In the present work, the biological treatment of real reject water (800 mg NH4+-N L-1) from anaerobic digestion of sewage sludge from a waste water treatment plant (WWTP) is carried out. The process was optimised with a Sequencing Batch Reactors (SBR) of 3 L using methanol for denitrification due to the lack of a readily biodegradable organic carbon source. Process kinetics were compared through the specific Ammonium Uptake Rate (sAUR) finding the appropriate operational sequence at 32ºC with an 8 hour cycle length. Every operational cycle was carried out with a solid retention time (SRT) of 11 days, hydraulic retention time (HRT) of 1 day and 2500 mg VSS L-1. In order to avoid nitrate formation, and thus to save costs, the oxygen concentration was maintained below 1 mg L-1 during the aerobic periods and pH remained within an optimal range (7.5-8.5) alternating different aerobic/anoxic sub-cycles inside the operational cycle. The total nitrogen removal was 0.8-0.9 kg N day-1 m-3. In order to make the process more economical metanol was substitute for the primary hidrolysate of the own WWTP obtaining a total nitrogen removal of 0.7 kg N day-1 m-3. The use of primary hidrolysate would lead to a cost reduction of 0.2-0.3 kg -1 N removed.The next step was to compare the SBR technology to obtain the nitrite route with the continuous technology using a chemostat reactor. In that a chemostat SHARON (Single-reactor High activity Ammonia Removal Over Nitrite) continuous reactor (4 L) was operated to develop the biological nitrogen removal via nitrite of reject water at 33 ºC. Methanol was added for denitrification In the same chemostat took place nitrification and denitrification alternating periods of 1 hour with a total HRT of 2. As a conclusion, the SBR would be a slightly cheaper process (1.01 versus 1.28 kg -1 N) due to the higher volumetric reaction rates and the SHARON process is a more stable system.

In the last decades and due to the Water Framework Directive implementation, the urban wastewater cycle management has become more complex. The concept of integrated urban wastewater system management is introduced, and it becomes necessary to consider some new data as the sewer system characteristics or the receiving body. In this sense, environmental decision support systems (EDSS) are very useful and powerful tools to support during the decision making process. A new EDSS for the integrated urban wastewater system management has been developed integrating data from several sources (bibliographic, theoretical or historical) and a real case-based virtual system able to perform simulations. Results demonstrate the benefits of using this kind of systems in comparison with a standard approach, which do not use the expert knowledge and encourages continuing with this research in order to improve the quality and efficiency of this type of EDSSs / En les darreres dècades, i degut a la implementació de la Directiva Marc de l’Aigua, la gestió del cicle urbà de l’aigua ha esdevingut més complexa. S’introdueix el concepte de gestió integrada de conca, i és necessari considerar certa informació, com les característiques de la xarxa de clavegueram o del medi receptor. D’aquesta manera, els sistemes de suport a la decisió ambiental (EDSS) són eines potentíssimes que faciliten la presa de decisions en aquest camp. S’ha desenvolupat un nou EDSS per a la gestió integrada de conca que utilitza una base sòlida de coneixement expert, integrant informació de diverses fonts (bibliogràfiques, teòriques o històriques) i dos sistemes virtuals basats en dades reals sobre els quals és possible realitzar simulacions. Els resultats demostren que aquest sistema presenta beneficis importants respecte a una gestió estàndard sense sistema expert, i esperona a prosseguir amb la recerca i el desenvolupament per a millorar-lo