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1.
Bioresour Technol ; 312: 123590, 2020 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-32504950

RESUMO

In the anammox process treating low-strength municipal wastewater, the effect of common seasonal temperature variation (15.1 °C-22.2 °C) on performance was studied. In autumn and winter, the nitrogen removal rate (NRR) decrement of 0.038kgN/(m3·d) (17.9 °C â†’ 15.1 °C) was nearly threefold higher than 0.014kgN/(m3·d) (22.2 °C â†’ 17.9 °C), which showed that lower temperature laid more negative impact on nitrogen removal. 15N isotope tracing tests confirmed that the contribution of denitrification to nitrogen removal was far less than anammox, and anammox contributed more at 15.1 °C (91.7%) than 21.9 °C (78.9%). Anammox bacteria could adapt to lower temperature after short-term acclimatization, especially the dominant genus Ca. Brocadia increased from 1.8% to 2.5% and its abundance was significantly correlated with nitrogen consumption (p < 0.05). Above findings suggest that the adaptability of Ca. Brocadia could provide the possibility to maintain nitrogen removal performance at lower temperature. In spring, the improved maximum anammox activity from 2.85 to 3.23mgNH4+-N/(gVSS·h) indicated the recovered removal capacity.

2.
J Hazard Mater ; 399: 122981, 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-32534390

RESUMO

Nitroaromatic compounds (NACs) in the environment can cause serious public health and environmental problems due to their potential toxicity. This study established quantitative structure-toxicity relationship (QSTR) models for the acute oral toxicity of NACs towards rats following the stringent OECD principles for QSTR modelling. All models were assessed by various internationally accepted validation metrics and the OECD criteria. The best QSTR model contains seven simple and interpretable 2D descriptors with defined physicochemical meaning. Mechanistic interpretation indicated that van der Waals surface area, presence of C-F at topological distance 6, heteroatom content and frequency of C-N at topological distance 9 are main factors responsible for the toxicity of NACs. This proposed model was successfully applied to a true external set (295 compounds), and prediction reliability was analysed and discussed. Moreover, the rat-mouse and mouse-rat interspecies quantitative toxicity-toxicity relationship (iQTTR) models were also constructed, validated and employed in toxicity prediction for true external sets consisting of 67 and 265 compounds, respectively. These models showed good external predictivity that can be used to rapidly predict the rat oral acute toxicity of new or untested NACs falling within the applicability domain of the models, thus being beneficial in environmental risk assessment and regulatory purposes.

3.
Chemosphere ; 252: 126624, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32443280

RESUMO

Currently, it is a major challenge for waste water treatment plants (WWTPs) to achieve enhanced nitrogen removal economically and effectively from carbon-limited sewage to meet gradually stringent discharge quality standards. Enhanced nitrogen removal can be achieved by endogenous denitrification (ED) treatment of low C/N municipal sewage, but its application is limited by the slow reaction rate. In this study, a novel process of Sludge Double Recirculation-Anaerobic/Aerobic/Anoxic (SDR-AOA) was developed to improve nitrogen removal efficiency via ED. ED was successfully enhanced by an extra sludge recirculation to post-anoxic zone and the denitrification rate increased from 0.1 to 0.17 kgN/(m3·d). Moreover, the pre-anaerobic zone enhanced the intracellular carbon storage, which might also favor the ED process. Overall, under an influent C/N of 2.67, nitrogen removal efficiency of 97.7% was achieved with effluent total inorganic nitrogen (TIN) of 1.56 ± 1.77 mg/L and nitrogen removal rate (NRR) of 0.14 kgN/(m3·d). Therefore, this study provides a convenient approach to improve the nitrogen removal efficiency of municipal sewage with low C/N.

4.
Bioresour Technol ; 310: 123468, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32386817

RESUMO

In this study, a novel process was developed to treat real sewage with a low chemical oxygen demand/total nitrogen ratio (COD/TN = 3.2) and to obtain enhanced nitrogen removal through Anaerobic ammonia oxidation (anammox). Anaerobic/aerobic/anoxic/aerobic (AOAO) reactor processes were amended with a fixed anammox biofilm in the anoxic zone. During an operational period of 212 days, an average effluent TN of 13.7 mg/L with a removal efficiency of 72.0% was obtained with an influent of 47.0 mg/L ammonium. Mass balance analysis suggested that the anammox resulted in removal of 33.6% of the TN. Besides, by adding sludge fermentation products, nitrite accumulation occurred via nitration while in the aerobic zone for the anammox process. This study demonstrated an alternative way to apply a sewage anammox process via excess sludge fermentation products triggering nitrite production in a continuous flow reactor.


Assuntos
Esgotos , Águas Residuárias , Reatores Biológicos , Desnitrificação , Fermentação , Nitrogênio , Oxirredução
5.
Bioresour Technol ; 310: 123471, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32388357

RESUMO

This study developed a two-stage process, including simultaneous enhanced biological phosphorus-removal and semi-nitritation (EBPR-SN) sequencing batch reactor (SBR), followed by Anammox SBR, to achieve advanced nitrogen (N) and phosphorus (P) removal from real sewage with low carbon/nitrogen (2.82). The long-term operation suggested that removal efficiencies for TIN (86.2 ± 3.5%) and P (95.0 ± 5.5%) were stably obtained, with nitrite accumulation ratio of 98.7% in EBPR-SN SBR. Mechanism analysis indicated contribution of anammox to N-removal being 57.3%-73.7% and superior P-removal due to the majority of removed organics (~74.5%) being stored by polyphosphate-accumulating organisms (PAOs). In EBPR-SN SBR, high-throughput sequencing showed ammonium-oxidizing bacteria was 0.03% while nitrite-oxidizing bacteria was not detected, and PAOs accounted for 30.07%. In Anammox SBR, Candidatus Brocadia (9.75%) was the only anammox bacteria. Remarkably, short aerobic hydraulic retention time (4.29 h) with low DO (0.3-1.2 mg/L) during the whole process provided desirable energy-saving.


Assuntos
Microbiota , Fósforo , Reatores Biológicos , Nitrogênio , Nutrientes , Esgotos
6.
Chemosphere ; 257: 127097, 2020 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-32470541

RESUMO

The feasibility of simultaneous partial nitrification, denitrification and phosphorus removal (SPNDPR) process was investigated in a single-stage anaerobic/micro-aerobic sequencing batch reactor for treating real sewage. Partial nitrification was maintained with average nitrite accumulation ratio of 90.3% during 266 days' operation. Removal efficiencies for NH4+-N (96.3%), total inorganic nitrogen (81.4%), and phosphorus (91.0%) were stably obtained when treated real sewage with low carbon/nitrogen (3.4), with simultaneous partial nitrification and denitrification efficiency of 73.1%. The mechanism analysis revealed that denitrifying glycogen-accumulating organisms (DGAOs) and denitrifying polyphosphate-accumulating organisms (DPAOs) played the main roles in N-removal and P-removal, respectively. Nitrite pathway and optimized use of the organic carbon available in the sewage were keys for the successful performance. Further microbial community illustrating that DGAOs Candidatus_Competibacter, DPAOs Dechloromonas, and ammonia-oxidizing bacteria Nitrosomonadaceae were main functional groups. Notably, sludge granulation was formed under long-term synchronous low dissolved oxygen and low sludge loading conditions, avoiding sludge bulking.

7.
Int J Biol Macromol ; 159: 98-107, 2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32416300

RESUMO

Herein, following the strategy of sustainable, environment protection, circular economy development, carboxylate-modification lignosulfonate polymer (M-LSP) was synthesized from lignosulfonate by solvent-free esterifying with maleic anhydride (MA) by one step, and was used to remove the dyes by adsorption. FT-IR and XPS were used to confirm successful preparation of M-LSP. The result is that: M-LSP is apt to adsorb cationic dye. In single system, the super adsorption performance of M-LSP for methylene blue (MB) is depended on the carboxyl content in M-LSP. M-LSP performs its remarkable adsorption performance for MB stably at pH 7.0 ~ 10.0, and the maximum adsorption capacity of M-LSP for MB is up to 613.5 mg/g according to Langmuir isotherm model. The Langmuir isotherm and pseudo-second-order kinetic models are more suitable to descript adsorption process of M-LSP for MB. In binary and ternary system, the M-LSP adsorbs the cationic dyes simultaneously, but selectively adsorbs MB. M-LSP can effectively remove cationic dyes in simulate dyestuff water. Moreover, the removal percentage of regenerated M-LSP decreases only 8.4% after 4 desorption-resorption cycles. The results indicated that M-LSP could be a candidate for remediation of real printing and dyeing or textile wastewater containing cationic dyes.

11.
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
12.
Biochem Pharmacol ; 177: 113988, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32330495

RESUMO

Chloroethylnitrosoureas (CENUs) are bifunctional antitumor alkylating agents, which exert their antitumor activity through inducing the formation of dG-dC interstrand crosslinks (ICLs) within DNA double strand. However, the complex process of tumor biology enables tumor cells to escape the killing triggered by CENUs, as for instance with the detoxifying activity of O6-methylguanine DNA methyltransferase (MGMT) to accomplish DNA damage repair. Considering the fact that most tumor cells highly depend on aerobic glycolysis to provide energy for survival even in the presence of oxygen (Warburg effect), inhibition of aerobic glycolysis may be an attractive strategy to overcome the resistance and improve the chemotherapeutic effects of CENUs. Especially, 3-bromopyruvate (3-BrPA), a small molecule alkylating agent, has been emerged as an effective glycolytic inhibitor (energy blocker) in cancer treatment. In view of its tumor specificity and inhibition on cellular multiple targets, it is likely to reduce the chemoresistance when chemotherapeutic drugs are combined with 3-BrPA. In this study, we investigated the effects of 3-BrPA on the chemosensitivity of two human hepatocellular carcinoma (HCC) cell lines to the cytotoxic effects of l,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and the underlying molecular mechanism. The sensitivity of SMMC-7721 and HepG2 cells to BCNU was significantly increased by 2 h pretreatment with micromolar dosage of 3-BrPA. Moreover, 3-BrPA decreased the cellular ATP and GSH levels, and extracellular lactate excreted by tumor cells, and the effects were more effective when 3-BrPA was combined with BCNU. Cellular hexokinase-II (HK-II) activity was also reduced after exposure to the treatment of 3-BrPA plus BCNU. Based on the above results, the effects of 3-BrPA on the formation of dG-dC ICLs induced by BCNU was investigated by stable isotope dilution high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The results indicated that BCNU produced higher levels of dG-dC ICLs in SMMC-7721 and HepG2 cells pretreated with 3-BrPA compared to that without 3-BrPA pretreatment. Notably, in MGMT-deficient HepG2 cells, the levels of dG-dC ICLs were significantly higher than MGMT-proficient SMMC-7721 cells. In general, these findings revealed that 3-BrPA, as an effective glycolytic inhibitor, may be considered as a potential clinical chemosensitizer to optimize the therapeutic index of CENUs.

13.
Environ Int ; 139: 105684, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32247103

RESUMO

Starting up or recovering partial nitritation is a major challenge for achieving or maintaining stable partial nitritation/anammox (PN/A) during mainstream wastewater treatment. This study presents a novel strategy for recovering the nitrite pathway by selectively reviving ammonium oxidizing bacteria (AOB) after thoroughly inhibiting AOB and nitrite oxidizing bacteria (NOB) using free nitrous acid (FNA). A sequencing batch reactor was operated for PN/A to treat real domestic wastewater for 423 days, during which twice FNA treatment was temporarily implemented. Results showed that with a single 0.45 mg/L FNA treatment on flocculent sludge, the NO3--N concentration during the aerobic period showed an uptrend again and the partial nitritation performance was deteriorated. In contrast, 1.35 mg/L FNA treatment induced the inhibition of both AOB and NOB leading to regressive ammonium oxidation, but a subsequently higher DO (1.5 mg/L) and longer aeration duration recovered partial nitritation. For the relative abundances of the acquired biomass related to nitrogen conversion, Nitrosomonas, Nitrospira and Nitrolancea increased to 9.65%, 10.27% and 4.35%, respectively, at the beginning of the 1.35 mg/L FNA treatment, and Nitrospira and Nitrolancea decreased to 2.80% and 0.03% whereas Nitrosomonas declined to 8.71% after 76 days. Ca. Brocadia showed less resilience after the 1.35 mg/L FNA treatment, with the relative abundance decreasing from 13.38% to 0.62% due to insufficient nitrite. Molecular ecological network analysis indicates that among anammox taxa, Ca. Kuenenia and Ca. Brocadia formed important links with other N cycle processes. Moreover, the proposed strategy shows operational flexibility because it can be easily used to control NOB in mainstream PN/A applications offered by flocculent sludge systems.

14.
Environ Sci Technol ; 54(10): 6353-6364, 2020 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-32343566

RESUMO

Anaerobic ammonium oxidation (anammox) has attracted extensive attention as a potentially sustainable and economical municipal wastewater treatment process. However, its large-scale application is limited by unstable nitrite (NO2--N) production and associated excessive nitrate (NO3--N) residue. Thus, our study sought to evaluate an efficient alternative to the current nitritation-based anammox process substituting NO2--N supply by partial-denitrification (PD; NO3--N → NO2--N) under mainstream conditions. Ammonia (NH4+-N) was partly oxidized to NO3--N and removed via a PD coupled anammox (PD/A) process by mixing the nitrifying effluents with raw wastewater (NH4+-N of 57.87 mg L-1, COD of 176.02 mg L-1). Excellent effluent quality was obtained with< 5 mg L-1 of total nitrogen (TN) despite frequent temperature fluctuations (25.7-16.3 °C). The genus Thauera (responsible for PD) was the dominant denitrifiers (36.4%-37.4%) and coexisted with Candidatus Brocadia (anammox bacteria; 0.33%-0.46%). The efficient PD/A allowed up to 50% reduction in aeration energy consumption, 80% decrease in organic resource demand, and lower nitrous oxide (N2O) production compared to conventional nitrification/denitrification process. Our study demonstrates that coupling anammox with flexible NO2--N supply has great potential as a stable and efficient mainstream wastewater treatment.

15.
Chemosphere ; 251: 126362, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32151808

RESUMO

In this manuscript, Fe(II) inhibition of anammox and its recovery were investigated, and the performance, kinetics and statistical features were comprehensively studied simultaneously. Anammox was suppressed and completely inhibited by the addition of 109.29 and 378.57 mg/L Fe(II), respectively, via uncompetitive inhibition. Nitrite inhibition of anammox was best fitted by the Edwards model and Aiba model. EDTA-2Na wash (0.5, 1.0, 1.5, and 2.0 mM) had a limited effect on anammox recovery, while the addition of 2.0 mM betaine accelerated anammox recovery. Prolonged betaine addition caused an unintended reduction of anammox activity, though it self-recovered after the withdrawal of betaine. The modified Boltzmann model most accurately simulated the processes of anammox recovery using the EDTA-2Na wash, betaine regulation and self-recovery, and the modified Stover-Kincannon model was able to assess the results of anammox recovery. The one-sample t-test was successfully applied to determine the effects of these three recovery strategies on inhibited anammox, which were short-term disinhibition or long-term recovery effects. The above-mentioned results demonstrate that an intermittent addition of betaine, which is a better alternative to frequently-used but poorly-degradable EDTA, may be a useful and environmentally friendly recovery strategy for Fe(II)-inhibited anammox reactor.


Assuntos
Betaína/química , Compostos Ferrosos/química , Modelos Químicos , Anaerobiose , Reatores Biológicos , Cinética , Nitrogênio , Oxirredução
16.
Bioresour Technol ; 306: 123108, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32169510

RESUMO

The dynamic response mechanism of Candidatus Accumulibacter clades to environmental factors in enhanced biological phosphorus removal (EBPR) was unclear. This study investigated the relationship between the transcriptional responses of Candidatus Accumulibacter clades and environmental dynamics. Results suggested that Candidatus Accumulibacter clade IIA only responded in initial 20 and 30 min of P-release and P-uptake stage, respectively, and was also the first clade to stop responding among the six Candidatus Accumulibacter clades. Clade IIC and IID responded at rising stage of P-release and P-uptake rate. Clade IA and IIB responded at decreasing stage of P-release and P-uptake rate. The transcriptional response duration of clade IIF was the longest, which constantly responded throughout anaerobic, anoxic and oxic phase. The transcriptional responses of Candidatus Accumulibacter clades to environmental dynamics revealed the microorganisms actually working in P-release and P-uptake, and gave a new insight into the transcriptional responses related to the EBPR performance.

17.
Bioresour Technol ; 306: 123119, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32192962

RESUMO

A novel partial nitrification-Anammox biofilm reactor (PNABR) operated under high dissolved oxygen (DO) with pre-anoxic - aerobic - anoxic operational mode was developed for efficient denitrogenation from mature landfill leachate. With DO concentration gradually increasing to 4.03 ± 0.03 mg/L, the ammonia oxidation rate (AOR) was enhanced to 25.8 mgNH4+-N/(L h), while nitrite oxidation bacteria (NOB) was inhibited effectively by alternating free ammonia (FA) and oxygen starvation. DO micro-distribution revealed that estimated 1900 µm of aerobic biofilm could protect anammox biofilm underneath from being inhibited by high DO. qPCR analysis further suggested that ammonia oxidation bacteria (AOB) abundance in whole biofilm was 6.12 × 109 gene copies/(g dry sludge), which was twice than found in the floc. Anammox bacteria accounted for 2.39% of total bacteria in whole biofilm, contributing 90.0% to nitrogen removal. Nitrogen removal rate (NRR) and nitrogen removal efficiency (NRE) finally reached 396.6 gN/(m3 d) and 96.1%, respectively.

20.
Bioresour Technol ; 305: 123083, 2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-32145699

RESUMO

A long-term experiment in an anaerobic ammonium oxidation (anammox) reactor showed that anammox consortia could perform a stable and efficient Fe(II)-dependent dissimilatory nitrate reduction to ammonium (DNRA) coupled to the anammox (DNRA-anammox) process by controlling the EDTA-2Na/Fe(II) ratio and pH, with a total nitrogen removal rate (TNRR) of 0.23 ± 0.01 kg-N/m3/d. Anammox bacteria (Candidatus Kuenenia) were the dominant and functional microbes in such a nitrate wastewater treatment system. Visual MINTEQ analysis showed that the EDTA-2Na/Fe(II) molar ratio affected the influent composition of Fe and EDTA species and hence nitrate removal, while pH influenced both nitrate removal and the coupling degree of the Fe(II)-dependent DNRA-anammox process due to its own physiology. The kinetic simulation results showed that excess EDTA-2Na imposed a competitive inhibition on the Fe(II)-dependent DNRA-anammox process, and the Bell-shaped (A), (B), (C) and Ratkowsky models could be used to explore the pH dependency of the Fe(II)-dependent DNRA-anammox process.

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