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Petroleum refineries generate large amounts of wastewaters, which can have acute/chronic toxicity toward aquatic organisms. Previous studies have shown that many contaminants can be responsible for this toxicity, among them ammonia, sulfide, cyanide, phenols and hydrocarbons. In the study reported herein, the cause of the chronic toxicity of a biotreated petroleum refinery wastewater was investigated by applying the TIE methodology using the microcrustacean Ceriodaphnia dubia. Five samples were analyzed, and the results suggest that copper is the primary toxicant, showing a strong correlation with wastewater toxicity in Phase III. Other metal contaminants, such as zinc and nickel, are present in the samples at toxic concentrations and these may also contribute (to a lesser degree) toward the toxicity. In the case of one sample, the toxicity was attributed to polycyclic aromatic hydrocarbons (PAHs), possibly benzo(a)pyrene, which was present at a concentration toxic to C. dubia. Although the values for the physicochemical parameters of the samples were below Brazilian environmental regulation limits (CONAMA 430), this was not sufficient to prevent chronic toxicity toward aquatic life, indicating that these limits are relatively high.

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Two experimental cells with household solid waste and healthcare solid waste were monitored in order to evaluate the pollution potential, and its toxicity effects corresponding to the chemical substances present in the leachates generated, correlating the physico–chemical composition with the ecotoxicity results (organisms Aliivibrio fischeri and Danio rerio). From the statistical evaluation of the physico–chemical analysis results, leachate generated in the household solid waste cell presented greater or equal values than to the healthcare solid waste cell, except for the turbidity parameter. The ecotoxicity results showed the same behaviour as that obtained with the physico–chemical analysis. A significant positive correlation was verified between chemical oxygen demand, alkalinity and ammonia nitrogen parameters with the leachate toxicity. This study concluded that healthcare solid waste presented less or equal polluting potential compared with household solid waste, and the co-disposal can be considered a viable alternative in sanitary landfills.

Petroleum refineries generate a large amount of effluents, which if released without appropriate treatment can cause chronic effects to organisms. Most studies show that many contaminants can be responsible for the toxicity, among them ammonia, sulfide, cyanide, phenol and hydrocarbons. The present study evaluated the cause of the chronic toxicity of a refinery wastewater from Brazil using the organism Ceriodaphnia dubia in short-term test. The results suggest that metals such as barium, manganese and strontium can be contributing for the toxicity of the wastewater. Besides this, conductivity could be contributing to the toxicity too, since the level is high for the test organism evaluated.