On June 5, Xie Jun's team of Pearl River Fisheries Research Institute published a research paper entitled "water treatment effect, microbial community structure, and metabolic characteristics in a field scale aquaculture water treatment system" in the international journal frontiers in microbiology. In this study, the multi-stage treatment system of large-scale aquaculture tail water was constructed by using pond engineering thinking, and better water treatment effect was obtained by optimizing the hydrodynamic conditions of the system; from the perspective of microbial activity and function, the micro ecological mechanism of nitrogen removal by biofilm immobilized microorganism in the tail water treatment unit was clarified, which provided a new perspective for integrated treatment of pond tail water and pond engineering The process model and theoretical guidance.
图1 Water treatment process in the field-scale aquaculture wastewater treatment system
The model of tail water treatment for intensive culture pond was established. This research started in 2013. The 600 mu intensive aquaculture community of Huizhou aquaculture base in the Dongjiang River Basin of the Pearl River Delta was upgraded. The abandoned drainage channels and ponds were transformed into multi-stage water treatment system according to local conditions, forming a multi-stage water treatment ecological unit of sedimentation tank, ecological ditch and biofilm filter (ecological water treatment, biological floating bed, biological brush filtration, etc.). With the application of engineering system thinking, a better water treatment effect is obtained by optimizing the hydrodynamic conditions (water flow rate, solid particle sedimentation rate, biofilm surface shear force, etc.) of the system. The pollutant removal rates are cod (74.4-91.2%), total nitrogen (66.9-86.8%) and total phosphorus (76.2-95.9%), which provides a new process scheme for the comprehensive treatment of pond tail water.
The micro ecological mechanism of nitrogen removal by biofilm immobilized microorganism in the tail water treatment system was elucidated. The research team carried out high-throughput analysis on the activity and function of microbial community in water body and biofilm of each unit of tail water treatment system by using metagenomic sequencing and microbial function evaluation technology. From the micro level of microbial metabolism, it was found that biofilm immobilized microorganisms enhanced the assimilation ability of water pollutants, in which the abundance and metabolic activity of denitrifying bacteria and phosphorus accumulating bacteria increased significantly 。 At the same time, most of the functional genes of denitrification were up-regulated in biofilm, which proved that biofilm microbial community enhanced nitrogen removal by increasing the number of denitrifying bacteria and metabolic capacity. This study will provide a theoretical basis for the enhanced regulation of biofilm microbial community denitrification in aquaculture tail water treatment system.
图2 Alpha-diversity indices (A) and dominant phylum compositions (B and C) of microbiota in the different sections of thefield-scale aquaculture wastewater treatment system
图3 Nitrogen metabolism pathways showing the changes of relative abundance of functional genes in the microbiota from the different sections of the field-scale aquaculture wastewater treatment system
The research and implementation of "green aquaculture" in Guangdong can provide important guidance and support for the national aquaculture development. The research was supported by the national key R & D program, National Natural Science Foundation of China, Guangdong provincial special project for promoting economic development, etc. Li Zhifei is the first author of the paper, and Xie Jun and Wang Guangjun are the corresponding authors. Full text link: https://www.frontiersin.org/articles/10.3389/fmicb.2020.00930
