[Diffusion of Microorganism and Main Pathogenic Bacteria During Municipal Treated Wastewater Discharged into Sea].

Numerous microorganisms, especially pathogens, exist in treated wastewater, which leads to possible risk to population health and marine ecological security when treated wastewater is discharged into the sea. This study selects Maidao municipal sewage treatment plant as the location. The microbial community and the dynamic distribution and seasonal variation of pathogens are analyzed by high-throughput sequencing technology. The results showed that the microbes in the discharge were distributed into 20 to 27 phyla, and the dominant phyla were Proteobacteria, Firmicutes, and Bacteroidetes, which were mainly distributed in 44 to 65 classes. The predominant pathogens are mainly composed of Gammaproteobacteria, Betaproteobacteria, and Epsilonproteobacteria in the Proteobacteria category. The proportion of most dominant phyla and classes in the sample decreased with an increase in diffusion distance. There were mainly 55 species pathogenic bacteria in the water discharging into the sea. The pathogenic genes in the discharge were mainly related to cancer, cardiovascular disease, immune system diseases, infectious diseases, metabolic diseases, and neurodegenerative diseases. When compared with the blank samples, it was found that the biomass of pathogenic bacteria decreased sharply with the diffusion by the seawater, and most of the pathogens were not detected 1000 m away from the seashore. Arcobacter spp. caused human and animal diarrhea and bacteremia, Acinetobacter spp. caused nosocomial infections, and Shewanella hafniensis posed a threat to seafood farming and fishing. The three species of pathogenic bacteria mentioned above occupied a fairly large proportion of the discharge into the sea.

[Influence of Different Patterns of Discharge on Microbial Diffusion in Municipal Treated Wastewater].

Numerous pathogens exist in treated wastewater, leading to possible population health and ecological security risks when treated waste water is reused or discharged. To investigate the influence of different patterns of discharge on microbial diffusion in the municipal treated waste water, high-throughput sequencing technology was used to analyze the bacterial community structure, dominant flora, and typical pathogens. It was found that those bacteria were distributed in 58 classes. There were 32 species with a relative abundance of more than 1%. While there were only 41 classes in the water sample taken as a direct discharge to the sea, and there were 28 species with relative abundances of more than 1%. The water sample collected as a discharge to the sea through a river displayed higher bacterial diversity than the sample collected as a direct discharge to the sea, indicating that the microorganisms in the treated waste water was more likely to diffuse in when directly discharged to the sea. The relative abundance of dominant bacteria decreased with an increase in the diffusion distance, while the relative abundance of Cyanobacteria increased as the diffusion distance increased. The relative abundance in the water sample collected as a discharge to the sea through a river was higher. The dominant bacteria in the two systems are to Proteobacteria, Bacteroidetes, and Firmicutes. However, the dominant bacteria at the class and species levels quite dissimilar in the two systems. The bacterial diversities near the outfall were much higher than that in the seawater (blank sample), and the abundance was higher, which related to sewage treatment. In addition, there was a certain amount of pathogens and potential pathogens, including Pseudoalteromonas haloplanktis and Pseudomonas anguilliseptica, which were highly pathogenic. Their relative abundances were still higher after dilution. Arcobacter spp. was related to human and animal diarrhea and bacterial and other diseases. Therefore, the detection of these types of bacteria when the treated waste water is discharged is very important.