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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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Crutchik, D., Morales, N., Vazquez-Padin, J. R., & Garrido, J. M. (2017). Enhancement of struvite pellets crystallization in a fullscale plant using an industrial grade magnesium product. Water Sci. Technol., 75(3), 609–618.
Abstract: A full-scale struvite crystallization system was operated for the treatment of the centrate obtained from the sludge anaerobic digester in a municipal wastewater treatment plant. Additionally, the feasibility of an industrial grade Mg(OH) (2) as a cheap magnesium and alkali source was also investigated. The struvite crystallization plant was operated for two different periods: period I, in which an influent with low phosphate concentration (34.0 mg P . L (-1)) was fed to the crystallization plant; and period II, in which an influent with higher phosphate concentration (68.0 mg P . L (-1)) was used. A high efficiency of phosphorus recovery by struvite crystallization was obtained, even when the effluent treated had a high level of alkalinity. Phosphorus recovery percentage was around 77%, with a phosphate concentration in the effluent between 10.0 and 30.0 mg P .L- 1. The experiments gained struvite pellets of 0.5- 5.0 mm size. Moreover, the consumption of Mg(OH) (2) was estimated at 1.5 mol Mg added . mol P recovered (-1). Thus, industrial grade Mg(OH) (2) can be an economical alternative as magnesium and alkali sources for struvite crystallization at industrial scale.
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Elangovan, K., Saravanan, P., Campos, C. H., Sanhueza-Gómez, F., Khan, M. M. R., Chin, S. Y., et al. (2023). Outline of microbial fuel cells technology and their significant developments, challenges, and prospects of oxygen reduction electrocatalysts. Front. Chem. Eng., 5, 1228510.
Abstract: The microbial fuel cells (MFCs) which demonstrates simultaneous production of electricity and wastewater treatment have been considered as one of the potential and greener energy production technology among the available bioelectrochemical systems. The air-cathode MFCs have gained additional benefits due to using air and avoiding any chemical substances as catholyte in the cathode chamber. The sluggish oxygen reduction reaction (ORR) kinetics at the cathode is one of the main obstacles to achieve high microbial fuel cell (MFC) performances. Platinum (Pt) is one of the most widely used efficient ORR electrocatalysts due to its high efficient and more stable in acidic media. Because of the high cost and easily poisoned nature of Pt, several attempts, such as a combination of Pt with other materials, and using non-precious metals and non-metals based electrocatalysts has been demonstrated. However, the efficient practical application of the MFC technology is not yet achieved mainly due to the slow ORR. Therefore, the review which draws attention to develop and choosing the suitable cathode materials should be urgent for the practical applications of the MFCs. In this review article, we present an overview of the present MFC technology, then some significant advancements of ORR electrocatalysts such as precious metals-based catalysts (very briefly), non-precious metals-based, non-metals and carbon-based, and biocatalysts with some significant remarks on the corresponding results for the MFC applications. Lastly, we also discussed the challenges and prospects of ORR electrocatalysts for the practical application of MFCs.
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Fra-Vazquez, A., Morales, N., Figueroa, M., del Rio, A. V., Regueiro, L., Campos, J. L., et al. (2016). Bacterial community dynamics in long-term operation of a pilot plant using aerobic granular sludge to treat pig slurry. Biotechnol. Prog., 32(5), 1212–1221.
Abstract: Aerobic granular sludge represents an interesting approach for simultaneous organic matter and nitrogen removal in wastewater treatment plants. However, the information about microbial communities in aerobic granular systems dealing with industrial wastewater like pig slurry is limited. Herein, bacterial diversity and dynamics were assessed in a pilot scale plant using aerobic granular sludge for organic matter and nitrogen elimination from swine slurry during more than 300 days. Results indicated that bacterial composition evolved throughout the operational period from flocculent activated sludge, used as inoculum, to mature aerobic granules. Bacterial diversity increased at the beginning of the granulation process and then declined due to the application of transient organic matter and nitrogen loads. The operational conditions of the pilot plant and the degree of granulation determined the microbial community of the aerobic granules. Brachymonas, Zoogloea and Thauera were attributed with structural function as they are able to produce extracellular polymeric substances to maintain the granular structure. Nitrogen removal was justified by partial nitrification (Nitrosomonas) and denitrification (Thauera and Zoogloea), while Comamonas was identified as the main organic matter oxidizing bacteria. Overall, clear links between bacterial dynamics and composition with process performance were found and will help to predict their biological functions in wastewater ecosystems improving the future control of the process. (c) 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1212-1221, 2016
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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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Lopez, D., Leiva, A. M., Arismendi, W., & Vidal, G. (2019). Influence of design and operational parameters on the pathogens reduction in constructed wetland under the climate change scenario. Rev. Environ. Sci. Bio-Technol., 18(1), 101–125.
Abstract: Under the climate change scenario, constructed wetlands (CWs) as an engineered system for treating domestic wastewater will face different challenges. Some of them are: (a) the increase of pathogens concentration in wastewater due to the rise of global temperature; (b) higher precipitation that can cause an increase of pathogens due to runoff; (c) the reuse of treated wastewater related to the water scarcity. These problems can affect the capacity of CWs for removal pathogens. In this context, the objective of this review is to provide an overview of the influence of design and operational parameters on pathogens reduction in CWs. To accomplish with this purpose, the published information (>30 studies) about the reduction of pathogens and the operational and design parameters in different CWs configurations and were gathered. With this data, statistical analyses were performed considering the most relevant variables which significantly influence the removal of pathogens in CWs. For this, principal component analyses (PCA) were achieved for determining, separately, the correlation of operational parameters with fecal coliform (FC) and total coliform (TC) removal. The results of PCA showed that FC and TC were correlated positively with mass removal rates of chemical oxygen demand (COD) and biological oxygen Demand (BOD5), total suspended solids (TSS) removal and the size of support medium. This study is the first approach that analyzes together the design and operational parameters which influence the pathogen removal in CWs. For this reason, these parameters and the increase on microorganism concentrations due to the climate change have to be considered for the future design of CWs.
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Mejia, H. F. G., Toledo-Alarcon, J., Rodriguez, B., Cifuentes, J. R., Porre, F. O., Haeger, M. P. L., et al. (2022). Direct recycling of discarded reverse osmosis membranes for domestic wastewater treatment with a focus on water reuse. Chem. Eng. Res. Des., 184, 473–487.
Abstract: The recycling of discarded membranes (end-of-life) represents a relevant alternative for sustainability of reverse osmosis (RO) desalination plants in the context of circular economy. This work evaluated the feasibility of using discarded commercial RO membranes in the treatment of domestic secondary wastewater to obtain water with a certain standard quality. Crossflow filtration tests were conducted to evaluate desalination and wastewater filtration performance at different operating pressures on RO membranes discarded from desalination plans at different working positions (primary M1; secondary M2). The standard manufacturer desalination tests showed a superior performance on M1 membranes, in terms of rejection (similar to 25 LMH, 97%), compared to M2 (similar to 33 LMH, 50%); both having a lower performance than a standard membrane (38 LMH +/- 15%; 99.6%). The failure is sufficient for discarding due to loss of lifespan. Moreover, in wastewater filtration tests using the secondary clarifier outlet effluent from a WWTP at different working pressures, both types of membranes were shown to be effective, with degrees of performance highly dependent on the working pressure. Thus, the operating values of permeate flux/salt rejection were between 56 and 59 LMH/ 96-97% for 600 psi: 33-34 LMH/ 94-96% for 300-psi and in the range of 10-11 LMH/ 90-94% for 80-psi test. Surface characterization of the membrane showed a pressure-related increase in fouling and bacterial adhesion post-filtration. Finally, the operating performance was verified in M1 wastewater filtration at 300 psi over long times (14 h), yielding stable and promising values (similar to 27 LMH; 96%). The permeate obtained has a low concentration of fecal coliforms (< 2 MPN/ 100 mL, 99.99% removal) and meets local standards for irrigation and drinking water in terms of conductivity, phosphorus and nitrogen concentration in treated water. (c) 2022 Institution of Chemical Engineers.
Keywords: Desalination; RO membranes; Discarded; Secondary wastewater; Water scarcity
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Palmeiro-Sanchez, T., Campos, J. L., & Mosquera-Corral, A. (2021). Bioconversion of Organic Pollutants in Fish-Canning Wastewater into Volatile Fatty Acids and Polyhydroxyalkanoate. Int. J. Environ. Res. Public Health, 18(19), 10176.
Abstract: The wastewater from the cookers of a tuna-canning plant was used as feedstock for the process. It was acidified in a continuous stirred tank reactor (CSTR) of 1.5 L to produce a mixture of volatile fatty acids (VFAs). The effluent contained 28.3 & PLUSMN; 8.7 g CODS/L and 25.0 & PLUSMN; 4.6 g CODVFA/L, 4.4 & PLUSMN; 1.6 g NH4+/L, and 10.9 & PLUSMN; 4.0 g Na+/L, which corresponds to about 28 g NaCl/L approximately. This was used to feed a PHA production system. The enriched MMC presented a capacity to accumulate PHAs from the fermented tuna wastewater. The maximum PHA content of the biomass in the fed-batch (8.35 wt% PHA) seemed very low, possibly due to the variable salinity (from 2.2 up to 12.3 g NaCl/L) and the presence of ammonium (which promoted the biomass growth). The batch assay showed a PHA accumulation of 5.70 wt% PHA, but this is a much better result if the productivity of the reactor is taken into account. The fed-batch reactor had a productivity of 10.3 mg PHA/(L h), while the batch value was about five times higher (55.4 mg PHA/(L h)). At the sight of the results, it can be seen that the acidification of fish-canning wastewater is possible even at high saline concentrations (27.7 g NaCl/L). On the other hand, the enrichment and accumulation results show us promising news and which direction has to be followed: PHAs can be obtained from challenging substrates, and the feeding mode during the accumulation stage has an important role to play when it comes to inhibition.
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Pedrouso, A., Morales, N., Rodelas, B., Correa-Galeote, D., del Rio, A. V., Campos, J. L., et al. (2023). Rapid start-up and stable maintenance of the mainstream nitritation process based on the accumulation of free nitrous acid in a pilot-scale two-stage nitritation-anammox system. Sep. Purif. Technol., 317, 123851.
Abstract: Two-stage partial nitritation (PN) and anammox (AMX) systems showed promising results for applying auto-trophic nitrogen removal under mainstream conditions. In this study, a pilot-scale (600 L per reactor) two-stage PN/AMX system was installed in a municipal wastewater treatment plant (WWTP) provided with a high-rate activated sludge (HRAS) system for organic carbon removal. The PN/AMX system was operated without tem-perature control (ranging from 11 to 28 degrees C) and was subjected to the same variations in wastewater charac-teristics as the WWTP (22 to 63 mg NH4+- N/L). The developed strategy is simple, does not require the addition of chemicals and is characterised by short start-up periods. The PN process was established by applying a high hydraulic load and maintained by in situ accumulated free nitrous acid (FNA) of 0.015-0.2 mg HNO2-N/L. Based on pH value, a controlled aeration strategy was applied to achieve the target nitrite to ammonium ratio in the effluent (1.1 g NO2--N/g NH4+-N) to feed the AMX reactor. Although NOB were not fully washed out from the system, nitrite accumulation remained (>99 %) stable with no evidence of NOB activity. In the AMX reactor, an overall nitrogen removal efficiency of 80 % was achieved. Regarding effluent quality, 12 +/- 3 mg TN/L was obtained, but 5 mg NO3--N/L was already in the HRAS effluent. The relative abundance of NOB showed a strong negative correlation with the FNA concentration, providing a good strategy for establishing PN under main-stream conditions.
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Pedrouso, A., Tocco, G., val del Rio, A., Carucci, A., Morales, N., Campos, J. L., et al. (2020). Digested blackwater treatment in a partial nitritation-anammox reactor under repeated starvation and reactivation periods. J. Clean Prod., 244, 9 pp.
Abstract: Wastewater source-separation and on-site treatment systems face severe problems in wastewater availability. Therefore, the effect of repeated short-term starvation and reactivation periods on a partial nitritation-anammox (PN/AMX) based processes were assessed treating digested blackwater at room temperature. Two sequencing batch reactors (SBR) were operated, one of them during 24 h/day the whole week (SBR-C, which served as control) and the other with repeated starvation/reactivation periods during the nights and the weekends (SBR-D), using simulated blackwater (300 mg N/L and 200 mg COD/L) as substrate. Results showed no remarkable differences in overall processes performance between both reactors, achieving total nitrogen removal efficiencies (NRE) around 90%. Furthermore, no significant variations were measured in specific activities, except for the aerobic heterotrophic one that was lower in SBR-D, presumably due to the exposure to anoxic conditions. Then, the technical feasibility of applying the PN/AMX system to treat real blackwater produced in an office building during working hours was successfully proved in a third reactor (SBR-R), with the same starvation/reactivation periods tested in SBR-D. Despite the low temperature, ranging from 14 to 21 degrees C, total NRE up to 95% and total nitrogen concentration in the effluent lower than 10 mg N/L were achieved. Moreover, the PN/AMX process performance was immediately recovered after a long starvation period of 15 days (simulating holidays). Results proved for the first time the feasibility and long-term stability (100 days) of applying the PN/AMX processes for the treatment (and potential reuse) of blackwater in a decentralized system where wastewater is not always available. (C) 2019 Elsevier Ltd. All rights reserved.
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Pina, S., Sandoval, A. M., Jara-Ulloa, P., Contreras, D., Hassan, N., Coreno, O., et al. (2022). Nanostructured electrochemical sensor applied to the electrocoagulation of arsenite in WWTP effluent. Chemosphere, 306, 135530.
Abstract: A sensitive electroanalytical method for the determination of arsenite, based on a heterostructure of aminated multiwalled carbon nanotubes and gold nanoparticles, was applied in an electrocoagulation (EC) treatment for the elimination of arsenite. A sensitive quantitative response was obtained in the determination of As3+ in a secondary effluent from a wastewater treatment plant from Santiago (Chile). The preconcentration stage was optimized through a Central Composite Face design, and the most sensitive peak current was obtained at 200 s and -600 mV of time and accumulation potential, respectively, after a differential pulse voltammetry sweep. Electroanalytical determination was possible in an interval between 42.89 and 170.00 mu g L-1 with a detection limit of 0.39 mu g L-1, obtaining recoveries over 99.1%. The developed method was successfully applied in an electrocoagulation treatment to remove 250 mu g L-1 of arsenite from a polluted effluent in a batch system. Complete arsenite removal was achieved using a steel EC system with a current density of 6.0 mA cm(-2) in less than 3 min of treatment.
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Sepulveda-Mardones, M., Campos, J. L., Magri, A., & Vidal, G. (2019). Moving forward in the use of aerobic granular sludge for municipal wastewater treatment: an overview. Rev. Environ. Sci. Bio-Technol., 18(4), 741–769.
Abstract: Activated sludge is one of the most widely implemented technologies for municipal wastewater treatment. Yet, more restrictive environmental standards demand for more efficient technologies. Aerobic granular sludge (AGS) is a promising alternative in this context since this technology has shown potential for simultaneous organic matter and nutrient removal using smaller bioreactors and consuming less energy. However, despite such engaging claims, only ca. 40 full-scale AGS systems have been installed worldwide after 30 years of development. This reduced implementation suggests the existence of significant bottlenecks for this technology, which currently only have partially been overcome. This overview aims to analyze the recent progress in R&D concerning aerobic sludge granulation for municipal wastewater treatment via the analysis of research articles and invention patents as well as to elucidate exiting technological gaps and development opportunities. Culturing methods aiming at fast granulation, long-term stability and excellent process performance are of utmost interest for promoting massive implementation of full-scale AGS systems. Moreover, the recovery of biomaterials from waste sludge could contribute to the implementation of the biorefinery paradigm in wastewater treatment plants.
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Vergara, C., Munoz, R., Campos, J. L., Seeger, M., & Jeison, D. (2016). Influence of light intensity on bacterial nitrifying activity in algal-bacterial photobioreactors and its implications for microalgae-based wastewater treatment. Int. Biodeterior. Biodegrad., 114, 116–121.
Abstract: The influence of irradiance on the nitrifying activity in photobioreactors of a bacterial consortium enriched from a wastewater treatment bioreactor was assessed using independent ammonium oxidation kinetic batch tests and respirometric assays. Culture irradiance below 250 μmol m(-2) s(-1) did not show a significant effect on nitrification activity, while irradiance at 500 and 1250 μmol m(-2) s(-1) caused a decrease of 20 and 60% in the specific total ammonium nitrogen removal rates and a reduction of 26 and 71% in the specific NO3- production rates, respectively. However, no significant influence of irradiance on the affinity constant of NH4+ oxidation was observed. The increasing nitrite accumulation at higher light intensities suggested a higher light sensitivity of nitrite oxidizers. Additionally, NH4+ oxidation respirometric assays showed a decrease in the oxygen uptake of 14 and 50% at 500 and 1250 μmol m(-2) s(-1), respectively. The experimental determination of the light extinction coefficient (lambda) of the nitrifying bacterial consortium (lambda = 0.0003 m(2) g(-1)) and of Chlorella sorokiniana (lambda = 0.1045 m(2) g(-1)) allowed the estimation of light penetration in algal-bacterial high rate algal ponds, which showed that photo inhibition of nitrifying bacteria can be significantly mitigated in the presence of high density microalgal cultures. 2016 Elsevier Ltd. All rights reserved.
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