Continuous treatment of aqueous phase of hydrothermal liquefaction of Spirulina in horizontal fixed bed anaerobic reactor using biostimulated sludge

• Ano de defesa: 2020
• Autor(a) principal: Bueno, Beatriz Egerland
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Anaerobic digestion; Digestão anaeróbia; Efluentes tóxicos; Hydrothermal liquefaction; Liquefação hidrotermal; Metano; Methane; Microalgae; Microalgas; Toxic effluent
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/74/74132/tde-15102021-114111/

Hydrothermal liquefaction is a process that converts wet biomass into biofuels, more specifically bio-crude oil. Nevertheless, along with this process, a wastewater is generated rich in nutrients and organic matter content, however presenting large amount of toxic compounds. Anaerobic digestion is a promising option for post-hydrothermal liquefaction wastewater (PHWW) treatment. In this study, the anaerobic digestion of PHWW from Spirulina, was evaluate using biostimulated sludge as strategy to optimize the process. The biostimulation was conducted in a sequential batch reactor fed with an organic acids solutions and methanol aiming the development of acetogenic and methanogenic microorganisms. Two PHWW anaerobic biodegradability assays were performed, one with biostimulated sludge and another with non-biostimulated sludge. Biostimulated sludge was able to reach higher methane yields at higher organic matter concentrations (11 and 16 g COD.L-1) in relation to the non-biostimulated sludge (7 g COD.L-1) and presented a lower degree of inhibition under the inhibitory conditions tested. Therefore, the biostimulation was a key process to select and favor potential microorganisms involved in a specialized uptake of recalcitrant compounds, such as Mesotoga and Methanomethylovorans genera, which were fundamental to the bioconversion of PHWW. An interesting strategy for the treatment of toxic compounds is the use of biomass adhered to inert supports forming biofilms. In this work, the use of immobilized biomass was evaluated for the anaerobic degradation of PHWW in batch assays and continuous treatment. Small lag phase periods and volatile fatty acids balance showed the advantages of the use of biomass immobilized in polyurethane foam. Continuous treatment in a horizontal anaerobic immobilized biomass (HAIB) reactor reached chemical organic demand (COD) removal efficiencies from 40 to 69%, operating with 0,8 e 1,6 g COD.L. d-1. A second HAIB reactor was operated for evaluating the benefits of using methanol as co-substrate in the anaerobic degradation PHWW from Spirulina. However, methanol did not present positive contribution for degrading the PHWW.