Contaminated Solid Waste Streams Soils Sediments and Sludges

Waste recycling plays a key role in the development of a sustainable economy (Suzuki, 1992). The classical approach, remediation without the production of recycled materials, does not contribute to durable material flows. Moreover, the production of reusable materials is a necessity to make waste treatment an attractive economic solution. Recycling, however, cannot be done without regard to the effort and costs needed. The overall environmental benefits should be positive and fit within the local economic and legal framework.

A practical way to qualify these benefits is found in three issues:

• the quality of the recycled products

• the amount of energy required per ton

Solid waste streams (contaminated soils, sediments, and sludges) can be recycled. The solids have to be transformed into usable products while the contaminants are removed or destroyed. If the contaminants are organic (such as mineral oil, PAH, solvents, BTEX, PCB), the use of bioreactors can result in environmental benefits (Riser-Roberts, 1998). In bioreactors populations of soil organisms degrade the contaminants to yield carbon dioxide, water, and harmless byproducts (Schlegel, 1986).

A prerequisite for the implementation of new technologies such as bioprocessing is the definition of the goals of recycling and treatment. In the Netherlands legal targets for recycled materials were set in the Dutch building materials law (Building Material Act, 1995). Depending on the content and the leaching of components, two different ways for using recycled materials in plants are defined:

• category 1 products, needing no further isolation

• category 2 products, needing further isolation and monitoring

In the Dutch practice, treatment processes are aimed at the production of category 1 recycled products. Although each country still has its own standards, and standardization is far away (Northcliff et al., 1998), it is clear that practical recycling standards accelerate the development needed to create sustainable technologies.

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