Palmeiro-Sanchez, T., Fra-Vazquez, A., Rey-Martinez, N., Campos, J. L., & Mosquera-Corral, A. (2016). Transient concentrations of NaCl affect the PHA accumulation in mixed microbial culture. J. Hazard. Mater., 306, 332–339.
Abstract: The present study explores the feasibility of the accumulation of polyhydroxyalkanoates (PHAs) under the presence of transient concentrations of added sodium chloride, by means of a mixed microbial culture (MMC). This culture was enriched on a mixture of volatile fatty acids (VFAs) containing 0.8 g Na+/L, as NaOH. This MMC presented a maximum PHA accumulation capacity of 53 wt% with 27 Cmol% HV. Accumulation experiments performed with added NaCI at concentrations of 7, 13 and 20 g/L shown that this salt provoked a decrease of the biomass PHA production rate, with an IC50 value close to 7 g NaCl/L. The accumulated PHA was lower than the corresponding value of the assay without the addition of salt. Furthermore, the composition of the biopolymer, in terms of HB:HV ratio, changed from 2.71 to 6.37 Cmol/Cmol, which means a HV decrease between 27 and 14 Cmol%. Summarizing, the PHA accumulation by a MMC non-adapted to saline conditions affected the polymer composition and lead to lower production yields and rates than in absence of added NaCl. (C) 2015 Elsevier B.V. All rights reserved.
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Pedrouso, A., Correa-Galeote, D., Maza-Marquez, P., Juarez-Jimenez, B., Gonzalez-Lopez, J., Rodelas, B., et al. (2021). Understanding the microbial trends in a nitritation reactor fed with primary settled municipal wastewater. Sep. Purif. Technol., 256, 117828.
Abstract: Partial nitritation was pointed out as the key step to implement the autotrophic nitrogen removal processes at low temperature. This study investigated the initiation and maintenance of a nitritation process with simultaneous COD removal in a sequencing batch reactor (SBR) run at 15 degrees C and fed with primary settled urban wastewater characterized by 42 +/- 10 mg TOC/L and 45 +/- 4 mg NH4+-N/L. A nitrite accumulation ratio of nearly 100% was observed and the long-term (354 days) process stability was successfully maintained despite the municipal wastewater composition fluctuations. The absence of nitrite oxidizing bacteria (NOB) activity was attributed to the free nitrous acid (FNA) in-situ accumulated at high levels (0.02-0.20 mg HNO2-N/L). Despite nitrate production was not observed, the quantification of bacterial groups indicated that NOB were present in the SBR sludge throughout the entire operational period. Ammonium oxidizing bacteria (AOB) abundance and community structure were significantly influenced by the organic matter present in the feeding. Average organic matter removal efficiencies of 80% were obtained without observing any detrimental effect over the nitritation process performance, due to the functional redundancy within both the chemoheterotrophic and AOB communities.
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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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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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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.
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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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