RECOVERY OF SEWER PIPELINES USING ANCHOR POLYETHYLENE SHEETS

Raising of problem. Microbiological corrosion, which occurs as a result of the vital activity of microorganisms in wastewater, causes the destruction of the vaulted part and significantly reduces the service life of reinforced concrete and concrete drainage pipelines. Partially destroyed pipelines of sewerage networks, operating in various hydrogeological conditions, often at great depths, must be restored using materials that can ensure the reliability of further operation in conditions of microbiological corrosion, cost-effectiveness and ease of repair. These are primarily polymer-based materials. The open method of repair and restoration work on sewer pipelines has significant advantages over trenchless, if their depth is insignificant and urban transport and pedestrian arteries do not interfere with the work. Thus, the development of a technology for repair and restoration of reinforced concrete and concrete collectors destroyed by microbiological corrosion using modern materials based on polymers is an urgent task. Purpose. Development of technology and sequence of repair and restoration work for the restoration of the destroyed vaulted part of sewer reinforced concrete and concrete pipelines by an open method using pneumatic formwork and protective anchor polyethylene sheets. Conclusion. As a result of the research, a technology and sequence of repair and restoration work was developed to restore sewer reinforced concrete and concrete collectors from 5 stages, including the stage of cleaning the collector from corrosion products and destroyed parts, installation of a pneumatic formwork and an anchor polyethylene sheet in the surviving chute part of the collector, installation of metal inventory formwork, restoration by concreting the arch on top of the anchor polyethylene sheet and dismantling of the pneumatic and metal inventory formwork.

THE INFLUENCE OF MICROORGANISMS ON THE PHYSICAL AND MECHANICAL PROPERTIES OF CONCRETE

The article considers the change in the physical and mechanical characteristics of cement stone made of the CEM I 42,5 N Portland cement in the process of bacterial and fungal corrosion for 6 months in the air and moisture conditions. It is established that the density of concrete during microbiological corrosion increases under constant moistening of the sample. However, after drying, a decrease in the density of concrete is recorded by 10 % under the influence of Bacillus subtilis bacteria and by 14 % under the influence of black mold. The degree of influence of microorganisms on the amount of water absorption of cement stone is established experimentally. Bacteria increases water absorption by 7 %, black mold increases water absorption by 10 %. Within 6 months, water absorption increased from 21 to 24,5 % for bacterial corrosion in indoor conditions, and from 24 to 29 % for fungal corrosion. When exposed to capillary moisture for 6 months, the water absorption of concrete increased to 30,4 % under the influence of Bacillus subtilis bacteria and to 37,3% under the influence of Aspergillus niger van Tieghem fungi. An increase in the water absorption of concrete is associated with an increase in porosity due to biodegradation. Under room conditions of exposure to bacteria, the porosity increases from 14,1 to 15,3 %, and from 14,3 to 17,9 % after exposure to black mold. With constant moistening, the porosity of cement concrete increases to 19,1 and 25,6 % with bacterial and fungal corrosion, respectively. The loss of compressive strength of cement stone is 13 % under the influence of bacteria and 15 % under the influence of fungi in the air for 6 months. In case of microbiological corrosion of concrete under conditions of constant wetting, the strength decreases by about 35 % in 6 months

CHANGES IN THE STRUCTURAL AND PHASE COMPOSITION OF CEMENT CONCRETE DURING MICROBIOLOGICAL CORROSION

The article considers the change in the structural and phase composition of cement stone made of Portland cement of the CEM I 42.5 N brand in the process of bacterial and fungal corrosion during 6 months when humidified. The X-ray images of cement stone show peaks that characterize the non-hydrated components of Portland cement alite, belite, tricalcium aluminate, four-calcium aluminoferrite and gypsum. By the method of X-ray phase analysis, it is found that during microbiological corrosion, the content of all phases of cement stone decreases. The aspergillus niger van Tieghem fungi have a stronger effect on the structural and phase composition of cement stone. Fungal microorganisms destroy the crystalline phases and absorb amorphous phases – calcium hydrosilicates C-S-H (I) and C-S-H (II) and tobermorite. When bacteria Bacillus subtilis affects the cement stone, the content of the calcite phase increases, which is a product of corrosion, while the action of black mold reduces the intensity of CaCO3 peaks. A decrease in the content of low-base calcium hydrosilicates and ettringite, as well as other crystalline phases, leads to a decrease in the compressive strength of the cement stone. During 6 months of microbiological corrosion of cement concrete under conditions of constant wetting, the compressive strength decreases by about 35 %.

Proteomic study of Desulfovibrio ferrophilus IS5 reveals overexpressed extracellular multi-heme cytochrome associated with severe microbiologically influenced corrosion

Microbiologically influenced corrosion (MIC) is recognized as a considerable threat to carbon steel asset integrity in the oil and gas industry. There is an immediate need for reliable and broadly applicable methods for detection and monitoring of MIC. Proteins associated with microbial metabolisms involved in MIC could serve as useful biomarkers for MIC diagnosis and monitoring. A proteomic study was conducted using a lithotrophically-grown bacterium Desulfovibrio ferrophilus strain IS5, which is known to cause severe MIC in seawater environments. Unique proteins, which are differentially and uniquely expressed during severe microbial corrosion by strain IS5, were identified. This includes the detection of a multi-heme cytochrome protein possibly involved in extracellular electron transfer in the presence of the carbon steel. Thus, we conclude that this newly identified protein associated closely with severe MIC could be used to generate easy-to-implement immunoassays for reliable detection of microbiological corrosion in the field.

Hydrogen Sulphide in Industrial Enterprises Water Management Infrastructure - The Factor of Chemical and Microbiological Corrosion Concrete Degradation of Water Facilities

The durability of concrete, the material which is widely used for water facilities depends on accumulation in operational environments (drain water, air-gas space) of hydrogen sulfide. Now the mechanism of corrosion destruction of concrete in drainage pipelines is represented as result of biogenous sulphuric acid aggression – influence of the sulphuric acid formed by thionic bacteria. The analysis of data on H2S concentration in drain waters of various industrial enterprises demonstrates that they create in gaseous operational media H2S concentration, sufficient for development in aerobic conditions of thionic bacteria. As the results of urban sewer networks inspection have shown, the correlation between concentration of H2S in aqueous phase and its concentration in air environment, between concentration of H2S in air environment and the corrosion rate of concrete’s coffering part is observed. Chemical and X-ray crystallography of this concrete showed that in corrosive concrete decreases pH, reaching in some examples of values 1-2, and sulfates collect. In dynamics of corrosion process the exponential growth of concentration in concrete of extremely acidophilic thionic bacteria is noted.

Long-term immersion corrosion of irons and steel in seawaters with calcareous deposition

The marine immersion corrosion of irons and steel under calcareous deposition (principally calcium carbonate) is known to be relatively low for shorter exposures (e.g. a few years). Herein the effect of calcareous deposition on corrosion is considered for exposures up to 1300 years. The data are derived from archaeological steel and iron shipwrecks, cast iron cannons and cannonballs, and wrought iron anchors in locations where there was direct evidence, in and on the corrosion products, of calcareous deposition. Such deposition promotes formation of calcium and ferrous carbonate layers of low permeability on and within rusts. These tend to inhibit both early and long-term corrosion rates. The data show that up to about 200y exposure corrosion losses as a function of time can be approximated closely by a linear function of time. Longer exposures follow a moderate power-law function, consistent with diffusion considerations. Comments are made about the likely interplay between calcareous deposition and microbiological corrosion.

Forecasting the durability of reinforced concrete under conditions of microbiological corrosion

The article presents data on the study of the kinetics of liquid corrosion of cement concrete infected with microorganisms Bacillus subtilis and Aspergillus niger. The equilibrium concentrations of calcium cations during fungal and bacterial corrosion of cement concrete in an aqueous medium are established. According to the profiles of calcium hydroxide concentrations in the thickness of cement concrete during fungal and bacterial corrosion, it was found that during fungal corrosion of concrete, the intensity of interaction of calcium hydroxide with the products of the vital activity of microorganisms is higher than during bacterial corrosion. In case of fungal corrosion under conditions of Aspergillus niger infection, citric acid has the greatest impact on concrete since its amount in the products of the vital activity of microorganisms is maximum. Profiles of concentrations of aggressive substances by the thickness of the concrete sample show that bacterial corrosion proceeds more slowly than fungal corrosion and allow us to calculate the time to reach the maximum concentration of aggressive substances at the surface of steel reinforcement in concrete. Corrosion of reinforcement in concrete with fungal corrosion will begin in 2.5 years after infection, with bacterial corrosion after 5.5 years.

Obtaining and investigation of the salts of cis – (2-((1h-benzo [d][1,2,3] triazol-1-yl) methyl) -1,3-dioxolan-4-yl) methyl benzoate with acetic and hydrochloric acid

New biocides (I and II) were synthesized against corrosive bacteria as a result of the reaction of cis–(2-((1H-benzo[d][1,2,3]triazol-1-yl)methyl)-1,3-dioxalan-4-yl) methyl benzoate based on benzotriazole with acetic and hydrochloric acid. Their physical-chemical properties were investigated and biocidal properties studied in various concentrations, as well as the effect of reagents on hydrogen sulfide corrosion. It was specified that the protective effect of the synthesized salts from hydrogen sulfide corrosion was 75 %, and the biocidal effect from microbiological corrosion was equal to 100 %.