Lexikon

within the context of REACH, an additive is a compond that has been intentionally added during the manufacturing process to stabilise the substance. Under other legislation additive can have other functions, e.g. pH-regulator or colouring agent.In REACH the term "additive" can also have other meanings outside the context of substance identification, for instance in relation to food or feed additives See REACH, article 2.

the integrated effect of more toxic substances, mixtures of chemical substances, xenobiotica or drogs, which can be quantified as the sum of the effects of the components, contrary to not additive effects, such as antagonism or sinergism.

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.

within the context of REACH, an additive is a compound that has been intentionally added during the manufacturing process to stabilise the substance. Under other legislation additive can have other functions, e.g. pH-regulator or colouring agent.
In REACH the term "additive" can also have other meanings outside the context of substance identification, for instance in relation to food or feed additives. (See REACH, article 2)
(Source: REACH Glossary)