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By increasing the concentration of ammonia nitrogen, the stable nitrification system was inhibited, and then boron was added to the reactor to improve the recovery of nitrification efficiency. The changes of the short-range nitrification system were characterized by the nitrogen conversion capacity, the activity of ammonia-oxidizing bacteria, the content of protein and polysaccharide, the morphology of sludge, and the particle size distribution of granular sludge. The results showed that the stable short-range nitrification system was affected by 800 mg/L ammonia nitrogen in a short period of time, and the stability of the sludge was weakened, and it could not be recover in the short term when the ammonia nitrogen concentration returned to 200 mg/L. Compared with the inhibition period, the removal rate of ammonia nitrogen increased from 50% to 95% during the recovery period. The accumulation rate of nitrite increased from 50% to 85%, the accumulation rate of nitrate decreased from 50% to 15%, and the specific ammonia nitrogen oxidation rate(SAOR) increased from 18.65 mg/(g·h) to 38.36 mg/(g·h). Specific oxygen consumption rate(SOUR) increased from 47.68 mg/(g·h) to 54.24 mg/(g·h), MLSS increased by 32% to 4.5 g/L, PN mass fraction in EPS increased by 23% and m(PN)/m(PS) increased by 35.96% compared with the inhibition stage. The concentration of the signal molecule AI-2 also increased from 0.021 ng/mL to 0.124 ng/mL. Therefore, this study illustrated that boron could promote the recovery of short-range nitrification system performance under the impact of high ammonia nitrogen concentration.

Partial denitrification has a stable nitrite accumulation capacity,which holds the dawn to the application of anaerobic ammonia oxidation. Compared to the segmented partial denitrification-anaerobic ammonia oxidation(PD-A),the integrated PD-A is more compact and convenient in operation. In this paper, the nitrogen removal mechanism of partial denitrification and anaerobic ammonia oxidation was introduced initially. Then, the starting method and process form of integrated PD-A were elaborated from the suspended sludge, biofilm, granular sludge and cell immobilization system. It was found that the spatial structure of the integrated PD-A was not only conducive to the retention of functional bacteria but also beneficial to the development of derivative process. Subsequently, the factors that have effects on PD-A were summarized from the aspects of carbon source, influent water matrix, and pH, etc. The methods to enhance PD-A were introduced. Finally, the application progress of PD-A and its derivative processes was summarized, and the development direction was discussed. It was found that integrated PD-A had broad prospects in nitrogen removal and resource utilization of urban sewage, which met the development requirements of China’s “dual carbon”.

On-site bioaerosol monitoring is essential for estimating microbial biomass and mitigating the risk of infection induced by aerosol transmission. This study introduces a novel electrostatic bioaerosol sampler, which is fabricated by the use of 3D printing, for rapid bioaerosol collection. Aerosol particles were charged and enriched in the sampler. Relationships between particle sizes and collection efficiencies under varying charging voltages were established using a charging model. The design of the sampler was optimized using commercial software, incorporating electrostatic field analysis, computational fluid dynamics (CFD), and particle trajectory simulations. To validate the sampler's collection efficiency, polystyrene (PS) spheres in an aerosol dispenser were atomized into an aerosol. The sampler collection efficiency exceeded 90% for particles larger than 1.2 μm under an applied voltage of 4.7 kV and an airflow rate of 2 L/min. The enrichment capacity was greater than 153,000 for particles larger than 1.2 μm under an applied voltage of 4.7 kV and an airflow rate of 8 L/min. With the merits of low cost, miniaturization, and high collection efficiency, the sampler can be used to collect samples on-site and in remote areas to verify the pathogens and reduce the risk of infection through aerosol transmission. [ABSTRACT FROM AUTHOR]