Using tannin-based coagulant in the control of solids in a biofloc cultivation system: evaluation of treatment performance and phytotoxicity

This study aimed to evaluate the performance of a commercial tannin-based coagulant on the control of suspended solids in a Nile tilapia (Oreochromis niloticus) cultivated in a biofloc system (BFT). The BFT systems involved 106 tilapias (average weight of 1.20 +/- 1.83 g) in producing water for the preliminary tests and 41 fish (average weight of 14.77 +/- 8.07 g) for further tests. The BFT system was fertilized with sugarcane molasses. Water quality was evaluated in terms of turbidity, apparent color, pH, alkalinity, total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity, total Kjeldahl nitrogen (TKN), nitrite (N-NO2-), nitrate (N-NO3-), phosphate (P-PO43-), chemical oxygen demand (COD), phenols and phytotoxicity to lettuce seeds (Lactuca sativa) was evaluated. Tannin-based coagulant was efficient for the BFT water clarification, removing 90.81% of turbidity on average. Overall, the parameters measured in the treated water remained within the recommended range for water in BFT systems. Furthermore, no adverse changes were observed in the phytotoxic classification using lettuce seeds based on the germination index for treated water. Overall, tannin-based coagulant was efficient and was considered environmentally and safety friendly for controlling suspended solids in BFT cultivation systems.

Automated summary

This study evaluated the performance of a commercial tannin-based coagulant in controlling suspended solids in a biofloc system. The results showed that the coagulant was efficient in clarifying the water and did not have adverse effects on other water quality parameters.