Gugliucci, Wanda (2023) Recovery of hydrothermal liquefaction wastewater: potential valorisation for agronomic purpose. [Tesi di dottorato]

	Testo Gugliucci_Wanda_35ciclo_COMPLETA.pdf Visibile a [TBR] Amministratori dell'archivio Download (6MB) | Richiedi una copia
Anteprima	Testo Gugliucci_Wanda_35ciclo_OSCURATA.pdf Download (4MB) | Anteprima

Abstract

The aim of this PhD project was to assess the potential use of of industrial wastewater, obtained from the hydrothermal liquefaction of organic wastes, as irrigation water for industrial crops. The impact of wastewater irrigation was evaluated by the chemical analyses of soil, microbiological analyses of the rhizospheres and physiological analyses of plants. The first chapter presented an overview of the main biomass conversion strategies with a particular emphasis on hydrothermal liquefaction process. This latter is an innovative eco-friendly technology for bioenergy production using high temperatures and pressures to break down the bonds of macromolecules contained in biomasses. The main products are a bio-oil (15 %), a biochar (15%) and wastewater (HTL-WW, 70%). Considering the significant concentration of this wastewater released during each production cycle, it has been deemed necessary to evaluate various valorisation strategies. The HTL-WW chemical composition reflects the feedstock used, including lignocellulosic residues, microalgae and organic wastes. Based on their composition, the HTL-WW could be therefore recycled in different biological processes, such as anaerobic digestion or microalgae cultivation. However, the HTL-WW obtained from organic wastes is characterised by a neutral pH and displays a high content of nutrients and minerals as well as organic matter. Moreover, this type of HTL-WW is free of human pathogens and hazardous chemicals. Consequently, the HTL-WW from organic wastes could be a good candidate as water irrigation, due to a severe drought and the exhaustion of water supplies occurring in the south Europe. The HTL-WW from organic wastes, is rich in nitrogen, phosphorus, potassium, organic carbon and minerals. However, the concentration of some chemical elements, such as electrical conductivity, chemical oxygen demand or ammonia were beyond the threshold values established by Italian law (DM183/2003). Therefore in the second chapter, the HTL-WW chemical composition was investigated to determine an optimal HTL-WW dilution, tested as water irrigation in a pot experiment with the model plant of Nicotiana tabacum L. These plants were grown in the greenhouse under controlled conditions and daily irrigated with diluted HTL-WW. Rhizosphere and plants were weekly sampled to evaluate, over time, the effect of wastewater irrigation both on the rhizosphere-associated microbiota, through culture-independent methods, and on the growth of tobacco plants, through the measurement of different biometric indices. Therefore, the total genomic DNA was extracted from rhizosphere and bulk soil samples and preliminarily analysed by Denaturing Gradient Gel Electrophoresis (PCR-DGGE) to determine the prokaryotic and eukaryotic communities’ structure. A deeper molecular analysis, amplicon based metagenomic sequencing, was employed to describe differences in microbial composition among treated and non-treated rhizo-soils. The sequences were analysed with QIIME2 software. Taxonomic assignment was obtained by the RDP classifier and the Greengenes or UNITE database for bacterial 16S rRNA and fungal ITS sequences. Based on these previous results, a second experiment was carried out on open field grown Ricinus communis L. plants, a key species for bioenergy production, as described in the third chapter. Moreover, to improve the crops production applying the sustainable agriculture practices, a selected Plant Growth Promoting Bacteria (PGPB) consortium was inoculated to the plants, individually or in combination with HTL-WW. The experimental design consisted of four different conditions, plants irrigated with only tap water, plants inoculated with PGPB consortium and irrigated with only tap water, plants irrigated with HTL-WW and plants inoculated with PGPB consortium and irrigated with HTL-WW. In this present work, the biometric indices and gas exchanges measurements as well as soil chemical analysis were performed. The sequencing data from plant rhizospheres were processed using ecological indeces and multivariate statistical analyses to determine key feature of castor oil microbiota significantly associated to given treatment/plant performance. This part of the work was conducted in collaboration with the University of Dundee. In the fourth and final chapter, a reflection of and future perspective derived from the of the entire PhD project is reported.

Downloads

Actions (login required)

Modifica documento