Viktor Stabnikov

Microbially induced calcium carbonate precipitation on surface or in the bulk of soil

Microbial precipitation of calcium carbonate takes place in nature by different mechanisms. One of them is microbially induced carbonate precipitation (MICP), which is performed due to bacterial hydrolysis of urea in soil in the presence of calcium ions. The MICP process can be adopted to reduce the permeability and/or increase the shear strength of soil. In this paper, a study on the use of Bacillus sp., which was isolated from tropical beach sand, to perform MICP either on the surface or in the bulk of sand is presented. If the level of calcium salt solution was below the sand surface, MICP took place in the bulk of sand. On the other hand, if the level of calcium salt solution was above the sand surface, MICP was performed on the sand surface and formed a thin layer of crust of calcium carbonate. After six sequential batch treatments with suspension of urease-producing bacteria and solutions of urea and calcium salt, the permeability of sand was reduced to 14 mm/day (or 1.6×10−7 m/s) in both cases of bulk and surface MICP. Quantities of precipitated calcium after six treatments were 0.15 and 0.60 g of Ca per cm2 of treated sand surface for the cases of bulk or surface MICP, respectively. The stiffness of the MICP treated sand also increased considerably. The modulus of rupture of the thin layer of crust was 35.9 MPa which is comparable with limestone.

Phosphate removal from the returned liquor of municipal wastewater treatment plant using iron‐reducing bacteria

Aim:  The application of iron‐reducing bacteria (IRB) to phosphate removal from returned liquor (liquid fraction after activated sludge digestion and anaerobic sludge dewatering) of municipal wastewater treatment plant (WWTP) was studied.

Production and applications of crude polyhydroxyalkanoate-containing bioplastic from the organic fraction of municipal solid waste

A considerable economic and environmental need exists for the further development of degradable plastic polyhydroxyalkanoates (PHAs), which are produced by bacteria. However, the production cost of this bioplastic, manufactured using conventional technologies, is several times higher than that of petrochemical-based plastics. This is a major obstacle for the industrial production of PHA bioplastic for non-medical use. The aim of this review is to evaluate suitable methods for the significant reduction in bioplastic production costs. The study findings are as follows: (1) The organic fraction of municipal solid waste can be used as a raw material through acidogenic fermentation; (2) non-aseptic cultivation using mixed bacterial culture can significantly reduce the production cost; (3) biotechnology of bacterial cultivation should ensure selection of PHA-accumulating strains; (4) applications of PHA-containing material in both construction industry and agriculture do not require expensive extraction of PHAs from bacterial biomass. The implementation of the above findings in the current manufacturing process of PHA-containing bioplastic would significantly reduce production costs, thereby rendering PHA-containing bioplastic an economically viable and environmentally friendly alternative to petrochemical-based plastics.

Construction Biotechnology: a new area of biotechnological research and applications

Abstract A new scientific and engineering discipline, Construction Biotechnology, is developing exponentially during the last decade. The major directions of this discipline are selection of microorganisms and development of the microbially-mediated construction processes and biotechnologies for the production of construction biomaterials. The products of construction biotechnologies are low cost, sustainable, and environmentally friendly microbial biocements and biogrouts for the construction ground improvement. The microbial polysaccharides are used as admixtures for cement. Microbially produced biodegradable bioplastics can be used for the temporarily constructions. The bioagents that are used in construction biotechnologies are either pure or enrichment cultures of microorganisms or activated indigenous microorganisms of soil. The applications of microorganisms in the construction processes are bioaggregation, biocementation, bioclogging, and biodesaturation of soil. The biotechnologically produced construction materials and the microbially-mediated construction technologies have a lot of advantages in comparison with the conventional construction materials and processes. Proper practical implementations of construction biotechnologies could give significant economic and environmental benefits.

Strengthening of Soft Marine Clay Using Bioencapsulation

Dredged or excavated soft marine clay can be improved by mixing it with cement or lime. However, these treatments are usually expensive. It is shown in this paper that soft marine clay can be strengthened through a bioencapsulation method in which the shear strength of clay aggregates can be substantially increased after the aggregates are treated with urease-producing bacteria, calcium chloride, and urea. We found that the bioencapsulation had increased the unconfined compressive strength of marine clay aggregates with a size of 5 mm from almost zero to more than 2 MPa. The strength of the bioencapsulated clay aggregates decreases with the increase in the size of the aggregate when the size is greater than 5 mm.

Basics of Construction Microbial Biotechnology

Construction Microbial Biotechnology is a new area of science and engineering that includes microbially-mediated construction processes and microbial production of construction materials. Low cost, sustainable, and environmentally-friendly microbial cements, grouts, polysaccharides, and bioplastics are useful in construction and geotechnical engineering. Construction-related biotechnologies are based on activity of different microorganisms: urease-producing, acidogenic, halophilic, alkaliphilic, denitrifying, iron- and sulfate-reducing bacteria, cyanobacteria, algae, microscopic fungi. The bio-related materials and processes can be used for the bioaggregation, soil biogrouting and bioclogging, biocementation, biodesaturation of water-satured soil, bioencapsulation of soft clay, biocoating, and biorepair of the concrete surface. Construction Microbial Biotechnology is progressing toward commercial products and large-scale applications. The biotechnologically produced materials and construction-related microbial biotechnologies have a lot of advantages over conventional construction materials and processes.

Development of Microbial Geotechnology in Singapore

Both nature processes and laboratory studies have shown that microorganisms can be used to improve the engineering properties of soil. As such, it is possible to develop methods that utilize the microbial process to treat soil in a way similar to that of cement. When more knowledge is accumulated through research findings and technology development, a new branch of geotechnical engineering - the Microbial Geotechnology can be established. The Microbial Geotechnology can have the following three applications: (a) biocementation to increase the strength of soil, (b) bioclogging to reduce the permeability of soil, and (c) biogas to increase the liquefaction resistance of sandy soil. Some types of microorganisms or bioprocesses that may contribute to the biocementation, bioclogging or biogas effects are identified and discussed. Some experimental data are presented to show that the permeability of sand can be reduced by four orders of magnitude and the strength of sand can be increased to a substantial value after the soil has been treated using bacteria. However, the whole study still stays at the laboratory stage and much more efforts are required to turn this scientific idea into viable technologies.

Biocement : green building- and energy-saving material

Cement and chemical grouts have often been used for soil strengthening. However, high cost, energy consumption, and harm to environment restrict their applications. Biocement could be a new green building- material and energy-saving material. Biocement is a mixture of enzymes or microbial biomass with inorganic chemicals, which can be produced from cheap raw materials. Supply of biocementing solution to the porous soil or mixing of dry biocement with clayey soil initiate biocementation of soil due to specific enzymatic activity. Different microorganisms and enzymes can be used for production of biocement.

Construction Biotechnological Plastics

Plastics that are used in the construction industry produce hazardous nonbiodegradable wastes after demolition of the buildings or temporal constructions. Recent investigations on bioplastic reveal a new and sustainable construction bioplastics made from the renewable organic sources that can be left in soil or composted after demolition because of their biodegradability. Bioplastics also have the potential to lead to the rise of new building materials with low embodied energy thus contributing to energy building efficiency. Cheap raw materials, continuous, and nonaseptic cultivation of mixed bacterial culture, and production of crude composite bioplastic as construction material with low embodied energy has to be used to enhance bioplastic cost-efficiency. Bioplastic can be produced as by-product of biorefinery using acidogenic fermentation or pyrolysis of lignocellulosic biomass, as well as by-product of biotreatment of solid or liquid municipal wastes.

Bioclogging and Biogrouts

Grouting is a process to fill the soil voids with fluid grout, which is used to control water flow in soil. Such common grouts as solutions or suspensions of sodium silicate, ultrafine cement, acrylates, acrylamides, and polyurethanes have such disadvantages as high viscosity and low depth of penetration in soil, high cost, and toxicity. Bioclogging or biogrouting is either using formation of microbial biopolymers or microbially induced precipitates of inorganic compounds in situ for water flow control. Biogrouting includes formation of impermeable layer of algal and cyanobacterial biomass; production of slime in soil by aerobic and facultative anaerobic heterotrophic bacteria, production of undissolved sulfides of metals by sulfate-reducing bacteria; formation of undissolved carbonates of metals by ammonifying bacteria and urease-producing bacteria; production of ferrous solution by iron-reducing bacteria, and precipitation of undissolved ferrous and ferric salts and hydroxides in soil by iron-oxidizing bacteria; self-decay of calcium bicarbonate with formation of calcium carbonate clogging. Bioclogging can be applied to diminish piping of the slopes and dams, prevention of soil erosion, construction of the channels, sealing of the aquaculture ponds, reservoirs, landfills, tunneling space before and after excavation in sandy soil or sedimentary rocks, and sealing of the sedimentary and fractured rocks.