Hazardous substances and their removal in recirculating aquaculture systems: A review

Aquaculture has great potential to feed and nourish the world’s growing population. However, the aquaculture products often increase at the expense of the environment. Sustainable aquaculture development is crucial to meeting the growing demand for aquatic food. Recirculating aquaculture system (RAS) is a green and sustainable aquaculture mode, which are not only increase the farm yield, but also significantly decrease the negative impact on the environment. Due to feed addition and excretion of aquaculture organisms, hazardous substances such as particulate matters, ammonia, nitrite and nitrate will accumulate in RAS and endanger the safety of reared organisms, resulting in adverse effects on the operation and production of the system. The water treatment unit of RAS plays a key role in ensuring optimal growth conditions for farmed organisms by filtering or degrading pollutants from aquaculture tail water and recycling the purified water, saving natural resources to a significant extent. Pollutants produced from the RAS farming (particulate matters, nitrogen pollutants, phosphate, carbon dioxide, antibiotics, steroids, heavy metals, etc.) and the hazards posed are reviewed, and the corresponding water treatment processes are summarized, and relevant suggestions are proposed, providing the theoretical basis for the stable operation of the RAS, system optimization and wider application.