A possible classification of hazardous sewage sludge using toxicity tests ‐ preliminary results

Abstract

Toxicity test are used worldwide to identify and assess hazard of chemical products or environmental samples to human and ecological health. The aim of this study was propose a preliminary hazard classification of sewage sludge samples using the acute toxicity tests with Vibrio fisheri, seed germination/root elongation test, cytotoxicity in vitro with cell culture and Salmonella/microssoma mutagenicity test. This classification was applied in the evaluation of two sets of treated sludge samples collected from five different São Paulo State Sewage Treatment Plants (STP). It was possible to observe that the different STP produced sludges with 7 different toxicity levels. The minimum hazard score obtained was 6 and maximum 16 in a range of zero to 40. The results of toxicity tests can provide important information about the hazard of treated sewage sludge, especially when interpreted in an integrated way. This preliminary classification seems to be a promising tool for assessing the degree of hazard of sewage sludge samples, but additional studies are still needed for its improvement.