The optimization of wastewater treatment technologies using biological processes is no longer limited to improving the removal of organic matter and nutrients, as it is possible to reduce area and energy consumption, and recover value-added by-products. In this context, the microalgae–bacteria consortium is an alternative for reducing costs, as microalgae produce the oxygen required by bacteria to oxidize organic matter through photosynthesis. Additionally, it is possible to extract different by-products such as lipids, biofertilizers, biogas, alginate-type exopolymers, and others. Furthermore, bioflocculation occurs naturally through the adhesion of microalgae to the surface of bacterial flocs, without the addition of chemical products. This review discusses the main systems that utilize the microalgae–bacteria consortium, the metabolism of the microalgae–bacteria consortium, and its performance in removing organic matter and nutrients, as well as the effect of operating conditions on the physical properties of the biomass. Among the highlighted systems are sequencing batch and single-batch reactors, high-rate ponds, and continuous flow reactors. Among the systems discussed in this work, the sequential batch reactor configurations found better biomass formation and production of extracellular polymeric substances and the continuous flow reactors showed lower installation and operating costs. From this perspective, the potential for full-scale application of each system can be evaluated once the optimum operating conditions have been defined and the limitations of each system have been understood.

This work studied the formation of aggregates used for wastewater treatment in high-rate algal ponds (HRAP). For this, the establishment of microalgae-bacteria aggregates in these systems was evaluated, considering strategies for the inoculation and start-up. Two HRAP were operated in parallel, at first in batch mode and then in continuous flow. The wastewater treatment was efficient, with removal rates around 80% for COD and N-ammoniacal. Volatile suspended solids and chlorophyll for the culture grew continuously reached a concentration of 548 ± 11 mg L⁻¹ and 7.8 mg L⁻¹, respectively. Larger photogranules were observed when the system was placed in a continuous regime. The protein fraction of extracellular polymeric substances was identified as a determinant in photogranules formation. During the continuous regime, more than 50% of the biomass was higher than 0.2 mm, flocculation efficiency of 78 ± 6%, and the volumetric sludge index of 32 ± 5 mL g⁻¹. The genetic sequencing showed the growth of cyanobacteria in the aggregate and the presence of microalgae from the chlorophytes and diatoms groups in the final biomass. GRAPHICAL ABSTRACT

O reconhecimento da importância da concessão de políticas públicas para a agricultura familiar, em diferentes contextos socioeconômicos, revela resultados importantes para a compreensão do desenvolvimento rural. Nesta Pesquisa objetivou-se, avaliar os impactos socioambientais associados às políticas públicas voltadas para a agricultura familiar nos assentamentos rurais, localizados nos Sítios Alto Alegre, Fortuna e Saquinho no município de Jericó-PB, o procedimento metodológico teve por base um diagnóstico situacional dos assentamentos do município, e buscou-se conhecer as políticas públicas rurais voltadas para a agricultura familiar e seus principais critérios de concessão, analisando-se, ainda, as dificuldades existentes nestes assentamentos, decorrentes da ausência ou ineficiência dessas políticas, a sua relação com o meio ambiente e a qualidade da subsistência dos assentados agricultores familiares para propor medidas de prevenção, mitigação e compensação dos impactos negativos gerados e indicar medidas de maximização para os impactos positivos resultantes das políticas públicas concedidas