Search

In the Anthropocene, nitrogen pollution is becoming an increasing challenge for both mankind and the Earth system. Microbial nitrogen cycling begins with aerobic nitrification, which is also the key rate-limiting step. For over a century, it has been accepted that nitrification occurs sequentially involving ammonia oxidation, which produces nitrite followed by nitrite oxidation, generating nitrate. This perception was changed by the discovery of comammox Nitrospira bacteria and their metabolic pathway. In addition, this also provided us with new knowledge concerning the complex nitrogen cycle network. In the comammox process, ammonia can be completely oxidized to nitrate in one cell via the subsequent activity of the enzyme complexes, ammonia monooxygenase, hydroxylamine dehydrogenase, and nitrite oxidodreductase. Over the past five years, research on comammox made great progress. However, there still exist a lot of questions, including how much does comammox contribute to nitrification? How large is the diversity and are there new strains to be discovered? Do comammox bacteria produce the greenhouse gas N

Anaerobic digestion (AD) has been widely adapted for blackwater treatment, however, the effect of water-conserving toilet generated blackwater on the AD process is still unknown. In this study, the anaerobic digestion process of dry toilet generated blackwater was investigated by means of a biomethane potential test. It was demonstrated that anaerobic digestion was inhibited and then adapted because of a high total ammonium nitrogen (TAN) level (3673.3 mg/L). The start-up period was 14.04 days and the biomethane potential of dry toilet blackwater was 402.36 mLCH4/gVS (55 days, 38 °C). Inhabitation and adaptation could be described as the increase of free ammonia nitrogen content and acetic acid concentration, followed by an enhancement of the relative abundance of acetic acid-type methanogens (from 33.53–61.52%). The main pathogen in dry toilet blackwater fermentation broth, Pseudomonas aeruginosa, kept multiplying in the first 8 days and then stabilized at a higher level than that of the beginning. This work showed the self-adjustment process and pathogen dynamics of dry toilet blackwater anaerobic digestion and highlights the significance of dry toilet blackwater characteristics when designing and maintaining anaerobic digestion sanitary treatment and reuse systems.

The basic principle of turbogenerator stator core magnetization test is introduced, aiming at the overheated condition of stator core during magnetization test of No.1 generator in Yingkou Power Plant of Huaneng International Electric Power Co.,Ltd., the causes of hot spots in the core during the test are analyzed, the test, inspection and treatment process are introduced,after treatment,the stator core of the generator can be operated.

In this paper, based on fxbw4-10/100 insulators, the flashover dynamic characteristics of iced insulators are studied. The insulators are artificially iced and flashover experiments are carried out with water of different conductivity in the laboratory, and different flashover voltages are obtained. The dynamic changes of insulator temperature field, electric field and potential are simulated by using finite element software. Finally, the influence of different physical parameters on insulator flashover characteristics is studied.

With the rapid development of power grid, large capacity units are continuously put into operation, which makes the small interference. This paper analyzes the influence of different regulation modes of AC exciter excitation system on the performance of generator excitation control system, demonstrates that PID excitation regulation can effectively improve the quality of excitation control, and simulation test is an effective measure to adjust the parameters of excitation system.

With the continuous access of new energy sources to the power grid, the requirements of the power grid for reactive power adjustment capability are also continuously improving, and stronger reactive power adjustment capability is needed to keep the power grid voltage in a controllable range.To maintain the terminal voltage level of the generator, improve the operation stability of the power system, a superior excitation control mode is proposed in this paper. The open loop control and PID control under full load and partial load conditions are compared. The conclusions have some reference value for the study of reactive power adjustment capability of hydro-generators.

In the present paper, partial discharge (PD) pulse waveforms of stator bar insulations subjected to various aging factors are investigated by means of extra-high frequency PD measurement technique. The test results indicated that both rising time of PD pulse and pulse width vary with aging time. Although different aging factors, such as electrical, electrical-thermal and thermal-mechanical stresses etc., result in different alteration in PD pulse waveform, it is observed that high frequency components in the time-frequency spectrum of PD pulse waveform add with aging time in all of specimens by joint time- frequency analysis (JTFA). If high frequency components in dispersion appear in JTFA spectrum, it is though that oxides with low-molecule weight are produced due to PD in the void and acidic matter deposited on the surface of dielectric around the void erodes the dielectric and results in electrical tree spreading out.