Displacement Phenomenon of Slow and Fast Growing Species in Microorganisms Association

In the process of the biological treatment of sewage, the multicomponent system of the substrate is converted by an association of microorganisms. The composition of species of microorganisms in the system depends on the substrate available and on the conversion of substrate. For this, a mathematical model is presented, which describes the change of the composition of species according to the rate of growth of the individual species on the basis of load (substrate available/biomass). The diversity of the biological system increases with decreasing load. The model is tested by practical examples.     

Basic Equations to Describe the Kinetic Isotope Effect during Microbial Substrate Transformation

The redistribution of stable isotopes allows specifying the pathway of substrate utilization and identifying the relevant kinetic parameters. To describe degradation kinetics and identify predominant metabolic pathway for microbial substrate transformation, new basic equations, which take into account the dynamics of heavier isotope in the substrate, intermediates, and products were added to the common model of microbial substrate transformation, which did consider isotope differences at any step of substrate transformation. Using the unified approach, we showed that the dynamic changes of isotope fractionation depend on the kinetic coefficients, the initial conditions, and the microorganisms participating in the reactions during microbial denitrification, anaerobic oxidation of methane by sulphate and nitrite, aerobic oxidation of methane gas, and anaerobic digestion of cellulose.     

Methane Production in a West Siberian Eutrophic Fen Is Much Higher than Carbon Dioxide Production: Incubation of Peat Samples,Stoichiometry, Stable Isotope Dynamics,Modeling

Water Resources - Homoacetogenic bacteria can play an important role in anaerobic degradation of organic matter in peatlands at low temperatures. However, little is known about the conditions when...     

Inhibition by nitrite ion in the process of methane anaerobic oxidation by microorganisms and fractionation dynamics of stable carbon and hydrogen isotopes

In the process of methane oxidation by nitrite ion, the latter, when in high concentration, inhibits the oxidation process. The effect of inhibition is incorporated in the proposed model, describing the dynamics of anaerobic oxidation of methane and its heavy fractions δ¹³CH₄ and δC²H¹H₃ by nitrite ion. Two substrates—methane and nitrite—are considered in a modified Monod function, describing the oxidation rate. The model is calibrated against experimental data given in [8]. The dynamic behavior of the system under a deficiency of methane or nitrite ion is described. The dynamics of δ¹³CH₄ and δC²H¹H₃ are shown to be governed by the oxidation dynamics of total methane CH₄. By contrast to the conventional opinion that Rayleigh equation corresponds to 1st-order kinetics in terms of substrate concentration, this study shows that Rayleigh equation can be derived from dynamic equations for methane with heavy isotopes (¹³C and ²H), whatever the kinetic type of total methane oxidation.     

The Effect of Fatty Acid Diffusion in Leachate on the Propagation of Concentration Waves in the Process of Municipal Solid Waste Decomposition

A distributed model of municipal solid waste decomposition is proposed. The main model parameters are concentrations of municipal solid waste, volatile fatty acids, and the biomass of methane-producing microorganisms. Numerical analysis of the model is made. Diffusion of fatty acids in leachate, which facilitates the formation of anaerobic conditions, is shown to cause the formation of concentration chemical waves propagating in the space. The area of initiation methane production is found to expand.     

Sequencing Batch Experiments with activated Sludge Consuming Glucose and Phenol

During the rather short solids retention time θ = 1.25 d phenol is not utilized by activated sludge and only glucose is consumed during the sequencing batch experiments. After glucose consumption the residual COD concentration (COD = 820 mg/l) is represented mainly by the phenol concentration. During the rather long solids retention time θ = 8 d phenol is consumed by activated sludge as well as glucose. In this case the residual COD concentration is much smaller (COD = 46 mg/l) and the ratio BOD₅/COD = 0.1 is small, too. The general model of biological treatment suggested by one the authors earlier can describe the sequencing batch experimental data rather well.     

Analysis of the mechanism and mathematical modeling of diethylhexylphthalate degradation in aquatic environment

Degradation mechanism of diethylhexylphthalate, a pollutant of water bodies, is analyzed. A modified first-order equation with a correction for a nondegradable fraction is suggested. The succession of biochemical reactions in the process of anaerobic degradation of monoethylhexylphthalate is considered, and two stages—ester hydrolysis and phthalic acid transformation into methane and carbon dioxide—are identified as limiting the overall rate. A one-dimensional distributed model is used to describe the degradation of three phthalates with different water solubility: diethylphthalate DEP, which has a relatively high solubility; dibutyl phthalate DBP, poorly soluble; and diethylhexylphthalate DEHP, almost insoluble. The physicochemical processes of sorption/desorption play an important role in the process of their degradation. The enzymatic splitting, carried out by microorganisms, reduces the concentration of dissolved diethylhexylphthalate and can facilitate desorption processes.     

Models and Design of Aerobic Biological Treatment Processes

Various models, applied to the design of aeration tanks, trickling filters and rotating discs, are compared. The adequacy of the models is established from the minimal mean square deviation of the measured and calculated values of the effluent concentration of a pollutant. It is shown that at the oxidation of simple substrates of the glucose type Moser's model is an adequate model and Monod's model is a particular case of this model. If a single substrate has a large concentration, activated sludge or biofilm become “saturated” and the oxidation kinetics follows the zero order. As the processing of the results of some experiments showed, the classical Monod model and its extreme case—the first-order equation of a reaction—are not adequate to the processes of the oxidation of multicomponent municipal sewage water. Equations for reactions of higher orders are true for them. The rate constant of the first-order reaction correlates well with the effluent concentration-influent concentration ratio, i.e., it is variable and depends on the treatment conditions and, above all, it is inversely proportional to the level of treatment.     

Successive recognition of significant and strong earthquake-prone areas: The Baikal–Transbaikal region

Doklady Earth Sciences - This report continues a series of works by the authors on earthquake-prone areas recognition by the algorithmic system FCAZ. For the first time, successive earthquake-prone...