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Universidade Federal de Santa Maria
Ci. e Nat., Santa Maria, v. 44, Ed. Esp. VI SSS, e20, 2022
DOI: 10.5902/2179460X68843
ISSN 2179-460X
Submitted: 9/12/2021 • Approved: 9/12/2021 • Published: xx/xx/ 2022
Special Edition
Aruani Letícia da Silva Tomoto I
Ana Paula Trevisan Lied I
Luiz Felipe Gomes Ferreira I
Julia Elizabeth Martins I
Dagoberto Yukio Okada II
Nicolas Roche III,IV
Simone Damasceno Gomes I
I Universidade Estadual do Oeste do Paraná, Cascavel, PR, Brazil
II Universidade Estadual de Campinas, Limeira, SP, Brazil
III Aix Marseille Univ, CNRS, INRAE, IRD, Coll France, France
IV Mohammed VI Polytechnic University, Benguerir, Morocco
ABSTRACT
Keywords: Nitrogen removal; Demonification kinetics; MABR-BS reactor
RESUMO
A remoção biológica de nitrogênio via Anammox se trata de uma tecnologia vantajosa no tratamento de efluentes nitrogenados com baixa relação Carbono/Nitrogênio, processo que torna essa via interessante para os mais diferentes tipos de indústrias, agroindústrias e estações de tratamentos de efluentes urbanos. Conseguir biomassa Anammox robusta para utilizar em plantas de escala real ainda é um desafio que motiva estudos de enriquecimento de biomassa e a busca por parâmetros cinéticos de velocidade de consumo de substrato que auxiliem na otimização da condução dos reatores. Diante do apresentado esse trabalho teve por objetivo realizar o estudo cinético do consumo de nitrogênio por processo Anammox em reatores de biofilme aerado em membrana operados em bateladas sequenciais (MABR-BS). 6 reatores MABR-BS foram utilizados, sendo cada um deles inoculado com um tipo de lodo Anammox, obtido do enriquecimento de lodos anaeróbios e aeróbios advindos de 3 diferentes fontes de lodo sendo elas, uma estação de tratamento de esgoto sanitário, uma estação de tratamento de lixiviado de aterro sanitário e uma estação de tratamento de efluente de abate de suínos. Para o estudo cinético foram utilizado 6 reatores confeccionados em frascos de vidro de volume total de 1L, com volume útil de 500 mL, sendo a relação 3:2 (v:v) entre efluente sintético (com 100mgN-NH4+.L-1) e lodo das fontes: R1 - lodo anaeróbio de reator UASB de tratamento de esgoto urbano; R2 - lodo misto de reator UASB, constituído por lodo de descarte e escuma sobrenadante; R3- lodo anaeróbio de tratamento de lixiviado de aterro sanitário; R4 - lodo misto constituído por lodo de lagoa aeróbia e anaeróbia da estação de tratamento de lixiviado de aterro sanitário; R5 - lodo anaeróbio da estação de tratamento de efluente de abate suíno e R6 - lodo aeróbio e anaeróbio da estação de tratamento de efluente de abate suíno. O aparato experimental contou com 3 aeradores acoplados a 3 fluxômetros com vazão de ar regulada em 1,0 L.min-1; 30 cm de membrana de silicone em formato curvilíneo com uma das entradas conectadas ao aerador e fluxômetro, a outra saída foi imersa em coluna de água de 75 cm, exercendo pressão negativa sobre o ar no interior da membrana tubular de silicone, obrigando o ar a sair pela microporosidade da membrana. A aeração foi intermitente, com intervalo de 9,6 minutos entre cada minuto de aeração, os reatores foram agitados em equipamento banho maria ajustado em 30 rpm e temperatura de 32°C. O ensaio cinético durou 24h e contou com uma amostragem a cada 2,5h. As eficiências de remoção de nitrogênio (em %) determinada no ensaio cinético foram de 61,36 (R1); 61,01(R2); 59,03 (R3); 56,70 (R4); 62,77 (R5) e 64,40 (R6). Com relação ao pH todos os reatores apresentaram pH inicial acima de 8,0 e pH final próximo à neutralidade. As velocidades específicas de remoção de nitrogênio (em mgN.gSSV-1h-1), foram em média de 29,43 (R1); 33,50 (R2); 33,62 (R3); 33,42 (R4); 28,90 (R5) e 30,34 (R6). O melhor desempenho no ensaio cinético foi obtido no reator R1, obtendo atividade específica de remoção de nitrogênio máxima de 57,61 mgN.gSSV-1h-1 e geração molar de nitrato residual com coeficiente estequiométrico de 0,018 mol.
Palavras-chave: Remoção de nitrogênio; Cinética da desamonificação; Reator MABR-BS
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NH4 + + 1,32 NO2- + 0,066HCO3- + 0,13H+ → 1,02N2 + 0,26 NO3- + 0,066CH2O0,5N0,15 + 2,03H2O |
(1) |
Nitrogen removal through the Anammox process can be carried out in two ways: i) in a single-phase reactor where partial nitritation and the Anammox process (NP/A) occur in the same reactor and ii) in separate reactors, where partial nitritation takes place in an aerobic reactor and the Anammox process in another anaerobic reactor. Equation 2 represents the NP/A process in a single-phase reactor (SLIEKERS et al., 2002).
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NH4 + + 0,85O2 → 0,44N2 + 0,11 NO3- + 1,43 H2O + 1,14H+ |
(2) |
Other benefits are attributed to the use of the Anammox metabolic route, including Morales et al. (2015) highlight the low energy consumption required by aerators, a reduction of approximately 50%, the low sludge generation due to the cell replication slow rate, and the important reduction in the emission of nitrous oxide greenhouse gas, of the order of 76 %.
However, in the conduction of Anammox reactors, difficulty in obtaining a robust Anammox sludge for the start-up of treatment plants is reported, due to the slow replication of this group of bacteria (2.6 to 11 days) (ZHANG et al., 2017; ZHU et al., 2008). In the literature, this delay to confirm the onset of Anammox activity has been reported: Tang et al. (2011) 214 days, Gupta, et al. (2019) 119 days, Casagrande et al. (2011) 110 and 170 days for the two study reactors.
Membrane aerated biofilm reactors (MABR) have shown promise for the rapid start-up of the Anammox process. Augusto et al. (2018) presented start-up data in 21 days when operating an MABR reactor fed with synthetic effluent and continuous feed, keeping the process stable for 150 days. The membrane aerated biofilm reactor consists of one-phase reactors that promote partial nitritation and Anammox activity in the same reactor.
MABR systems use microporous membrane technology as a way of transport and dispersion of the DO, that is, they allow only enough DO to be dispersed in the reactors for partial nitritation, due to membrane (in silicone material or microporous carbon) due to its porosity, allows a low concentration of DO (~0.2 mg.L-1) to disperse in the reactors, allowing the bacteria present in the sludge to form a biofilm adhered to the membrane, where partial nitritation occurs (AUGUSTO et al., 2018, LI et al., 2016; GONG et al., 2008). It is noteworthy that the literature data report the use of this reactor model for the Anammox process only with continuous feed, which is unexplored with sequential batch feed.
Kinetic studies of substrate consumption rate are important because they aim to demonstrate whether the nitrogen consumption temporal behavior can be optimized, or even attest to whether the time used for substrate degradation in reactors is being insufficient for microorganisms, also helping to generate mathematical models that collaborate in the bacteria behavior prediction (WANG, et al., 2021; MARTINS et al., 2018).
In this sense, this work aimed to carry out the nitrogen consumption kinetic study by the Anammox process in a membrane aerated biofilm reactors operated in sequential batches (MABR-BS). 6 MABR-BS reactors were used, each one of them inoculated with a specific sludge Anammox, obtained from the enrichment of anaerobic sludges coming from 3 different sludge sources, namely, urban sewage treatment plant, landfill leachate treatment plant sanitary, and swine slaughter effluent treatment plant.
2 Materials and Methods
To carry out the kinetic study of nitrogen consumption by the Anammox process, MABR reactors operated in sequential batches were used.
2.1 Experimental apparatus
Six glass vials with a volume of 1L, with 500 mL of useful volume and 500 mL of volume equivalent to the head-space were used as reaction environment; 3 aerators coupled to 3 flowmeters to control the air flow; 30 cm of silicone membrane in a curved shape with one of the inlets connected to the aerator and flowmeter, with an air flow regulated at 1.0 L.min-1, the other outlet was immersed in a 75 cm water column, with the function to exert negative pressure on the air insufflated inside the tubular silicone membrane, forcing the air to exit through the porosity of the membrane. Aeration was intermittent, with an interval of 9.6 minutes between each minute of aeration, the reactors were kept in a water bath equipment with agitation at 30 rpm and temperature at 32°C (Figure 1).
Figure 1 – Details of the MABR experimental apparatus in Sequential Batch
2.2 Inoculum
The inoculum used in the kinetic test demonstrated the Anammox activity from 20 days of operation of the MABR-BS reactors, but prior to the test, the reactors went through 261 days with synthetic feed to promote the enrichment of the Anammox biomass, with the objective of forming robust biomass. The raw sludge was collected in 3 effluent treatment stations and received the following nomenclature according to the place of sludge collection used in the inoculation: R1 - anaerobic sludge from a UASB domestic sewage treatment reactor; R2 - mixed sludge from a UASB reactor, consisting of waste sludge and supernatant foam; R3- anaerobic sludge from landfill leachate treatment; R4 - mixed sludge consisting of aerobic and anaerobic pond sludge from the landfill leachate treatment plant; R5 - anaerobic sludge from the swine slaughter effluent treatment plant and R6 - aerobic and anaerobic sludge from the swine slaughter effluent treatment plant.
The 6 reaction units were conducted with a 2:3 (v:v) ratio between anaerobic inoculum and synthetic effluent, which correspond to the R1, R3, and R5 reactors and in a 1:1:3 (v:v) ratio between the aerobic inoculum, anaerobic inoculum, and synthetic effluent, corresponding to reactors R2, R4, and R6.
2.3 Synthetic substrate
The synthetic substrate was adapted from Van de Graaf et al. (1996) following the formulation: NH4Cl (100mg.L-1); NaHCO3 (1.5g.L-1); KH2PO4 (0.0272g.L-1); MgSO4·7H2O (0.3g.L-1); CaCl2·2H2O (0.18g.L-1); trace element solution I (for 1L of ultrapure water: EDTA, 5g; FeSO4·7H2O, 9.15g) 1 mL of the solution per liter of synthetic effluent; Trace element solution II (for 1L of ultrapure water: EDTA, 15g; ZnSO4·7H2O, 0.43g; CoCl2·6H2O, 0.24 g; MnCl2·4H2O, 0.99g; CuSO4·5H2O, 0.25g ; Na-MoO4·2H2O, 0.22g; NiCl2·6H2O, 0.19g; Na2SeO3 (anhydrous), 0.10g; H3BO4, 0.014g) 1mL of the solution per liter of synthetic effluent.
2.4 Kinetic Assay
The kinetic assay was carried out with a cycle time (TC) of 24h, corresponding to a load of 0.025 KgN.m-3.d-1. The parameters oxygen, temperature, and biomass agitation were controlled at ~0.5mg.O2.L-1; 32°C and ~30rpm, respectively. Samples were collected every 2.5h. Table 1 shows the initial conditions of the kinetic test for reactors R1 to R6.
It is noteworthy that all reactors received, in the enrichment step (261 days) prior to the kinetic assay, the same amount of sludge at the start (4.0 gL-1) and fed with the same synthetic substrate, but the enrichment process from the Anammox biomass, promoted a natural selection of microorganisms causing at the time of the test different volatile suspended solids concentration between them. Although the test feed is synthetic, the initial assay data suffered interference from the previous batch.
Table 1 – Initial conditions of the kinetic assay performed in Anammox MABR-BS reactors
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Parameters |
R1 |
R2 |
R3 |
R4 |
R5 |
R6 |
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N-NH4+ (mg.L-1) |
122.33 |
157.53 |
120.71 |
101.50 |
100.00 |
100.00 |
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N-NO2- (mg.L-1) |
0.56 |
12.07 |
0.82 |
0.51 |
0.21 |
0.21 |
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N-NO3- (mg.L-1) |
15.60 |
0.29 |
11.83 |
9.46 |
10.78 |
11.53 |
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SSV (g.L-1) |
2.64 |
5.93 |
0.41 |
2.55 |
3.82 |
1.71 |
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pH |
8.33 |
8.70 |
8.6 |
8.55 |
8.73 |
8.77 |
Source: Authors, 2021
2.5 Kinetic parameters
The parameters substrate consumption rate (rs) and the specific substrate consumption rate (µs) were evaluated, which were determined from the exponential regression of substrate concentrations as a function of time, resulting from experimental kinetic assays, according to equations 3 and 4, respectively.
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(3) |
rs = substrate consumption rate (mgN. L-1.h-1)
S-= substrate concentration (mgN.L-1)
T = time (h)
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|
(4) |
Where:
µs = specific substrate consumption rate (mgN.gVSS-1h-1)
X = biomass concentration express in Volatile Suspended Solid (mgVSS-1.L-1)
2.6 Physicochemical analyses
The kinetic behavior of the reactors was followed in relation to the analyses: Ammoniacal Nitrogen (N-NH4+), Nitrate (N-NO3-), Nitrite (N-NO2-), pH and Inorganic Carbon. The analysis of Volatile Suspended Solids (SSV) was performed before the start of the kinetic test as an indirect measure of the biomass content. All analyzes were performed according to the APHA (2005), except for the Inorganic Carbon analysis which followed the IC method, using a TOC/TN/IC analyzer (TOC-LCPH/CPN, Shimadzu, Kyoto, Japan) following the manufacturer's recommendations.
2.7 Molecular Biology Analysis
After 261 days of enrichment of Anammox biomass, reactors with mixed biomass from the 3 initial biomass collection sites underwent PCR (Polymerase Chain Reaction) analysis in comparison with universal primer and showed the presence of Anammox bacteria in all studied sludges Candidatus Anammoxoglobus Propionicus.
2.8 Stoichiometric coefficients
In this study, the stoichiometric coefficients of partial nitritation and Anammox activity (NP/A) in a single-phase reactor were calculated according to equations 5 to 10, according to Third et al. (2001).
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(5) |
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(6) |
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(7) |
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(8) |
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(9) |
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(10) |
3 Results and Discussion
Figure 2 shows the 6 reactors’ temporal behavior in relation to the consumption of ammoniacal nitrogen, nitrite, nitrate, and inorganic carbon. Highlighting the positive result that in all reactors in the study, all the ammoniacal nitrogen present at the beginning of the kinetic assay was consumed.
In the 6 reactors, nitrite values were low, below 2.0 mg.L-1, which is characteristic of reactors in which the Anammox process and Partial Nitritation occur simultaneously. In these reactors, as nitrite is formed, it is already consumed along with ammoniacal nitrogen in the Anammox process, in the ratio 1:1.32 (NH4+:NO2-) (equation 1). As the consumption of nitrite is higher, there is no noticeable reduction of the two compounds in the same proportion (STROUS, et al., 1999).
About the nitrate behavior, all reactors showed similar behavior, with nitrate growth over time, this behavior is characteristic of active Anammox reactors that, according to equations 1 and 2, the process releases residual nitrate. Table 2 shows the residual nitrate and equivalent stoichiometric coefficient values for each reactor, as well as the removed ammoniacal nitrogen +nitrite concentration and the stoichiometric coefficients generated with the average data obtained in the kinetic test.
Figure 2 – Temporal behavior of nitrogen and inorganic carbon forms in MABR-BS R1 to R6 reactors
About the nitrate generation, all reactors showed similar behavior, with nitrate growth over time, this behavior is characteristic of active Anammox reactors that, according to equations 1 and 2, the process releases residual nitrate. Table 2 shows the residual nitrate and equivalent stoichiometric coefficient values for each reactor, as well as the removed ammoniacal nitrogen + nitrite concentration and the stoichiometric coefficients generated with the average data obtained in the kinetic assay.
Table 2 – Reactors Behavior in the kinetic assay in relation to input and output parameters of greater importance for the Anammox process, as well as in relation to stoichiometric coefficients
|
Parameters |
R1 |
R2 |
R3 |
R4 |
R5 |
R6 |
|
Residual Nitrate (mg.L-1) |
37.84 |
49.22 |
40.69 |
46.04 |
37.31 |
32.01 |
|
N-NH4+ + N-NO2- removal (mg.L-1) |
84.99 |
84.61 |
81.75 |
78.52 |
86.93 |
89.20 |
|
N removal efficiency (%) |
61.36 |
61.01 |
59.03 |
56.70 |
62.77 |
64.40 |
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O2 Stoichiometric coefficient |
1.00 |
1.40 |
1.50 |
1.69 |
1.58 |
1.51 |
|
NO3- Stoichiometric coefficient |
0.018 |
0.31 |
0.33 |
0.45 |
0.37 |
0.32 |
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N2 Stoichiometric coefficient |
0.44 |
0.48 |
0.43 |
0.42 |
0.46 |
0.43 |
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H2O Stoichiometric coefficient |
1.94 |
1.96 |
1.95 |
1.94 |
1.98 |
1.96 |
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H+ Stoichiometric coefficient |
0.10 |
0.07 |
0.09 |
0.11 |
0.03 |
0.07 |
Source: Authors, 2021
According to Table 2, the reactor that showed most approximated the stoichiometric coefficient to the theoretical value for nitrate formation in equation 2 (0.11 mol) was the R1 reactor, with 0.018 mol of nitrate generated for each 1 and 1.32 mol of NH4+ and NO2- removed to gaseous form N2. From an environmental point of view, the best result is related to the R1 reactor, as it has the lowest stoichiometric coefficient in nitrate production, thus, this reactor had the highest removal of ammoniacal nitrogen and nitrite with the lowest generation of nitrate, which in the environment becomes a toxic agent (CAO, 2018).
Martins et al. (2018) when performing a similar assay, reached a molar ratio between ammonium, nitrite, and nitrate of 1:1.24:0.34 for synthetic effluent with an input of 73/67 between N-NH4+ and N-NO2-, being the amount of nitrate found in that study like reactors R2, R3, R5, and R6. Yao et al. (2015) fed an Anammox reactor with synthetic effluent with 1:1.32 between N-NH4+ and N-NO2- and found 0.11 mol as a stoichiometric coefficient for nitrate, while the theoretical expected stoichiometry was 0.26, corroborating with a practical stoichiometric value of nitrate lower than the theoretical value, as found in reactor R1 in this research.
To demonstrate the molar nitrate formation behavior in relation to time, Figure 3 is shown. During the kinetics experimental time, all reactors showed concomitant activity of nitrate formation through Anammox microorganisms and nitrate-forming bacteria (BON) that act in the conventional N removal cycle, this inference is possible since the stoichiometric coefficient for nitrate in the Anammox reaction is 0.11 (Third et al., 2001) while there were peaks with a maximum value of 3.01 mol of nitrate in reactor 6, indicating mixed BON/Anammox activity.
Figure 3 – Temporal variation of molar nitrate formation, obtained by stoichiometric calculation, in MABR-BS R1 to R6 reactors
Figure 4 – pH temporal variation in the kinetic assay conducted in MABR-BS R1 to R6 reactors
Only reactor 5 showed, in Figure 3, NO3- generating activity predominant Anammox, since approximately 18h the stoichiometric nitrate coefficients formation were compatible with the theoretical reference value and from then on the amount of moles of NO3- increases, indicating that in this case, the cycle time could be adopted as 18h.
Figure 4 shows the pH values during the kinetic test in the 6 reactors. In all reactors, the initial pH was above 8.0, decaying to close to neutrality, due to the partial nitritation process that consists of the nitrogen transformation from the ammoniacal form to the nitrite form, with simultaneous consumption of alkalinity by the ammonia-oxidizing bacteria (BON) (7.14 mg of CaCO3 per mg of N-NH4+) (METCALF & EDDY, 2003). Alkalinity consumption can also be seen in all graphs in Figure 2, through the consumption of carbon in inorganic form. The fastest alkalinity consumption was noted in reactor R2, in which in 2.5h the alkalizing level dropped from 1.5g to 0.12g. This higher consumption in R2 can be explained by the higher biomass concentration (5.93g.L-1 expressed in VSS).
Table 3 shows the average and maximum nitrogen removal rates and the specific average and maximum nitrogen removal rates, obtained in the kinetic assay in reactors R1 to R6.
Table 3 – Nitrogen consumption velocities and specific nitrogen consumption velocities were expressed as mean values for each MABR-BS reactor in the study
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Kinetic parameters |
R1 |
R2 |
R3 |
R4 |
R5 |
R6 |
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rs average (mgN. L-1.h-1) |
29.73 |
33.64 |
35.62 |
33.74 |
29.11 |
30.82 |
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rs maximum (mgN. L-1.h-1) |
58.08 |
56.19 |
56.32 |
47.85 |
40.35 |
43.70 |
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µs average (mgN.gSSV-1h-1) |
29.43 |
33.50 |
33.62 |
33.42 |
28.90 |
30.34 |
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µs maximum (mgN.gSSV-1h-1) |
57.71 |
56.02 |
53.88 |
47.46 |
40.09 |
43.12 |
Source: Authors, 2021
Chini et al. (2016) when operating an Anammox EGSB reactor (Expanded Granular Sludge Bed) fed with synthetic effluent, reached an average rate of the N removal reaction (rs) of 19.53 and 28.66 mg.L-1.h-1, for the ammonium and nitrite forms, respectively. In the present study, the total rs kinetic parameter for sum (N-NH4+ + N-NO2-) was maintained in all reactors above 29 mgN.L-1.h-1 and reached in reactors R1, R2, and R3 maximum values of (rs) higher than the sum of the velocities of those authors (19.53 + 28.66 = 49.19 mgN.L-1.h-1), indicating the compatibility of the sludges in the present study with the high-performance Anammox sludge used by Chini et al. (2016).
Figure 5 – Specific nitrogen consumption rate and exponential mathematical models better adjusted to the biological nitrogen removal behavior achieved in MABR-BS reactors
The kinetic data obtained by Equation 2 (µs) were fitted to the exponential mathematical model, and the equations that describe the behavior of the specific general consumption rate of nitrogenous forms (N-NH4+ + N-NO2-) are shown in Figure 5.
Table 4 – The specific rate of Nitrogen Consumption by Anammox microorganisms reported in the literature
|
Parameters |
Valor de µs |
Reactor model |
Fed conditions |
Authors |
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µs (mgN-NH4+.gVSS-1.h-1.;mgN-NO2-.gVSS-1.h-1) |
Assay 1: 20.11 and 30.03; Assay 2: 19.38 and 14.22 for N-NH4+ and N-NO2-, respectively |
Anammox sludge activity tests conducted in batch |
Synthetic feed, rich in ammonium and nitrite. |
Chini et al., (2016) |
|
µs (mgN.gVSS-1.d-1) |
0.4 as maximum value |
RBS reactor inoculated with Anammox enriched Sludge from municipal WWTP, with 3 months of enrichment. |
Synthetic feed, with 273 mg.L-1 of NanO2 and 210 mg.L-1 of (NH4)2SO4 and micronutrient solution. |
Noophan et al., (2015) |
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µs (mgN-NH4+.gSSV-1.h-1.;mgN-NO2-.gSSV-1.h-1) |
342.01 and 337.80 to N-NH4+ and N-NO2-, respectively |
SBR, testing different power ratios H2N2:NH4+:NO2-. |
Synthetic fed with a maximum ratio of 100:65 between NH4+:NO2-. |
Yao et al., (2015) |
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µs (mgN.gSSV-1.d-1) |
850 for the 1st day of the experiment; after 100 days of operation 528. |
SBR with temperature control at 15°C and 30°C. |
Synthetic fed 1:1 ratio between NH4+:NO2-. |
Wang et al., (2021) |
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µs (mgN.gSSV-1.h-1) |
67,1; 64,2; 72,5; 61,0 |
SBR with different agitation ranges. |
Synthetic fed with NH4+:NO2- 31,6/32,8 73/67 92,2/67,3 |
Martins et al., (2018) |
Source: Authors, 2021
The kinetic assays that presented the highest correlation coefficients (r2) between the practical values and the mathematical model used in the adjustment were the assays performed in reactors R1 and R6 with r2 = 0.9042 and r2 = 0.9052, respectively. The lowest correlation was found in reactor R4 with r2 = 0.7183. Yao et al. (2015) also used an exponential model to adjust the data reaching r2 = 0.98 and r2 = 0.97 for the consumption of ammonia and nitrite, respectively.
To corroborate the results of the present work with other research, Table 4 presents similar works on Anammox nitrogen removal kinetics assays.
Most research presented in Table 3, showed specific nitrogen removal rate compatible with the average and maximum values of µs found in the present study reactors. Between all research, the results presented by Martins et al. (2018), had had the input conditions closer to the present study, and the reaction rate was very similar corroborating more precisely with the present result.
An important observation to be made when studying the kinetics of the Anammox process is related to the assays performed by Wang et al. (2021), which reached an initial rate of 850 mgN.gVSS-1.d-1 and maintained even lower a high N removal rate with 528 mgN.gVSS-1.d-1, demonstrating the high performance of Anammox reactors operated with high applied nitrogen loading rates.
In accordance with the previous comment, reactors R1, R2 and R4, observing Figure 5, showed signs of entering a low linear rate in the range of 8 to 16h, indicating that to take advantage of the exponential phase of nitrogen consumption, the time of detention could be reduced allowing for the amplification of the nitrogen load rate to be applied.
4 Final Considerations
Kinetic assays showed that there is an exponential progression in nitrogen consumption as a time function, where the highlight was the R1 reactor, which presented µsmax of 57.71 mgN.gVSS-1.h-1. Reactors R1, R2 and R4 presented a more visual exponential phase that varied between 8 and 16h, indicating that the hydraulic detention time has the potential to be reduced, optimizing the Anammox nitrogen removal process.
The reactor with the best correlation of the fit of the data to the model and with the lowest residual nitrate production index was the R1 reactor, which was inoculated with anaerobic sludge from a domestic sewage wastewater treatment plant. Related to the nitrate production in the other reactors, all presented similar behavior with molar production of nitrate 3 times greater than the theoretical stoichiometry. The R4 reactor showed the highest nitrate production (R4 = 0.44 mol of N-NO3-, theoretical = 0.11 mol of N-NO3-).
It is important to highlight that although Anammox biomass was developed in all reactors, the biomass source with the best performance was the sludge collected in the domestic sewage wastewater treatment plant. This result is positive because this sludge is an easily accessible source of biomass and has great microbiological diversity, which can be easily exploited in the development of robust biomass for application in full-scale Anammox reactors.
The MABR-BS model proved to be satisfactory in terms of nitrogen removal rate, corroborating the results of the literature and showing indications that the reactors in particular R1, R2 and R4 have the potential to react positively to the increase in load in future research.
Acknowledgments
To Capes for the doctoral scholarship/social demand, the research funding agencies Campus France, Fundação Araucária, and CNPq for the financial support.
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Authorship contributions
1 – Tatiane Martins de Assis (Corresponding author)
PhD in Concentration in Water Resources
https://orcid.org/0000-0002-8795-1823 • tatianemassis@yahoo.com.br
Contribution: Conceptualization, Investigation, Formal Analysis, Methodology, Resources, Software, Validation, Visualization, Writing – original draft, Writing – review & editing
2 – Aruani Letícia da Silva Tomoto
PhD student in Agriculture Engineering in Water resources and environmental sanitation area
https://orcid.org/0000-0003-4953-2086 • arutomoto@gmail.com
Contribution: Investigation, Formal Analysis, Methodology
3 – Ana Paula Trevisan Lied
PhD student in Agriculture Engineering in Water resources and environmental sanitation area
https://orcid.org/0000-0002-1575-3983 • anapaullatrevisan@gmail.com
Contribution: Investigation, Formal Analysis, Methodology
4 – Luiz Felipe Gomes Ferreira
Graduating in Agricultural Engineering
https://orcid.org/0000-0003-4651-4405 • luiz.ferreira6@unioeste.br
Contribution: Investigation, Formal Analysis, Methodology
5 – Julia Elizabeth Martins
Graduating in Agricultural Engineering
https://orcid.org/0000-0003-2456-046X • julia.martins2@unioeste.br
Contribution: Investigation, Formal Analysis, Methodology
6 – Dagoberto Yukio Okada
Professor, PhD in Civil Engineering
https://orcid.org/0000-0003-1859-9851 • dagokada@ft.unicamp.br
Contribution: Conceptualization, Data curation, Supervision
7 – Nicolas Roche
PhD in Process Engineering, Professor and Researcher in Environmental Sciences
https://orcid.org/0000-0001-8790-0578 • nicolas.roche@univ,amu.fr
Contribution: Conceptualization, Data curation, Supervision
8 – Simone Damasceno Gomes
Professor in Water Resources and Environmental Sanitation, PhD in Agronomy Science
https://orcid.org/0000-0001-7639-8500 • simone.gomes@unioeste.br
Contribution: Conceptualization, Data curation, Writing – review & editing, Project administration, Supervision
How to quote this article
ASSIS, T. M.; TOMOTO, A. L. S.; LIED, A. P. T.; FERREIRA, L. F. G.; MARTINS, J. E.; OKADA, D. Y., ROCHE, N.; GOMES, S. D. Industrial reuse of petrochemical effluents: A case study of ultrafiltration and reverse osmosis. Ciência e Natura, Santa Maria, v. 44, Ed. Esp. VI SSS, e20, 2022. DOI: 10.5902/2179460X68843.