Avviamento e monitoraggio di un reattore a scala pilota con biomassa granulare anammox

L’argomento di tesi è relativo alla rimozione dell’azoto dalle acque reflue attraverso trattamenti biologici innovativi. Nello specifico riguarda la rimozione dell’azoto ammoniacale tramite batteri definiti dalla vecchia letteratura come “impossibili”, perché non ritenuti esistenti. L’ossidazione anaerobica dell’ammonio ad azoto molecolare a spese del nitrito, che funge da elettron accettore, è l’incredibile processo scoperto agli inizi degli anni 90, promosso dai batteri chiamati anammox. La tesi di laurea si inserisce in un progetto volto a valutare l’applicabilità del processo anammox al refluo conciario trattato dall’impianto di depurazione Cuoidepur S.p.A. (Pi). Durante la fase sperimentale è stato avviato e monitorato un reattore gas-lift di 7 litri a scala pilota, inoculato con una biomassa granulare proveniente dal reattore CANON dell’impianto di Olburgen (NL). Il reattore è stato condotto con refluo sintetico e in condizioni anaerobiche, in modo da favorire il metabolismo anammox. Non è stato possibile testare l’effetto del refluo conciario sul processo anammox, con processo continuo, dal momento che si è manifestata un’inattesa precipitazione di minerali sulla superficie della biomassa granulare, dovuta a condizioni operative descritte nel presente elaborato e che ha portato ad un graduale peggioramento dell’attività della biomassa. Tuttavia la biomassa è stata riattivata con successo raggiungendo alte attività specifiche (raddoppiate nell’arco della sperimentazione) e, non di meno, il fenomeno osservato si inserisce tra le possibili problematiche che possono essere riscontrate durante la conduzione di reattori a biomassa granulare e rimane di interesse e monito per future applicazioni. The thesis topic relates to the removal of nitrogen from wastewater through innovative biological treatments. Specifically, it concerns the removal of ammoniacal nitrogen by bacteria defined by old literature as "impossible", because they were not considered to exist. The anaerobic oxidation of ammonium to molecular nitrogen at the expense of nitrite, which acts as an electron acceptor, is the incredible process discovered in the early 1990s, promoted by bacteria called anammox. This thesis is part of a project aimed at assessing the feasibility of the anammox process to the tannery wastewater treated by the Cuoidepur S.p.A. wastewater treatment plant, located in the province of Pisa . During the experimental phase, a 7-litre pilot-scale gas-lift reactor was initiated monitored and conducted with synthetic wastewater in anaerobic conditions in order to favour the anammox metabolism. Granular biomass from the real-scale CANON reactor in Olburgen (NL) was used as inoculum after one one-year storage at 4°C. The biomass was reactivated successfully, reaching high specific activities (doubling over the period of the experiment). It wasn’t possible to test the effect of the tanning wastewater on the anammox process, through a continuous process, due to an unexpected precipitation of minerals on the surface of the granular biomass. This occurred as a result of the operating conditions described in the present work that led to a gradual decline in biomass activity. Nevertheless, the phenomenon observed is one of the possible problems that can be encountered during the operation of granular biomass reactors and remains of interest and concern for future applications

Advanced treatment of landfill leachate through combined Anammox-based biotreatment, O3/H2O2 oxidation, and activated carbon adsorption : technical performance, surrogate-based control strategy, and operational cost analysis

The complexity of landfill leachate makes it difficult to treat it with a single biological/ physical/chemical process. Moreover, the dynamic leachate characteristics pose a challenge for effective process control. Therefore, a combined treatment, consisting of a one-stage partial nitrification-Anammox process, an O-3/H2O2 process, and a granular acti-vated carbon filtration (GAC) process, was investigated. Meanwhile, a novel surrogate-based ozone dose control strategy for O-3/H2O2 process was evaluated. Results show that this three-stage process offers high removal of total nitrogen (> 90%), COD (chemical oxygen demand, 60-82%), and micropollutants (atrazine, alachlor, carbamazepine, and bisphenol A, > 96%), satisfying discharge requirements. In the combined post-treatment, ozone dosing for COD removal can be real-time controlled by UVA(254) reduction monitoring, based on a specific correlation between COD and UVA(254) changes. On the other hand, O-3/H2O2 pre-treatment controlled at a 50% UVA(254) reduction shows to be the optimal point, when adsorption is designed as the main step for COD removal. Cost analysis shows that post-treatment with low (high) organic load i.e., COD =)540 mg/L, a combination with O-3/H2O2 (GAC) as the main step appears to be more cost-effective. Therefore, a dynamic operation strategy in response to the leachate change is recommended

Surrogate-based follow-up of activated carbon adsorption preceded by ozonation for removal of bulk organics and micropollutants from landfill leachate

Although combined ozonation with activated carbon (AC) adsorption is a promising technique for leachate treatment, little is known about how ozone-induced changes in leachate characteristics affect the organics adsorption, especially in view of emerging micropollutants (MPs) removal. Furthermore, the online monitoring of MPs is challenging but desirable for efficient treatment operation. This study investigates how preceding ozonation impacts the adsorption of bulk organics (expressed as chemical oxygen demand (COD)) and ozone-recalcitrant MPs, i.e., primidone, atrazine and alachlor, in leachate using batch and column adsorption tests. Additionally, a new surrogate-based model was evaluated for predicting MPs breakthrough. Batch tests revealed that ozonation results in a decreasing apparent affin-ity of COD towards AC, but the non-adsorbable part did not obviously change. The adsorption of MPs in ozonated leachate was (1-41%) higher than that in non-ozonated leachate, especially for the more hydrophobic alachlor and atrazine, due to a reduced sites competition from bulk organics. Column adsorption showed that ozonation delayed COD and MPs breakthrough due to the reduced COD loading and sites competition, respectively. An increased empty bed contact time (EBCT, 10-40 min) led to an increased COD uptake by a factor of 3.0-3.2 for ozonated and non-ozonated leachates, while MPs adsorption also increased, suggesting that pore blockage rather than site competition could be the dominant inhibitory effect. The data from column adsorption demonstrate the applicability of developed surrogate-based model for predicting MPs breakthrough. Particularly, the fitting parameters were not affected by change of leachate characteristics, while they were impacted by change of EBCT

Evaluating the suitability of granular anammox biomass for nitrogen removal from vegetable tannery wastewater

In the present study, the potential inhibitory effect of biologically pre-treated vegetable tannery wastewater (TW) on anammox granular biomass was evaluated. Beside high organic and chemicals load, vegetable TW are characterised by high salinity and high tannins concentration, the latter belonging to a group of bio-refractory organic compounds, potentially inhibitory for several bacterial species. Recalcitrant tannin-related organic matters and salinity were selected as the two potential inhibitory factors and studied either for their separate and combined effect. Parallel batch tests were performed, with biomass acclimated and non-acclimated to salinity, testing three different conditions: non-saline control test with non-acclimated biomass (CT); saline control test with acclimated biomass (SCT); vegetable tannery wastewater test with acclimated biomass (TWT). Compared with non-saline CT, the specific anammox activity in tests SCT and TWT showed a reduction of 28 and 14%, respectively, suggesting that salinity, at conductivity values of 10 mS/cm (at 25 °C), was the main impacting parameter. As a general conclusion, the study reveals that there is no technical limitation for the application of the anammox process to vegetable TW, but preliminary biomass acclimation as well as regular biomass activity monitoring is recommended in case of long-term applications. To the best of our knowledge, this is the first work assessing the impact of vegetable TW on anammox biomass