VOLATILE ORGANIC-COMPOUNDS IN DIGESTED UNITED-KINGDOM SEWAGE SLUDGES

This paper describes a liquid-liquid extraction method using GC-ECD/FID detection developed for the analysis and identification of volatile organic compounds (VOCs) in liquid sewage sludges. The VOCs studied were as follows: 1,1-DCE; 1,2-DCE; 1,2-DCA; chloroform (CCl3H); 1,1,1-TCA; 1,1,2-TCA; TCE; carbon tetrachloride (CCl4); tetrachloroethene (PCE); 1,1,2,2-tetrachloroethane (1,1,2,2-PCA); benzene; toluene; ethylbenzene; o-, and m- plus p-xylene. n-Pentane was the most efficient of several solvents at extracting the VOCs from sludges, and recoveries of all but two were >80 %. The VOC concentrations of 12 digested sludges obtained from rural, urban, and industrial treatment works in northwest England were investigated. Total VOC concentration ranged from 4.62 to 568 mg/kg dry weight (260-15 400 mug/L), with a mean of 105 mg/kg (2810 mug/L). Toluene was present at the greatest concentration. There was a significant correlation between concentrations of ethylbenzene, m- plus p-xylene, o-xylene, TCE, and PCE in the sludge samples. There was no apparent relationship between the sludge VOC concentrations and the volume of industrial input to the sewage treatment works (STW), influent treatment, population served, and sludge solids content. The sludge application to agricultural land was unlikely to increase the VOC concentration of the soil to levels which may cause concern for human health and the environment.