Basic principles, agents and feasibility of bioremediation of soil polluted by organic compounds

Abstract

Soil bioremediation is a rapidly developing field due to its potential for effective and inexpensive cleanup of a broad range of inorganic and organic pollutants. It usually refers to the use of biological processes that transform pollutants to innocuous products and microorganisms, plants and enzymes can promote these processes. In the case of the degradation of an organic pollutant, it is possible to increase the degradation rates by inoculating specific microbial species (bioaugmentation) into the polluted soil or stimulating the activity of indigenous microbial populations (biostimulation) by increasing nutrient concentrations and adjusting redox conditions. Enzymes can be used to detoxify pesticide-polluted soils if the product of the reaction is less toxic than the pollutant molecule. Plants can be used to restore polluted soils and this process is called phytoremediation. The general strategies for phytoremediation include: 1) phytoextraction, with the accumulation of the pollutant into shoots; 2) phytodegradation, the pollutant is taken up and degraded by plant enzymes; 3) phytovolatilization, the pollutant is taken up and transferred to air via plant. However, it is believed that the most successful strategy in the remediation of organic polluted soils is the use of the plant-rhizosphere system. Through rhizodeposition plants can stimulate the microbiota of the rhizosphere soil to markedly increase the degradation of the organic pollutant. A successful bioremediation requires a) to understand the ecology, the physiology and the evolution of microorganisms involved in the transformation of the pollutant; b) to know the biogeochemical processes involved in the plant-based remediation approach. Engineering design and application, as well as engineering and regulatory questions are also needed to choose, develop and conduct an appropriate bioremediation.