Lexikon

an amendment-enhanced bioremediation technology for the treatment of POPs involves the creation of sequential anoxic and oxic conditions. The treatment process involves the following:

1. Addition of solid phase DARAMEND® organic soil amendment of specific particle size distribution and nutrient profile, zero valent iron, and water to produce anoxic conditions.

2. Periodic tilling of the soil to promote oxic conditions.

3. Repetition of the anoxic-oxic cycle until the desired cleanup goals are achieved.

The addition of DARAMEND® organic amendment, zero valent iron, and water stimulates the biological depletion of oxygen, generating strong reducing anoxic conditions within the soil matrix. The diffusion of replacement oxygen into the soil matrix is prevented by near saturation of the soil pores with water. The depletion of oxygen creates a low redox potential, which promotes dechlorination of organochlorine compounds. A cover may be used to control the moisture content, increase the temperature of the soil matrix and eliminate runon/run off.

The soil matrix consisting of contaminated soil and the amendments is left undisturbed for the duration of the anoxic phase of treatment cycle typically 1-2 weeks. In the oxic phase of each cycle, periodic tilling of the soil increases diffusion of oxygen to microsites and distribution of irrigation water in the soil. The dechlorination products formed during the anoxic degradation process are subsequently removed trough aerobic oxic biodegradation processes, initiated by the passive air drying and tilling of the soil to promote aerobic conditions.

Addition of DARAMEND® and the anoxic-oxic cycle continues until the desired cleanup goals are achieved. The frequency of irrigation is determined by weekly monitoring of soil moisture conditions. Soil moisture is maintained within a specific range below its water holding capacity. Maintenance of soil moisture content within a specified range facilitates rapid growth of an active microbial population and prevents the generation of leachate. The amount of DARAMEND® added in the second and subsequent treatment cycles is generally less than the amount added during the first cycle.

The additive enhanced bioremediation was successfully applied for toxaphene and DDT contaminated soil and sediment.

bioremediation uses microorganisms to degrade organic contaminants in soil, sludge, and solids either excavated or in situ. The microorganisms break down contaminants by using them as a food source or cometabolizing them with a food source. Aerobic processes require an oxygen source, and the end products typically are carbon dioxide and water.

Anaerobic processes are conducted in the absence of oxygen, and the end products can include methane, hydrogen gas, sulfide, elemental sulfur, and dinitrogen gas.

Ex situ bioremediation includes slurry-phase bioremediation, in which the soils are mixed in water to form a slurry to keep solids suspended and microorganisms in contact with the soil contaminants, and solid-phase bioremediation, in which the soils are placed in a cell or building and tilled with added water and nutrients.

Land farming, biopiles, and composting are examples of ex situ, solid-phase bioremediation. In situ bioremediation is bioremediation in place, rather than ex situ. In situ techniques stimulate and create a favorable environment for microorganisms to grow and use contaminants as a food and energy source. Generally, this means providing some combination of oxygen, nutrients, and moisture, and controlling the temperature and pH. Sometimes, microorganisms that have been adapted for degradation of specific contaminants are applied to enhance the process.

Source: US-EPA, Clu-In: http://www.clu-in.org/techfocus/default.focus/sec/Bioremediation_of_Chlorinated_Solvents/cat/Overview/

soil bioremediation based on aerobic oxidation means that the soil remediation is based on aerobic biodegradation. The microbiological biodegradation occurs in this case on a high redoxpotential of +0,8-+0,6 Volt. The degrading microorganisms utilise the pollutant as enbergy sources. The source of oxigen is the atmospheric air, soil air, or dissolved oxigen in soil moisture or ground water. If the oxigen-concentration is low, the technologist can increase it by aeration of the soil or the groundwater as well as by adding peroxide substances or other oxigene release compounds ORC to serve as oxigene source for the activation of the aerobic soil microbes.