Comparison of treatment performance and microbial community evolution of typical dye wastewater by different combined processes.

The degradation of typical dye wastewater is a focus of research in the printing and dyeing industry. In this study, a combined micro-electrolysis and microbial treatment method was established to treat refractory dye wastewater, and the pivotal factors in the microbial treatment were optimized. In the series and coupled modes, the removal rates of chroma reached 98.75% and 92.50%, and the removal rates of chemical oxygen demand (COD) reached 96.17% and 82.29%, respectively. The high-throughput sequencing results showed that the microbial communities in the microbial system varied at different treatment stages. From the culture stage to the domestication stage, the dominant phylum was Proteobacteria; however, the community abundance of microorganisms decreased. A combination of micro-electrolysis and biological methods can alter the characteristics of the microbial community, increase the number of dominant phyla, and increase the abundance of microorganisms. The degradation effect of the series mode and the overall strengthening effect of micro-electrolysis on the microorganisms were better than those of the coupled mode. In actual wastewater, the maximum removal rates of chroma, COD, total nitrogen (TN), ammonia nitrogen (NH3-N), and total phosphorus (TP) are 97.50%, 98.90%, 94.35%, 93.95%, and 91.17%, respectively. Three-dimensional fluorescence spectrum analysis showed that microbial processes could significantly degrade fluorescent components in wastewater, and methanogenic active enzymes in anaerobic processes could continue to react. The combined process can realize the efficient treatment of toxic dye wastewater by reducing the toxicity of wastewater and efficiently degrading organic matter, which has important guiding significance for the treatment of refractory dye wastewater.

Effect of return activated sludge diversion ratio on phosphorus removal performance in side-stream enhanced biological phosphorus removal (S2EBPR) process.

In this study, a lab-scale continuous flow side-stream enhanced biological phosphorus (P) removal (S2EBPR) reactor was operated for 247 days treating synthetic wastewater with influent carbon to phosphorus (C/P) ratio of 25.0 g COD/g P and influent PO43--P of 7.4 ± 0.3 mg P/L. The effect of the return activated sludge (RAS) diversion ratio on S2EBPR reactor was investigated by comparing P removal performance, microbial activity, and community structure. The results showed that the RAS diversion ratio of 8.0%, by yielding a side-stream sludge retention time (SRTSS) of ∼60 h, resulted in the lowest effluent PO43--P concentration of 0.5 ± 0.3 mg P/L. The results of in situ process profiles and ex situ P release and uptake batch tests under different RAS diversion conditions showed that the more anaerobic P release was obtained in the side-stream reactor, the higher the P removal efficiency and EBPR activity were achieved. The stoichiometric ratios observed in EBPR activity tests indicated a polyphosphate accumulating organisms (PAOs) metabolism mainly dependent on the glycolysis pathway. The results of microbial ecology analysis revealed that the optimized SRTSS would give a competitive advantage to PAOs in the S2EBPR process. By obtaining statistically reliable results, this study would provide guidance for wastewater treatment plants to achieve optimal P removal performance in S2EBPR configuration.

[Community Composition of nirS-type Denitrifying Bacteria in the Waters of the Lower Reaches of the Fenhe River and Its Relationship with Inorganic Nitrogen].

In order to assess the waters of the lower reaches of the Fenhe River and the interaction with inorganic nitrogen, Illumina high-throughput sequencing technology was used to analyze samples based on the analysis of water quality indicators of nine rivers. The community structure and diversity of nirS-type denitrifying bacteria was diagnosed and statistical analysis was carried out to analyze the relationship between these communities and inorganic nitrogen content. The results show that the lower reaches of the Fenhe River are seriously polluted with inorganic nitrogen and the overall water quality standard was classified as V. The range of calculated Shannon index values was 3.36-7.54, indicating that the diversity of the denitrifying bacterial community is high in this basin. The relative abundance of the dominant genera represented 89.8% of the total community, which included Rhodobacter, Pseudomonas, and Thauera. The DO, pH, and inorganic nitrogen content were the main factors affecting the denitrifying bacterial community in the lower reaches of the Fenhe River. The dominant genus, Rhodobacter, and the genus Thauera were negatively correlated with NO3--N and NO2--N, and were positively correlated with NH4+-N. Pseudodomomas was the dominant genus in the Jishan and Hejin areas, and in the Fenhe River feeding into the Yellow River, and was negatively correlated with NO3--N and NO2--N but positively correlated with NH4+-N. The dominant genera of nirS-type denitrifying bacteria in the lower reaches of the Fenhe River promote denitrification and play a role in reducing the content of nitrate nitrogen in the water.

[Analysis of Nitrate Pollution Sources in the Rainy Season of the Lower Fenhe River].

Through the application of multi-isotope tracing, IsoSource model calculation, and microbial detection, the source of nitrate pollution in the lower reaches of the Fenhe River was screened, and the contribution rate of each source was calculated. The results showed that the main forms of nitrogen-containing substances in the lower reaches of the Fenhe River are NO3--N and NH4+-N and that the NO3--N content in 77.8% of the samples exceed the national drinking water standard. The abundance of denitrifying microorganisms in Jishan, Hejin, and the Fenhe River into the Yellow River is high, and many dominant bacteria participate in denitrification, resulting in nitrogen fractionation. The contents of δ15N-NO3- and δ18O-NO3- in the isotopes ranged from 5.30‰ to 12.90‰ and from 1.3‰ to 1.8‰, respectively. Manure and sewage were the main sources of nitrate in the Linfen section, accounting for 68% of the total nitrate source. In the Xiangfen section, the main sources of nitrate in the river were manure and sewage, at 37.5%, and agricultural fertilizer, at 37%. Agrochemicals are the main sources of nitrate in the Hejin section of the river, with a contribution ratio of 49.3%.