Resumen de Evaluation and comparison of advanced treatment technologies to enhance the removal of pharmaceutical active compounds from wwtp secondary effluent
During the last 20 years, the presence of several pharmaceutical active compounds (PhACs) in water bodies has garnered increasing attention and worldwide concern. The effluents from wastewater treatment plants (WWTPs) are one of the main sources of PhACs in aquatic environments.. Advanced tertiary treatments are required to improve the quality of WWTP effluents discharged into sensitive receiving water bodies and those utilized for potable reuse, industrial reuse and irrigation purposes. This thesis has focused on the combination of advanced biological, adsorption, filtration and oxidation processes. In particular the studied technologies were biological activated carbon coupled with ultrafiltration (BAC-UF) and UV-C activated peroxydisulfate and peroxymonosulfate (UV/PDS and UV/PMS). In this context, the main objective of this thesis is to assess the application of former mentioned advanced treatment technologies for an effective elimination of PhACs from secondary effluents of WWTPs. The strategy to evaluate these techniques as tertiary treatments is based on assessing their removal capacity, identifying the main removal mechanisms, calculating the costs required for the effective PhACs removal (80%) and finally to assess their environmental footprint. The BAC-UF technology has been evaluated at pilot-scale during one year of operation, assessing the removal of 15 PhACs at environmentally relevant concentration. The evaluation carried out with the BAC-UF pilot plant allowed to identify a clear evolution in the removal capacity of this system, in according to which two differentiated phases were identified. With respect to UV/PDS and UV/PMS technologies, they were preliminarily assessed with a set of lab-scale experiments treating both synthetic mineral water and real WWTP secondary effluent. Then, these technologies were validated at pilot-scale simulating real operating conditions. The validation of these results during pilot-scale experiments clearly indicated the potential for these novel techniques to be applied as tertiary wastewater treatment, since average removal values greater than 80% for both systems were obtained with 416 mJ/cm² of UV fluence and 0.4 mM of oxidant. Finally the comprehensive evaluation of the advanced treatment technologies studied in this thesis identified some of the practical factors limiting the potential application of BAC-UF, UV/PDS and UV/PMS technologies. Among them, with regard to the BAC-UF technology, the energetic consumption of the UF (6.6 x 10-1 kWh/m³) and the need to regenerate spent activated carbons, were the factors with the greatest environmental and economic footprint. The factors contributing the most were indeed electricity and GAC reactivation, respectively with a contribution of 49.1% and 27.4%. On the other hand, the two AOP alternatives, although showing similar removal efficiency, significantly differed when operating cost and environmental sustainability were considered. With respect to this analysis, PMS production resulted to be a critical factor having a negative impact on the environment and on operating costs. Keeping in mind the framework outlined by these considerations, UV/PDS technology can have the potential for real-case applications, although it requires further investigations for its optimization.
To sum up, the present thesis contributes to cast a wide net on advanced wastewater treatment alternatives for the removal of PhACs. The current work provides information regarding the applicability of the studied technologies, insights on their removal mechanism and calculation of the operating costs required. These findings have been then broadened with an environmental sustainability assessment of each treatment option and compared among state-of-the-art technologies.
