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1.
Bioresour Technol ; 312: 123597, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32506044

RESUMO

The specific nitrate reduction pathway in Pseudomonas putida Y-9 under aerobic conditions was studied. Strain Y-9 removed 82% of the nitrate accompanied by an accumulation of ammonium and a decrease of total nitrogen. Ammonium inhibited nitrate transformation (removal efficiency was 22.65%), illustrating that nitrate assimilation exists in strain Y-9. The detectable ammonium in the supernatant during the nitrate reduction process came from intracellular locations in strain Y-9. The nirBD that encodes nitrite reductase had an important role in strain growth and ammonium production. A 15N isotope experiment demonstrated that strain Y-9 can conduct dissimilatory nitrate reduction to ammonium (DNRA) and nirBD controls this process. This further indicated that the loss of total nitrogen is due to denitrification. All results highlighted that strain Y-9 performs simultaneous nitrate assimilation, DNRA, and denitrification under aerobic conditions, and nirBD controls the assimilation and DNRA process. Thereinto, nitrate assimilation dominates the removal of nitrate.


Assuntos
Compostos de Amônio , Pseudomonas putida , Desnitrificação , Nitratos , Nitrogênio , Óxidos de Nitrogênio
2.
Bioresour Technol ; 312: 123593, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32526666

RESUMO

Heterotrophic nitrification and aerobic denitrification (HN-AD), which is primarily performed by bacteria rather than fungi, is an attractive approach for nitrogen removal. In this study, a red yeast, Sporidiobolus pararoseus Y1, was isolated and shown to exhibit optimal growth and nitrogen removal efficiency on glucose, followed by citrate, sucrose, acetate and starch. The nitrogen removal efficiency increased with increasing initial concentrations of NH4+-N, NO2--N and NO3--N from 14 to 140 mg·L-1. At an initial nitrogen concentration of 140 mg·L-1, the maximum removal efficiencies of NH4+-N, NO2--N and NO3--N were 98.67%, 97.13% and 83.51% after 72 h incubation, while those of corresponding total nitrogen were 88.89%, 81.31% and 70.18%, respectively. The nitrification (amoA) and denitrification genes (nirK and napA) were amplified from Y1. These results suggest that yeast are also capable of HN-AD, which can be used to remove nitrogen in wastewater systems.


Assuntos
Compostos de Amônio , Basidiomycota , Produtos Biológicos , Aerobiose , Carbono , Desnitrificação , Processos Heterotróficos , Nitrificação , Nitritos , Nitrogênio
3.
Chemosphere ; 256: 127092, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32559887

RESUMO

Although nitrogen removal from wastewater is essential to prevent eutrophication, the biological processes employed to this end are characterized by several disadvantages, including high energy consumption and the production of large quantities of sludge. Thus, in this study, the organic matter and nitrogen removal efficiencies of the new sulfate reduction, denitrification/anammox and partial nitrification (SRDAPN) process were examined using an anaerobic-anoxic-oxic biofilter reactor. The results showed that the organic matter removal efficiency of the new process at loading rate 1.0 kg COD/m3 per day was 97%. With a circulation flow from the oxic to the anoxic column that was 3 times influent, the nitrogen removal efficiency of the sulfur denitrification and nitrification (SRDN) process without anammox, was 66%, while that of the SRDAPN process with anammox was 76%. Additionally, nitrogen consumption by the anammox reaction in the anoxic column was 13.8% for nitrite-nitrogen and 10.5% for ammonium-nitrogen, and the withdrawal of excess sludge was not required throughout the 170 days of operation. Microbial community analysis showed that acetogenic sulfate reducing bacteria and acetoclastic methanogens coexisted in the anaerobic column, and in the anoxic column, the total relative abundance of anammox bacteria, including Candidatus Brocadia, which coexisted with heterotrophic denitrifying bacteria and sulfur denitrifying bacteria, was 17-18%. Thus, this study established the SRDAPN process as an energy saving and high removal efficiency process.


Assuntos
Sulfatos/química , Eliminação de Resíduos Líquidos/métodos , Compostos de Amônio , Bactérias , Reatores Biológicos/microbiologia , Desnitrificação , Nitrificação , Nitritos , Nitrogênio , Oxirredução , Esgotos/microbiologia , Enxofre , Águas Residuárias/química , Águas Residuárias/microbiologia
4.
Bioresour Technol ; 309: 123423, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32361617

RESUMO

This study investigated innovative start-up strategies of a pilot-scale sequencing batch reactor (SBR) for single-stage deammonification using activated sludge as the sole inoculum source. In 24 m3 aerobic oxidizing bacteria cultivation plant, nitrogen loss efficiency was suggested to be an indicator for determining duration of cultivation. In 12 m3 ANAMMOX (ANaerobic AMMonium OXidation) cultivation plant, combined strategy (sequential fed-batch and continuous modes) was adopted to promote ANAMMOX activity from activated sludge. Both the cultivated sludge were inoculated in 24 m3 pilot-plant for single-stage SBR with deammonification. The feed distribution strategy was used to cultivate ANAMMOX bacteria selectively resulting in nitrogen removal rate of 0.73 kg/m3/d and nitrogen removal efficiency of 86.5 ± 1.9% within 254 days. Candidatus Brocadia sp. 40 was enriched from undetectable to 22.7% relative abundance. These findings indicated that fast start-up of the deammonification process was possible without ANAMMOX seed sludge in pilot-scale reactor with various variables.


Assuntos
Compostos de Amônio , Esgotos , Anaerobiose , Bactérias , Reatores Biológicos , Nitrogênio , Oxirredução
5.
Bioresour Technol ; 311: 123489, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32417657

RESUMO

The freshwater anammox-based process would usually experience performance fluctuation and need adoption period when subjected to saline wastewater according to previous studies. In this study, the performance of nitrite-limited freshwater one-stage partial nitritation/anammox (PNA) process subjected to saline wastewater was investigated. The results showed that the nitrite-limited freshwater system could smoothly adapt to the salinity of 0.25%. The stable nitrogen removal could be achieved until the salinity of 2.5%, at which the desirable average NRR of 0.74 ± 0.1 kg/m3/d was achieved. The microbial community analysis showed that during the whole experiment, the main functional microbes were from genus Nitrosomonas and genus Kuenenia, which were through to be the crucial factors for achieving the excellent performance. This study indicates the nitrite-limited strategy is admissible for stabilizing the performance of freshwater one-stage PNA process subjected to saline wastewater in actual application.


Assuntos
Compostos de Amônio , Salinidade , Reatores Biológicos , Água Doce , Nitrogênio , Nitrosomonas , Oxirredução , Águas Residuárias
6.
Water Res ; 179: 115877, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32402861

RESUMO

Recent reports on the occurrence and contribution of dissimilatory nitrate reduction to ammonium (DNRA) in marine, inland water, and soil systems have greatly improved our understanding of the global nitrogen (N) cycle. This also promoted the investigation of the role and ecological features of DNRA in anthropogenic ecosystems. However, so far, the use of DNRA in municipal wastewater treatment plants (WWTPs), which are one of the most common and largest biotechnologically artificial water ecosystems, has not been investigated. Accordingly, this study focused on the abundance, activity, community structure, and diversity of DNRA bacteria in full-scale WWTPs. DNRA bacteria were detected in all treatment units in six tested municipal WWTPs, even in aerobic zones (dissolved oxygen > 2 mg L-1). Although the relative abundance of DNRA bacteria (0.2-4.0%) was less than that of denitrifying bacteria (0.7-10.1%) among all investigated samples, the abundance of DNRA bacteria still reaches 109 gene copies g-1. However, 15N-isotope tracing indicated that the potential DNRA rates were significantly lower (0.4-2.1 nmol N g-1 h-1) than those of denitrification (9.5-15.7 nmol N g-1 h-1), but higher than anammox rate (0.3-1.3 nmol N g-1 h-1). The DNRA bacterial community structure was primarily affected by temperature gradient despite the treatment process. High-throughput sequencing analysis targeting the DNRA nrfA gene showed that Nitrospira accounted for the largest proportion of nrfA genes among all samples (6.2-36.3%), followed by Brocadia (5.9-22.1%). Network analysis further indicated that Nitrospira played an important role in both the DNRA bacterial community and entire bacterial community in municipal WWTPs. These results suggest that the ecological habitats of DNRA bacteria in anthropogenic ecosystems were far more abundant than previously assumed. However, the contribution to N transformation by the widespread DNRA was not significant in traditional municipal WWTPs.


Assuntos
Compostos de Amônio , China , Desnitrificação , Ecossistema , Nitratos , Nitrogênio , Oxirredução , Águas Residuárias
7.
Water Res ; 180: 115813, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32438139

RESUMO

In this study, a novel coupling process with partial nitritation-anaerobic ammonium oxidation (anammox) (PNA) and sulfur autotrophic denitrification (SAD) was studied using an upflow biofilm reactor with mechanical vibration. At a lower dissolved oxygen (DO) concentration (0.40 ±â€¯0.20 mg L-1), ammonia could be efficiently removed from synthetic wastewater by the coupling system with a total nitrogen removal efficiency (NRE) of 98% and an influent NH4+-N concentration of 600 mg L-1. In this system, the nitrate, which was produced during the anammox reaction, could be timely reduced by the SAD reaction. Compared with the conventional PNA and SAD processes, coupling the PNA and SAD processes in a single reactor prevented nitrite accumulation in the SAD reaction and reduced the total sulfate production by 59%. The high-throughput sequencing analysis supported that the SAD bacteria (Thiobacillus) and anammox bacteria (Candidatus Kuenenia) could coexist on the elemental sulfur stone. Additionally, sulfur consumption and sulfate production were increased under a high DO concentration. The sulfate production/nitrate reduction ratio and changing profile of the substrate suggested that the short-cut SAD process mainly occurred in this coupling system. Otherwise, batch experiments also suggested that the nitrite removal rate in the anammox process was 34.5 times higher than that in the SAD process. The outcomes of these experiments revealed that most of the nitrite, as an intermediate product in the SAD reaction, served as an electron acceptor for the anammox reaction. A stoichiometric calculation of this coupling process indicated that the novel reaction scheme with a high NRE was successfully achieved. Under an ideal short-cut SAD process, almost 55% of the sulfur consumption could be reduced in this coupling system. The coupling system provides a new perspective for nitrogen removal in a single reactor and further promotes anammox and SAD performance in wastewater treatment processes.


Assuntos
Compostos de Amônio , Desnitrificação , Reatores Biológicos , Nitrogênio , Oxirredução , Enxofre , Águas Residuárias
9.
Water Sci Technol ; 81(1): 62-70, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32293589

RESUMO

Nitrification of ammonium nitrogen (NH4+-N)-bearing synthetic wastewater was performed in a batch-activated sludge reactor by varying the initial ammonium nitrogen concentration up to 400 mg/L at a pH of 8.1 ± 0.2 and temperature of 36 ± 2 °C for developing the process kinetics using acclimatised biomass. Maximum ammonium nitrogen removal efficiency of 98.3% was achieved with initial ammonium nitrogen and mixed liquor suspended solids concentration of 235 mg/L and 2,180 mg/L, respectively, at 48 h batch period. Based on the experimental results, kinetic constants for ammonia nitrogen removal following Monod's approach were obtained as maximum substrate removal rate coefficient = 0.057 per day, yield coefficient = 0.336 mg volatile suspended solids/mg ammonium nitrogen, half velocity constant = 12.95 mg NH4+-N/L and endogenous decay constant = 0.02 per day. Nitrification is a consecutive reaction with ammonium oxidation as the first step followed by nitrite oxidation. The overall rate of nitrite and nitrate formation was observed to be 1.44 per day and 0.34 per day, respectively.


Assuntos
Compostos de Amônio , Nitrificação , Reatores Biológicos , Cinética , Nitritos , Nitrogênio , Esgotos , Águas Residuárias
10.
Water Sci Technol ; 81(1): 109-120, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32293594

RESUMO

A simple model for online forecasting of ammonium (NH4+) concentrations in sewer systems is proposed. The forecast model utilizes a simple representation of daily NH4+ profiles and the dilution approach combined with information from online NH4+ and flow sensors. The method utilizes an ensemble approach based on past observations to create model prediction bounds. The forecast model was tested against observations collected at the inlet of two wastewater treatment plants (WWTPs) over an 11-month period. NH4+ data were collected with ion-selective sensors. The model performance evaluation focused on applications in relation to online control strategies. The results of the monitoring campaigns highlighted a high variability in daily NH4+ profiles, stressing the importance of an uncertainty-based modelling approach. The maintenance of the NH4+ sensors resulted in important variations of the sensor signal, affecting the evaluation of the model structure and its performance. The forecast model succeeded in providing outputs that potentially can be used for integrated control of wastewater systems. This study provides insights on full scale application of online water quality forecasting models in sewer systems. It also highlights several research gaps which - if further investigated - can lead to better forecasts and more effective real-time operations of sewer and WWTP systems.


Assuntos
Compostos de Amônio , Baías , Previsões , Modelos Teóricos , Águas Residuárias , Qualidade da Água
11.
Bioresour Technol ; 307: 123231, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32224425

RESUMO

Two agricultural wastes, Chinese medicinal herbal residue and spent Pleurotus ostreatus substrate, were developed to remove ammonium and phosphate from swine wastewater. These adsorbents were mesoporous materials with abundant smooth layered pores, and rough protuberances and grooves, respectively. Their adsorption capacities were 1131.65 and 1631.79 mg N g-1, and 63.41 and 62.58 mg P g-1 at pH 8.0, dosage of 0.2 g L-1 and contact time of 360 min. And kinetics data of ammonium and phosphate fitted best with the intra-particle diffusion and pseudo-second-order models, respectively. Based on the point of zero charge, FTIR and XPS analyses, ammonium was removed mainly by electrostatic attraction, ion exchange and surface precipitation, while phosphate was by ligand exchange, surface complexation and precipitation. Therefore, the two agricultural wastes have great potential to synchronously remove ammonium and phosphate from swine wastewater.


Assuntos
Compostos de Amônio , Poluentes Químicos da Água , Adsorção , Animais , Concentração de Íons de Hidrogênio , Cinética , Fosfatos , Suínos , Águas Residuárias
12.
Bioresour Technol ; 309: 123377, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32315917

RESUMO

This study presents a novel denitratation/anammox biofilter (DABF) for nitrate removal from secondary effluent, where denitratation (NO3-→NO2-) is coupled with anammox (NO2- +NH4+→N2) instead of denitritation (NO2-→N2). Total nitrogen (TN) was removed by 81.90% in this DABF when the average effluent TN concentration was 7.82 mg/L. Meanwhile, organic carbon source consumption and backwash sludge production in the DABF were reduced by 63% and 70%, respectively, compared to conventional denitrifying biofilter (DNBF). Nitrogen banlance analysis indicates that 93% of the nitrogen gas produced in DABF was via anammox. Batch tests confirmed that the DABF biofilm reduced nitrite using ammonium as the electron donor, and accumulated nitrite during denitratation, thus providing nitrite for the anammox bacteria. Moreover, high-throughput sequencing approach also revealed that the anammox bacteria Candidatus Brocadia dominated the community, which could also be responsible for the stable processes in DABF by interacting with the other denitrifying bacteria.


Assuntos
Compostos de Amônio , Desnitrificação , Anaerobiose , Reatores Biológicos , Carbono , Nitrogênio , Oxirredução , Águas Residuárias
13.
Bioresour Technol ; 309: 123390, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32325379

RESUMO

The effectiveness of the modification of wheat straw biochar using FeCl3 and HCl, alone or combined, on ammonium adsorption was evaluated using kinetic and isotherm models. The adsorption mechanisms were studied by comparative analysis of the surface properties of the biochars before and after ammonium adsorption. The results indicate that the modification methods enhanced the ammonium adsorption capacity by at least 14%, due to the increased OH and OCO functional groups and specific surface area, and increased Fe3+/Fe2+ redox coupling serving as an electron shuttle. It can be concluded that chemical modification of wheat straw biochars using FeCl3 and HCl increased the effectiveness of biochars for the treatment of ammonium-contaminated wastewater.


Assuntos
Compostos de Amônio , Adsorção , Carvão Vegetal , Ácido Clorídrico , Ferro
14.
Chemosphere ; 250: 126245, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234617

RESUMO

Hydrothermal experiments with magnesium, ammonium, and phosphate (MAP) solution at a temperature of 120 OC for 24 h and pH (9 and 10), whilst effects of varying Mg2+/Ca2+/HCO-3 ratios on struvite crystallization were examined. The study was performed to investigate their effects on the quality and quantity of crystals using the XRPD Rietveld refinement and SEM method. Obviously, the struvite crystallization was inhibited through the forming of calcite, dolomite, hydroxyapatite, sylvite, and Mg-whitlockite under different pH conditions. In the absence of Ca2+ and HCO-3 ions, struvite and dittmarite were formed at pH solutions (9 and 10). Struvite proportion reduced with pH (9 and 10) under Mg2+/Ca2+/HCO-3 ratios (1:1:1 and 2:1:1), and depleted under the Mg2+/Ca2+/HCO-3 ratio of 1:2:2. An obvious change in morphologies of crystals into nanosized particles was observed. Results of the low proportion of struvite for experiments with Mg2+/Ca2+/HCO-3 molar ratios may be a drawback for phosphate recovery.


Assuntos
Cálcio/química , Estruvita/química , Compostos de Amônio , Carbonato de Cálcio , Cálcio na Dieta , Cristalização , Íons , Magnésio , Compostos de Magnésio/química , Fosfatos/química
15.
Chemosphere ; 253: 126719, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32298909

RESUMO

A lab-scale membrane bioreactor (MBR) was employed to carry out the partial nitritation/Anammox (PN/A) process from conventional activated sludge. Seed sludge was cultivated under microaerobic conditions for 10 days before seeding into the MBR. The bacterial community was analyzed on the basis of cloning and sequencing of 16S rRNA gene. Relative slow ammonia oxidation rates (3.2-13.0 mgN/L/d) were established in the microaerobic cultivation period. In the continuous MBR operation, the nitritation was achieved in the first 16 days and the reactor produced a balanced ratio between ammonia and nitrite which favored the proliferation of Anammox bacteria. Efficient transition from PN to PN/A was achieved in two months which was supported by appearance of reddish spots on the reactor inner wall and the concurrent consumption of ammonium and nitrite. The PN/A performed a robust and high-rate nitrogen removal capability and achieved a peak nitrogen removal of 1.81 kg N/m3/d. 16S rRNA gene-based analysis indicated that "Nitrosomonas sp." and "Candidatus Jettenia sp." accounted for ammonia oxidation and nitrogen depletion, respectively. Denitratisoma facilitated denitrification in the reactor. The present study suggested that a pre-cultivation of seed sludge under microaerobic conditions assists fast realization of PN and further convoyed efficient transition from PN to PN/A. Knowledge gleaned from this study is of significance to initiation, operation, and control of MBR-PN/As.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Amônia , Compostos de Amônio , Bactérias/genética , Reatores Biológicos/microbiologia , Desnitrificação , Nitritos , Nitrogênio , Nitrosomonas/genética , Oxirredução , RNA Ribossômico 16S/genética , Esgotos/microbiologia
16.
Chemosphere ; 253: 126637, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32278910

RESUMO

A kinetic study was carried out in a sequencing batch reactor (SBR) (125 mg NH4+-N/L) inoculated with a physiologically stable nitrifying sludge not previously acclimated to sulfur compounds and fed at different initial sulfide concentrations (2.5-20.0 mg HS--S/L). Up to 10.0 mg HS--S/L, the nitrifying process kept stable and complete, reaching an ammonium consumption efficiency (ENH4+) of 100% and a nitrate yield (YNO3-) of 0.95 ± 0.03 mg NO3--N/mg NH4+-N consumed. At 15.0 and 20.0 mg HS--S/L, after an initial alteration in the nitrite oxidizing process, the YNO2- was decreasing throughout the cycles and the YNO3- increasing, obtaining in the last cycle at 20.0 mg HS--S/L, an ENH4+ of 100%, a YNO2- of zero, and a YNO3- of 0.80 mg NO3--N/mg NH4+-N consumed. At the end of the period at 20.0 mg HS--S/L, the specific rates of ammonium consumption and nitrate formation were 15 and 55% lower than their respective values in the control period without sulfide addition, showing that the sludge had a better metabolic adaptation for ammonium oxidizing activity than for nitrite oxidizing activity. The sludge acquired a higher sulfide oxidation capacity along the cycles. Bacterial population dynamics assessment indicated that the ammonium oxidizing bacteria (AOB) community was more diverse and stable than the nitrite oxidizing bacteria (NOB) community. The use of consortia with a previously stabilized nitrifying activity in SBR may constitute an alternative for eliminating simultaneously ammonium by nitrification and sulfide by sulfide oxidation and be implemented for the treatment of wastewater with ammonium and sulfide.


Assuntos
Compostos de Amônio/metabolismo , Sulfetos/metabolismo , Eliminação de Resíduos Líquidos/métodos , Bactérias/metabolismo , Reatores Biológicos/microbiologia , Cinética , Nitratos/metabolismo , Nitrificação , Nitritos/metabolismo , Oxirredução , Dinâmica Populacional , Esgotos/microbiologia , Compostos de Enxofre/metabolismo , Águas Residuárias
17.
J Environ Manage ; 266: 110607, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32314745

RESUMO

The major targets of constructed wetlands (CWs) during wastewater treatment include achieving high-quality effluent and maintaining stable effluent quality. Plant species diversity can increase nitrogen (N) removal efficiency and improve effluent quality by decreasing the effluent N concentrations, including nitrate (NO3--N), ammonium (NH4+-N) and total inorganic nitrogen (TIN) concentrations in CWs. However, the effect of plant diversity on the stability of effluent quality in response to perturbation in the form of an increased NH4+/NO3- ratio in influent has not been studied. This study conducted a microcosm experiment and assembled four plant species richness levels (1, 2, 3 and 4) and 15 species compositions by using 90 simulated CW microcosms to investigate the effect of plant diversity on the effluent N concentrations and their stability with an increase in the influent NH4+/NO3- ratio from 0:100 to 33:67 in the later stage of the experiment. The results showed that (1) plant species richness maintained a positive effect on effluent quality under an increased influent NH4+/NO3- ratio; (2) high species richness enhanced the stability of effluent water quality; (3) the presence of Phragmites australis in the community decreased the effluent TIN concentration and improved its stability under perturbation; and (4) the presence of Typha latifolia had a positive effect on N removal efficiency under perturbation. The establishment of communities with high plant species richness and proper species (such as P. australis) could simultaneously improve the effluent quality and stability in CWs for treating wastewater with increased NH4+/NO3- ratio.


Assuntos
Compostos de Amônio , Áreas Alagadas , Nitrogênio , Plantas , Eliminação de Resíduos Líquidos , Águas Residuárias
18.
Chemosphere ; 251: 126361, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32143079

RESUMO

One of the challenges for the application of the ANAMMOX (anaerobic ammonium oxidation) process for nitrogen removal in the mainstream municipal wastewater treatment is the disturbances in the feeding influent, in terms of the organic material, ammonium concentration, flow rate and temperature. Past experimental and mathematical simulation researches were mainly carried out under stable feeding condition. It is not clear how the ANAMMOX responds to the feeding disturbances. In this study, a 1D (one-dimensional) biofilm model was used to examine the behavior of feeding disturbances in the single-stage granule PN-A (partial nitrification -ANAMMOX) process. The results indicated that the feeding disturbances could be mitigated by maintaining a small amount of ammonium in the bulk liquid. A cascade control strategy based on DO (dissolved oxygen) manipulation to derive the preset bulk ammonium set-point value (i.e., 2 mg N/L) was shown to be successful in achieving the maximum TN (total nitrogen) removal percentage of above 95% under dynamic feeding conditions. The long-term simulation showed that the small bulk ammonium accumulation could also suppress the NOB (nitrite-oxidizing bacteria) growth.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Compostos de Amônio/análise , Bactérias , Biofilmes , Reatores Biológicos/microbiologia , Nitrificação , Nitrogênio/análise , Oxirredução , Oxigênio/análise , Esgotos , Águas Residuárias/análise
19.
Sci Total Environ ; 722: 137859, 2020 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-32182513

RESUMO

Ammonium is a paradoxical chemical because it is a nutrient but also damages ecosystems at high concentration. As the most eco-friendly method of water restoration, phytoremediation technology still faces great challenges. To provide more theoretical support, we exploited six common submerged macrophytes and selected the most ammonium-tolerant and -sensitive species; then further explored and compared the mechanisms underlying ammonium detoxification. Our results showed the activity of glutamate dehydrogenase (GDH) in the ammonium-tolerant species Myriophyllum spicatum leaves performed a dose-response curve (increased 169% for NADH-dependent GDH and 103% for NADPH-dependent GDH) with the [NH4+-N] increasing from 0 to 100 mg/L while glutamine synthetase (GS) activity slightly changed. But for the ammonium-sensitive species, Potamogeton lucens, the activity of GDH recorded no major changes, while the GS increased slightly (17%). Based on this, we conclude that the alternative pathway of GDH is more important than the pathway catalyzed by GS in determining the tolerance of submerged macrophytes to high ammonium concentration (up to 100 mg N/L). Our present study identifies submerged macrophytes that are tolerant of high concentrations of ammonium and provides mechanistic support for practical water restoration by aquatic plants.


Assuntos
Potamogetonaceae , Compostos de Amônio , Ecossistema , Glutamato Desidrogenase , Glutamato-Amônia Ligase , Nitrogênio
20.
Chemosphere ; 252: 126527, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32213375

RESUMO

Thermophilic nitrification has been proven in lab-scale bioreactors at 50 °C. The challenge is now to develop a solution for thermophilic nitrogen removal, integrating nitrification with denitrification and aerobic carbon removal. This pioneering study aimed at a single-sludge nitrification/denitrification process at 50 °C, through exposing nitrification in a step by step approach to anoxia and/or organics. Firstly, recurrent anoxia was tolerated by a nitrifying community during long-term membrane bioreactor (MBR) operation (85 days), with high ammonium oxidation efficiencies (>98%). Secondly, five organic carbon sources did not affect thermophilic ammonium and nitrite oxidation rates in three-day aerobic batch flask incubations. Moving to long-term tests with sequencing batch reactors (SBR) and MBR (>250 days), good nitrification performance was obtained at increasing COD/Ninfluent ratios (0, 0.5, 1, 2 and 3). Thirdly, combining nitrification, recurrent anoxia and presence of organic carbon resulted in a nitrogen removal efficiency of 92-100%, with a COD/Nremoved of 4.8 ± 0.6 and a nitrogen removal rate of 50 ± 14 mg N g-1 VSS d-1. Overall, this is the first proof of principle thermophilic nitrifiers can cope with redox fluctuations (aerobic/anoxic) and the aerobic or anoxic presence of organic carbon, can functionally co-exist with heterotrophs and that single-sludge nitrification/denitrification can be achieved.


Assuntos
Reatores Biológicos , Compostos de Amônio , Carbono , Desnitrificação , Nitrificação , Nitrogênio , Oxirredução , Esgotos , Eliminação de Resíduos Líquidos
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