Optimising coagulation/flocculation using response surface methodology and application of floc in biofertilisation

Abstract Aquaculture effluent generation, an environmentally crucial process requires effective treatment. Simple methods like coagulation and flocculation are considered effective. In this study, chitosan from Black tiger shrimp, Penaeus monodon, was used to remove ammonia (NH3) and turbidity. Response surface methodology-optimised dosages (5.00, 12.50, and 20.00 mg·L−1), pH (5.00, 6.25, and 7.50), and settling times (5.00, 7.50, and 30.00 min) were applied. Water spinach, Ipomea aquatica, received an application for organic fertiliser after the nutrient status of the recovered floc was later determined. Results showed that at a dose of 16.25 mg·L−1, a pH of 7.5, and a settling time of 17.5 min, chitosan cleared 92.16% of the turbidity. After 30 min of settling, 84.42% of the NH3 was eliminated at 5 mg·L−1 and 7.5 pH. Both macronutrients (P, K, N, Mg, and Ca) and micronutrients (Co, Cu, Fe, Mn, Ni, Se, and Zn) are present in the newly discovered floc. Floc had safe low Pb and Ni levels. Plants treated with floc showed superior growth compared to those with commercial liquid fertiliser, confirming nutrient absorbability. Conclusively, this study provides an eco-friendly wastewater treatment method.