Carbon and nitrogen treatment in industrial wastewaters using bioelectrochemical systems
- Autores: Anna Vilajeliu Pons
- Directores de la Tesis: Jesús Colprim Galcerán (dir. tes.), Sebastià Puig Broch (dir. tes.), Maria Dolors Balaguer Condom (dir. tes.)
- Lectura: En la Universitat de Girona ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Deepak Pant (presid.), Marta Coma Bech (secret.), Théodore Bouchez (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The presence of carbon (organic matter) and nitrogen (ammonium) in municipal and industrial (livestock farming, agriculture and factories) wastewaters is a serious worldwide concern. These undesired products are being continuously generated in our society. They contribute to the environmental pollution, reducing the water quality and increasing the eutrophication phenomena frequency. Nowadays, activated sludge and anaerobic digestion are the most used technologies in wastewater treatment plants (WWTPs) to remove these contaminants. However, both technologies are not efficient for the nitrogen treatment. In activated sludge, nitrification entails a strong economic cost for aeration. It consumes about 1/3 of the WWTP energy balance. In anaerobic digestion, nitrogen is not treated and it requires an additional post-treatment. For these reasons, it is necessary to explore alternative technologies able to simultaneously remove carbon and nitrogen from wastewater in a more efficient and sustainable way.
The utilization of a bioelectrochemical system (BES) allows the removal organic matter and nitrogen from wastewater with concomitant bioelectricity generation. In bioanodes of a BES, exoelectrogenic microorganisms can oxidize organic matter, releasing electrons and protons to the cathode. In biocathodes, electrotrophic microorganisms can perform denitrification. Moreover, this technology gives versatile operational options for nitrification. For these reasons, this thesis aims to asses a simultaneous carbon and nitrogen removal BES looking for its future implementation treating industrial wastewater as swine manure.
In the first chapters, this PhD thesis demonstrates the viability of BES to treat complex matrices as swine manure, removing carbon and nitrogen and generating electricity. Then, different BES designs were evaluated to optimize both nutrient removal and electrochemical performance by modifying: I) the anode/ cathode configurations; II) the external resistance control; III) the anode/cathode electron donors/acceptors and IV) the nitrification oxygen set-point.
In order to look for a real applicability, the mL-scale BES reactors were scaled-up and operated at long-term. It was observed that both treatment performances and electricity production achieved at mL-scale (0.6 L) could be reproduced at L-scale (65 L). The assessment of different electrode materials (granular graphite and stainless steel) at L-scale allowed the identification of their limitations and its future applicability. Granular graphite (widely used at mL-scale BES) declined its efficiency overtime at L-scale due to electrode crushing. However, stainless steel highlighted as a better appropriate electrode for scaled-up BES long-term operation of for treating complex wastewaters.
On the way to increase BES sustainability, strategies for increasing the electrochemical efficiencies were investigated. The BES power output was improved by applying either an external resistance control (Maximum power point tracking, MPPT) at mL-scale or different electric circuit connections at L-scale. Moreover, the MPPT incremented the bacterial abundance and promoted the selection of putatively exoelectrogenic bacteria.
Finally, the BES microbiomes were evaluated from the microbiological and electrochemical perspective. Different microbiological techniques from the quantitative (qPCR) and qualitative (PCR-DGGE, 454-pyrosequencing, T-RFLP, FISH and SEM) point of view were used to quantify and identify the microbial communities. Microbiological and engineering data were used to relate the microorganisms with their putative role on nutrient removal and electricity production (electrogenic, nitrifying and denitrifying community). Last but not least, microcosms were successfully used for characterizing the extracellular electron transfer thermodynamics and electroactive steps for anoxic ammonium oxidation.
In conclusion, results presented in this PhD thesis supports that bioelectrochemical systems have the potential of being an alternative technology for simultaneous carbon and nitrogen removal with concomitant electricity production treating industrial wastewaters as swine manure. In the near future, it can become a cheaper and more sustainable alternative than current processes for wastewater treatment.
