Integration of Biochar Filtration into Aquaponics: Effects on Particle Size Distribution and Turbidity Removal

Abstract

Small- and large-scale biochar-based filtrations were conducted to investigate the potential of biochar as a low-cost renewable filtration medium in aquaponics. The small-scale experimental design investigated the effects of 2 biochar media sizes (1 – 3 mm [referred to as fine biochar] and 3 – 5 mm [referred to as coarse biochar]), 3 biochar bed heights (2.5, 5.0 and 10.0 cm) and 3 loading rates (5, 10 and 15 m3/m2/d) on particle size distribution as well as turbidity removal efficiency. Both biochar sizes (fine and coarse) were able to clarify fish effluent. However, fine biochar led to better filtration characteristics compared to coarse biochar. Results indicated that biochar filter bed heights and loading rates affected the filtration performances. Using deeper filters combined with lower loading rates led to greater removal of suspended particles and turbidity compared to shallower filters and/or higher loading rates. Results from the large-scale filtration, using a mixture of fine and coarse biochar media (size of 1 – 5 mm), revealed that the ideal loading rate for maximizing the removal of turbidity from fish effluent in high-intensity aquaponic system for production of Nile tilapia and greenhouse plants (with 80 m3 total volume of water, 40 kg/m3 average stocking density and 15 kg/d feeding rate) was 10 m3/m2/d. This study suggests that biochar-based filtration could be incorporated into aquaponics as a polishing step before sending the water to plant growth systems.