Βιολογική απομάκρυνση φωσφόρου με παράλληλη νιτρωδοποίηση-απονιτρωδοποίηση με συστήματα επεξεργασίας υγρών αποβλήτων με χαμηλό λόγο άνθρακα προς Άζωτο

Ανδρεαδάκης, Δημήτρης; Andreadakis, Dimitris

dc.contributor.author	Ανδρεαδάκης, Δημήτρης	el
dc.contributor.author	Andreadakis, Dimitris	en
dc.date.accessioned	2023-01-11T07:35:20Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/56581
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.24279
dc.rights	Default License
dc.subject	Enhanced biological phosphorus removal	en
dc.subject	Polyphosphate accumulating organisms	en
dc.subject	Free nitrous acid inhibition	en
dc.subject	Free ammonia inhibition	en
dc.subject	PAO/GAO competition	en
dc.subject	Βιολογική απομάκρυνση φωσφόρου	el
dc.subject	Πολυφωσφορικά βακτήρια	el
dc.subject	Βακτήρια συσσώρευσης γλυκογόνου	el
dc.subject	Μηχανισμοί αναχαίτισης πολυφωσφορικών	el
dc.subject	Επεξεργασία στραγγιδίων	el
dc.title	Βιολογική απομάκρυνση φωσφόρου με παράλληλη νιτρωδοποίηση-απονιτρωδοποίηση με συστήματα επεξεργασίας υγρών αποβλήτων με χαμηλό λόγο άνθρακα προς Άζωτο	el
dc.title	Biological phosphorus removal coupled with nitritation-denitritaion for low carbon/nitrogen wastewater treatment systems	en
dc.contributor.department	Sanitary Engineering Laboratory, Department of Water Resources and Environmental Engineering	el
heal.type	doctoralThesis
heal.classification	Environmental Engineering	en
heal.dateAvailable	2024-01-10T22:00:00Z
heal.language	el
heal.language	en
heal.access	embargo
heal.recordProvider	ntua	el
heal.publicationDate	2022-07-17
heal.abstract	The side-treatment of reject water has emerged an attractive option over the past years due to its potential for relieving nutrient loading of the main-stream processes, while removing nitrogen at a reduced cost. This is achieved by the suppression of Nitrite Oxidizing Bacteria (NOB) due to the high Free Ammonia (FA) concentrations that characterize reject waters and the implementation of the nitritation/denitritation pathway, which compared to conventional nitrification/denitrification, has a lower demand in oxygen and carbon. While these conditions are beneficial for nitrogen removal, this is not the case for enhanced biological phosphorus removal (EBPR), as polyphosphate accumulating organisms (PAOs) have been reported to be severely inhibited by nitrite accumulations. More specifically, free nitrous acid (FNA), which is the protonated form of nitrite, has been revealed to be the actual inhibitor of PAOs, meaning that the severity to which PAOs are inhibited by nitrite increases significantly at lower pH. The degree to which PAOs have been reported to be inhibited by FNA itself varies in the literature, as does the tolerance of each respiration pathway (aerobic/anoxic), with contradictory conclusions. In addition, it has recently come to light that FA is also an inhibitor of PAOs, although research on this matter is rather limited as of this point. Regardless, the conditions of nitritation/denitritation appear to be hostile for PAOs and the application of EBPR, raising the question if the coupling of these processes is feasible. The goal of this dissertation is to provide an answer to this question. To this end, the following objectives were established: First was an extensive assessment of the inhibitory effect of FNA on PAOs, both under aerobic and anoxic conditions, with consideration to biomass acclimation to the inhibitor. This aims to settle disputes in the literature but also determine the mode of inhibition which has yet to be established. Second was to determine the effect of FA on PAOs along with its respective mode of inhibition, for which little information is available. Third was to assess the combined effect of FNA and FA on PAOs and develop a unified inhibition model. Fourth was the assessment of the effect of FNA and FA on the main antagonistic microbial group towards PAOs, namely glycogen accumulating organisms (GAOs). This assessment is of value, as a possible higher tolerance of GAOs to these inhibitors could indicate that PAOs face the danger of washing out even in relatively mild inhibitory conditions. Fifth was to develop strategies for the proliferation of PAOs and the suppression of GAOs under inhibitory conditions, and sixth was to optimize conditions for the prevalence of PAOs in high nitrogen loading systems and assess the limits of EBPR under these conditions, ultimately completing the aim of this work. In order to investigate the effects of FNA and FA on PAOs and GAOs, a laboratory-scale sequencing batch reactor (SBR) was set-up in the Sanitary Engineering Laboratory of the School of Civil Engineering, NTUA for their cultivation. The SBR operated from September 2017 to April 2021 with several resets and intermediate breaks, depending on the investigation phase. The SBR’s configuration was altered for each experimental period based on the specific goals of that phase but was generally based on the alternation of an anaerobic phase, at the start of which feed would enter via pump, an aerobic phase, achieved via air pump and an anoxic phase. While these phases were automated, settling and decanting was carried out manually, once per day. Feed consisted of synthetic wastewater, that was prepared on a daily basis, the composition of which was specific to each investigation. During each experimental period, once the reactor had displayed a steady performance, a series of ex-situ batch experiments were conducted on sludge retrieved from the SBR. The effect of FNA and FA on PAOs was determined based on their effect on the aerobic and anoxic phosphorus uptake rate (PUR) of the biomass. In the case of GAOs, the effect of FNA and FA was evaluated based on their effect on the maximum growth rate of the biomass. This required the development of a very highly GAO-enriched biomass (>90% of the total microbial population). In addition to the ex-situ experiments, a series of strategies, based on the choice of substrate and the SBR configuration, for the promotion of PAOs over GAOs, were evaluated in-situ. The investigation regarding the effect of FNA on PAOs revealed that both aerobic and anoxic PUR are significantly inhibited by FNA and to the same degree (meaning that FNA affects PAOs regardless of the respiration pathway). For an acclimated biomass, FNA was found to inhibit PUR by 50% at the concentration of 1.5 μg N/L and by 100% at a concentration just over 13 μg N/L. PUR inhibition by FNA was determined to be best described by a non-competitive inhibition model with an inhibition constant of KiFNA=1.5 μg N/L. The investigation regarding the effect of FA on PAOs concluded that FA is also a strong inhibitor of PAOs, with PUR being inhibited by more than 90% at the FA concentration of 30 mg N/L. Similarly to the case of FNA, FA appeared to inhibit the aerobic and anoxic pathway to the same degree. PUR inhibition by FA was determined to be best described by an uncompetitive inhibition model with a KiFA in the range of 8-10 mg N/L. In the case of anoxic PUR inhibition, the inhibition model proposed by Levenspiel gave the most satisfactory fit with the experimental data. The simultaneous presence of FA and FNA has a much more adverse effect on PUR compared to when PAOs were exposed to a single inhibitor. An enzymatic inhibition model was developed to describe simultaneous inhibition of PUR by FNA and FA, based on the separate inhibition models that were established. The combined inhibition model gave very satisfactory predictions when FNA and FA were assumed to be capable of binding to the same enzyme-substrate complex, and less accurate predictions when FNA and FA were assumed to be incapable of binding to the same complex. This inhibition model may be used to predict the performance of PAOs throughout a specific set of conditions (NH4 & NO2 concentrations, pH and temperature) but also determine an optimum variation of pH for PUR throughout the processes of nitritation and denitritation. The investigation regarding the effect of FNA on GAOs revealed that GAOs are also inhibited by FNA, although generally to a lesser extent than PAOs. Interestingly, the effect of FNA on the growth of GAOs appears to be pH dependant, with FNA affecting GAOs significantly more at higher pH values (At pH=7, GAO growth was inhibited by 50% at the FNA concentration of 10 μg N/L, while at the pH of 8, the same degree of inhibition was observed at the concentration of 3 μg N/L). In comparison to PAOs, GAOs appear to have a significantly higher tolerance to FNA at low pH, while at relatively high pH (8), the tolerance of the two microbial groups to FNA are similar. However, the investigation on the effect of FA on GAOs revealed that GAOs were not affected by the inhibitor, up to a concentration of 16.3 mg N/L, which was the highest FA concentration studied. It may therefore be concluded that the prevailing conditions in high nitrogen loading systems may provide a significant advantage to GAOs, endangering the sustainability of PAOs. A series of feeding strategies that were examined revealed that strategies that have been applied successfully for the suppression of GAOs and the proliferation of PAOs, may not hold up under the inhibitory conditions of nitritation/denitritation systems. However, one strategy that proved most successful was the promotion of PAOs via the denitritation pathway, using propionate as the sole carbon source. The strategy relies on the fact that all known GAOs appear incapable of reducing nitrite with propionate and is achieved by providing PAOs priority in the utilization of nitrite over common heterotrophs. At a volumetric nitrogen loading rate (vNLR) of 0.1 kg N/m3 d, this strategy achieved a highly PAO-enriched biomass (approximately 50% of the total microbial community), in which the population of GAOs was significantly low. The biomass displayed a steady capacity for excellent P-removal both under aerobic and anoxic conditions, performing at an average PUR of 25 and 10 mg P/g VSS h under aerobic and anoxic conditions, respectively. However, a downside of this strategy is that due to the relatively slow denitritation rates of PAOs, its application may require greater anoxic retention times, limiting the potential for treatment of high vNLRs. In a second stage of operation, the increase of the vNLR from 0.1 to 0.15 kg N/m3 d, resulted in the biomass performing at half its former capacity. Based on the combined inhibition model, a series of mathematical simulations were performed in order to evaluate the potential for EBPR alongside nitritation/denitritation in high nitrogen loading systems. The theoretical configuration that was examined was optimized with regard to appropriate alteration of aerobic and anoxic conditions, as to prevent nitrite accumulation and retain a relatively high pH at relatively high values, providing PAOs with an exclusive denitritation period (as to employ the GAO suppression strategy) after the rapid removal of a significant nitrite portion by common heterotrophs which may be achieved by providing a regulated carbon dose, and the quality of the treated effluent. The viability of EBPR was evaluated for several vNLRs up to 0.3 kg N/m3 d, considering the overall inhibition of PAOs, the adequacy of the GAO suppression strategy, the necessity for pH control as to minimize PAO inhibition and the effective achievement of NOB shunt. Based on the results of the simulations and their evaluation, it was concluded that a vNLR of 0.2 kg N/m3 d could allow sufficient and relatively safe EBPR without the need for pH manipulation. Higher vNLR’s, may allow EBPR with some pH control which is costly, while vNLR’s above 0.3 kg N/m3 d likely forbid the application of EBPR, as the inhibitory conditions alone would severely compromise the sustainability of PAOs. In conclusion, the side-stream treatment of reject water with EBPR alongside nitritation/denitritation is feasible, although its application faces certain challenges and requires a series of prerequisites. For one, the GAO-suppression strategy demands the supply of propionate, which would likely need to be provided via fermentation of primary sludge under specific conditions. In general, the implementation of this treatment should only be considered when EBPR in the main treatment facilities is challenged due to a low carbon content of the wastewater. In this case, the simultaneous removal of nitrogen and phosphorus with the same carbon source in order to minimize the demand for external carbon, is a viable option. Otherwise, the limitations of operating at a low vNLR, such as the need for greater reactor volumes, may outweigh the benefits of this approach.	en
heal.advisorName	Νουτσόπουλος, Κωνσταντίνος	el
heal.advisorName	Noutsopoulos, Constantinos	en
heal.committeeMemberName	Noutsopoulos, Constantinos	en
heal.committeeMemberName	Mamais, Daniel	en
heal.committeeMemberName	Malamis, Simos	en
heal.committeeMemberName	Lyberatos, Gerasimos	en
heal.committeeMemberName	Tsihrintzis, Vassilios A.	en
heal.committeeMemberName	Melidis, Paraschos	en
heal.committeeMemberName	Stasinakis, Athanasios	en
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Πολιτικών Μηχανικών	el
heal.academicPublisherID	ntua
heal.fullTextAvailability	false