Cultivo de microalgas com efluente de maltaria para obtenção de biocombustíveis

Abstract

The production of malt generates wastewater with phosphate and nitrogen concentrations, which even after biological treatment, need physical-chemical treatment to render it possible for the effluent to be discharged into bodies of water. Otherwise, these substances could cause the eutrophication phenomenon. The physical-chemical treatment, besides having a high cost, can cause the contamination of riverbeds with residual chemical coagulants, altering the quality of the receiving body of water. Biological processes have appropriate characteristics to help fight pollution, such that there are various studies and research on the microorganisms. The use of microalgae in wastewater treatment is a viable alternative from an economic point of view compared to conventional secondary and tertiary systems. The microalgae cultures can be used for removing nitrogen and phosphorus from wastewater, adding value to the process due the possibility of using the obtained microalgae biomass for other purposes, for example in the production of biofuels. The objective of this work was to use malthouse wastewater in the cultivation of microalgae, in order to increase productivity in carbohydrates and/or lipid of microalgae biomass, providing the removal of pollutants through the use of these as nutritional source. The biologically treated wastewater of the malthouse was subjected to physicochemical characterization, identifying the levels of mainly of nitrogen and phosphorous compounds. The phosphate concentrations are legally high and after some adjustments in the nitrogen levels, it appears promising in the supply of nutrients. For selection of microalgae were used of microalgae Spirulina, Chlorella, Scenedesmus and Synecochoccus. After the addition of 30% of the malthouse in the w astewater the concentrations levels of carbohydrate increased reaching 30,07% for Spirulina platensis LEB 52, 24,67% for Spirulina platensis Paracas, 25,50% for Scenedesmus obliquus, 48,93% to Chlorella homosphaera, 26,38% to Chlorella minutissima and 49,86% to Synechococcus nidulans. Despite the high concentrations of carbohydrates in biomass of microalgae Chlorella homosphaera and Synecochoccus nidulans, the highest productivity in carbohydrates were obtained by microalgae Spirulina platensis LEB 52 (27,05 mg.L-1d-1) and Spirulina platensis Paracas (20,77 mg.L-1d-1). The cultivation of microalgae was efficient in the removal of nitrogen and phosphorous compounds from the wastewater of malt house, reaching levels of up to 93,13% removalto 89,76% nitrate and phosphate. The use of 50% of effluent in the cultivation of microalgae Spirulina platensis LEB 52, in a tank raceway type were efficient on the removal of nitrate and phosphate, although with smaller cell concentration and productivity of carbohydrate (12,26 mg.L-1d-1) also lower when used 30% of the wastewater. In conclusion, the use of malthouse wastewater in the cultivation of microalgae is a viable alternative for cost reduction for the growth medium, as well as the use of microalgae in the removal of nitrogen and phosphorous compounds as an alternative to conventional treatments for removal of pollutants. The process also makes itpossible to add value to an effluent through the reduction of production costs of biofuelsfrom microalgae.