Biorremediação de efluentes agroindustriais por microalgas e valorização da biomassa algal numa economia circular

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BIOREMEDIATION OF AGRO-INDUSTRIAL EFFLUENTS MEDIATED BY MICROALGAE

Publication . Sousa, Catarina Viegas de; Gonçalves, Maria Margarida; Silva, Luísa

Every year, large amounts of agro-industrial effluents are produced all over the world and its sustainable management is still a technological challenge. This thesis addresses the remediation of four agro-industrial effluents (aquaculture, cattle, swine, and poultry) and an industrial effluent (landfill leachate) by treatment with biomass ash and microalgae. The pre-treatment with biomass ash allowed the partial precipitation of total solids, reduction of the turbidity and microbial load of the effluents, resulting in a partially treated effluent and a precipitate rich in mineral and organic components. The aqueous effluents were treated in batch and semi-continuous modes with the microalgae Chlorella vulgaris (Cv), Auxenochlorella protothecoides (Ap), Tetradesmus obliquus (To), Isochrysis galbana (Ig), Microchloropsis salina (Ms), and Spirulina major (Sm). Maximum biomass yields were reached for microalgae Cv (193.6 to 879.8 mg L-1 day-1) and To (236.7 to 811.7 mg L-1 day-1) in agro-industrial effluents. The remediation of effluents allowed reaching discharge values mandatory by law for total nitrogen and total phosphorus, COD, BOD5, and total solids. The precipitate obtained in the pre-treatment of the effluents and the algal biomass showed positive effects as biostimulants for the germination of watercress (Nasturtium officinale) and wheat (Triticum aestivum) seeds. The microalgae biomass was characterised and evaluated as a food supplement for mussels (Mytilus edulis) for 45 days, with changes in the contents of lipids, carbohydrates, and ash of the mussels being observed. The torrefaction of algae biomass and its mixtures with lignocellulosic biomass made it possible to obtain biochars with potential for energy recovery, use as biostimulants for seed germination, or as adsorbents for cationic pigments. The work carried out allowed to demonstrate the feasibility of treating the studied effluents by chemical precipitation and bioremediation with microalgae and to suggest different ways of valuing the solid by-products generated.

2022-02Tese de doutoramento

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Fundação para a Ciência e a Tecnologia

Número da atribuição

SFRH/BD/131178/2017