V. P. Murygina

Kinetics of the degradation of aliphatic hydrocarbons by the bacteria Rhodococcus ruber and Rhodococcus erythropolis

Consumption of aliphatic hydrocarbons by the bacteria Rhodococcus ruber Ac-1513-D and Rhodococcus erythropolis Ac-1514-D grown on mixed n-alkanes and diesel fuel was studied. Consumption of diesel fuel hydrocarbons by the strains was less intense in comparison with the n-alkane mixture. The strains showed differences in growth rate and consumption of the substrates, which suggests that they possess different mechanisms of hydrocarbon uptake.

Laboratory simulation study of the solid-phase aerobic fermentation of nitrocellulose-containing wastewater sludge

The solid-phase aerobic degradation of nitrocellulose-containing sludge from the Aleksin Chemical Industrial Complex was studied by laboratory simulation with the use of activated indigenous microflora. This method applied to control physicochemical parameters (pH and aeration rate) led to an average nitrocellulose removal efficiency of about 26.3% during the first 9 days. The kinetic characteristics of the fermentation process were determined: the rate constants of nitrocellulose degradation varied from 0.026 to 0.036 day−1, and the half-life times were 20–27 days. Optimum operating conditions for nitrocellulose degradation by an indigenous microbial community were achieved at a sediment humidity level higher than 70%. Sodium humate was introduced into the test sludge as a rich source of organic materials in order to intensify the process of solid-state fermentation. Comparative analysis of the results revealed only an insignificant effect of physiological humate doses on nitrocellulose degradation. The maximum efficiency of nitrocellulose removal increased from 26.3% (base sample) to 29.4% upon the introduction of 1.6% sodium humate.

Effect of cavitational disintegration of surplus activated sludge on methane generation in the process of anaerobic conversion

The effect of mechanical pretreatment of surplus activated sludge from the wastewater treatment facilities of a plant producing chips (LLC “Frito Lay Manufacturing,” Kashira, Moscow oblast) in a cavitation disintegrator on methane generation in the process of anaerobic conversion is investigated. In laboratory conditions, cavitation disintegration pretreatment of the activated sludge results in a two- to sixfold increase in the transfer of various types of organic materials from the cell suspension into the aqueous phase. It is demonstrated that cavitation pretreatment of the activated sludge makes it possible to produce 31% extra methane as compared to the amount produced from the original sludge.

The optimization of the conversion of agricultural waste into volatile fatty acids under anaerobic conditions

The selection of a biocatalyst was performed and the first optimal microbial association was obtained. This association was capable of converting products of depolymerization of sawdust, straw, and lignin into volatile fatty acids with an acid-producing activity that was greater by 1.3 times than the initial methane activity. The largest percentages of butyric acid (40%) and ethanol (14%) were obtained from biomass out of straw in concentrations of soluble organic substances from 2.5 to 6.3 gCOD/L. Using biomass from sawdust and lignin at concentrations of organic substances from 4.0 to 8.0 gCOD/L and a duration of the conversion process of up to 18 days we obtained an output of butyric acid that was two times smaller than that on a biomass from straw.

Influence of various degradation conditions on the properties of gas-generating soils in the process of their decontamination

The properties of gas-generating soils (GGS) in the process of biofermentation under anaerobic and aerobic conditions are studied. The degradation of organic matter (OM) in a soil under natural occurrence conditions (without free access of air oxygen) at temperatures from 10 to 12°C is demonstrated to proceed at a specific reaction rate of k = 0.096 year−1. The main phase of gas generation (biogas formation) is shown to take 15 years, with the content of methane in the biogas being 60−80 vol %. It has been established that, under the conditions of forced aeration of the GGS array, the specific reaction rate of OM degradation increases 10-fold, to 0.9673 year−1, with a nearly complete decomposition of OM taking 1.5−2.0 years. A prerequisite for achieving of the predicted result is the maintenance of the environment humidity at a level not lower than 50%. Application of an alternative method, a thermal treatment of GGS increases the degree of OM decomposition to 59% within 4 h at 200°C and to 75% within 2 h at 300°C. In this case, residual organic substances are carbonized in the course of thermal treatment, transforming into a material resistant to microbiological decomposition. In fact, after heating at 200−300°C, GGS becomes inert from the gas-geochemical point of view.

Effect of a preliminary physicochemical treatment of bituminous crusts resulting from oil pollution on the bioremediation of upland swamps with oil decomposers

Physicochemical preprocessing of a bituminous crust resulting from oil pollution by various reagents capable of hydrolyzing its structure, followed by aerobic degradation of hydrocarbons (HC) with the Rhoder bacterial oil-degrading preparation, was carried out. The crust was hydrolyzed with hydrogen dioxide, calcium hydroxide, and alkaline hydrolysate of crop production waste in concentrations from 2 to 20%. The best results in the destruction of the bituminous crust were obtained for processing the upper layer (0−2 cm) of the soil with calcium hydroxide, which resulted in an increase of the humidity of the hydrolyzed layer from 24 to 77%. The destruction of the bituminous crust with chemical agents made it possible to increase the effectiveness of biodegradation of HC from 9.97 to 26.40% in the upper soil layer and from 0.00 to 48.20% in the bottom soil layer. The kinetic characteristics of biodegradation after preprocessing, namely the rate constants of degradation and half-lives of HC were determined, the maximum values of which were found to be 0.015 day−1 and 47 days and 0.032 day−1 and 22 days for the upper and bottom soil layers, respectively.

Regulation of the physicochemical and biotechnological process parameters of the liquid-phase aerobic degradation of nitrocellulose-containing wastewater sludge

The physicochemical process parameters of the liquid-phase aerobic degradation of nitrocellulose- containing sludge from the Aleksin Chemical Industrial Complex was studied by laboratory simulation with the use of activated indigenous microflora. The intensification of the aeration process and the saturation of sediments with atmospheric oxygen in a concentration of no lower than 7.7 (mg O2)/L, the maintenance of the pH values of a bioreactor medium in an alkaline range (7.8–8.0), and the moistening of bottom sediments to 90% led to a nitrocellulose removal efficiency of no lower than 55.1% after 31 days. The kinetic characteristics of the fermentation process were determined: the rate constant of nitrocellulose degradation was 0.032 day–1 and the half-life time was 22 days. Upon the annealing of sediment after fermentations, it was found that the residual combustible component was most likely pure cellulose, which was formed as a result of the degradation (elimination of nitro groups) of parent nitrocellulose. An activated sludge concentrate (10% on a total sediment weight basis) with a 99% moisture content and a 18.7% ash content from the Aleksin Aeration Station was added to the test sediment mass in order to enrich indigenous microflora and to increase the efficiency of nitrocellulose biodegradation. The stimulating influence of activated sludge microorganisms on the biodegradation of nitrocellulose was not detected because of their low cellulolytic activity.