Biorreatores heterotróficos microalgais aplicados ao tratamento de efluentes agroindustriais

Abstract

The nutrient cycling from microalgae-based processes is a potential technological route to be applied in wastewater treatment plants. The pollutant conversion in parallel with microalgal sludge formation results in a renewable feedstock for bioproducts, contributing to more sustainable wastewater treatment processes. In this sense, the aims of this work were: (i) develop a bioreactor applicable to the conversion of organic matter, nitrogen and phosphorus into products of microalgal metabolism; (ii) evaluate the performance of the heterotrophic bioreactor when subjected to organic shock loads; (iii) evaluate the kinetics of consumption of organic matter, nitrogen, and phosphorus; (iv) evaluate the biomass production kinetics; (v) determine the life cycle assessment of the integrated process of obtaining bioproducts at the agroindustrial wastewater treatment through microalgal heterotrophic bioreactors. The nutrient cycling by Phormidium autumnale in agroindustrial wastewater presented a pronounced variation in removal efficiency as a function of evaluated pollutant (chemical oxygen demand 95.57%–98.90%; total nitrogen 61.85%–88.23%; total phosphorus 77.82% 90.64%). However, the numerical indices of process performance, besides framing the wastewater from the point of view of international legislation, demonstrate that the bioreactor support organic shock loads typical to that of the poultry and swine slaughterhouse industry can generate. Life cycle assessment demonstrated that the sustainability metrics of the integrated energy and nutrient recovery process from agroindustrial wastewater to produce biodiesel and animal feed resulted in net energy ratio (NER) of 0.41, reduction of 98% of the water footprint, global warming potential of 47×106 kgCO2eq/year, eutrophication potential of 5×104 kg eq PO4/year, acidification potential of 7×104 kg SO2-eq/year and ozone depletion potential of 3.33 kg CFC-11-eq/year. In this sense, the nutrient cycling from microalgae-based processes has proven to be a sustainable approach to wastewater treatment plants, and their implementation and dissemination can help to support a change towards resource recovery and a sustainable circular economy.