Treatment of Aquaculture Recirculating Water by Tri-Stage Biofilm Process

Tri-stage biofilm processing was used to treat aquaculture recirculating water.The removal performance and mechanism of major contaminants in the water were investigated.Under proper operating conditions(pH = 7.5-8.5,T = 28-32 ℃,ρ(DO) = 0.5-1.0 mg /L and ρ(FA) = 5-10 mg /L),the removal efficiencies of CODCr,NH4 +-N and TN were 94.4%,91.6% and 70.1% respectively,and the average of ρ(NO2--N) in the effluent was less than 5.2 mg /L.This indicates that tri-stage biofilm processing can be applicable for the biotreatment of aquaculture recirculating water with low ratio of ρ(C) /ρ(N),to satisfy the standard of recycled water for fishing and eliminate the potential threat of NO2--N to aquaculture animals.