Optimization of Maerua Decumbent bio-coagulant in paint industry wastewater treatment with response surface methodology

Abstract

Eco-friendly bio-coagulants are desirable in water treatment because they are safe for human health and the environment. Efficient use of bio-coagulants in the treatment of industrial wastewater requires a search for an optimum combination of process parameters. This study applied response surface methodology (RSM) for optimization of coagulation and flocculation of paint industry wastewater using bio-coagulant Maerua Decumbent. Measurement of elemental compositions and functional groups for Maerua decumbent bio-coagulant used Perkin-Elmer Series II CHNS/O 2400 Elemental Analyser and FTIR model 8400, respectively. Experimental design and optimization of the process parameters and their interactions used the Design Expert Software Version 10 and the central composite design (CCD). Maerua decumbent comprised of 38.51, 3.84, 42.21, 1.25, and 0.31% C, H, O, N, and S, respectively. Functional groups included OH, CH, NH, CO, CO, and CN groups. The optimum conditions for the removal of turbidity, Chemical oxygen demand (COD), lead, and chromium were Maerua dosage 0.8–1.2 kg m−3, pH 5–7, and settling time 48–60 min. At the optimum conditions, Maerua achieved 99.2, 78.6, 100.0, and 99.9% removals of turbidity, COD, lead, and chromium, respectively, which compared favourably with of 98.6, 66.2, 96.2, and 94.4% for alum. Quadratic models developed in the study predicted pollutants removal to within 4%.