Bioremediation and Biodesaturation of Soil

Abstract

Soil, surface water, groundwater, and atmosphere on the construction sites are often contaminated by pollutants, which are toxic substances for human, animals, and plants. There are known physical and chemical methods of the remediation of polluted soil but biological methods are often most cost effective but usually much slower than physical and chemical methods. Bioremediation of the polluted construction site can be performed in situ, on site or off site. Bioaggregation of soil particles using microbially induced calcium carbonate precipitation (MICP) can be used to control water erosion of sand and the release of the sand-associated pollutants to environment. Small dosage of precipitated calcium, 6.4 g/m² of sand or 9 g Ca/kg of sand can diminish erosion of sand as well as release of chemical pollutants by three times and release of bacteriological pollutant by 10 times. Dosage of precipitated calcium by MCP of 0.8 g/kg of coarse sand decreased the content of lead in the removed coarse sand by 50 % of initial content. MICP co-precipitate radionuclides ⁹⁰Sr, ⁶⁰Co, and metal contaminants such as Cd and this can be used to prevent their dispersion in environment. Specific case of ground improvement is partial soil biodesaturation that diminishes the risk of soil liquefaction and accompanying damages of infrastructure during the earthquake. Biogas bubbles produced by denitrifying bacteria decrease water saturation of sand and risk of saturated sand liquefaction. MICP can be used to stabilize the biogas bubbles in the sand pores. However, the biogas bubbles can be removed from sand by water flow, while the biosealed biogas bubbles became stable. The sequential biogas production in saturated sand and biosealing of the gas bubbles in sand pores could be useful for sustainable mitigation of sand liquefaction in case of groundwater upflow through saturated sand.