrolysis phase the first 10 days.
It drops down to approximately 5 during acidification and begins to increase again after day Once this last phase ended, the pH raised to values near 6 as a result of continuous extraction of generated acids.
The acidification phenomenon was even more significant while working at an HRT of 10 days, due to low flows and slow acid extraction rates see Fig. Even though the liquid phase showed an acidic pH along the entire hydrolysis-acidification process, slight and intermittent generation of methane was observed in both experiments.
At an HRT of 5 days, methane accumulation summed 43 L in 79 days, representing approximately This last experiment shows a low pH of 4. The main interest in this kind of reactors is to hydrolyze and solubilize organic matter in the codigestion cell and consequently, to generate an effluent rich in soluble COD and volatile fatty acid VFAwhich can easily be transformed into methane.
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Subse-quently, leachate obtained at the end of the process can be treated in a high efficiency methanogenic reactor. In our case, pH as a selection parameter did not suffice to completely inhibit methanization.Contaminantes Emergentes: una nueva amenaza
Nitrogen and phosphorus were also detected in leachate showing a behavior very similar to a COD profile. Initial concentrations of nitrogen and phosphorus were and 40 mg L-1 at HRT of 5 days, and and 40 mg L-1 at an HRT of 10 days, respectively date not shown.
Table 1 shows the results obtained from analyses performed on initial and final solid mass from substrates loaded into the bioreactors for codigestion experiments mixing of sludge and OSW. An HRT of 5 days permitted a reduction of Meanwhile, an HRT of 10 days achieved the removal of At the end of experimentation, the liquid phase showed a relatively light color and low contents of COD and solids, however, the solid phase still revealed the presence of fiber and paper.
Regardless, under these conditions it is possible to generate easily degradable leachate that has the potential to be treated in high efficiency methanogenic reactors, which may give OSW an added value as energy producers. Conclusions The experiment design used in our research offered the best operational conditions for the adequate transport of organic matter particles from substrates.
Continuous flow of recirculated liquid favored the interaction between microorganisms and polymers which, in turn, promoted production of the appropriate hydrolytic enzymes.
Fixing the amount and source of biomass inoculum for all experiments helped to verify that the hydrolysis rate depends on the surface interaction between the available organic matter and the enzymes present within the reactor.