Nitrogen migration law and recycling strategy in an innovative recirculating aquaculture system: Enhancing performance through electrocoagulation

Abstract

In this study, electrocoagulation (EC), a green and efficient water treatment technology, was used to improve the performance of the Litopenaeus vannamei (L. vannamei) RAS. The main objective was to investigate the nitrogen migration law of the innovative L. vannamei RAS, establish a nitrogen recovery strategy, and promote the sustainable development of the L. vannamei RAS. It was found that 34.22 % of input nitrogen (NInput) accumulated in live shrimp, 3.83 % and 0.69 % of NInput existed in shed shrimp shell and dead shrimp, 41.31 % of NInput was removed by the water treatment equipment, 9.75 % of NInput was removed through water exchange, and 2.89 % of NInput accumulated in the RAS. Under the action of the EC, the removal of nitrogen by a microscreen drum filter (MDF), moving-bed biofilm reactor (MBBR) and foam separator (FS) increased by 26.39 %, 9.52 %, and 9.10 %, respectively. Moreover, a Chlorella vulgaris culture system was used to recycle the waste nitrogen of the L. vannamei RAS, with a nitrogen recovery rate of 80.84 %. These findings indicate that EC can significantly enhance the nitrogen removal of RAS, and the Chlorella vulgaris can be used for the efficient recovery of the waste nitrogen from RAS.