Avaliação ecotoxicológica de lodo de estação de tratamento de água

Abstract

The disposal of sludge with a high concentration of aluminum in the environment has as a consequence the contamination of the environment and the biota present there. An important environmental issue that is currently being researched is the disposal of water treatment plant waste. The objective of this study was to evaluate the toxicological effect of the aluminum present in the sludge on the ecosystems in different Bioindicators. For analysis in the terrestrial ecosystem, different vegetable species were used, such as tomato, lettuce, spring onion, cabbage, cucumber and arugula seeds, and the Escape test with E. andrei earthworms, and in the aquatic ecosystem by means of organisms such as the microcrustacean Daphnia similis. The seeds were exposed to different concentrations of the aluminum present in the sludge and were evaluated for germination and growth inhibition parameters. To evaluate the toxicity of aluminum-contaminated soils, the escape behavior of earthworms was analyzed. The principle of the method consists in exposing the organisms to samples of the elutriate and to culture water for control purposes. The preliminary and definitive tests with Daphnia similis was based on the NBR 12713/2016 standards. All seeds when exposed to aluminum sulfate showed total inhibition of germination. The highest CL50 was of the lettuce seed with 77.82%. The seed with the lowest LC50 was chive, with 2.95%. The concentrations 50%, 75% and 100% showed avoidance rates of 80% each, indicating limited habitat function. It was observed that the (CE-50) of Dapnhia species is 80.45%, in a confidence interval of 79.95 to 80.94%. As for the mortality of microcrustaceans to elutriate exposure, 100% mortality of the test organisms was not observed at any of the concentrations used in the definitive test. Therefore, since it is still a terrestrial ecosystem, the WTP sludge presented itself as a toxic effluent to the living organisms present in the soil. The species Dapnhia showed toxicity at high concentrations of aluminum, causing adverse effects to the environment. The risk would be in the disposal of sludge to aquatic fauna in concentrations above 80%. This study showed that the bioindicators used are suitable for ecotoxicological tests on water treatment plant sludge, since all presented the sludge as toxic to the aquatic and terrestrial environment.