•Anammox granules were fast-transformed using a nitrification-denitrification sludge.•Maximum nitrogen removal rate of the EGSB reactor reached 7.25±0.16 gN/L/d.•Candidatus Brocadia and Candidatus ...Kuenenia were enriched in the sludge.•Anammox bacteria abundance increased from 2.5% to 29.0% after 300 days.
A lengthy start-up period has been one of the key obstacles limiting the application of the anammox process. In this investigation, a nitrification-denitrification sludge was used to start-up the anammox EGSB process. The transformation process from nitrification-denitrification sludge to anammox granule sludge was explored through the aspects of nitrogen removal performance, granule properties, microbial community structure, and evolution route. A successful start-up of the anammox process was achieved after 94 days of reactor operation. The highest nitrogen removal rate (NRR) obtained was 7.25±0.16 gN/L/d at a nitrogen loading rate (NLR) of 8.0 gN/L/d, and the corresponding nitrogen removal efficiency was a high 90.61±1.99%. The results of the microbial analysis revealed significant changes in anammox bacteria, nitrifying bacteria, and denitrifying bacteria in the sludge. Notably, the anammox bacteria abundance increased from 2.5% to 29.0% during the operation, and Candidatus Kuenenia and Candidatus Brocadia were the dominant genera. Distinct-different successions on Candidatus Brocadia and Candidatus Kuenenia were also observed over the long-term period. In addition, the settling performance, anammox activity and biomass retention capacity of the granules were significantly enhanced during this process, and the corresponding granule evolution route was also proposed. The results in this study indicate the feasibility of using available seed sludge source for the fast-transformation of anammox granules, it is beneficial to the large-scale application of anammox process and the utilization of excess sludge.
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•A concept of AnMBR-PN/A process was proposed for mainstream treatment.•In-situ FA/FNA exposure eliminated Nitrospira while retained Nitosonomas community.••DO limitation prevented switch of the NOB ...community in the mainstream conditions.•The effluent TN of the mainstream PN/A system was lower than 10 mg-N/L.•Enhanced hydrodynamic shear force resulted in sludge settleability deterioration.
In this pilot-scale study, an innovative mainstream treatment process that couples the anaerobic membrane reactor (AnMBR) with a one-stage PN/A system was proposed for advancing the concept of carbon neutrality in the municipal wastewater treatment plant. This work demonstrates the start-up procedure of a pilot-scale one-stage PN/A system for mainstream treatment. The 255-day start-up of the one-stage PN/A system involved the cultivation of ammonium-oxidizing bacteria (AOB) from the activated sludge, suppression of nitrite-oxidizing bacteria (NOB), investigation of in-situ growth kinetics of anammox bacteria (AnAOB), and the 50-day operation of the pilot-scale AnMBR-PN/A process for natural mainstream treatment. It is verified in the pilot-scale system for the first time that the in-situ free ammonia (FA) and free nitrous acid (FNA) exposure could effectively eliminate the Nitrospira (the NOB genus) while retaining the Nitosonomas (the AOB genus) community in the suspended sludge. NOB community rebounding was not detected even at the mainstream conditions with low nitrogen concentrations (Influent ammonium concentration=38±6 mg-NH4+-N/L) by intermittent aeration to control the system dissolved oxygen (DO) below 0.5 mg/L. The results of the mainstream treatment showed that the average effluent total nitrogen (TN) in the coupled process was generally lower than 10 mg-N/L, which meets the discharge limits of most prefectures in Japan. The investigated results of the in-situ anammox bacteria (AnAOB) growth kinetics suggested that the promoted start-up strategy of taking advantage of the warm months with higher mainstream temperature to achieve the rapid in-situ growth of the AnAOB is applicable in the investigated regions. From the perspective of the removal performance of the TN and organic substance, the AnMBR-PN/A process has great potential as the layouts of the carbon-neutral mainstream wastewater treatment plants.
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•A pilot-scale AnMBR with 5 m3 succeeded in treating municipal wastewater at 25 °C.•Stable biogas yield and organic removel are obtained during long-term operation.•Theoretical net energy potential ...was 0.174 kWh/m3 and bio-energy recovered by 69%.•Practical net energy potential was −0.014 kWh/m3 and bio-energy recovered by −8%.•The AnMBR exhibited promising net energy potential compared with the CAS process.
The potential of bio-energy recovery from real municipal wastewater was investigated using a one-stage pilot-scale submerged anaerobic membrane bioreactor (AnMBR) for a range of HRTs from 24 h to 6 h at ambient temperature around 25 °C. This pilot-scale AnMBR demonstrated a high COD removal efficiency of over 90% during an operation of 217 days for municipal wastewater treatment. The energy balance of the AnMBR was calculated from both theoretical and practical aspects. The theoretical net energy potential was calculated as 0.174 kWh/m3 by applying operational data to empirical equations, obtaining a bio-energy recovery efficiency of 69.4%. The practical net energy potential was estimated as −0.014 kWh/m3 using the powers of engines applied in a full-scale wastewater treatment plant. This is considerably lower than that of the conventional activated sludge process. These results are evidence of the potential of the AnMBR and feasibility in the treatment of municipal wastewater treatment.
•A 1670-L mainstream IFAS type PN/A at decreasing temperatures of 25, 20 and 15°C.•The NLR was 0.21–0.24 kg-N/m3/d and the NRE was 65.9–75.4%.•Insufficient treatment capacity of AOB results in ...reduction of nitrogen removal at 15°C.•Candidatus Brocadia and Candidatus Kuenenia were main AnAOB and almost enriched on carriers.•NOB was suppressed by the strategy of intermittent aeration and low DO.
Partial nitritation-anammox (PN/A) is a promising deammonification process to develop energy-neutral wastewater treatment plants. However, the mainstream application of PN/A still faces the challenges of low nitrogen concentration and low temperatures, and has not been studied under a realistic condition of large-scale reactor (kiloliter level), real municipal wastewater (MWW) and seasonal temperatures. In this research, a pilot-scale one-stage PN/A, with integrated fixed-film activated sludge (IFAS) configuration, was operated to treat the real MWW pretreated by anaerobic membrane bioreactor. The removal efficiency of total nitrogen (TN) was 79.4%, 75.7% and 65.9% at 25, 20 and 15°C, corresponding to the effluent TN of 7.3, 9.7 and 12.0 mg/L, respectively. The suppression of ammonium-oxidizing bacteria (AOB) and anammox bacteria (AnAOB) occurred at lower temperatures, and the significant decrease in AOB treatment capacity was the reason for the poorer nitrogen removal at 15°C. Biomass retention and microbial segregation were successfully achieved. Specifically, Candidatus_Brocadia and Candidatus_Kuenenia were main AnAOB genera and mainly enriched on carriers, Nitrosomonas and uncultured f_Chitinophagaceae were main AOB genera and mainly distributed in suspended sludge and retained by sedimentation tank. Moreover, nitrite-oxidizing bacteria (NOB) were sufficiently suppressed by intermittent aeration and low dissolved oxygen, the presence of heterotrophic bacteria upgraded the PN/A to a simultaneous partial nitritation, anammox, denitrification, and COD oxidation (SNADCO) system, which improved the overall removal of TN and COD. The results of this investigation clearly evidence the strong feasibility of PN/A as a mainstream nitrogen removal process in temperate climates.
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* The PNA, denitratation/anammox, and DAMO/anammox process are reviewed together. * Denitratation/anammox-based process is promising in mainstream treatment. * DAMO and denitratation processes ...realize the higher nitrogen removal efficiency. * The utilization of metabolism diversity of functional microbe is worth exploring. * An effective waste treatment system concept is proposed.
Anammox technology has been widely researched over the past 40-year from the laboratory-scale to full-scale. It is well-known that in actual applications, the solo application of anammox is not feasible. Since both ammonium and nitrite are prerequisites based on the reaction mechanism, the pre-treatment of wastewater is necessary. With the combination of anammox process and other pre-treatment processes to treat the actual wastewater, many types of anammox-based processes have been developed with distinct nitrogen removal performance. Thus, in order to heighten the awareness of researchers to the developments and accelerate the application of these processes to the treatment of actual wastewater, the main anammox-based processes are reviewed in this paper. It includes the partial nitritation/anammox process, the denitratation/anammox (PD/A) process, the denitrifying anaerobic methane oxidation/anammox (DAMO/A) process, and more complex deuterogenic processes. These processes have made the breakthroughs in the application of the anammox technology, such as the combination of nitrification and PD/A process can achieve stability and reliability of nitrogen removal in the treatment of mainstream wastewater, the PD/A process and the DAMO/A have brought about further improvements in the total nitrogen removal efficiency of wastewater. The diversity of functional microbe characteristics under the specific condition indicate the wide application potential of anammox-based processes, and further exploration is necessary. A whole waste treatment system concept is proposed through the effective allocation of above mentioned processes, with the maximum recovery of energy and resources, and minimal environmental impact.
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•Two UASB processes were investigated by continuously feeding with starch wastewater.•The predominant methanogenic pathways in the two processes were different.•Different surface ...attachments were observed on the granules in the two processes.•The microbial function of the one-stage UASB shifted to hydrogen fermentation.
Poor processing stability has been cited as the fatal shortcoming of the up-flow anaerobic sludge blanket (UASB) reactor treating starch wastewater (SW). In this study, the SW treatment performance in a one-stage UASB reactor and a pre-acidification equipped UASB process were evaluated together with the microbial dynamics. The results revealed that the pre-acidification provided improvements in terms of the substrate utilization diversity and the stability of the microbial community structure on the UASB reactor. Anaerolineaceae/Methanosaeta was the core functional microbiota in the pre-acidification equipped UASB reactor, indicated the superior abilities on the acetogenic methanogenesis of granules. The genus of Methanobacterium, a hydrogenotrophic methanogen was dominant in the archaeal community in the one-stage UASB reactor. The granules performed very strong hydrogen affinity in methane production, a small amount of propionate was detected in the effluent. These were abnormal, which suggested the high hydrogen turn-over rate in the one-stage UASB reactor.
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•Mass flows of C and N were redesigned by AnMBR-PN/A.•Removal efficiencies of COD and TN were 90.3%-95.1% and 75.0%-81.7%, respectively.•48.4%-63.1% of C was captured as CH4 and ...26.7%-39.7% of C was captured as sludge.•8.5%-16.1% of N was entrapped by membrane and 45.3%-58.1% of N was removed by PN/A.•AnMBR and PN/A mutually complement each other ensured excellent system performance.
A pilot-scale anaerobic membrane bioreactor (AnMBR) integrated with a one-stage partial nitritation-anammox (PN/A) reactor was operated for the treatment of municipal wastewater (MWW) at seasonal temperatures of 15–25 °C. The removal efficiencies of COD and total nitrogen (TN) were always > 90% and > 75% respectively. The methanogenesis and PN/A were identified as the primary removal pathways of COD and TN, respectively, and were suppressed at low temperatures. With the temperature dropped from 25 °C to 20 °C to 15 °C, the methane-accounted COD decreased from 63.1% to 59.6% to 48.4%, and the PN/A-accounted TN decreased from 58.1% to 51.7% to 45.3%. The AnMBR and PN/A mutually complement each other in this combined process, as the AnMBR removed 8.5%-16.1% of TN by sludge entrainment and the PN/A reactor removed 2.6%-3.4% of COD by denitrification and aerobic oxidation. These results highlighted the strong feasibility of applying the AnMBR-PN/A process to the treatment of MWW in temperate climate.
The accurate detection of biomarkers for acute myocardial infarction (AMI) plays an important role in clinical diagnosis and management process. In this work, we developed an electrochemical ...biosensor by using magnetic metal organic framework (MMOF) nanocatalysts and DNA nanotetrahedron (NTH) based dual-aptamer probes for nonenzymatic detection of cardiac troponin I (cTnI), a gold standard biomarker for the early diagnosis of AMI. Firstly, the NTH-assisted dual-aptamer (Tro4 and Tro6) capture probes were immobilized on the screen-printed gold electrode (SPGE) for the highly enhanced capture the target cTnI with steady support and optimized interface density. Then, the MMOF Fe3O4@UiO-66 nanozymes were decorated by bimetallic Cu@Au nanoparticles and two kinds of aptamer. This fabricated nonenzymatic nanoprobe1 (NP1) can be applied for recognizing the cTnI specifically and amplifying the current signal by catalyzing the oxidation of hydroquinone (HQ) to benzoquinone (BQ) with H2O2. The target proteins were captured to fabricate a supersandwich-like structure on a SPGE interface. Furthermore, the nanoprobe2 (NP2) of Cu@Au nanozymes labeled with dual-complementary DNA (cDNA) to the dual-aptamer, were anchored on the NP1 through DNA hybridization, leading to the formation of cluster-based nanoprobes for further enhancing detection sensitivity. Finally, this enzyme-free electrochemical aptasensor exhibited great analytical performance with a dynamic range of 0.05–100 ng/mL, a low detection limit of 16 pg/mL, high selectivity and good repeatability. The fabricated aptasensor has great potential development in the field of clinic disease diagnostics for AMI.
•An enzyme-free electrochemical aptasensor was proposed for analysis of cTnI.•Three-dimensional nanotetrahedron-dual-aptamer probe can capture cTnI specifically.•Magnetic metal organic framework Fe3O4@UiO-66/Cu@Au was introduced as nanocarrier.•Cluster-based nanoprobe can amplify the signal significantly based on LBL assembly.•The proposed approach demonstrated detection limits as low as 16 pg/mL for cTnI.
An ultrasensitive voltammetric aptasensor was constructed to analyze cardiac troponin I (cTnI). It is based on DNA nanotetrahedron (NTH) linked dual-aptamer (dAPT) and magnetic metal organic ...frameworks (mMOFs) of type Fe
3
O
4
@UiO-66. Firstly, the DNA NTH linked dAPT (Tro4 and Tro6) were immobilized on a gold electrode for improving the capture efficiency of cTnI. The novel mMOFs Fe
3
O
4
@UiO-66 was then decorated by Au@Pt nanoparticles (Au@PtNPs), horseradish peroxidase (HRP), G-quadruplex/hemin (GQH) DNAzyme, and two types of aptamers to form signaling nanoprobes. In the presence of cTnI, an aptamer-protein-nanoprobe sandwich-type structure is formed. Afterward, the nanoprobes including enzyme, GQH DNAzyme and Fe
3
O
4
@UiO-66/Au@PtNP were utilized to catalyze the oxidation of hydroquinone by hydrogen peroxide for the electrochemical signals amplification, typically at a working potential of −0.1 V (vs. Ag/AgCl). The voltammetric signal increases linearly in the 0.01 to 100 ng·mL
−1
cTnI concentration range, and the detection limit is 5.7 pg·mL
−1
.
Graphical abstract
An ultrasensitive voltammetric aptasensor was constructed to analyze cardiac troponin I (cTnI) based on DNA nanotetrahedron linked dual-aptamer and magnetic metal organic frameworks of type Fe
3
O
4
@UiO-66. The results indicated the aptasensor has a wide linear response range (0.01 to 100 ng/mL) and low detection limit (5.74 pg/mL) for cTnI. GE: gold electrode; MCH: 6-Mmercapto-1-hexanol; HRP: horseradish peroxidase; HQ: hydroquinone; BQ: benzoquinone.
The sensitive and accurate detection of cardiac troponin I (cTnI) is critical for myocardial infarction diagnosis. In this work, a dual-aptamer-based electrochemical (EC) biosensor was designed for ...cTnI detection based on the DNA nanotetrahedron (NTH) capture probes and multifunctional hybrid nanoprobes. First, the NTH-based Tro4 aptamer probes were anchored on a screen printed gold electrode (SPGE) surface through the Au–S bond, providing an enhanced spatial dimension and accessibility for capturing cTnI. Then, the hybrid nanoprobes were fabricated by using magnetic Fe3O4 nanoparticles as nanocarriers to load a large amount of cTnI-specific Tro6 aptamer, natural horseradish peroxidase (HRP), HRP-mimicking Au@Pt nanozymes and G-quadruplex/hemin DNAzyme. This signaling nanoprobes are capable of specifically recognizing the target cTnI based on the Tro6 aptamer and amplifying the signals to improve the detection sensitivity via enzymatic processes. We found the remarkable enhanced effect of EC signal to be attributed to the co-catalysis effect of hybrid nanozymes, HRP and DNAzyme. The target cTnI was sandwiched between the two types of aptamers (Tro4 and Tro6) on the electrode interface. Finally, this EC aptasensing platform exhibited great analytical performance with a wide dynamic range of 0.01–100 ng mL−1 and a low detection limit of 7.5 pg mL−1 for cTnI. The high selectivity, sensitivity and reliability of EC aptasensor can provide great potential in the clinic disease diagnostics.
•An electrochemical dual-aptamer-based biosensor was proposed for analysis of cTnI.•Three-dimensional DNA nanotetrahedron-aptamer probe can capture cTnI specifically.•Nanoprobes amplify the signal via co-catalysis of nanozyme, enzyme and DNAzyme.•The method showed high selectivity and sensitivity with detection limit of 7.5 pg mL−1.
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