Estudo da eficiência de remoção de micropoluentes emergentes por um sistema combinado Uasb-Fbp

Abstract

The study of the emergent micropollutants (EM) (e.g. drugs, natural hormones and their byproducts, cleaning and personal hygiene products) has been gaining great interest in the scientific community since their effects (e.g. aquatic toxicity, selection of pathogenic bacteria, endocrine disruption and genotoxicity) can be very harmful to human health and to the balance of fauna and flora. The main route of contamination of these compounds is the inadequate disposal, in the sanitary facilities, of unused or expired medicines and the release of domestic effluents, derived from showers, lavatories, laundries and excreta of individuals who may contain oral medications and natural hormones. Investigations regarding the removal of EM in wastewater treatment plants have been conducted in high-cost technologies such as activated sludge, membranes etc., installed in developed countries. In view of the above, there was the necessity of the development of efficient and low cost treatments systems capable of reducing the environmental impacts caused by the presence of these compounds. So the aim of this study was to evaluate the efficiency of removal of some micropollutants (Estrone - E1, Estradiol - E2, 17 Ethinylestradiol - EE2, Trimethoprim - TMP, Sulfamethoxazole - SMX, Diclofenac - DCF and Bisphenol A - BPA) using a combined anaerobic-microaerobic system (up-flow anaerobic sludge blanket reactor - UASB) and aerobic, with natural and forced aeration (biological trickling filter - BTF). The UASB reactor, with a useful volume of 3.7 L, operated with hidraulic retention time (HRT) of 7 h and organic loading rate (OLR) of 3.7 kg / m3.day. On the other hand, the FBP, with 38 L of useful volume and conduit shavings as filter media, worked with a HRT of 72 h, OLR of 0.03 kg COD / m2.day and superficial application rate (SAR) of 0.32 m3 / m2.day, characterizing as a low-rate system. The research was carried out in six distinct phases, involving acclimatization (Phase I); Insertion of the micropollutants (Phase II). Iplementation of the microaeration in the UASB reactor, using synthetic air (20% mol O2), from a gas mass flow controller with flow rate of 1.0 mL / min (Phase III); Addition of a bubbling column (4 L of useful volume and HRT of 5 h) upstream of the FBP (Phase IV), aiming to increase the availability of dissolved oxygen in the stream and the column aeration desactivation and reactivation (Phases V and VI), respectively, to evaluate the effectiveness of the aeration system. The UASB-FBP system showed a great operational stability during all operation phases, with removal of organic matter in the form of COD, higher than 90%, with most of it being removed still in the UASB reactor. This was shown to be inefficient in the removal of micropollutants when operated under restricted anaerobic conditions, with2 maximum removal efficiency of 58.03% for Bisphenol A - phase III and a minimum of 1,11% for Diclofenac - phase VII. However, the microaeration (phase III) has greatly improved the removal of these micropollutants, with efficiencies between 51.59% and 58.03% for all evaluated compounds: BPA - 58.03%; For DCF - 53.0%; For E2, 17 - 52.59%; For E1 - 51.59%; For EE2 - 55.2%; For SFX - 56.73% and for TMP - 52.55%. In all stages of operation, the removal of these compounds in the FBP was very efficient, presenting a maximum average removal of 82.88% for Sulfamethoxazole in phase V, mainly with the increase in dissolved oxygen concentration in the medium, carried out by forced aeration with the aid of a bubbling column, reinforcing the fact that the availability of oxygen contributes effectively to the increase in the emergent micropollutants removal. Thus, it was concluded that the system under study is presented as a great alternative to the treatment of drugs and hormones in sanitary sewage.