Ecotoxicological aspects of solvent disposal

Choice of particular solvents is a major issue arising from health, safety and environmental legislation. Selection needs to be made carefully as there can be unexpected consequences. For example, whereas most organic solvent-based paints have an inherent biostatic activity preventing microbial spoilage, water-based paints often require the addition of biocides to prevent this. There is concern that the operation of waste water treatment plants may be adversely affected by effluents from such systems [10]. 

Spent solvents recovered from chemicals used in manufacturing plant or from those used in cleaning processes consist of a mixture of substances which can be difficult to process for re-use. Recovery also produces residues for which landfill is one option for disposal. 

Thermal oxidation is a widely used route and the resultant energy is available to be utilised to save fuel and hence energy costs. A particularly efficient option is use of spent solvent as a fuel for cement manufacture, where it offers an attractive alternative to the practice of burning powdered coal. This combines a second use of the solvent molecules, with a net reduction in environmental emission compared to the coal fired case. 

The methodology for terrestrial hazards assessment is developing but there are to date few data to allow classification. Methodologies for risk assessment are becoming available. 

In conclusion, the general use of organic solvents results in insignificant exposure of the terrestrial compartment. 

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