Control of suspended solids and nitrogenous compounds through bioremediation and artificial substrates in an emerging BFT System for Nile Tilapia

The effects of bioremediation with Bacillus spp. and an artificial substrate were compared on water quality, zootechnical and hematological parameters of Nile tilapia (Oreochromis niloticus) in a BFT system (biofloc technology). Twelve experimental units were divided into three groups: bioremediator (1.0g of bacilli per m3 of water daily); insertion of artificial substrate (AS); and control; in quadruplicate. Both treatments reduced NH3 (bioremediador 0.73 mg.L-¹ and AS 0.69 mg.L-¹) than the control group (1.33 mg. L-¹), meanwhile the bioremediator increased nitrite (31.71 mg.L-¹) compared to the control (12.76 mg. L-¹) and the AS did not diverge between treatments. AS (1.75 mL), bioremediator (3.10 mL) and control (3.87 mL) presented lower floc volume, respectively. The treatments reduced the food conversion ratio (bioremeaditor 0.84 and AS 0.86) than control group (1.07), meanwhile the AS promoted higher specific growth rate (3.05 %.day-¹) compared to the bioremediator (2.97 %.day-¹) and control (2.94 %.day-¹) which did not diverge between treatments. The percentage of circulating thrombocytes varied significantly among treatments, being highest in the bioremediator group (46.4 %), followed by the artificial substrate group (34.0 %) and the control (18.5 %). The bioremediator and AS led to improvements in water quality by removal of NH3 and floc volume maintenance; promoted better zootechnical performance and changed the hematological profile for Nile tilapia. Keywords: Bacillus; biofloc; bioremediation; Oreochromis niloticus.