Remediation Of Soil
This method deals with cleaning of of saturated zone contaminated by decomposable contaminants and is directly derived from pump&treat technology by incorporation of the biological factor into this traditional technology. The principle is based on optimising condtions in the saturated zone of the rock environment for the course of the biodegradation process. It uses the natural biodegradation activity of the micro-flora present or it uses insulated bacteria strains and for stimulation of their activity it applies aeration of pumped water and and enrichment of nutrients (in particular, nitrogen and phosphorus) or other means for the allocation of acceptors of electrons.
The core of in-situ biodegradation technology is based on pumping and re-infiltration of groundwater. The groundwater circulates through the system: pumped bores – aerating tank with dosing of nutrients (or bioreactor) – infiltration bores or grooves – contaminated zone – pumped bores. Optimal configuration of infiltration and pumped objects and ensuring sufficient speed of flowing or supply of dissolved oxygen (or alternative acceptors of electrons) and nutrients is important for this manner of soil remediation
The basic factors influencing the efficiency of biodegradation of the saturated in-situ zone are the biological dissolubility of the contaminant, the concentration of the contaminant, the permeability of the rock environment, homogeneity/heterogeneity, sufficient concentration of micro-flora with biodegradation potential, sufficient acceptors of electrons, the presence of nutrients, the absorption capacity of the soil and the content of organic carbon.
Soil remediation by ex-situ biodegradation
It is a method of biochemical degradation of decomposable contaminates in the case of shallow located and accessible sources of contamination or in cases of less permeable and heterogenous environments before the commencement of decontamination the material is exploited and relocated to the suitable “biofield, decontamination area”. In this ex-situ manner DEKONTA has resolved about 70% of its soil remediation projects. The principle of this method is based on the relatively fast process of biological decomposition with the possibility to change the character of soil and optimal distribution of bacterial preparate, nutrients and oxygen. Decontamination is always implemented in an area protected against infiltration and outflow of contaminated water and has the official status of "biofield". Before the application of micro-organisms, the contaminated material is homogenised and after the achievement of the optimal ratio between the source of carbon (contaminant) and other nutrients it is enriched by the necessary nutrients. In the case that the contaminated soil has a significant ratio of clay part, it is possible to lighten its structure by the addition of organic materials, i.e. wood chips, wood pieces, etc. The soil is in layers to the level of 50-70 cm in the case of absence of an aeration system or to the level of 150-200 cm in the case of the use of the aeration system of the soil layer. After modification of the soil, inoculation is performed by spraying bacterial suspension from the bioreactor. The supply of oxygen is ensured by turning over, pouring, cultivation, aerating or forced aeration of the soil. During the degradation process the optimal moisture of soil is maintained and redistribution of nutrients is performed. The basic factors influencing the efficiency of biodegradation are the biological degradability of the contaminant, the concentration of the contaminant, permeability, additional aeration, temperature, the rate of homologisation, sufficient concentration of micro-flora with biodegradation potential, moisture, the presence of nutrients, the absorption capacity of the soil and the content of organic carbon.