Utilização de microalgas para pós tratamento de efluente de fossa séptica biodigestora: um estudo preliminar

Abstract

The quality of life of the population, among many elements, is directly linked tosanitation infrastructure such as access to drinking water, sewage collection and treatment. In this way, new low-cost and high-efficiency technologies for removing pollutants have been increasingly explored, one of these alternatives being the insertion of the Septic Tank Biodigester (FSB). This aims to treat rural wastewater by anaerobic systems. However, the quality of the effluent is not desirable for disposal in water bodies, requiring post treatment. An alternative to this treatment is the inoculation of microalgae, as they have the potential to remove nutrients and pollutants, so that there isno severe environmental imbalance at the time of disposal. Based on this point, this work aimed to use TSE (Treated Sewage Effluent) for a microalgae culture medium, in order to assess whether it is possible to have potential algal development in wastewater. First, there was a previous survey of the ideal conditions for cultivation and then the analyzes were started. The experiment was divided into three stages, in which a culture medium was used in the first stage, with alternative sources of nitrogen and phosphorus such as NaNO3, NH4OH and KH2PO4 and for the second and third stages the effluent itself was used. A controlled system with a temperature of 25°C, 24-hour lighting and continuous agitation was considered. During the experiment, several analyzes such as pH, turbidity, electrical conductivity (EC), and biomass analyzes such as Fourier transform infrared spectroscopy (FTIR), elemental Analysis of Carbon, Hydrogen, and Nitrogen (CHN) and microscopy were performed. As a result, it was possible to observethe adaptation of microalgae in the FSB effluent, as well as that the process of inoculation of algae for post-treatment is efficient in terms of growth response time withthe nutritional conditions and pre-existing pH. It was also observed that in systems with higher agitation speed (which promotes better gas exchange between the aqueous medium and the atmosphere), the microalgae developed much faster than in non-aeratedsystems. In addition, the use of algae can be seen as a promising way to polish the effluent treated by the FSB, provided that the lighting conditions, pH and optimization of gas exchange between the solution and the atmosphere are considered.