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1.
Sci Total Environ ; 750: 141665, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33182169

RESUMO

Reusing microplastics and zeolite waste as free ammonia (FA)-mitigating carrier particle was proven a value-added step towards promoting the serviceability of fluidized bed bioreactor (FBBR) in treating wastewater with a low carbon to nitrogen ratio (i.e. C/N <3.0) in this study. Ammonia (NH4+) adsorption property capacitates zeolite as an FA mitigator. The microplastics and reused zeolite were processed into reused-zeolite/microplastic composite particle (RZ), whose merit of FA mitigation was fully developed via an optimally thermal modification to process modified-zeolite/microplastic particle (MZ). The 171-day biological nutrient removal (BNR) performance in a single integrated fluidized bed bioreactor (SIFBBR) shows that the bioreactor with MZ particle (SIFBBR-MZ) achieved nitrogen removal efficiency 10.0% higher than the bioreactor with RZ particle (SIFBBR-RZ) over the enhanced short-cut nitrification and denitrification. Analysis of microbial community structure unveils that the long-term lower FA inhibition favored more significant ammonia-oxidizing bacteria (AOB) enrichment and acclimated specific MZ biofilm predominant by nitrite (NO2-) denitrifier, contributing to the outperformance in nitrogen removal. Apart from fluidization energy conservation, the techno-economic analysis confirms that using MZ as an FA-mitigating carrier could be of great benefit for FBBR system: realizing waste utilization, reducing carbon addition and alleviating sludge treatment.


Assuntos
Nitrogênio , Águas Residuárias , Amônia , Reatores Biológicos , Carbono , Desnitrificação , Nitrificação , Plásticos , Eliminação de Resíduos Líquidos
2.
Sci Total Environ ; 750: 142296, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33182197

RESUMO

This study proposed a novel one-stage plug-flow microaerobic sludge blanket (PMSB) with membrane aerated for treating low carbon to nitrogen (C/N) ratio municipal sewage. The performance of simultaneous nitrification, denitrification, and anammox in the reactor was investigated. The results illustrated that the removal efficiencies of ammonium and total nitrogen (TN) were 93.2% and 87.1% with a C/N ratio of 4. High throughput sequencing revealed that aerobic bacteria, anaerobic bacteria and facultative anaerobe could co-exist at the same time in the sludge blanket. Meanwhile, a notable correlation between the oxygen concentration and the distance of the membrane module was analyzed. It was shown that the microbial community of functional bacteria developed in different aeration sites due to the oxygen concentration gradient. Microbial community structure was analyzed depending on the sludge stratification in the sludge blanket.


Assuntos
Nitrificação , Esgotos , Reatores Biológicos , Desnitrificação , Nitrogênio , Oxirredução
3.
Sci Total Environ ; 753: 141746, 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-33207482

RESUMO

This study explored the effects of adding phosphogypsum (PPG), medical stone (MS), and both (PPM) during composting on nitrogen transformation, nitrogen functional genes, the bacterial community, and their relationships with NH3 and N2O emissions. Adding MS and PPM reduced NH3 emissions by 25.78-68.37% and N2O emissions by 19.00-42.86%. PPG reduced NH3 emissions by 59.74% but slightly increased N2O emissions by 8.15%. MS was strongly correlated with the amoA-dominated nitrification process. PPG and PPM had strong correlations with nirS- and nirK-dominated, and nosZ-dominated denitrification processes, respectively. PPM promoted nitrification and denitrification processes more than PPG and MS. Different functional bacteria had key roles in nitrification and denitrification during different composting stages. Firmicutes probably contributed to the conversion and release of nitrogen in the thermophilic period, whereas Proteobacteria, Chloroflexi, Bacteroidetes, and other phyla might have played important roles in the cooling and maturation periods. PPM obtained the greatest reductions in NH3 and N2O release via the regulation of environmental variables, nitrogen functional genes, and the bacterial community. Overall, these results provide insights at a molecular level into the effects of PPG and MS on nitrogen transformation and NH3 and N2O emissions during composting.


Assuntos
Compostagem , Bactérias/genética , Sulfato de Cálcio , Desnitrificação , Genes Bacterianos , Nitrificação , Nitrogênio , Óxido Nitroso/análise , Fósforo , Solo
4.
Sci Total Environ ; 752: 141885, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-32890835

RESUMO

In agriculture, the applied nitrogen (N) can be lost in the environment in different forms because of microbial transformations. It is of special concern the nitrate (NO3-) leaching and the nitrous oxide (N2O) emissions, due to their negative environmental impacts. Nitrification inhibitors (NIs) based on dimethylpyrazole (DMP) are applied worldwide in order to reduce N losses. These compounds delay ammonium (NH4+) oxidation by inhibiting ammonia-oxidizing bacteria (AOB) growth. However, their mechanism of action has not been demonstrated, which represent an important lack of knowledge to use them correctly. In this work, through chemical and biological analysis, we unveil the mechanism of action of the commonly applied 3,4-dimethyl-1H-pyrazole dihydrogen phosphate (DMPP) and the new DMP-based NI, 2-(3,4-dimethyl-1H-pyrazol-1-yl)-succinic acid (DMPSA). Our results show that DMP and DMPSA form complexes with copper (Cu2+) cations, an indispensable cofactor in the nitrification pathway. Three coordination compounds namely [Cu(DMP)4Cl2] (CuDMP1), [Cu(DMP)4SO4]n (CuDMP2) and [Cu(DMPSA)2]·H2O (CuDMPSA) have been synthesized and chemical and structurally characterized. The CuDMPSA complex is more stable than those containing DMP ligands; however, both NIs show the same nitrification inhibition efficiency in soils with different Cu contents, suggesting that the active specie in both cases is DMP. Our soil experiment reveals that the usual application dose is enough to inhibit nitrification within the range of Cu and Zn contents present in agricultural soils, although their effects vary depending on the content of these elements. As a result of AOB inhibition by these NIs, N2O-reducing bacteria seem to be beneficed in Cu-limited soils due to a reduction in the competence. This opens up the possibility to induce N2O reduction to N2 through Cu fertilization. On the other hand, when fertilizing with micronutrients such as Cu and Zn, the use of NIs could be beneficial to counteract the increase of nitrification derived from their application.


Assuntos
Nitrificação , Óxido Nitroso , Agricultura , Fertilizantes/análise , Óxido Nitroso/análise , Solo , Microbiologia do Solo
5.
Mar Pollut Bull ; 160: 111671, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33181944

RESUMO

This study investigated the co-effect of microplastic polyvinylchloride and antibiotics tetracycline to partial nitrification process in treating high ammonia wastewater. The average ammonia oxidation rate of all reactors was 53.58, 56.17 and 42.08 mg·N/L·h in round 1, round 7 and round 13, respectively. The ammonia oxidation rate was reduced to 89.40%, 79.08%, 80.60%, 73.37%, 69.50%, 75.72%, 98.93% and 66.04% from 1st round of test to 13th round of test at reactor R1 to R8. The average nitrosation rate was always over 80% in all conditions tested. Tetracycline removal rate was attributed to sludge adsorption in all reactors and was increased continuously with the increment of tetracycline concentration. The nitrous oxide emission was keep decreasing from round 1 to round 13 in all reactors tested. The microbial community results revealed that with the existence of tetracycline and microplastics, the relative abundance of Bacteroidetes were reduced and Proteobacteria were increased.


Assuntos
Nitrificação , Plásticos , Amônia , Antibacterianos , Reatores Biológicos , Microplásticos , Oxirredução , Esgotos
6.
Water Sci Technol ; 82(9): 1795-1807, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33201844

RESUMO

A micro-pressure swirl reactor (MPSR) was developed for carbon and nitrogen removal of wastewater, in which dissolved oxygen (DO) gradient and internal circulation could be created by setting the aerators along one side of the reactor, and micro-pressure could be realized by sealing most of the top cap and increasing the outlet water level. In this study, velocity and DO distribution in the reactor was measured, removal performance treating high-concentration wastewater was investigated, and the main functional microorganisms were analyzed. The experiment results indicated that there was stable swirl flow and spatial DO gradient in MPSR. Operated in sequencing batch reactor mode, distinct biological environments spatially and temporally were created. Under the average influent condition of chemical oxygen demand (COD) concentration of 2,884 mg/L and total nitrogen (TN) of 184 mg/L, COD removal efficiency and removal loading was 98% and 1.8 kgCOD/(m3·d) respectively, and TN removal efficiency and removal loading reached up to 90% and 0.11 kgTN/(m3·d) respectively. With efficient utilization of DO and simpler configuration for simultaneous nitrification and denitrification, the MPSR has the potential of treating high-concentration wastewater at lower cost.


Assuntos
Nitrogênio , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Desnitrificação , Nitrificação , Eliminação de Resíduos Líquidos
7.
J Environ Qual ; 49(5): 1445-1452, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33016443

RESUMO

Volatilization of NH3 following urea application or livestock urine deposition can result in significant loss of N to the environment. Urea hydrolysis to NH4 + results in an increase in pH, which in turn promotes transformation of NH4 + to NH3 . Accurately predicting changes in soil pH following urea (or urine) application will allow successful simulation of NH3 volatilization. The magnitude of the pH change depends on the soil's pH buffering capacity (pHBC). However, as actual pHBC values are not generally available, pHBC proxies (e.g., cation exchange capacity) have been used in modeling studies. In a 34-d laboratory incubation study, we measured soil pH and mineral N (NH4 + and NO3 - ) following a large application of urea (800 mg N kg-1 soil) to four soils with a range of pHBC values. In a second incubation, pH changes and mineral N dynamics were monitored in soil treated with sheep urine (773 mg N kg-1 soil) in the absence and presence of the nitrification inhibitor dicyandiamide. In both incubations, pH changes associated with urea hydrolysis and subsequent nitrification of NH4 + were predicted well using measured pHBC data. Our results confirmed that pHBC is base-type dependent (values greater when measured using KOH than NH4 OH). Soil pHBC is easily measured, and the use of a measured value (determined using NH4 OH) can improve model simulations of pH in the field and, potentially, lead to improved estimates of NH3 loss from animal-deposited urine patches and urea-treated soil.


Assuntos
Solo , Ureia , Animais , Concentração de Íons de Hidrogênio , Nitrificação , Ovinos , Volatilização
8.
Water Sci Technol ; 82(6): 1070-1080, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055397

RESUMO

A novel coupling process using an aerobic bacterial reactor with nitrification and sulfur-oxidization functions followed by a microalgal reactor was proposed for simultaneous biogas desulfurization and anaerobic digestion effluent (ADE) treatment. ADE nitrified by bacteria has a potential to be directly used as a culture medium for microalgae because ammonium nitrogen, including inhibitory free ammonia (NH3), has been converted to harmless NO3-. To demonstrate this hypothesis, Chlorella sorokiniana NIES-2173, which has ordinary NH3 tolerance; that is, 1.6 mM of EC50 compared with other species, was cultivated using untreated/treated ADE. Compared with the use of a synthetic medium, when using ADE with 1-10-fold dilutions, the specific growth rate and growth yield maximally decreased by 44% and 88%, respectively. In contrast, the algal growth using undiluted ADE treated by nitrification-desulfurization was almost the same as with using synthetic medium. It was also revealed that 50% of PO43- and most metal concentrations of ADE decreased following nitrification-desulfurization treatment. Moreover, upon NaOH addition for pH adjustment, the salinity increased to 0.66%. The decrease in metals mitigates the bioconcentration of toxic heavy metals from wastewater in microalgal biomass. Meanwhile, salt stress in microalgae and limiting nutrient supplementation, particularly for continuous cultivation, should be of concern.


Assuntos
Chlorella , Microalgas , Anaerobiose , Nitrificação , Águas Residuárias
9.
Huan Jing Ke Xue ; 41(11): 5037-5049, 2020 Nov 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124247

RESUMO

The aim of this study was to characterize the changes of the microbial community in WWTPs based on hybrid-MBBR process in the Yangtze River Delta in a low temperature season, and to obtain the regularity of the microbial distribution. High-throughput sequencing of Illumina miSeq was conducted to analyze the microbial community structure of activated sludge and suspended carrier biofilm in the aerobic area of five WWTPs. The results showed that the number of microbial species in the suspended carrier biofilm was lower than that of the activated sludge in the same plant, and the species distribution was more uneven. The addition of a suspended carrier can improve the microbial diversity of the system, while the influent and operation mode have a certain selectivity to the microbial community composition of the system. The bacteria with high relative abundance in each plant primarily included Nitrospira, Mycobacterium, Defluvicoccus, Hyphomacrobium, and Macrocharacters,etc. The addition of suspended carriers significantly enhanced the enrichment of Nitrospira. The amount of nitrifying bacteria in the suspended carrier accounted for 86.12%-95.36% of that of the whole system. A certain relative abundance of denitrifying bacteria was detected in the suspended carrier in the aerobic area of each plant. Combined with the results of the measurement of water quality along the process and the lab-scale experiment, it was confirmed that significant SND occurred on the suspended carrier biofilm in the aerobic area, which enhanced the TN removal of the system.


Assuntos
Reatores Biológicos , Nitrificação , Biofilmes , Desnitrificação , Nitrogênio/análise , Rios , Estações do Ano , Esgotos , Temperatura
10.
Huan Jing Ke Xue ; 41(11): 5097-5105, 2020 Nov 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124253

RESUMO

A continuous flow reactor was inoculated at 25-28℃ with mature partial nitrification granular sludge. In order to avoid the granular sludge being crushed because of the sludge backflow through the peristaltic pump, a built-in sedimentation zone was used for internal backflow. The experiment investigated the influence of the different anaerobic time to aeration time ratio (1:1, 2:1, and 1:2) on the stability of a continuous-flow partial nitrification granular sludge system. The results showed that when the controlled anaerobic time to aeration time ratio was 1:1 and 2:1, the partial nitrification performance was good and the nitrite accumulation rates were 85.2% and 94.5%, respectively. When the controlled anaerobic time to aeration time ratio was 1:2, the partial nitrification performance gradually deteriorated, and the ammonia nitrogen removal rate and nitrite accumulation rate at the end of the stage decreased to 64.1% and 58.7%, respectively. Batch test results showed that intermittent aeration and continuous aeration can better inhibit the relative activity of NOB in the partial nitrification system to a certain extent. The longer the anaerobic time, the better the NOB activity inhibition. However, too long an anaerobic time will also lead to ammonia nitrogen removal rate. In the process of partial nitrification, the long-term stable operation of continuous flow partial nitrification process can be realized by 1:1 and coordinated control of other control conditions. An analysis of sludge performance indicated that in the anaerobic time to aeration time ratio range of 1:1-1:2, the longer the anaerobic time, the more stable the granular sludge structure. The shorter the anaerobic time, the smaller the selection pressure in the reactor, resulting in poor sludge sedimentation performance and partial disintegration of partial nitrification granular sludge. An EPS chemical analysis and a three-dimensional fluorescence spectroscopic analysis showed that the PN content was higher and the PN/PS value was higher when the anaerobic time and aeration time ratio was 2:1.


Assuntos
Reatores Biológicos , Nitrificação , Anaerobiose , Nitritos , Nitrogênio , Esgotos
11.
Huan Jing Ke Xue ; 41(8): 3691-3698, 2020 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124343

RESUMO

The long-term effects of a decreasing temperature on the nitrification performance, biofilm characteristics, and nitrifier community in a moving-bed biofilm reactor (MBBR) and integrated fixed-film activated sludge (IFAS) system were investigated at various temperatures (20, 15, and 10℃) to explore the adaptability of nitrifying biofilm systems to low temperatures. During the experiment, the extracellular polymeric substances (EPS) in the biofilms increased with decreasing temperature, which resulted in an increased biofilm mass and thickness. As there was only a biofilm phase in the MBBR to remove ammonia, the part of the carriers in the MBBR at 10℃ became plugged, which partially led to a deterioration in the effluent water quality. This indicated that the IFAS system was more adaptable to low temperatures than was the MBBR. Meanwhile, the results for the nitrifier activities showed that, although the nitrification contribution rate of the suspended phase in the IFAS system always dominated during the experiment, that of the fixed phase with regards to the ammonia uptake rate (AUR) gradually increased from 30.72% at 20℃ to 39.85% at 10℃. This indicated that the biofilm played an enhanced role in nitrification in the IFAS system. Moreover, the qPCR results revealed that the nitrifier copies of the number of biofilms increased slightly with decreased temperature, and coincided with an increase in biomass, which partially compensated for the decreased nitrification activity. These findings provide a theoretical basis for the application of the biofilm systems to wastewater treatment.


Assuntos
Biofilmes , Esgotos , Reatores Biológicos , Nitrificação , Temperatura
12.
Huan Jing Ke Xue ; 41(8): 3707-3714, 2020 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124345

RESUMO

In this study, three SBR reactors R1, R2, and R3 were set up and operated using (A/O)3-SBR gradient aeration, (A/O)3-SBR constant aeration, and the conventional (A/O)-SBR mode, respectively. The nutrient removal performance and aerobic granular sludge characteristics under these aeration modes were explored using real municipal wastewater as the influent matrix. The experimental results revealed that for the R1, R2, and R3 particles during the stable period, the average removal rate of COD was 88.68%, 89.05%, and 88.96%, respectively, the average removal rate of TN was 76.97%, 71.99%, and 64.92%, respectively, the average removal rate of TP was 96.28%, 85.05%, and 78.97%, respectively, and the proportion of denitrifying phosphorus accumulating bacteria to phosphorus accumulating bacteria was 25.52%, 19.60%, and 12.77%, respectively. The results showed that the operation mode of anaerobic, aerobic, and anoxic was more conducive to the enrichment of denitrifying phosphorus accumulating bacteria (DPAOs), and that the gradient aeration was more enriched than the constant aeration mode, which is of great significance to low-intensity municipal domestic sewage treatment with an insufficient carbon source. At the same time, the dissolved oxygen in the aeration section of R1 was reduced step-by-step, which improved the simultaneous nitrification and denitrification rates of particles and the utilization rate of the internal carbon source, which was beneficial for the efficient removal of TN. The particle size of the three groups of reactors was 727.368, 815.072, and 895.041 µm respectively. As the transfer rate of the matrix decreased with particle size, the microorganisms in R2 and R3 may have caused anaerobic respiration to release harmful gas, thus damaging the particle structure, such that the particles in R2 and R3 were less dense than those in R1. In addition, the PN/PS values of R1, R2, and R3 were 6.31, 5.63, and 4.83, respectively, and the EPS content (in terms of VSS) was 103.97, 92.22, and 76.98 mg·g-1, respectively, at the time of particle stabilization, which revealed that the mode of intermittent gradient aeration was beneficial to stimulate the secretion of EPS. This was especially the case for the secretion of PN, which increased the PN/PS value, enhanced the cell hydrophobicity, and made the particles dense and stable.


Assuntos
Fósforo , Esgotos , Reatores Biológicos , Desnitrificação , Nitrificação , Nitrogênio , Eliminação de Resíduos Líquidos
13.
Huan Jing Ke Xue ; 41(8): 3765-3772, 2020 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124352

RESUMO

The effective inhibition of nitrite oxidizing bacteria (NOB) is the key to realizing satisfactory nitrite accumulation and achieving effective nitritation. In order to explore the selective effect of hydroxylamine (NH2 OH) on ammonia oxidizing bacteria (AOB) and NOB, a sequencing batch reactor (SBR) with the operation mode of anaerobic/aerobic/anoxia (A/O/A) was used to observe the start-up of nitritation at different concentrations and frequencies of NH2 OH. The results showed that when 5 mg·L-1 of NH2 OH was added once every 2 cycles, the nitrite accumulation rate (NAR) increased from 0.1% to 57.4% in 6 days, and was maintained at (62.0±4.6)% until the end of the trials. In the typical cycle on day 6, the NN4+-N dropped from 26.05 mg·L-1 to 8.06 mg·L-1, thus producing 9.02 mg·L-1 of NO2--N and 6.70 mg·L-1 of NO3--N. Meanwhile, the ratio of the maximum activity of AOB (rAOB) to NOB (rNOB) increased from 1.05 on day 1 to 4.22 on day 9. Moreover, qPCR results indicated that the abundance of AOB and NOB decreased to 30.2% and 19.1%, respectively, on day 9 in comparison to the original sample. The results indicate that the selective effect of AOB and NOB based on NH2 OH is expected to provide a feasible application for the rapid start-up nitritation of municipal wastewater.


Assuntos
Amônia , Nitritos , Bactérias/genética , Reatores Biológicos , Hidroxilamina , Hidroxilaminas , Nitrificação , Oxirredução , Esgotos
14.
Huan Jing Ke Xue ; 41(8): 3787-3796, 2020 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124355

RESUMO

The ammonia oxidation process is a rate-limiting step in nitrification. Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are the major drivers of ammonia oxidation. Their distribution and relative contributions to nitrification are the research highlights in the nitrogen cycle. Real-time quantitative polymerase chain reaction (qPCR) was used to study the distribution of aerobic ammonia-oxidizing microorganisms in the surface sediments of mangrove in the Sanya River, and the relative contribution rates of AOB and AOA to nitrification were calculated through the determination of the potential nitrification rates (PNR). The results showed that, in most sampling sites, the abundance of AOA amoA genes was higher than that of AOB amoA genes. The abundance of AOB was higher during the winter, whereas that of AOA was higher during the summer, and the ratio of AOA to AOB abundance was lower during the winter. The dissolved oxygen (DO) content, pH, total organic carbon (TOC) content, and nitrate concentration greatly influenced the abundance of AOB and AOA. The potential nitrification rates of AOB and AOA were both higher during the summer than during the winter, and the relative contribution rate of AOA to nitrification was higher during the winter, whereas that of AOB was higher during the summer. There were no significant correlations between the PNR and amoA genes abundance of AOB and AOA.


Assuntos
Amônia , Nitrificação , Archaea/genética , Bactérias/genética , Oxirredução , Filogenia , Rios , Microbiologia do Solo
15.
Huan Jing Ke Xue ; 41(10): 4644-4652, 2020 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124397

RESUMO

To promote the application of ANAMMOX process in landfill leachate treatment, a pilot reactor based on the ANAMMOX process was established at a landfill site. In this paper, we aim to further analyze the influence of different coupling modes of denitrification (DN) and partial nitrification and ANAMMOX (PN-ANAMMOX) on the diversity of microbial community. The DN+(PN-ANAMMOX) process could effectively treat the mature leachate. However, with an increase in organic matter in the influent, the oxygen demand of PN zone increased, and the enrichment of Nitrosomonadaceae in the PN zone was limited. The lack of substrate supply for ANAMMOX zone further limited the enrichment of Brocadiaceae as well; thus, the total nitrogen removal rate (TNRR) remained at 0.44 kg ·(m3 ·d)-1. In the DN-(PN-ANAMMOX) process, Saprospiraceae with denitrifying ability was enriched in the DN zone, and the organic matter was gradually degraded and removed; thus, a good low-carbon environment was provided for the subsequent PN-ANAMMOX process. Nitrosomonadaceae and Brocadiaceae were enriched in the functional zones, and the TNRR and total nitrogen removal efficiency (TNRE) of the DN-(PN-ANAMMOX) were further elevated to 0.55 kg ·(m3 ·d)-1 and 94.65%, respectively. Moreover, the direct treatment of mature leachate with 2233 mg ·L-1 NH4+-N and 2712 mg ·L-1 COD was finally realized. In addition, Candidatus Kuenenia was better adapted to leachate and high substrate concentration wastewater, and it became the dominant genus in the ANAMMOX zone.


Assuntos
Microbiota , Poluentes Químicos da Água , Reatores Biológicos , Desnitrificação , Nitrificação , Nitrogênio , Oxirredução
16.
Water Sci Technol ; 82(5): 954-966, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33031073

RESUMO

The sewage treatment system in this study was operated with only the first stage of a French system of vertical wetlands, composed of two units in parallel and running with an extended feeding cycle (7 days). This research sought to evaluate and relate continuous variables measured in situ (dissolved oxygen (DO), pH and redox potential) throughout the feeding cycle, with measurements at distinct heights along the filter vertical profile. Additionally, the influence of the surface organic sludge deposit was investigated. A close link between the hydraulic behaviour and the effluent quality was verified, with both being related to the batch volume and the instantaneous hydraulic loading rate. The drop in DO as the feed days progressed could be related to the loss of hydraulic conductivity. A thicker sludge layer decreased the aeration capacity of the filter. The effluent was observed to be aerated when percolating through the medium. DO and pH data suggested that nitrification varied along the filter depth, the batch duration and the feed cycle. The monitored parameters may be indicative of the behaviour of other parameters.


Assuntos
Esgotos , Áreas Alagadas , Clima , Nitrificação , Oxigênio
17.
Bioresour Technol ; 317: 124037, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32866838

RESUMO

A two-stage anoxic/oxic combined membrane bioreactor (A/O-A/O-MBR) was operated for 81 d to treat landfill leachate under different reflux ratios (R). The best performance was found under R = 150%, where the chemical oxygen demand (COD), ammonium (NH4+-N) and total nitrogen (TN) removal was 85.6%, 99.3%, and 80.7%, respectively. Particularly, the highest pollutant removal was achieved in the second-stage A/O, where the COD and TN removal capacity was 78.88 and 11.74 g/d, respectively. Meantime, DOM removal was 83.9%, where the removal of aromatic protein substances I and II, fulvic acids-like compounds, soluble microbial products and humic acids-like compounds was 93.4%, 86.4%, 72.0%, 86.6% and 59.4%, respectively. The gene functions of microbial community in the process showed that amoA, hao, nirK and nosZ, etc. were the core genes for nitrification and denitrification. The carbon source for denitrification might come from the conversion of refractory organic matters in landfill leachate.


Assuntos
Nitrogênio , Poluentes Químicos da Água , Bactérias/genética , Reatores Biológicos , Desnitrificação , Nitrificação
18.
Sci Total Environ ; 741: 140494, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886976

RESUMO

Here, we examined the effects of low and high concentrations of perfluorooctanesulfonate (PFOS) on rhizosphere soil N cycling processes in the presence of Lythrum salicaria and Phragmites communis over 4 months. Compared with the control group, the nitrate nitrogen (NO3--N) content of the bulk soil in the low PFOS (0.1 mg kg-1) treatment significantly decreased (27.7%), the ammonium nitrogen (NH4+-N) content significantly increased (8.7%), and the pH value and total organic carbon (TOC) content slightly increased (0.3% and 1.1%, respectively). Compared with the low PFOS treatment, the content of NO3-N, NH4+-N and pH value in the bulk soil of the high PFOS treatment (50 mg kg-1) significantly increased (1.0%, 53.8% and 61.8%, respectively), and the TOC content significantly decreased (8.2%). Soil protease levels were high in the low PFOS treatment, but low in the high PFOS treatment. PFOS produced inverted U-shaped responses in the potential nitrification (1.5, 3.0, and 1.1 mg N d-1 kg-1 in no, low, and high PFOS, respectively), denitrification (0.19, 0.30, and 0.22 mg N d-1 kg-1 in no, low, and high PFOS, respectively), and N2O emission rates (0.01, 0.03, and 0.02 mg N d-1 kg-1 in no, low, and high PFOS, respectively) of bulk soil. The abundance of the archaea amoA gene decreased with increasing PFOS concentration, whereas that of bacterial amoA increased; inverted U-shaped responses were observed for narG, nirK, nirS, and nosZ. In the PFOS-contaminated rhizosphere soil, the observed changes differed from those in the bulk soil and differed between treatments. P. communis tended to upregulate each step of the nitrogen cycle under low PFOS conditions, whereas L. salicaria tended to inhibit them. Under high PFOS conditions, both test plants tended to act as inhibitors of the soil N-cycle; thus, the effects of PFOS on soil N transformation were plant-specific.


Assuntos
Rizosfera , Solo , Ácidos Alcanossulfônicos , Desnitrificação , Fluorcarbonetos , Nitrificação , Nitrogênio/análise , Ciclo do Nitrogênio , Microbiologia do Solo
19.
Water Sci Technol ; 82(1): 120-130, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32910797

RESUMO

In order to investigate the effect of temperatures and operating modes on extracellular polymeric substances (EPS) contents, three sequencing batch reactors (SBRs) were operated at temperatures of 15, 25, and 35 °C (R15 °C, R25 °C, and R35 °C, respectively), with two SBRs operated under alternating anoxic/oxic conditions (RA/O and RO/A, respectively). Results showed that higher contents of tightly bound EPS (TB-EPS) and total EPS appeared in R15 °C, while loosely bound EPS (LB-EPS) dominated in R35 °C. In all three kinds of EPS (LB-EPS, TB-EPS and total EPS) assessed, protein was the main component in R15 °C and R25 °C, while polysaccharides dominated in R35 °C. Moreover, compared with RO/A, RA/O was favorable for the production of the three kinds of EPS. Furthermore, three kinds of EPS and their components were augmented during the nitrification process, while they declined during the denitrification process under all conditions except for R35 °C.


Assuntos
Matriz Extracelular de Substâncias Poliméricas , Esgotos , Reatores Biológicos , Nitrificação , Temperatura
20.
Sheng Wu Gong Cheng Xue Bao ; 36(8): 1493-1503, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32924348

RESUMO

Nitrite is a by-product of the nitrogen cycle. The excessive nitrite not only constrains growth and metabolism of bacteria, but also impairs health of humans and aquatic organisms. On the other hand, the continuous maintaining of nitrite accumulation could achieve the shortcut nitrification process, and reduce energy consumption of biological nitrogen removal to save cost. This article reviews the biological processes and causes of nitrite accumulation in the water environment, and summarizes the factors that affect the accumulation of nitrite, to provide reference for wastewater treatments, including improving the nitrogen removal efficiency, reducing operating costs, decreasing discharge of sewage and nitrite nitrogen in natural water.


Assuntos
Nitritos , Poluentes Químicos da Água , Água , Reatores Biológicos , Nitrificação , Nitritos/metabolismo , Esgotos , Água/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
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