Coagulation/flocculation process using Moringa oleifera bio-coagulant for industrial paint wastewater treatment: optimization by D-optimal experimental design

Pollution from paint discharges causes an imbalance in the aquatic ecosystem due to its diverse and toxic chemical composition. Faced with the stricter environmental regulations and the increasing exhaustion of water resources, the recycling of wastewater for reuse has become a priority. The aim of this work is to study experimentally the optimization by the D-optimal design of the treatment of paint wastewater by coagulation-flocculation process using a bio-coagulant extracted from Moringa oleifera seeds. The main parameters studied are the turbidity of the effluent, the dose of bio-coagulant, the time and the stirring speed influencing the process in order to eliminate the high rate of suspended matters. Statistical parameters such as the coefficient of determination R-2 (0.9915), the prediction coefficient Q(2) (0.846), the reproducibility (0.9993) and the adjusting coefficient R-2 indicate a good adequacy of the developed model. The use of bio-coagulant has shown a significant reduction in turbidity with a yield of 99.9% under optimal conditions: coagulant dose 2.5 ml, coagulation time 5 min, the coagulation speed 210.5 rpm, flocculation time 12.5 min and a flocculation speed 30 rpm. The obtained results show that coagulation-flocculation is the best solution for the clarification of paint wastewater.