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With the increasing use of animal and plant proteins, pollution due to nitrogen sources is attracting increasing attention. In particular, the amount of nitrogen-containing sewage discharged into the environment has increased significantly, causing eutrophication of water bodies and environmental degradation of water quality. Traditionally, nitrifying bacteria perform ammonia nitrification under aerobic conditions, while denitrifying bacteria perform nitrate/nitrite denitrification under anaerobic conditions. However, heterotrophic nitrifying and aerobic denitrifying microorganisms (HNADs) perform ammonia nitrification and nitrate/nitrite denitrification under the same aerobic conditions using an organic carbon source, which is a much simpler and more efficient process. In this review, the distribution and evolutionary relationships of novel HNADs strains are presented, and the influencing factors, metabolic pathways, key enzymes, and practical applications of HNADs are reviewed.

In order to improve the performance of a micro-electro-mechanical system (MEMS) accelerometer, three algorithms for compensating its temperature drift are proposed in this paper, including deep long short-term memory recurrent neural network (DLSTM-RNN, short DLSTM), DLSTM based on sparrow search algorithm (SSA), and DLSTM based on improved SSA (ISSA). Moreover, the piecewise linear approximation (PLA) method is employed in this paper as a comparison to evaluate the impact of the proposed algorithm. First, a temperature experiment is performed to obtain the MEMS accelerometer’s temperature drift output (TDO). Then, we propose a real-time compensation model and a linear approximation model for neural network methods compensation and PLA method compensation, respectively. The real-time compensation model is a recursive method based on the TDO at the last moment. The linear approximation model considers the MEMS accelerometer’s temperature and TDO as input and output, respectively. Next, the TDO is analyzed and optimized by the real-time compensation model and the three algorithms mentioned before. Moreover, the TDO is also compensated by the linear approximation model and PLA method as a comparison. The compensation results show that the three neural network methods and the PLA method effectively compensate for the temperature drift of the MEMS accelerometer, and the DLSTM + ISSA method achieves the best compensation effect. After compensation by DLSTM + ISSA, the three Allen variance coefficients of the MEMS accelerometer that bias instability, rate random walk, and rate ramp are improved from 5.43×10−4mg, 4.33×10−5mg/s12, 1.18×10−6mg/s to 2.77×10−5mg, 1.14×10−6mg/s12, 2.63×10−8mg/s, respectively, with an increase of 96.68% on average.

The objective of this research was to compare different methods for the separation and purification of hyaluronic acid from Streptococcus zooepidemicus ATCC39920 for their ease of use and reliability. The most appropriate conditions of pretreatment stage were heated to 70 °C for 1 h and kept at room temperature for 5 h. The fermented broth was diluted with the equal volume deionized water. Ten milligrams chitosan was slowly added to 1 L of solution with stirring for 30 min, followed by the addition 20 g diatomaceous earth-type filter aid. The mixture was stirring for 1 h. Then, the mixture was filtrated with diatomite, microfiltration (MF) membranes (5 μm in pore diameter), and ultrafiltration (UF) membranes (MWCO 50KD) to achieve the separation stage.The retentate was washed by the equal volume deionized water and when the volume concentration ratio (VCR) reached 4, the UF stage ended. Finally, the purification procedure adopted Sevag process to remove protein. The overall yield of HA could reach 62.53 % and the removal rate of protein could reach 95.22 %.

The treatment of dormitory and refectory mixed wastewater by a submerged flat membrane bioreactor (MBR) was studied. The A/O MBR system treated wastewater 4 m3/d. The mean removal efficiency of BOD5 and CODCr was more than 95% with the influent concentration of 100~500 mg/L BOD5 and 120-900 mg/L CODCr. It was proved that active carbon treatment reduced effluent chroma effectively. At the steady working period (MLSS 8,000~15,000 mg/L), TN and NH3-N removal efficiencies were more than 85%, and that of TP was between 50% and 95%. Besides, this paper studied the membrane fouling mechanism and revealed that membrane fouling was affected by MLSS, particle size distribution of sludge and composition of raw water. We found that the diameter of sludge particles changes with the MLSS. We also found the small particles caused membrane fouling. The results proved that submerged flat MBR was suitable to treat small-or-medium-size domestic and industrial wastewater and would have a promising future.