Montagem e operação de um biorreator de leito fixo utilizando resíduos da construção civil para tratar efluentes por consórcio microalga-fungo

Abstract

The construction industry is one of the largest generators of waste in the world, and most of these materials are wrongly disposed. In addition, inappropriate disposal of effluents, such as those from the dairy industry, also generates serious environmental problems in relation to Chemical Oxygen Demand (COD), Total Nitrogen (TN) and Total Phosphorus (TP). In this sense, the objective of this work was to assemble and operate an aerated fixed bed bioreactor using construction wastes - CWs, to optimize the tertiary treatment of dairy wastewater, using microalga-fungus symbiosis (Tetradesmus obliquus and Fusarium sp.). The CWs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, the reactors were operated at room temperature, under continuous aeration of 1.5 vvm, magnetically stirred at the bottom of the tank, under a light intensity of 100 μmol.m-2.s-1. In the first stage, to verify bed filling and maintenance of microbial activity, the reactors were operated for 6 days with the lowest organic load, followed by emptying and refeeding of the effluent (new batch cycle). In the second stage, the reactors were named as R1, R2, R3 and R4, with different organic loads, having COD ~ 1350, 3150, 660 and 11,550 mg.L-1, TN ~ 60, 75, 173 and 385 mg.L-1; and TP ~ 10, 24, 55 and 86 mg.L-1, respectively. The CWs were characterized as irregular (smooth and porous in texture), crystalline, with hydroxyl, carboxylic and alkene groups on their surface, which would facilitate microbial adhesion. After treatment, residual COD concentrations of 58.70 ± 2.38, 309.36 ± 19.83, 40.45 ± 11.50, and 95.19 ± 15.86 mg.L-1 were obtained for R1-R4, respectively; emphasizing that R2 did not work properly. For TN, the residual concentrations were 4.40-6.36 ± 0.10-0.23, 12.33 ± 0.36, 10.74 ± 0.44 and 33.38 ± 2.18 mg.L-1, for R1-R4, respectively. In turn, for residual TP, 0.17 ± 0.02, 1.12 ± 0.01, 4.16 ± 0.02, 8.28 ± 0.02 mg.L-1, for R1-R4, respectively. In terms of cellular biomass, after the bed filling phase, there was production of microbial sludge between 140-1250 mg.L-1 The study contributed to research on sustainable bioreactors and strategies for reusing urban and industrial solid waste.