Chitosan coagulant: coagulation/flocculation studies on turbidity removal from aquaculture wastewater by response surface methodology

Aquaculture wastewater treatment currently relies heavily on chemical coagulants to facilitate processes such as coagulation, flocculation, and sedimentation. However, eco-friendly alternatives are needed to make the industry more sustainable. In this study, we explored the potential of chitosan extracted from Pacific whiteleg shrimp, Litopenaeus vannamei shell as a biocoagulant to treat aquaculture wastewater. The coagulation/flocculation behaviour of chitosan was studied for turbidity removal using a suspension of kaolin clay and aquaculture wastewater. The impact of initial turbidity, chitosan dosage, and pH of the kaolin clay suspension was examined using one-variable-at-a-time analysis. The results were then used to establish the range for the Box-Behnken design in response surface methodology. Chitosan was found to be effective in removing turbidity, with 97.58 +/- 0.02% removal achieved in the kaolin clay suspension at 1 mg/L chitosan dosage and pH 7. In the aquaculture wastewater analysis, 10 mg/L chitosan dosage resulted in 90 +/- 0.72% turbidity removal. The Box-Behnken design in response surface methodology resulted in an optimal turbidity removal of 94 +/- 0.61%, achieved using a chitosan dosage of 18.25 mg/L, pH 7, sedimentation time of 18.1 min, and desirability of 0.974. The optimal model for determining the relationship between variables was a quadratic polynomial model with R-2 = 0.9908. Our study demonstrates the effectiveness of chitosan as a biocoagulant for turbidity removal from aquaculture wastewater. These results offer promising potential for the development of more sustainable alternatives to chemical coagulants in the industrial sector.