BIOREMEDIATION OF SOIL CONTAMINATED WITH PETROLEUM HYDROCARBONS: PROCESS EVALUATION THROUGH BIOSLURRY REACTOR AND BIOELECTROCHEMICAL SYSTEM APPROACHES

Excessive use of petroleum hydrocarbons (PHCs) leads to high pollution of water and soil environments. the use of bioslurry and microbial electrochemical treatment (MET) approaches has emerged as an effective and feasible technique with a high remediation potential, especially for soils polluted with petroleum hydrocarbons, which often contain the highest pollution levels and are hard to treat with conventional approaches. Therefore, the main objective of this thesis was to develop a sustainable approach to bioslurry and a MET system for the effective and efficient treatment of PHCs from the soil. The biodegradation of soil polluted with PHCs was investigated in a mesocosm consisting of six bioslurry reactors using different external stimulants such as nutrients, activated sludge, synthetic surfactants, and long-chain rhamnolipids. The comparative analysis revealed that the combination of activated sludge, nutrients, and biosurfactant showed a 79.4% reduction in PHCs after ten days in the mesocosm experiment compared to the control treatment. A reactor system that includes boron-doped diamond as an electro-fenton-based anode and biological processes driven by long-chain rhamnolipids was developed to test the effectiveness of degrading soil contaminated with petroleum hydrocarbons. In addition, the parameters that affect the optimum conditions, such as changes in intermediate generation, pH, hydroxide concentration, and soil organic matter composition, were also studied. The study showed that the combination of systems led to a PHC degradation rate of 93.6% in 72 hours, which is 40% higher as compared to a single system due to the excellent synergistic effects. To enhance the degradation of PHCs and electron transfer, 10 mg/L, 50 mg/L, and 100 mg/L of rhamnolipid biosurfactants were added to the anolyte of MET. The results showed that rhamnolipids at a dose of 100 mg/L facilitated the degradation of PHCs (72 %) and promoted the highest bioelectricity generation (9.5 Am-2) in 20 days. Furthermore, the biosurfactants induced a special microbial enrichment associated with electrochemically active bacteria like Geobacter and Desulfovibrio and oil-degrading bacteria like Pseudomonas and Acinetobacter. The treatment of soil polluted with PHCs using double chamber MET designed for treating soil polluted with PHCs fed with biochar ex-situ applications in aqueous systems was investigated over long operational periods (up to 155 days). The study has shown a significant improvement in the biodegradation efficiency and electricity generation of PHCs from polluted soil by adding rice straw biochar. This work demonstrated that by adding an optimal dose of biochar (8% w/w), the maximum current density was 3.5 A/m-2, and the highest PHC reduction rate was achieved at 87.8 % in 20 days. However, excessive biochar use (12% w/w) caused adverse effects, with extracellular electron transfer efficiency diminished by 87.5% compared to the biochar dose (8%). Finally, a life cycle assessment was also conducted using SimaPro 9.1 software to compare the environmental performance of bioslurry and MET treatment using primary data from the experiment, identify the significant environmental hotspots of the system, and assess its environmental impact category with the ReCiPe 2016 characterization method. The results showed that the bioelectrochemical systems of MET treatment options present the most environmentally favorable option compared to the bioslurry treatment process due to the offset of the environmental loads from the avoided impacts contributed by their value-added by-product, which is the generation of electricity, which leads to outweighs a factor of 1.6 for the Global warming potential (GWP) offset of the environmental loads incurred by the system. The overall findings of this study suggest that MET technology could be used to treat petroleum hydrocarbon-contaminated soil systems while also recovering energy effectively.

L'uso eccessivo di idrocarburi petroliferi (PHC) porta a un elevato inquinamento dell'acqua e dell'ambiente del suolo. La fuoriuscita di contaminazione da petrolio greggio è ora comune durante le trivellazioni petrolifere offshore, il trasporto e il trasferimento a terra in molte parti del mondo. I PHC nel suolo possono anche modificare le proprietà fisiche e chimiche del suolo e del sottosuolo. Hanno un effetto fitotossico sulla germinazione dei semi, sulla crescita delle colture e sui raccolti. Pertanto, per ridurre il pericolo di esposizione, ripristinare la funzione del suolo e fornire servizi ecosistemici, è necessaria la bonifica della contaminazione per il ripristino e il risanamento del suolo colpito per vari usi, compresa l'agricoltura. Per questo motivo, l'uso di bioslurry e trattamento elettrochimico microbico (MET) è emerso come una tecnica efficace e fattibile con un elevato potenziale di bonifica, soprattutto per i suoli inquinati da idrocarburi petroliferi, che spesso contengono i livelli di inquinamento più elevati e sono difficili da trattare con approcci convenzionali. Tuttavia, i meccanismi coinvolti nel modo in cui l'aggiunta di uno stimolante esterno migliora la biodegradazione del PHC nel bioreattore e quelli coinvolti nel trasferimento extracellulare di elettroni nel sistema MET non sono ancora completamente compresi. Pertanto, l'obiettivo principale di questa tesi è stato quello di sviluppare un approccio sostenibile al bioslurry e un sistema MET per il trattamento efficace ed efficiente dei PHC dal suolo. La biodegradazione del suolo inquinato da PHC è stata studiata in un mesocosmo costituito da sei reattori bioslurry che utilizzano diversi stimolanti esterni quali nutrienti, fanghi attivi, tensioattivi sintetici e ramnolipidi a catena lunga. L'analisi comparativa ha rivelato che la combinazione di fanghi attivi, nutrienti e biotensioattivo ha mostrato una riduzione del 79,4% dei PHC dopo dieci giorni nell'esperimento del mesocosmo rispetto al trattamento di controllo. È stato sviluppato un sistema di reattori che include diamante drogato di boro come anodo basato sull'elettro-fentone e processi biologici guidati da ramnolipidi a catena lunga per trattare il suolo contaminato da idrocarburi di petrolio.