Display omitted
•High nitrite production increased with NTR achieving at around 90%.•PD effluent was suitable for the feeding source of ANAMMOX process.•External carbon demand for PD was reduced ...after domestic wastewater addition.•Specific NO3−-N reduction rate was as high as 4.56gN/g VSS/d.•Thauera genus responsible for nitrite production was dominated with 54.9–72.9%.
Partial-denitrification (PD, NO3−-N→NO2−-N) has been successfully developed to produce nitrite (NO2−) with acetate as the sole carbon source. In this study, a PD sequencing batch reactor (SBR) fed with high-nitrate (NO3−: 1000mgN/L) was firstly developed with carbon source obtained from domestic wastewater (NH4+: 59.3mgN/L, chemical oxygen demand (COD): 186.6mg/L) as well as a small quantity of external organic matter. The results showed that PD was not degenerated with domestic wastewater addition, and a high nitrite production was still achieved with the nitrate-to-nitrite transformation ratio (NTR) maintained at 90% in the 173-days operation period. By optimizing the nitrate and domestic wastewater feeding volume as well as external carbon dosage, the PD effluent was suitable for ANAMMOX process with a NO2−-N/NH4+-N of 1.46 and COD/NO2−-N of 1.32 obtained under the influent volume of domestic wastewater of 2.8L, as well as nitrate of 0.4L, and the external carbon demand was reduced to COD/NO3−-N of 1.7. Nitrate reduction rate was fit to Monod kinetics, with a maximum specific NO3−-N reduction rate of 4.56gN/g VSS/d and nitrate half-saturation constant of 6.9mgN/L, respectively. High-throughput sequencing analysis revealed that the diversity of microbial communities was increased with the domestic wastewater added, but the denitrifiers of Thaura genus that was responsible for high nitrite production was still dominant in PD reactor with a percentage of 54.9–72.9%. This study indicated that the high-nitrate and domestic wastewater could be simultaneously treated via the novel PD-ANAMMOX process in a cost-effective way.
This paper presents a review on the sources of failures of transformer in the substation. Different investigations and test analyses have been conducted to identify the root causes of failure of the ...transformer in the power system, and to identify the preventive measures to avoid these breakdowns. The review work has been presented with the focus on bushing-failure, which has been identified as one of the major causes of transformer breakdown in different reported studies. In determining the lifespan of the insulation of the high voltage bushing, along with different factors, moisture effect has also been considered in presenting the degradation analysis. On-line measurement has been preferred over off-line measurements due to its benefits measuring the reliability and uninterrupted functioning of the future generation, transmission and distribution systems. Post fire-outbreak, external inspection of the damaged bushing along with analytical results, obtained with the aid of Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis, have also been included in this study. In the analysis, electric field and equipotential lines with different oil levels have been simulated using COMSOL Multiphysics software.
Display omitted
•EPDPR was feasible to achieve stable nitrite accumulation and phosphorus removal.•High NTR and PO43−-P removal efficiency of 75.3% and 92.3% were achieved.•High activity of ...DGAONO3-NO2 over DPAONO3 and DGAONO3 was the key to achieve EPDPR.•Cluster I of Defluviicoccus was responsible for the high nitrite accumulation.•EPDPR/anammox might enhanced nutrient removal from nitrate and municipal sewage.
In this study, a novel process was developed by combining endogenous partial denitrification (EPD, NO3−-N → NO2−-N) with denitrifying phosphorus removal (DPR) in an anaerobic/anoxic/aerobic sequencing batch reactor (SBR) to achieve a stable nitrite accumulation and phosphorus removal from high-strength nitrate (NO3−-N: 186.5 mg/L) and municipal wastewater (NH4+-N: 52.6 mg/L, chemical oxygen demand (COD): 242.7 mg/L). After 138-day, high nitrate-to-nitrite transformation ratio (NTR) of 75.3% and PO43−-P removal efficiency of 92.3% were achieved by controlling the anaerobic drainage ratio and anoxic/aerobic durations. During the anaerobic stage (2.5 h), carbon source in raw municipal wastewater was efficiently utilized by phosphorus-and-glycogen accumulating organisms (PAOs and GAOs) to enhance intracellular carbon storage (69.9% in anaerobic COD consumption), providing sufficient carbons for subsequent anoxic EPD and DPR. During the anoxic stage (2.5 h), high activity of DGAONO3-NO2 (denitrifying GAOs conducting NO3−-N → NO2−-N) over DPAONO3 and DGAONO3 (DPAOs and DGAOs conducting NO3−-N → N2) in nitrate denitrification (77.7% > 8.2% and 5.7%) facilitated the nitrite accumulation and phosphorus uptake. In the last short aerobic stage (10 min), further phosphorus was removed by aerobic PAOs without initiating ammonia/nitrite oxidation. Thus, effluent NO2−-N/NH4+-N ratio of 1.02:1 (close to the theoretical value of 1.32:1 for anammox process) with limited NO3−-N, PO43−-P and COD (1.8, 0.4 and 23.5 mg/L, respectively) were obtained. This provides the potential for advanced nutrient removal from nitrate and municipal wastewaters by combining EPDPR with anammox. Microbial community analysis revealed that Cluster I of Defluviicoccus-GAO group (∼7%) dominated the high nitrite accumulation performance, while Accumulibacter-PAO group (15 ± 3%) was responsible for the P removal performance.
Display omitted
•The feasibility of achieving mainstream EPD-Anammox was first demonstrated.•Around 90% of nitrogen removal was achieved with a low C/N (∼2.9).•Nitrogen removal via anammox accounted ...for 49.8%, reducing oxygen and carbon demands.•An appropriate NO2−-N/NH4+-N (∼1.2) was achieved without complex control process.•Denitrifying GAOs (36.6%) were responsible for the high nitrite accumulation.
Successful application of mainstream anammox would be favorable for energy- and resource-efficient sewage treatment. This study presents a new strategy to achieve mainstream anammox, which combined with endogenous partial denitrification (EPD) for treating sewage wastewater. In this EPD-Anammox system, nitrite was stably produced by EPD with a nitrate-to-nitrite transformation ratio of 80%. Through adjusting the volume exchange ratio of EPD-reactor after anaerobic reaction, a suitable NO2−-N/NH4+-N ratio of ∼1.20 for anammox reaction was achieved. Further, results showed a stable, high nitrogen removal efficiency (90%) with an effluent total nitrogen of 5.8 mg N/L under low C/N (∼2.9). Anammox contributed 49.8% of the overall nitrogen removal owing to the steady nitrite supply from EPD. Denitrifying glycogen-accumulating organisms (GAOs, 36.6%) having potential for endogenous denitrification and Candidatus Brocadia (34.6%) were respectively dominated in the EPD-SBR and anammox-UASB and responsible for the high nitrite accumulation and anammox reaction.
Display omitted
•Continuously fed PD coupling with anammox process was established in UASB reactor.•TN removal achieved 89.1% with effluent TN as low as 6.56 mg/L at 17.5 °C.•Capability of NO2–-N ...production by PD maintained stable with NTR over 90% in UASB.•Protein and tightly-bound layer of EPS had important role in sludge settleability.
In this study, the synergy of high nitrite (NO2–-N) accumulated partial-denitrification (PD) and anammox in a continuously fed upflow anaerobic sludge blanket (UASB) reactor was verified for simultaneous nitrate (NO3–-N) and ammonia (NH4+-N) removal. A 225-days operation demonstrated that the relatively low total nitrogen (TN) concentration of 6.56 mg/L in effluent could be achieved with influent NH4+-N and NO3–-N both of 30 mg/L, resulting in a high TN removal of 89.1% at 17.5 °C. Batch tests revealed that the NO3–-N-to-NO2–-N transformation ratio (NTR) of PD stabilized at 90% during the whole operation, which played a crucial role in the desirable performance. However, the PD and anammox activity was negatively impacted by the limited mass transfer with serious sludge flotation. Significantly, hydrodynamic mixing optimization by adjusting liquid recirculation ratio effectively enhanced the nitrogen removal. Moreover, protein composition and tightly-bound structure of EPS played an important role in the sludge stability.
Display omitted
•Co-gasification reactivity and synergy of petroleum coke and MSW hydrochar were studied.•Overall synergistic effect was enhanced at lower temperature and higher hydrochar ...proportion.•Synergistic effect was enhanced as conversion increased but weakened at mid-late co-gasification.•Inhibition of active Ca/K transformation was first enhanced and then weakened as conversion increased.•Active AAEM transformation during co-gasification could well correlate synergy mechanism.
In this work, the influences of the gasification temperatures (1000–1150°C) and blended ratios (3:1, 1:1, 1:3) on the co-gasification reactivity and synergy of petroleum coke (PC) and municipal solid waste (MSW)-derived hydrochar (HTC) were studied using a thermogravimetric analyzer (TGA). Chemical fractionation analysis (CFA) coupled with an inductively coupled plasma optical emission spectrometer (ICP-OES) was adopted for quantitatively investigating the active alkali/alkaline earth metal (AAEM) transformation (i.e., active AAEM content variation) during co-gasification in order to correlate the synergy mechanism of co-gasification. The results indicated that the co-gasification reactivity of the blended chars was enhanced with increasing gasification temperatures and HTC char proportions. The variations of the synergy behaviour on co-gasification reactivity at different conversions showed continuously enhanced synergistic effect at early co-gasification stage and decreased synergistic effect with further co-gasification. Moreover, higher gasification temperatures and HTC char proportions were more favourable for the continuous enhancement of the synergistic effect as co-gasification conversions increased. The overall synergistic effect on co-gasification reactivity was more obvious at higher HTC char proportions and lower gasification temperatures. The relative transformation ratio (P) was proposed to characterize the active AAEM content variation during co-gasification. P was negative when more active AAEM remained in blended chars, meaning that there was inhibition effect on the active AAEM transformation. It was found that the inhibition effect on the active Ca/K transformation was first enhanced and then weakened whereas the promotion effect on the active Na transformation showed an opposite trend with increasing conversion of co-gasification, which well correlated the synergy behaviour variations during PC-HTC blended char co-gasification. This work not only revealed synergy mechanism of petroleum coke and MSW-based hydrochar co-gasification but also provided reference data for the design and operation of industrial gasification units consuming mixture of petroleum coke and waste biomasses.
With the tremendous growth in the number of scientific papers being published, searching for references while writing a scientific paper is a time-consuming process. A technique that could add a ...reference citation at the appropriate place in a sentence will be beneficial. In this perspective, the context-aware citation recommendation has been researched for around two decades. Many researchers have utilized the text data called the context sentence, which surrounds the citation tag, and the metadata of the target paper to find the appropriate cited research. However, the lack of well-organized benchmarking datasets, and no model that can attain high performance has made the research difficult. In this paper, we propose a deep learning-based model and well-organized dataset for context-aware paper citation recommendation. Our model comprises a document encoder and a context encoder. For this, we use graph convolutional networks layer, and bidirectional encoder representations from transformers, a pre-trained model of textual data. By modifying the related PeerRead dataset, we propose a new dataset called FullTextPeerRead containing context sentences to cited references and paper metadata. To the best of our knowledge, this dataset is the first well-organized dataset for a context-aware paper recommendation. The results indicate that the proposed model with the proposed datasets can attain state-of-the-art performance and achieve a more than 28% improvement in mean average precision and recall@k.
ABSTRAKProyeksi energi memiliki peran penting dalam perencanaan pengembangan sistem distribusi listrik. Penelitian ini bertujuan untuk menentukan lokasi, jumlah dan penambahan kapasitas transformator ...yang diperlukan di area jaringan Tangerang. Metode prakiraan proyeksi energi dilakukan secara mikrospasial dengan membagi area layananan dalam bentuk grid – grid yang kecil (kelurahan). Selanjutnya pengelompokan (clustering) dilakukan berdasar karakteristik geografis, demografi, ekonomi dan kelistrikan wilayah untuk memperkirakan kerapatan beban. Hasil clustering yang terdiri dari 100 kelurahan, terkelompok menjadi 5 cluster dengan pertumbuhan beban per cluster rata-rata sebesar 8,4 %. Hasil perhitungan kapasitas transformator untuk wilayah Tangerang untuk 10 tahun adalah 250 kVA, 630 kVA, 1000 kVA dan 1250 kVA, dengan asumsi pembebanan transformator maksimal 80 %. Disamping itu prakiraan beban pada tingkatan transformator distribusi mengalami penambahan 3.064 unit gardu distribusi.Kata kunci: Prakiraan Beban, Transformator , Micro-spatial, Cluster, Tangerang ABSTRACTEnergy projection has important role in the planning of electricity distribution systems development. This study set out to investigate location, number and capacity of the transformers in Tangerang network area. A microspatial energy projection forecasting method was used by dividing the service area into small grids. Furthermore, clustering is carried out based on geographical, demographic, economic and electrical characteristics of the region to predict the load density. The clustering results consist of 100 grids grouped into 5 clusters with an average load growth 8.4% per cluster. As the result, the transformers capacity for the Tangerang area for the next 10 years are 250 kVA, 630 kVA, 1000 kVA and 1250 kVA, with the assumption that the maximum transformer loading is 80%. In addition, the estimated load at the distribution transformer level has an additional 3,064 distribution substations.Keywords: Load Forecasting, Transformer, Micro-spatial, Cluster, Tangerang
The need to reduce greenhouse gas emissions and fossil fuel consumption has increased the popularity of plug-in electric vehicles. However, a large penetration of plug-in electric vehicles can pose ...challenges at the grid and local distribution levels. Various charging strategies have been proposed to address such challenges, often separately. In this paper, it is shown that, with uncoordinated charging, distribution transformers and the grid can operate under highly undesirable conditions. Next, several strategies that require modest communication efforts are proposed to mitigate the burden created by high concentrations of plug-in electric vehicles, at the grid and local levels. Existing transformer and battery electric vehicle characteristics are used along with the National Household Travel Survey to simulate various charging strategies. It is shown through the analysis of hot spot temperature and equivalent aging factor that the coordinated strategies proposed here reduce the chances of transformer failure with the addition of plug-in electric vehicle loads, even for an under-designed transformer while uncontrolled and uncoordinated plug-in electric vehicle charging results in increased risk of transformer failure.
•Charging algorithm for battery electric vehicles, for high penetration levels.•Algorithm reduces transformer overloading, for grid level valley filling.•Computation and communication requirements are minimal.•The distributed algorithm is implemented without large scale iterations.•Hot spot temperature and loss of life for transformers are evaluated.
PDF
