| Phosphorus is an essential element that constitutes plants and animals and other living organisms, and the lack of phosphorus in water bodies will limit the primary productivity, and the problem of phosphorus shortage has gradually attracted the attention of the world, however, the high concentration of phosphorus leads to the eutrophication of water bodies, which affects the production and life of human beings, jeopardizes the health of the water bodies, and results in serious economic losses, so the research on the removal of phosphorus and the recovery of phosphorus resources is of great significance. According to the 2024 China Ecological and Environmental Status Bulletin, in 2023, 72.7% of China's inland important fishery waters exceeded the total phosphorus standard, an increase of 17.1% year-on-year; the area of marine natural important fishery waters exceeded the standard for reactive phosphate was 73.0%, and the area of seawater key aquaculture areas exceeded the standard for reactive phosphate was 71.8%, an increase of 5.5% and 5.3% year-on-year. The development of aquaculture is particularly important in the context of the ‘Big Food Concept’. According to the 《2024 China Fisheries Statistics Yearbook》report shows that China's total aquatic product output in 2023 was 71.16 million tons, an increase of 4.39% year-on-year, of which the aquaculture production accounted for 81.6%. 2022-2024 the China's provinces and municipalities have introduced the standard of aquaculture tail water discharge, in Shandong Province, for example, DB37 4676-2023 《seawater aquaculture tail water discharge standards》 proposed that Total phosphorus primary discharge limit 0.7 mg/L, secondary discharge limit 1.0 mg/L. In recent years, with the rapid development of aquaculture tailwater phosphorus removal technology, phosphorus removal technology based on physical, chemical, biological and ecological methods provides strong support in aquaculture tailwater phosphorus removal and recycling, and the current aquaculture tailwater phosphorus removal technology has made some progress, but the deep removal of phosphorus from the tail water and phosphorus recovery technology still needs to be explored, and strengthening the deep removal of aquaculture tail water is a necessary guarantee for the sustainable development of aquaculture. This paper classifies the phosphorus in the water, discusses the principle and current status of aquaculture tailwater phosphorus removal technology, and summarizes and discusses the application of phosphorus removal in the tailwater of the current aquaculture model. The principles and current status of phosphorus removal technology in aquaculture tailwater were discussed in terms of physical, chemical, and biological methods of phosphorus removal. The study shows that the physical method of phosphorus removal technology in aquaculture is mainly based on adsorption and membrane separation technology, in which the high adsorption saturation of adsorbent materials and renewable is the key to adsorption of phosphorus removal, and the physical principle of membrane separation technology is the selective permeability of the membrane. The retention of pollutants is achieved through the concentration difference between the two sides of the membrane, hydraulic pressure difference, potential difference. The current membrane separation technology research methods continue to innovate, and generally combine the membrane separation technology and biological method applied to aquaculture tail water phosphorus removal technology. Chemical phosphorus removal technology in precipitation, electro-flocculation, crystallization and depth oxidation is also an important means of aquaculture tail water phosphorus removal technology, but also to achieve the main means of phosphorus resource recovery, should not be ignored. Biological phosphorus removal technology is the main means of phosphorus removal in aquaculture tail water, mainly including biofilm reactor, Biofloc, microalgae biological purification, bacterial and algal synergistic reactor, artificial wetland and other technologies. Among them, biofilm reactor and Biofloc mainly rely on the role of phosphate accumulating organisms (PAOs) and denitrifying phosphate accumulating organisms (DPAOs), both of which have different processing capacity and biological response to phosphorus in aerobic, anaerobic and anoxic stages, PAOs absorb phosphorus in aerobic, release phosphorus in anaerobic; DPAOs release phosphorus in anaerobic, and absorb phosphorus in anoxic stage. Microalgae biological purification technology is mainly through the photosynthesis of microalgae and microalgae growth to take up the phosphorus in the water to achieve the removal of phosphorus. Microalgae bioreactor is a bacterial-algae synergistic reactor formed by combining microalgae and biofilm reactor to carry out phosphorus removal together. Artificial wetland is a comprehensive phosphorus management method integrating physical, chemical and biological methods, and it is gradually becoming the important method of phosphorus management in aquaculture tail water. Current aquaculture modes such as recirculating aquaculture system(RAS), pond aquaculture and other modes, in which RAS mostly use biofilm reactors, bacterial and algal synergistic bioreactors and multi-level integrated aquaculture systems and other treatment methods, and in recent years, artificial wetlands are also gradually applied in the treatment of phosphorus in RAS tailwater, and artificial wetlands are used in conjunction with sediment fuel cells and microbial fuel cells for the removal of phosphorus from aquaculture tailwater. The artificial wetland is combined with sediment fuel cell and microbial fuel cell to remove phosphorus from aquaculture tail water. In the treatment of phosphorus in recirculating aquaculture tailwater, the biological ecological method is gradually used as the main method to treat phosphorus in tailwater, supplemented by physicochemical methods. The pond aquaculture tailwater phosphorus management is also based on bio-ecological methods, such as ‘three ponds and two dams’, artificial wetlands, multi-level integrated aquaculture treatment system and other methods to remove phosphorus. This paper analyses the aquaculture tail water phosphorus removal technology, which can provide new ideas for tail water phosphorus treatment and phosphorus resource recovery, and promote the green development of aquaculture. |
