We utilise Bioremediation as a treatment process that uses biological processes to break down, or degrade, hazardous substances into less toxic or nontoxic substances thereby cleaning up contaminated soil or water. We enhance the process by the addition of non indigenous living organisms and/or nutrients to the soil or water in order to achieve accelerated results, known as Bioaugmentation.
Specific bioremediation technology uses microorganisms to degrade organic contaminants (i.e. petroleum products including petrol, diesel and kerosene) in excavated soil, sludge and solids ex situ. It can also be used to make metals or metalloids less toxic or mobile.
Ex situ bioremediation includes slurry phase bioremediation, in which the soils are mixed in water to form a slurry, and solid-phase bioremediation, in which the soils are placed in a cell or building and tilled with added water and nutrients. Commonplace solid phase bioremediation technologies include Land Farming, Composting, Biopiles and Windrows.
Bioventing is an in situ remediation technology that uses indigenous microorganisms to biodegrade organic constituents adsorbed to soils in the unsaturated zone. Bioventing is most often used at sites with mid-weight petroleum products (i.e. diesel fuel), because lighter products can be removed more rapidly using Soil Vapour Extraction (SVE) whilst heavier products generally take longer to biodegrade. The activity of the indigenous bacteria is enhanced by inducing air (or oxygen) flow into the unsaturated zone (using extraction or injection wells) and, if necessary, by adding nutrients.
The effectiveness of bioventing is determined by the permeability, structure and stratification of the soils, which affect how and where soil vapours will flow within the soil matrix when extracted or injected, and the biodegradability of the petroleum constituents, which affects the rate and degree of metabolisation by the microorganisms.
Land farming is an above-ground remediation technology that usually involves spreading excavated contaminated soils in a thin layer on the ground surface (sometimes forming windrows) and stimulating aerobic microbial activity within the soils through aeration and/or the addition of minerals, nutrients, and moisture. If contaminated soils are shallow (i.e., less than 1 m below ground surface), it may be possible to effectively stimulate microbial activity without excavating the soils. Land farming has been proven effective in reducing concentrations of nearly all the constituents of petroleum products typically found at underground storage tank sites.
Biopiles involves heaping contaminated soils into piles (or "cells") and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. Biopiles are similar to land farms in that they are both above-ground, engineered systems that use oxygen, generally from air, to stimulate the growth and reproduction of aerobic bacteria which, in turn, degrade the petroleum constituents adsorbed to soil. While land farms are aerated by tilling or ploughing, biopiles are aerated most often by forcing air to move by injection or extraction through slotted or perforated piping placed throughout the pile.