Avaliação do uso de microalgas na remoção de nutrientes e metais de efluente contendo soro de queijo

Abstract

Microalgae have shown promise for several applications due to their high capacity to absorb or adsorb diverse components present into the medium where they are found and for synthesizing products of high commercial value. Since its cultivation presents low cost and easy maintenance, the evaluation of its potential in diverse technological applications has become relevant. The main elements required by the metabolism of these microorganisms are carbon, nitrogen and phosphorus. As these components are present in effluents from several industries such as cheese whey and final effluent from the dairy industry, the cultivation of these microorganisms in order to reduce the levels of such elements is a possible alternative for treatment waste. Moreover, the aim of the current work was to evaluate the ability of microalgae to treat the effluent from the dairy industry. The first assay was performed using Chlorella vulgaris and Spirulina platensis in standard culture medium. Subsequently, assays were performed with C. vulgaris in medium containing cheese whey with and without treatment. Since, 0.1 g/L of the microalga was inoculated at different concentrations of cheese whey diluted in BBM medium. Finally, the efficiency of increases in the inoculum concentration was evaluated, at concentrations of 0.2, 0.4 and 1.0 g/L, in the effluent treatment. In this case, medium containing 10% of whey cheese was used. The microalgae capacity was measured through carbon, nitrogen, phosphorus, COD, lactose and metal removal analyzes. It was also evaluated the production of protein, ethanol, biomass and chlorophyll. In the preliminary tests, both microalgae removed carbon, nitrogen and phosphorus, being able to be used in the treatment of wastewater. As C. vulgaris presented a higher growth rate and promising results in assays with basal medium, it was used in the treatment of cheese whey. In the effluent without treatment tests, maximum removal achieved was: 50% carbon, 59% nitrogen, 90% COD, 53% phosphorus and 76% lactose. Ethanol production (in the presence of 25, 50 and 100% cheese whey), chlorophyll (in BBM medium and medium containing 1% cheese whey) and protein (in BBM medium and in the presence of 1 and 10% of cheese whey) were verified. For the treated cheese whey, there was no increase in the removal of these elements in relation to the without treated cheese whey. However, there was accumulation of protein at all effluent concentrations. Increases in the inoculum concentration resulted in the reduction of carbon, reaching 89% and nitrogen, 78%. In this case, the removal of metals (Calcium, Iron, Magnesium, Potassium and Calcium) by green algae was also obtained, which was not possible in the previous tests. It can be concluded that the microalgae Spirulina platensis and Chlorella vulgaris have great potential for effluent treatment. The latter was able to remove compounds present in the effluent from the dairy industry that lead to pollution of the environment. In addition, under certain conditions, it was possible to produce compounds of commercial interest such as ethanol, chlorophyll and protein.