TRATAMENTO DE ESGOTO SANITÁRIO POR ELETROBIORREATOR A MEMBRANA VISANDO A REMOÇÃO DE NUTRIENTES E A MINIMIZAÇÃO DA COLMATAÇÃO DA MEMBRANA

Abstract

Membrane electro-bioreactors (EMBR) are considered a new technology with high potential for wastewater treatment since it allows the simultaneous application of electrochemical, biodegradation, and membrane filtration processes in a single reactor, which lead to obtain excellent quality final effluent. In this context, the main objective of this study was to design, operate and evaluate the potentiality and efficiency of the EMBR system applied to sanitary wastewater treatment, with emphasis on organic matter and nutrients removal, and membrane fouling process reduction. Firstly, preliminary tests were carried out to determine the specific aeration demand (SAD) and critical flux. Then, three phases were performed in this study. Phase 1, in which run 1 was executed, the EMBR was operated for 30 days and evaluated without the application of electric current, for comparison purposes. In phase 2, it was evaluated the effects of the application of electric current of 5 A.m-2 (run 2) and 15 A.m-2 (run 3) on the performance of the EBRM. Aiming the system stability and minimization of the fouling process, the results obtained in the preliminary tests indicated that the best SAD was 3 m3.m-2.h-1 and the critical flux was 7, 2 Lm-2.h-1. By comparing the results obtained in run 1, run 2 and run 3, we verified that the electric current application provided a significant improvement in the efficiency of the bioreactor with regard to the removal of organic matter (COD), ammoniacal nitrogen (amoniacal-N), color and, mainly, phosphorus (PO43--P). Besides that, it was also observed that the microorganisms’ growth rate and autotrophic and heterotrophic biomass activities were higher with electric current application, which was attributed to the electro-stimulation phenomenon. Regarding to membrane fouling process, high fouling rates were observed throughout the experimental period, which was mainly due to the high-membrane packing density. However, it was verified that the fouling process may have been favored by some other factors, such as: the presence of the Zooglea bacteria; the increase of COD concentration in the mixed liquor; and the lowest concentration of EPS, which resulted in sludge deflocculation. Furthermore, the application of the current density of 15 A.m-2, compared with the current density of 5 A.m-2, was only significant for the removal of ammoniacal nitrogen, which was attributed to the higher nitrogen load applied in run 3. In addition, the higher current density caused a deterioration in the mixed liquor characteristics. Therefore, it could be concluded that the application of electric current, especially at 5 A.m-2, is a potential alternative for improvement of the effluent quality of membrane bioreactor (MBR) systems, mainly regarding to the removal of organic matter and phosphorus from sanitary wastewater, besides being more attractive from the energetic point of view.