Estudio sobre nitritación parcial en frío inoculada mediante nitrificación de lodos municipales

Abstract

[EN] This thesis develops an alternative process to nitrification/denitrification (N/DN) for nitrogen removal from municipal sewage at temperatures between 13-26ºC, due to drawbacks of N/DN systems: high consumption of energy and organic carbon, and production of a great amount of sludge. The partial nitritation (PN) start-up from fully nitrifying municipal sludge was studied through a pilot-scale sequencing batch reactor (SBR) fed with contaminated tap water by ammonium sulfate ((NH4)2SO4), which simulated real sewage from anaerobic digestion. The analysis of the samples by using several tests (nitrogen test, kinetic test and volatile suspended solids test) and the control of certain parameters (pH, dissolved oxygen (DO), ammonium concentration in the influent (TAN), etc.) were carried out to keep the process under stable conditions and to know the system behaviour in the nitrogen removal at low temperatures. The final challenge was to generate a suitable effluent for the subsequent anammox step with an ammonium conversion between 50-57% and a high suppression of the activity of nitrite oxidizing bacteria (NOB) by the growth of ammonium oxidizing bacteria (AOB), the limitation on the duration of the aerobic SBR phase and the control of the solid retention time (SRT). After an exhaustive analysis of the results, the success of the research was confirmed since the effluent from the pilot plant showed an acceptable NOB inhibition with an average nitrite accumulation (NAR) of 89% and a partial conversion of ammonium to nitrite through a final ammonium nitrogen conversion between 41-62% and a N-NO2 - /N-NH4 + ratio of 1.20±0.30; in spite of a low NOB activity in the reactor and the loss of biomass due to excess sludge washout in the effluent. To overcome these small limitations in the future, several improvements have been suggested. On the basis of the above, this study provides a good background for the next research on the anammox reaction at low temperatures, which is going to be carried out by the Department of Water Technology and Environmental Engineering of University of Chemistry and Technology (UCT) from Prague (Czech Republic).

[ES] Esta tesis desarrolla un proceso para eliminación de nitrógeno de agua residual municipal a bajas temperaturas (13-26 ºC). En este proyecto, se estudia la puesta en marcha de la nitritación parcial a partir de lodos municipales totalmente nitrificantes (pH, rendimiento de operación, temperatura, sólidos suspendidos, etc.) para producir un efluente apropiado para el posterior anammox y remplazar la nitrificación/desnitrificación con mayor consumo energético en el tratamiento de agua residuales.