Crutchik, D., Barboza, J., Vazquez-Padin, J. R., Pedrouso, A., del Rio, A. V., Mosquera-Corral, A., et al. (2023). Integrating food waste management into urban wastewater treatment: Economic and environmental impacts. J. Environ. Manage., 345, 118517.
Abstract: Food waste is the main component of municipal solid waste (MSW) and its sustainable management is a global challenge. Co-treatment of food waste and urban wastewater in wastewater treatment plants (WWTPs) could be a plausible management strategy to reduce the MSW amount that is disposed in landfills, while converting its organic fraction into biogas in the WWTP. However, the increased organic load in the wastewater influent would impact the capital and operating costs of the WWTP, mainly due to the increase in sludge production. In this work, different scenarios for co-treatment of food waste and wastewater were studied from both economic and environmental perspectives. These scenarios were designed based on different sludge disposal and management options. The results showed that the co-treatment of food waste and wastewater would be more environmentally friendly than their separate treatment, but its economic feasibility strongly depends on the ratio between the management costs of MSW and sewage sludge.
|
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.
|
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.
|
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.
|
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.
|
Pedrouso, A., Aiartza, I., Morales, N., Vazquez-Padin, J. R., Rogalla, F., Campos, J. L., et al. (2018). Pilot-scale ELAN (R) process applied to treat primary settled urban wastewater at low temperature via partial nitritation-anammox processes. Sep. Purif. Technol., 200, 94–101.
Abstract: A single stage partial nitritation and anammox granular pilot scale reactor (600 L) was operated to treat primary settled sewage in an urban wastewater treatment plant. The fed wastewater contained low total nitrogen concentrations of 6-25 mg TN/L and the system operated without temperature control ranging from 18 to 12 degrees C. A control strategy, based on the pH value, was applied to stop the aeration supply. The pH set-point was fixed at 6.0 and allowed obtaining a total nitrogen removal efficiency approximately of 50% treating a load of 67 mg TN/(L.d) without the addition of any chemicals. Although nitrite oxidizing bacteria were present in the inoculated sludge, when the pH-based control was implemented (day 30) the ammonium oxidation was favored compared to the nitrite oxidation activity. Then, the system operated stable the rest of the operational period (days 30-94) despite the presence of organic matter in the wastewater and the high variability of nitrogen load and temperature during the operation. Nitrogen was autotrophically removed accomplishing the stringent discharge limits (10 mg TN/L) and nitrate concentrations in the effluent lower than 3 mg NO3--N/L. Both biomass concentration and granules size increased during the operational period indicating the growth of the biomass inside the reactor and therefore the potential treatment capacity.
|
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.
|
Pedrouso, A., del Rio, A. V., Morales, N., Vazquez-Padin, J. R., Campos, J. L., & Mosquera-Corral, A. (2021). Mainstream anammox reactor performance treating municipal wastewater and batch study of temperature, pH and organic matter concentration cross-effects. Process Saf. Environ. Protect., 145, 195–202.
Abstract: The anammox process is an energy efficient promising alternative to biologically remove the nitrogen. Thus, a 5-L anammox granular reactor was inoculated with sludge coming from a sidestream partial nitritation and anammox reactor (>200 mg TN/L and 30 degrees C) and it was directly subjected to 15 +/- 1 degrees C treating mimicked municipal wastewater (50 mg TN/L). Results indicated that an acclimation period (commonly used) to progressive reach the mainstream conditions is not needed, shortening the start-up periods. The long-term anammox process stability was proved to treat synthetic wastewater with decreasing alkalinities and nitritified primary settled municipal wastewater. The low pH values (6.2 +/- 0.1) of the municipal wastewater fed did not affect the process stability. Residual organic matter concentrations augmented the nitrogen removal efficiency from 80 % (with the synthetic medium) to 92 % achieving effluent concentrations below 10 mg TN/L. Finally, the effect of pH (6-8), temperature (15-30 degrees C) and organic matter concentration (0-75 mg TOC/L) over the specific anammox activity (SA(Amx)) was evaluated at short-term. pH and temperature and their interactions exerted significant influence on the SAAmx value while the TOC concentrations itself did not significantly change the SA(AMX). (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
|
Pedrouso, A., Vazquez-Padin, J. R., Crutchik, D., & Campos, J. L. (2021). Application of Anammox-Based Processes in Urban WWTPs: Are We on the Right Track? Processes, 9(8), 1334.
Abstract: The application of partial nitritation and anammox processes (PN/A) to remove nitrogen can improve the energy efficiency of wastewater treatment plants (WWTPs) as well as diminish their operational costs. However, there are still several limitations that are preventing the widespread application of PN/A processes in urban WWTPs such as: (a) the loss of performance stability of the PN/A units operated at the sludge line, when the sludge is thermally pretreated to increase biogas production; (b) the proliferation of nitrite-oxidizing bacteria (NOB) in the mainstream; and (c) the maintenance of a suitable effluent quality in the mainstream. In this work, different operational strategies to overcome these limitations were modelled and analyzed. In WWTPs whose sludge is thermically hydrolyzed, the implementation of an anerobic treatment before the PN/A unit is the best alternative, from an economic point of view, to maintain the stable performance of this unit. In order to apply the PN/A process in the mainstream, the growth of ammonia-oxidizing bacteria (AOB) should be promoted in the sludge line by supplying extra sludge to the anaerobic digesters. The AOB generated would be applied to the water line to partially oxidize ammonia, and the anammox process would then be carried out. Excess nitrate generated by anammox bacteria and/or NOB can be removed by recycling a fraction of the WWTP effluent to the biological reactor to promote its denitrification.
|
Valenzuela-Heredia, D., Panatt, C.:, Belmonte, M., Franchi, O., Crutchik, D., Dumais, J., Vazquez-Padin, J. R., et al. (2022). Performance of a two-stage partial nitritation-anammox system treating the supernatant of a sludge anaerobic digester pretreated by a thermal hydrolysis process. Chem. Eng. J., 429, 131301.
Abstract: A two-stage system (partial nitritation (PN) and anammox processes) was used to remove nitrogen from the dewatering liquor originating from the thermal hydrolysis/anaerobic digestion (THP/AD) of municipal WWTP sludge. Two strategies were tested to start up the PN reactor: 1) maintaining a fixed hydraulic retention time (HRT) and increasing the ammonium loading rate (ALR) by decreasing the feeding dilution ratio and 2) feeding undiluted dewatering liquor and gradually decreasing the HRT. With diluted feeding, the reactor performance had destabilization episodes that were statistically correlated with the application of high specific ammonium (> 0.6 g NH4+-N/(g TSS.d)) and organic (> 0.7 g COD/(g TSS.d)) loading rates. The second strategy allowed stable PN reactor operation while treating ALR up to 4.8 g NH4+-N/(L.d) and demonstrating that dilution of THP/AD effluents is not required. The operating conditions promoted the presence of free nitrous acid levels (> 0.14 mg HNO2-N/L) inside the PN reactor that inhibited the proliferation of nitrite oxidizing bacteria.
Batch activity tests showed that the inhibitory effects of organic compounds present in the THP/AD dewatering liquor on the ammonia oxidizing bacteria activity can be removed in the PN reactor. Thus, aerobic pretreatment would not be necessary when two-stage systems are used. The PN reactor effluent was successfully treated by an anammox reactor.
An economic analysis showed that using two-stage systems is advantageous for treating THP/AD dewatering liquor. The implementation of an aerobic pre-treatment unit is recommended for WWTPs capacities higher than 5.10(5) inhabitants equivalent when one-stage systems are used.
|
