Optimization of C/N ratios for nutrient removal in aquaculture system culturing African catfish, (Clarias gariepinus) utilizing Bioflocs Technology

• Bioflocs Technology could potentially serve as sustainable aquaculture wastewater treatment.
• Nutrient removal efficiency of BFT was determined at various C/N ratios of 10, 15, 20, 25 and 30.
• Optimum dosage of C/N 15 achieved 98.7% ammonia removal with bioflocs formation of 92.5 mL L−1.
• BFT was proven to be suitable to sustain water quality for the cultivation of Clarias gariepinus.

Development of aquaculture industry is restricted due the undesirable environmental impact associated with the effluent discharge that is rich in inorganic nitrogenous compound and organic matters. This situation could be improved through the implementation of Bioflocs Technology (BFT). BFT can enhance the water quality in aquaculture system by introducing natural nutrient recycling characteristics with the induction of appropriate carbon/nitrogen (C/N) ratio. However, the natural condition of aquaculture system, which is rich in inorganic nitrogen, could not sustain BFT. Thus, additional carbon is required to obtain a suitable C/N ratio for effective formation of bioflocs complex. This study focused on the determination of optimum C/N ratio by varying the dosage of carbon introduced into the system. Five different C/N ratios (i.e. 10, 15, 20, 25, 30) were evaluated in treating the aquaculture system culturing Clarias gariepinus to an acceptable water quality. Bioflocs density and water quality parameters were monitored throughout the treatment period. The highest removal of ammonia was achieved at 98.7% with the formation of 92.5 mL L−1 of bioflocs concentration at an optimum C/N ratio of 15. The results show that the utilization of BFT can potentially provide a sustainable and low maintenance treatment of aquaculture system.