ИСТИНА

As a result of man-made activities, gas-generating grounds (GG) have been accumulating for decades, containing impurities of decomposing organic substances and capable of producing biogas, consisting of combustible components - hydrogen and methane. Such grounds include soils enriched with organic matter, landfills for municipal solid waste, soils of irrigation fields and sewage sludges. As the territories containing GG are often used for housing construction, the development of methods for decontamination of grounds capable of generating toxic and explosive biogas is highly relevant. The most promising method of GG neutralization is a conversion in the properties of grounds, aimed primarily at suppressing their gas functions by various physical (mechanical, hydrodynamic, aerodynamic, thermal effects on GG), chemical (hydrolysis, chemical precipitation and oxidation of pollution) and biological (activation of microflora and bioaugmentation) methods in situ. Studies were conducted on simulation of suppressing gas formation in the course of deactivation of gas-generating grounds (GG) by their chemical and biological treatment in anaerobic conditions. The chemical and gas-geochemical characteristics of GGs sampled from wells of different depths drilled within the area of a construction site (Moscow, NEAD) were examined. Simulation of an anaerobic gas generation process showed that the gas generation rate under conditions of natural occurrence (8–10°C) within the boundaries of identified anomalous zones would be about 215 l/(t·year) in the center and 157 l/(t·year) in the north of the site. The kinetics of organic substances degradation revealed the rate constant for gas-forming substrates degradation of 0.013 year-1 for the central zone, and 0.009 year-1 for the northern zone. According to the calculations, the main gas generation phase would be completed within 55 years in the central zone, and within 79 years in the northern one, while methane volume content of in the gas mixture would be 9–12%. Simulation of chemical suppressing residual gas generation showed that 10-fold reduction of gas generation intensity could be achieved by adding 45% calcium hypochlorite solution at a rate of 1% of the overall soil volume into the GG-massive in the central anomalous zone. The gas generation in grounds after their chemical treatment would vary in the range from 1.6 to 35 l/(t·year), i.e. the process of gas generation in fill-up grounds would be suppressed almost completely. Simulation of biological process of gas generation suppression in the northern zone, caused by the presence of oil pollution, made it possible to predict that applying the certified oil degrader Rhoder at a dose of 1·109 CFU/ml would significantly raise the rate of hydrocarbon degradation up to 1.02 year-1 and at the same time enhanced reducing the half-life decay period of hydrocarbons from 79 years to 0.68 years.