ABSTRACT
In recent years there has been increased interest in the behaviour and fate of organic contaminants during sewage treatment processes. Unlike heavy metals, comparatively little is known about the range and concentration of synthetic organic chemicals that enter sewage treatment works, the efficiency with which they are degraded or removed during treatment, and their typical concentrations in sewage sludge and treated effluent. The main reason for this is the extremely large, and ever-increasing, number of organic compounds which are potentially involved. In the U.K., it has been estimated that somewhere between 10000 and 20000 organic chemicals are currently in either domestic or industrial use and the number is probably increasing by about 1000 annually (Waggott and Wheatland, 1978). Potentially, any of these compounds may enter sewage treatment works and partition onto sludge solids during treatment. The subsequent fate of organic contaminants following disposal of sewage sludges to land or to sea, is important if an understanding of their environmental impact is to be gained. As an initial step in this process, general investigative work is needed to obtain information on the range and concentration of compounds present in sewage sludges. This may be achieved, for example, by ‘broad spectrum’ extraction techniques followed by chromatographic separation and identification using mass spectrometry. This type of approach has been adopted by several workers e.g. US. EPA (1982), Jacobs and Zabik (1983) and, more recently, Webber and Lesage (1987). In these studies a wide range of organic contaminants were identified in US and Canadian sludges, and it was found that some sludges were highly contaminated. For example, high concentrations of compounds such as butylbenzenephthalate, di-(2-ethylhexyl) phthalate, toluene, methyl bromide, chloroethane, vinyl chloride and pentachlorophenol have been reported.
