Belmonte, M., Hsieh, C. F., Campos, J. L., Guerrero, L., Mendez, R., Mosquera-Corral, A., et al. (2017). Effect of Free Ammonia, Free Nitrous Acid, and Alkalinity on the Partial Nitrification of Pretreated Pig Slurry, Using an Alternating Oxic/Anoxic SBR. Biomed Res. Int., , 7 pp.
Abstract: The effect of free ammonia (NH3 or FA), free nitrous acid (HNO2 or FNA), and total alkalinity (TA) on the performance of a partial nitrification (PN) sequencing batch reactor (SBR) treating anaerobically pretreated pig slurry was studied. The SBR was operated under alternating oxic/anoxic (O/A) conditions and was fed during anoxic phases. This strategy allowed using organic matter to partially remove nitrite (NO2-) andnitrate (NO3-) generated during oxic phases. The desired NH4+ to NO2- ratioof 1.3gN/gNwas obtained when an Ammonium Loading Rate (ALR) of 0.09 gNH(4)(+)N/L d was applied. The system was operated at a solid retention time (SRT) of 15-20 d and dissolved oxygen (DO) levels higher than 3 mg O-2/L during the whole operational period. PN mainly occurred caused by the inhibitory effect of FNA on nitrite oxidizing bacteria (NOB). Once HNO2 concentration was negligible, NH4+ was fully oxidized to NO(3)(-)in spite of the presence of FA. The use of biomass acclimated to ammonium as inoculum avoided a possible effect of FA on NOB activity.
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Carrera, P., Campo, R., Mendez, R., Di Bella, G., Campos, J. L., Mosquera-Corral, A., et al. (2019). Does the feeding strategy enhance the aerobic granular sludge stability treating saline effluents? Chemosphere, 226, 865–873.
Abstract: The development and stability of aerobic granular sludge (AGS) was studied in two Sequencing Batch Reactors (SBRs) treating fish canning wastewater. R1 cycle comprised a fully aerobic reaction phase, while R2 cycle included a plug-flow anaerobic feeding/reaction followed by an aerobic reaction phase. The performance of the AGS reactors was compared treating the same effluents with variable salt concentrations (4.97-13.45 g NaCl/L) and organic loading rates (OLR, 1.80-6.65 kg CODs/(m(3).d)). Granulation process was faster in R2 (day 34) than in R1 (day 90), however the granular biomass formed in the fully aerobic configuration was more stable to the variable feeding composition. Thus, in R1 solid retention times (SRT), up to 15.2 days, longer than in R2, up to 5.8 days, were achieved. These long SRT5 values helped the retention of nitrifying organisms and provoked the increase of the nitrogen removal efficiency to 80% in R1 while it was approximately of 40% in R2. However, the presence of an anaerobic feeding/reaction phase increased the organic matter removal efficiency in R2 (80-90%) which was higher than in R1 with a fully aerobic phase (75-85%). Furthermore, in R2 glycogen-accumulating organisms (GAOs) dominated inside the granules instead of phosphorous-accumulating organisms (PADS), suggesting that GAOs resist better the stressful conditions of a variable and high-saline influent. In terms of AGS properties an anaerobic feeding/reaction phase is not beneficial, however it enables the production of a better quality effluent. (C) 2019 Elsevier Ltd. All rights reserved.
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Carrera, P., Mosquera-Corral, A., Mendez, R., Campos, J. L., & del Rio, A. V. (2019). Pulsed aeration enhances aerobic granular biomass properties. Biochem. Eng. J., 149, 7 pp.
Abstract: The reduced footprint of Aerobic Granular Sludge (AGS) systems constitutes a good alternative to conventional treatments, despite their associated drawbacks (long start-up periods and high aeration requirements for granules formation and integrity). This study presents a pulsed aeration regime as a strategy to overcome these problems. Two AGS sequencing batch reactors (SBRs) were operated treating low-strength wastewater (190 mg COD/L) with pulses of 1 s ON/2 s OFF (R1) and continuous aeration (R2). Initially, different superficial gas velocities (SGV) of 3.6 cm/s (R1) and 1.2 cm/s (R2) were imposed for the same airflow (448 L/cycle). The granulation process was completed in 38 days for R1 whereas it took 48 days for R2. Denser and smaller granules were formed with pulsed regime and phosphate accumulating organisms were developed faster. The removal efficiencies were practically the same in both SBRs, being of 85% for COD, 95% for phosphorus and 30% for nitrogen. After granules formation the airflow in both reactors was reduced. For a SGV of 1.2 cm/s both systems behaved similarly. The minimum SGV required to maintain a uniform mixture of the biomass inside the reactor was 1.2 (R1) and 0.5 cm/s (R2), meaning less air consumption in the pulsed system (149 L/cycle) compared to the continuous one (179 L/min). Therefore, pulsed aeration successfully reduced granulation periods and aeration requirements in AGS systems.
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del Rio, A. V., Buys, B., Campos, J. L., Mendez, R., & Mosquera-Corral, A. (2015). Optimizing upflow velocity and calcium precipitation in denitrifying granular systems. Process Biochem., 50(10), 1656–1661.
Abstract: The denitrification process was studied in two granular biomass denitrifying reactors (USB1 and USB2). In USB1 large quantities of biomass were accumulated (9.5 gVSS L-1) allowing for the treatment of high nitrogen loads (3.5 g NO3--N L-1 d(-1)). As the biomass granulation process is not immediate the effects of different upflow velocities (0.12-5.5 m h(-1)) and calcium contents (5-200 mg Ca2+ L-1) were studied in order to speed up the process. Obtained results indicate that the optimum values for these parameters, which allow for the stable operation of USB1, are of 0.19 m h(-1) and 60 mg Ca2+ L-1. Then these optimum conditions were applied to USB2 where the effects of concentrations from 335 to 1000 mg NO3--N L-1 were tested. In these conditions nitrate concentrations of 1000 mg NO3--N L-1 are required for denitrifying granular biomass formation. Summarizing denitrifying granules can be formed at low upflow velocities and in hard or extremely hard water composition conditions if sufficient high nitrogen loads are treated. (C) 2015 Elsevier Ltd. All rights reserved.
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del Rio, A. V., da Silva, T., Martins, T. H., Foresti, E., Campos, J. L., Mendez, R., et al. (2017). Partial Nitritation-Anammox Granules: Short-Term Inhibitory Effects of Seven Metals on Anammox Activity. Water Air Soil Pollut., 228(11), 9 pp.
Abstract: The inhibitory effect of seven different metals on the specific anammox activity of granular biomass, collected from a single stage partial nitritation/anammox reactor, was evaluated. The concentration of each metal that led to a 50% inhibition concentration (IC50) was 19.3 mg Cu+2/L, 26.9 mg Cr+2/L, 45.6 mg Pb+2/L, 59.1 mg Zn+2/L, 69.2 mg Ni+2/L, 174.6 mg Cd+2/L, and 175.8 mg Mn+2/L. In experiments performed with granules mechanically disintegrated (flocculent-like sludge), the IC50 for Cd+2 corresponded to a concentration of 93.1 mg Cd+2/L. These results indicate that the granular structure might act as a physical barrier to protect anammox bacteria from toxics. Furthermore, the presence of an external layer of ammonia oxidizing bacteria seems to mitigate the inhibitory effect of the metals, as the values of IC50 obtained in this study for anammox activity were higher than those previously reported for anammox granules. Additionally, the results obtained confirmed that copper is one of the most inhibitory metals for anammox activity and revealed that chromium, scarcely studied yet, has a similar potential inhibitory effect.
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del Rio, A. V., Pichel, A., Fernandez-Gonzalez, N., Pedrouso, A., Fra-Vazquez, A., Morales, N., et al. (2018). Performance and microbial features of the partial nitritation-anammox process treating fish canning wastewater with variable salt concentrations. J. Environ. Manage., 208, 112–121.
Abstract: The partial nitritation-anammox (PN-AMX) process applied to wastewaters with high NaCl concentration was studied until now using simulated media, without considering the effect of organic matter concentration and the shift in microbial populations. This research work presents results on the application of this process to the treatment of saline industrial wastewater. Obtained results indicated that the PN-AMX process has the capability to recover its initial activity after a sudden/acute salt inhibition event (up to 16 g NaCl/L). With a progressive salt concentration increase for 150 days, the PN-AMX process was able to remove the 80% of the nitrogen at 7-9 g NaCl/L. The microbiological data indicated that NaCl and ammonia concentrations and temperature are important factors shaping PN-AMX communities. Thus, the NOB abundance (Nitrospira) decreases with the increase of the salt concentration, while heterotrophic denitrifiers are able to outcompete anammox aftet a peak of organic matter in the feeding. (C) 2017 Elsevier Ltd. All rights reserved.
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del Rio, A. V., Stachurski, A., Mendez, R., Campos, J. L., Surmacz-Gorska, J., & Mosquera-Corral, A. (2017). Short- and long-term orange dye effects on ammonium oxidizing and anammox bacteria activities. Water Sci. Technol., 76(1), 79–86.
Abstract: The effects of orange azo dye over ammonia oxidizing bacteria (AOB) and anammox bacteria activities were tested. Performed batch tests indicated that concentrations lower than 650 mg(orange)/L stimulated AOB activity, while anammox bacteria activity was inhibited at concentrations higher than 25 mg(orange)/L. Long-term performance of a continuous stirred tank reactor (CSTR) for the partial nitritation and a sequencing batch reactor (SBR) for the anammox process was tested in the presence of 50 mg(orange)/L. In the case of the partial nitritation process, both the biomass concentration and the specific AOB activity increased after 50 days of orange azo dye addition. Regarding the anammox process, specific activity decreased down to 58% after 12 days of operation with continuous feeding of 50 mg(orange)/L. However, the anammox activity was completely recovered only 54 days after stopping the dye addition in the feeding. Once the biomass was saturated the azo dye adsorption onto the biomass was insignificant in the CSTR for the partial nitritation process fed with 50 mg(orange)/L. However, in the SBR the absorption was determined as 6.4 mg(orange)/g volatile suspended solids. No biological decolorization was observed in both processes.
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Jungles, M. K., Val del Rio, A., Mosquera-Corral, A., Campos, J. L., Mendez, R., & Costa, R. H. R. (2017). Effects of Inoculum Type and Aeration Flowrate on the Performance of Aerobic Granular SBRs. Processes, 5(3), 10 pp.
Abstract: Aerobic granular sequencing batch reactors (SBRs) are usually inoculated with activated sludge which implies sometimes long start-up periods and high solids concentrations in the effluent due to the initial wash-out of the inoculum. In this work, the use of aerobic mature granules as inoculum in order to improve the start-up period was tested, but no clear differences were observed compared to a reactor inoculated with activated sludge. The effect of the aeration rate on both physical properties of granules and reactor performance was also studied in a stable aerobic granular SBR. The increase of the aeration flow rate caused the decrease of the average diameter of the granules. This fact enhanced the COD and ammonia consumption rates due to the increase of the DO level and the aerobic fraction of the biomass. However, it provoked a loss of the nitrogen removal efficiency due to the worsening of the denitrification capacity as a consequence of a higher aerobic fraction.
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Morales, N., del Rio, A. V., Vazquez-Padin, J. R., Gutierrez, R., Fernandez-Gonzalez, R., Icaram, P., et al. (2015). Influence of dissolved oxygen concentration on the start-up of the anammox-based process: ELAN (R). Water Sci. Technol., 72(4), 520–527.
Abstract: The anammox-based process ELAN (R) was started-up in two different sequencing batch reactor (SBR) pilot plant reactors treating municipal anaerobic digester supernatant. The main difference in the operation of both reactors was the dissolved oxygen (DO) concentration in the bulk liquid. SBR-1 was started at a DO value of 0.4 mg O-2/L whereas SBR-2 was started at DO values of 3.0 mg O-2/L. Despite both reactors working at a nitrogen removal rate of around 0.6 g N/(L d), in SBR-1, granules represented only a small fraction of the total biomass and reached a diameter of 1.1 mm after 7 months of operation, while in SBR-2 the biomass was mainly composed of granules with an average diameter of 3.2 mm after the same operational period. Oxygen microelectrode profiling revealed that granules from SBR-2 where only fully penetrated by oxygen with DO concentrations of 8 mg O2/L while granules from SBR-1 were already oxygen penetrated at DO concentrations of 1 mg O2/L. In this way granules from SBR-2 performed better due to the thick layer of ammonia oxidizing bacteria, which accounted for up to 20% of all the microbial populations, which protected the anammox bacteria from non-suitable liquid media conditions.
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Morales, N., del Rio, A. V., Vazquez-Padin, J. R., Mendez, R., Campos, J. L., & Mosquera-Corral, A. (2016). The granular biomass properties and the acclimation period affect the partial nitritation/anammox process stability at a low temperature and ammonium concentration. Process Biochem., 51(12), 2134–2142.
Abstract: Extensive research on the anammox-based processes under mainstream conditions is currently in progress. Most studies have used a long acclimation period for the partial nitritation-anammox (PN-An) sludge at a low temperature and ammonium concentration. However, in this study, the results demonstrated that PN-An granular biomass produced under sidestream conditions (30 degrees C and 1000 mg NH4+-N/L) can operate at 15 degrees C and 50 mg NH4+-N/L without acclimation. The nitrogen removal efficiency was 70% and was stable for 60 days. The long-termoperation of the system with progressive adaptation provided important information for process optimization. Control of the dissolved oxygen (DO) concentration was crucial to maintain the balance between ammonia oxidizing bacteria (AOB) and anammox bacteria activities. A calculation of the oxygen penetration depth inside the granules is proposed to estimate an adequate DO level, which allows for the definition of the aerobic and anoxic zones that depend on the temperature, the size distribution and the granule density. However, the development of NOB was difficult to avoid with DO control alone. The selective washing-out of the floccular biomass, which contains mainly NOB, is proposed, leaving the granular fraction with the AOB and anammox bacteria in the system. (C) 2016 Published by Elsevier Ltd.
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Morales, N., del Rio, A. V., Vazquez-Padin, J. R., Mendez, R., Mosquera-Corral, A., & Campos, J. L. (2015). Integration of the Anammox process to the rejection water and main stream lines of WWTPs. Chemosphere, 140, 99–105.
Abstract: Nowadays the application of Anammox based processes in the wastewater treatment plants has given a step forward. The new goal consists of removing the nitrogen present in the main stream of the WWTTPs to improve their energetic efficiencies. This new approach aims to remove not only the nitrogen but also to provide a better use of the energy contained in the organic matter. The organic matter will be removed either by an anaerobic psychrophilic membrane reactor or an aerobic stage operated at low solids retention time followed by an anaerobic digestion of the generated sludge. Then ammonia coming from these units will be removed in an Anammox based process in a single unit system. The second strategy provides the best results in terms of operational costs and would allow reductions of about 28%. Recent research works performed on Anammox based processes and operated at relatively low temperatures and/or low ammonia concentrations were carried out in single-stage systems using biofilms, granules or a mixture of flocculent nitrifying and granular Anammox biomasses. These systems allowed the appropriated retention of Anammox and ammonia oxidizing bacteria but also the proliferation of nitrite oxidizing bacteria which seems to be the main drawback to achieve the required effluent quality for disposal. Therefore, prior to the implementation of the Anammox based processes at full scale to the water line, a reliable strategy to avoid nitrite oxidation should be defined in order to maintain the process stability and to obtain the desired effluent quality. If not, the application of a post-denitrification step should be necessary. (C) 2015 Elsevier Ltd. All rights reserved.
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Pedrouso, A., del Rio, A. V., Campos, J. L., Mendez, R., & Mosquera-Corral, A. (2017). Biomass aggregation influences NaN3 short-term effects on anammox bacteria activity. Water Sci. Technol., 75(5), 1007–1013.
Abstract: The main bottleneck to maintain the long-term stability of the partial nitritation-anammox processes, especially those operated at low temperatures and nitrogen concentrations, is the undesirable development of nitrite oxidizing bacteria (NOB). When this occurs, the punctual addition of compounds with the capacity to specifically inhibit NOB without affecting the process efficiency might be of interest. Sodium azide (NaN3) is an already known NOB inhibitor which at low concentrations does not significantly affect the ammonia oxidizing bacteria (AOB) activity. However, studies about its influence on anammox bacteria are unavailable. For this reason, the objective of the present study was to evaluate the effect of NaN3 on the anammox activity. Three different types of anammox biomass were used: granular biomass comprising AOB and anammox bacteria (G1), anammox enriched granules (G2) and previous anammox granules disaggregated (F1). No inhibitory effect of NaN3 was measured on G1 sludge. However, the anammox activity decreased in the case of G2 and F1. Granular biomass activity was less affected (IC50 90 mg/L, G2) than flocculent one (IC50 5 mg/L, F1). Summing up, not only does the granular structure protect the anammox bacteria from the NaN3 inhibitory effect, but also the AOB act as a barrier decreasing the inhibition.
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Pedrouso, A., del Rio, A. V., Morales, N., Vazquez-Padin, J. R., Campos, J. L., Mendez, R., et al. (2017). Nitrite oxidizing bacteria suppression based on in-situ free nitrous acid production at mainstream conditions. Sep. Purif. Technol., 186, 55–62.
Abstract: The application of autotrophic nitrogen removal processes in the main line of wastewater treatment plants will contribute to achieve its self-energy-sufficiency. However, the effective suppression of nitrite oxidizing bacteria (NOB) activity at the conditions of low temperature and low ammonium concentration (mainstream conditions) was identified as one of the main bottlenecks. In this study, stable partial nitritation at 16 degrees C and 50 mg NH4+-N/L was achieved maintaining inside the reactor free nitrous acid (FNA) concentrations inhibitory for NOB (>0.02 mg HNO2-N/L), without dissolved oxygen concentration control, The FNA inhibitory concentration was generated by the partial nitritation process, and its stimulation was studied with two different inhibitors: sodium azide and nitrite. The microbiological analysis revealed that, throughout the operational period with inhibitory FNA levels, the NOB populations (dominated by Nitrospira) were effectively washed out from the reactor. This is an advantage that allowed maintaining a good stability of the process, even when the FNA concentration was not enough to inhibit the NOB, taking about 40 days to develop significant activity. The observed delay on the NOB development is expected to enable the establishment of corrective actions to avoid the partial nitritation destabilization. The use of the FNA to achieve a stable partial nitritation process is recommended to profit from the natural pH decrease associated to the nitritation process and from its favoured accumulation at low temperatures as those from the mainstream. In this research study an analysis about the influence of ammonium and alkalinity concentrations was also performed to know in which scenarios the FNA inhibitory concentration can be achieved. (C) 2017 Elsevier B.V. All rights reserved.
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Pichel, A., Fra, A., Morales, N., Campos, J. L., Mendez, R., Mosquera-Corral, A., et al. (2021). Is the ammonia stripping pre-treatment suitable for the nitrogen removal via partial nitritation-anammox of OFMSW digestate? J. Hazard. Mater., 403, 123458.
Abstract: Treating the organic fraction of municipal solid waste (OFMSW) can be performed by coupling the anaerobic digestion (AD) and partial nitritation-anammox (PN-AMX) processes for organic matter and nitrogen removal, respectively. Besides, an ammonia stripping (AS) step before the AD benefit the removal of organic matter. In the present study, the operation of two PN-AMX sequencing batch reactors with and without AS pre-treated OFMSW digestate (AS-SBR and nAS-SBR, respectively) was assessed. The specific anammox activity decreased by 90 % for increasing proportions of fed OFMSW in both cases, indicating no differences over the anammox activity whether the AS pre-treatment is implemented or not. For 100 % OFMSW proportion, the AS-SBR achieved better effluent quality than the nAS-SBR (127 +/- 88 vs. 1050 +/- 23 mg N/L) but with lower nitrogen removal rates (58 +/- 8 vs. 687 +/- 32 g N/(L.d)). Still, the latter required successive re-inoculations to obtain higher removal rates. Changes in the microbial communities were mainly correlated to sCOD/N ratios in the OFMSW, being Candidatus Brocadia the dominant anamnmox species. The results proved the AS to be a suitable pre-treatment, despite the higher sCOD/N ratios in the OFMSW digestate, achieving good synergy between the PN-AMX and heterotrophic denitrification processes.
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Pichel, A., Moreno, R., Figueroa, M., Campos, J. L., Mendez, R., Mosquera-Corral, A., et al. (2019). How to cope with NOB activity and pig manure inhibition in a partial nitritation-anammox process? Sep. Purif. Technol., 212, 396–404.
Abstract: The treatment of pig manure can be performed by anaerobic digestion to diminish the organic matter content and produce biogas, and the resulting digestate has to be subsequently treated for the removal of nitrogenous compounds. The partial nitritation-anammox (PN-AMX) process constitutes an interesting alternative. In the present study, three different short experiments were initially performed to study the influence of nitrite oxidizing bacteria (NOB) present in the inoculum and the pig manure composition over the start-up of the PN-AMX process. The presence of NOB in the inoculum showed to be more crucial than the available anammox activity for a good performance of the PN-AMX process. Batch activity experiments showed a reduction of at least 44.4% in the maximum specific anammox activity due to the pig manure, probably owed to its conductivity (between 6 and 8 mS/cm). In the subsequent long-term operation of the PN-AMX process with non-diluted pre-treated pig manure, the NOB were successfully limited for DO concentrations of 0.1 mg O-2/L, and a nitrogen removal rate (NRR) of 0.1 g N/(L.d) was achieved despite the presence of significant NOB activity in the start-up. A strict control of the DO concentration, with an optimal range of 0.07-0.10 mg O-2/L, was fundamental to balance the removal of nitrogen by PN-AMX and prevent NOB activity. The presence of organic matter, with a ratio sCOD/N in the influent between 0.18 and 1.14 g/g, did not hinder the PN-AMX process, and the contribution of heterotrophic denitrification to the removal of nitrogen was less than 10%.
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