Caracterização do esgoto sanitário e avaliação da eficiência da ETE/UFLA na remoção de fármacos e desreguladores endócrinos

Abstract

Microcontaminants are compounds that occur in the environment at low concentrations, being of the order of micrograms per liter (μg L-1) or lower. Many of them are able to interact with the endocrine system of humans and animals causing organic imbalance and damage to health. Recent research has shown that biological treatment systems associated with the tertiary treatment of sanitary effluents present good efficiency in the removal of these microcontaminants. The following classes of microcontaminants were studied: endocrine disrupters (estradiol, ethinyl estradiol, estrone, estriol, 4-octylphenol, 4-nonylphenol and bisphenol A), pharmaceuticals (diclofenac, ibuprofen, paracetamol, naproxen and genfibrozil) and the stimulant caffeine . It was evaluated the presence and the efficiency in the removal of each of them by the Effluent Treatment Station of the Federal University of Lavras (ETE / UFLA), in Minas Gerais, composed of UASB (Upflow Anaerobic Sludge Blanket) reactors and Submerged Aerated Biological Filter (FBAS), followed by sand filter and tertiary treatment with chlorine and ultraviolet radiation. A benchtop UV reactor was built to simulate the operation of the station reactor that was not functioning during the monitored period. In the bench scale reactor, the inactivation of total and thermotolerant coliforms in five times of contact with the UV radiation (10, 20, 30, 40 and 50 seconds) was evaluated, as well as their efficiency in the removal of microcontaminants in 10 and 40 seconds. Chlorination tests were also carried out in the ETE / UFLA chlorination system in order to know the lowest dose to obtain residual chlorine minimum of 0.5 mg L-1 and the capacity of this dose to remove microcontaminants, inactivate coliforms and form trihalomethanes. Laboratory chlorination tests evaluated the effects of contact time and organic matter concentration on the formation of trihalomethanes in the chlorinated effluent. For the chlorination tests, EPA 551.1 methodology was used with liquid-liquid extraction and gas chromatographic analysis coupled to mass spectrometry - GC-MS. For the quantification of microcontaminants, a Strata SAX cartridge preconcentration step and determination of the compounds by chromatography (GC-MS), using a previous stage of derivatization were used. The pharmaceuticals diclofenac, ibuprofen, paracetamol and naproxen were found; endocrine disrupters estrone, estradiol, 4 -octylphenol and bisphenol A, the lipid regulator genfibrozil and the caffeine stimulant and the rates of removal ranged from 59 to 100%. The highest inactivation of total coliforms by UV occurred in 40 seconds of exposure. No formation of trihalomethane was found in any of the chlorination conditions evaluated.