Chemical and mutagenic evaluation of sludge from a large wastewater treatment plant.

Digested sludges from a wastewater treatment plant were analyzed to assess their level of contamination by some organic (polychlorobiphenyls (PCBs) and chlorinated pesticides) and inorganic (heavy metals) micropollutants and their mutagenicity features. The heavy metal content in none of the samples exceeded the limits set out in EEC Directive 276/86; as far as PCBs are concerned, the sludges analyzed indicated a level of contamination up to two orders of magnitude higher than some Italian agricultural soils. Mutagenicity assays on either crude or fractionated sludge extracts using Salmonella typhimurium tester strains TA98 and TA100 gave negative results, thus suggesting the absence of genotoxic contaminants in the samples investigated.