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Microbially induced calcium carbonate precipitation (MICP) is a phenomenon based on urease activity of halotolerant and alkaliphilic microorganisms that can be used for the soil bioclogging and biocementation in geotechnical engineering. However, enrichment cultures produced from indigenous soil bacteria cannot be used for large-scale MICP because their urease activity decreased with the rate about 5 % per one generation. To ensure stability of urease activity in biocement, halotolerant and alkaliphilic strains of urease-producing bacteria for soil biocementation were isolated from either sandy soil or high salinity water in different climate zones. The strain Bacillus sp. VUK5, isolated from soil in Ukraine (continental climate), was phylogenetically close in identity (99 % of 16S rRNA gene sequence) to the strain of Bacillus sp. VS1 isolated from beach sand in Singapore (tropical rainforest climate), as well as to the strains of Bacillus sp. isolated by other researchers in Ghent, Belgium (maritime temperate climate) and Yogyakarta, Indonesia (tropical rainforest climate). Both strains Bacillus sp. VS1 and VUK5 had maximum specific growth rate of 0.09/h and maximum urease activities of 6.2 and 8.8 mM of hydrolysed urea/min, respectively. The halotolerant and alkaliphilic strain of urease-producing bacteria isolated from water of the saline lake Dead Sea in Jordan was presented by Gram-positive cocci close to the species Staphylococcus succinus. However, the strains of this species could be hemolytic and toxigenic, therefore only representatives of alkaliphilic Bacillus sp. were used for the biocementation studies. Unconfined compressive strengths for dry biocemented sand samples after six batch treatments with strains VS1and VUK5 were 765 and 845 kPa, respectively. The content of precipitated calcium and the strength of dry biocemented sand at permeability equals to 1 % of initial value were 12.4 g Ca/kg of dry sand and 454 kPa, respectively, in case of biocementation by the strain VS1. So, halotolerant, alkaliphilic, urease-producing bacteria isolated from different climate zones have similar properties and can be used for biocementation of soil.

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. Methods and Results: An enrichment culture and two pure cultures of IRB, Stenotrophomonas maltophilia BK and Brachymonas denitrificans MK identified by 16S rRNA gene sequencing, were produced using returned liquor from a municipal WWTP as carbon and energy source, and iron hydroxide as oxidant. The final concentration of phosphate increased from 70 to 90 mg l )1 in the control and decreased from 70 to 1 mg l )1 in the experiment. The mass ratio of removed P to produced Fe(II) was 0AE17 g P g )1 Fe(II). The strain S. maltophilia BK showed the ability to reduce Fe(III) using such xenobiotics as diphenylamine, m-cresol, 2,4-dichlorphenol and p-phenylphenol as sole sources of carbon under anaerobic conditions. Conclusions: Bacterial reduction of ferric hydroxide enhanced the phosphate removal from the returned liquor. Significance and Impact of the Study: The ability of the facultative anaerobes S. maltophilia BK and B. denitrificans MK to reduce Fe(III) was shown. These micro-organisms can be used for anaerobic removal of phosphate and xenobiotics by bacterial reduction of ferric ions.

Bioclogging and biocementation can be used to improve the geotechnical properties of sand.These processes can be performed by adsorption of urease-producing bacterial cells on the sand grain surfaces, which is followed by crystallization of calcite produced from the calcium salt and urea solution due to bacterial hydrolysis of urea. In this paper, the effect of intact cell suspension of Bacillus sp. strain VS1, suspension of the washed bacterial cells, and culture liquid without bacterial cells on microbiallyinduced calcite precipitation in sand was studied. The test results showed that adsorption/retention of urease activity on sand treated with washed cells of Bacillus sp. strain VS1was 5 -8 times higher than that treated with culture liquid. The unconfined compressive strength of sand treated with the suspension of washed cells was 1.7 times higher than that treated with culture liquid. This difference could be due to fast inactivation of urease by protease which was present in the culture liquid. The adsorption of bacterial cells on sand pre-treated with calcium, aluminum, or ferric salts was 29 to 37% higher as compared with that without pretreatment. The permeability of sand varied with the content of precipitated calcium. For bioclogging of sand, the content of precipitated calcium had to be 1.3% (w/w) or higher. The shear strength of biotreated sand was also dependent on the content of precipitated calcium. To achieve an unconfined compressive strength of 1.5 MPa or higher, the content of precipitated calcium in the treated sand had to be 4.2% (w/w) or higher. These data can be used as the reference values for such geotechnical applications as bioclogging for reduction of permeability of sand and biocementation for increasing the shear strength of soil.

A method to construct an aquaculture pond in sand using microbial biocementation is presented in this paper. The microbially induced calcium carbonate precipitation process was used to form a lowpermeability layer in sand for the construction of a water pond model in the laboratory. The test results indicated that the permeability of sand was reduced from the order of 10 À4 m/s to 10 À7 m/s when an average 2 . 1 kg of calcium (Ca) per m 2 of sand surface was precipitated. The bending strengths of the walls and the base of the model pond were in the range of 90-256 kPa. The unconfined compressive strengths for the samples taken from the walls and the base of the pond were in the range of 215-932 kPa.

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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.