The cyanobacterium Arthrospira (Spirulina) platensis, one of the most studied and cultivated photosynthetic microorganisms, has been largely produced for obtaining biomass with high contents of protein, vitamins, minerals, amino acids, polyunsaturated fatty acids, and pigments. This biomass shows potential use as human food supplement and animal feed. Consequently, several studies are made aiming to improve biomass productivities, using different sources of carbon and nitrogen as well as environmental conditions such as light intensity, pH, and temperature. Nevertheless, studies assessing the possibility of reusing Arthrospira cultivation medium were not found in the literature. This method, besides reducing the cost of nutrients, could also provide environmental benefits, by avoiding soil salinization and eutrophication in water bodies. This project aims to study the reuse of effluent medium from Arthrospira (Spirulina) platensis cultivation treated with powdered activated carbon and different coagulants. The effluent, obtained from A. platensis batch cultivation in bench-scale open ponds, using sodium nitrate as a nitrogen source, will be treated by physic-chemical processes, employing different concentrations of powdered activated carbon and ferric chloride or ferric sulphate. The treated medium will be used in a new cultivation of the same microorganism. Using a randomized block design, the efficiency of medium treatments will be evaluated by means of multivariate analysis of variance, considering the parameters of effluent characterization, cell growth kinetic parameters, and A. platensis biomass composition as dependent variables.Key-words: Arthrospira (Spirulina) platensis, microbial biomass, culture medium effluent, powdered activated carbon, coagulant.
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