To improve the removal efficiency for dissolved wastes within CycloBio (CB) fluidized sand biofilters
(FSBs) in recirculating aquaculture systems, we investigated their structural design and optimization
using computational fluid dynamics (CFD) modeling tools, an orthogonal test method, and experimental
verification. Results showed thatthe effects of structural parameters on bed expansion from large to small
were: cone height, cone diameter and slot width. The best combination was: cone height 60 mm, cone
diameter 165 mm, and slot width 1.0 mm. The solid phase was well distributed not only in the radial
direction, but also in the axial direction in the optimized CB FSB. The bed expansion (40%–120%) was
increased about 13%. Energy savings were 21%–28% at the same bed expansion. When the optimized CB
FSB was used to treat synthetic aquaculture wastewater, with three bed expansions and four levels of C/N,
total ammonia nitrogen removal rate expressed per unit of expanded bed volume was high, from 629 to
881 g m−3 day−1. All results indicated thatthe structure ofthe optimized CB FSB was more reasonable and
that the combination of CFD simulation and the orthogonal test method could be successfully applied to
structural optimization