Procesos alternativos para el tratamiento a alta presión de lodos edar

Resumen

The present PhD Dissertation titled ¿Alternative High Pressure Processes for Sewage Sludge Treatment¿ is included in the framework of the NovEDAR_Consolider Project (CSD2007-00055): Conception of the Sewage Treatment Plant of the XXI Century, promoted by the Spanish Ministry of Education and Science. The general aim of that Project is the study, design and optimization of novel processes or processes with certain level of maturity in order to implement the wastewater treatment plant (WWTP) of the 21st century. Spanish and Dutch research groups, extensively expertise in the fields related to wastewater and sewage sludge, work within that Project: from specialists on processes for wastewater and sewage sludge treatment, to specialists on related modeling, economy and ecotoxicology, among others. NovEDAR_Consolider Project encouraged conducting collaborations in between the different research groups. Thus, particularly for the case of the present PhD Dissertation, it is to be highlighted that the study to carry out and the objectives to achieve are included in the scope of the sludge line on WWTPs. The main objective consists on the study of different processes, a priori considered as high pressure processes (> 1bar), that may be implemented and optimized with the aim of improving the sewage sludge treatment and management. Energy saving and recovery is a key point in this Dissertation. In addition, a study on the anaerobic oxidation of ammonium biological process, the so called Anammox, is included in this Dissertation; the reason: the optimum implementation of this quite young process as connection between the sludge line and upstream section of the water line could involve several important benefits for the operation in novel WWTPs. The following highlighted key points are included in the present PhD Dissertation: 1.- Introducing of the Advanced Thermal Hydrolysis process (ATH), a novel pretreatment for the Anaerobic Digestion (AD) of sewage sludge: detailed comparative study with the Thermal Hydrolysis (TH) process. The ATH process takes advantage of a peroxidation plus direct steam injection synergistic effect in order to improve sewage sludge solubilization, dewaterability and biodegradability. In this work, ATH process proved to be a promising alternative from the energy saving and recovery point of view [in the sense of expediting methane (CH4) production in the AD]. A wide range of operating conditions was studied in detail: temperatures from 90 to 170 ¿C, operation times from 5 to 40 min, and with or without the addition of different hydrogen peroxide (H2O2) doses. Work conducted in collaboration University of Cádiz (Spain) - University of Valladolid (Spain). 2.- Study on the Hydrothermal Oxidation in the field of the sludge line of WWTPs. To be highlighted is the implementation of a complete kinetic study on the SCWO of Isopropanol (IPA) as auxiliary fuel/co-fuel for the optimization of the design and operation of the sewage sludge SCWO. The experimentation was conducted in a SCWO continuous flow tubular reactor system: temperatures from 400 ¿C to 500 ¿C, 250 bar and residence times from 4 to 80 seconds. The developed equations can be applied on the design, optimization and scale-up of the SCWO process in the sewage sludge treatment framework. Work carried out in the University of Cádiz (Spain). 3.- Anammox bacteria cultivation in a membrane bioreactor (MBR) looking forward to finding out the optimal operating conditions of the Anammox process, which main objective is to control/reduce the ammonium (NH4+) concentration of the WWTPs¿ effluents (the reader should take into account that NH4+ has, to some extent, a refractory behavior in the processes studied in the present PhD Dissertation: Thermal Hydrolysis, Advanced Thermal Hydrolysis, Anaerobic Digestion and Supercritical Water Oxidation). In fact, as it can be checked in the corresponding chapter of this PhD Dissertation, a cultivation of Anammox bacteria with a growth rate four-fold higher than that one commonly reported in the up to date literature. Work conducted in collaboration University of Cádiz (Spain) - Delft University of Technology (The Netherlands).