Integrated coagulation-flocculation with nanofiltration and reverse osmosis membrane for treating sugar cane industry effluent

Sugarcane industries, like other agro-food industries, generate significant volumes of wastewater containing high concentrations of organic and inorganic pollutants. Among the proposed treatment solutions, the anaerobic membrane bioreactor (AnMBR) has proven highly effective in degrading organic pollutants but has limitations in removing color and inorganic pollutants. To address this gap, integrating other technologies with AnMBR is necessary. In this study, we propose coupling AnMBR with either Coagulation-flocculation followed by nanofiltration or reverse osmosis for treating wastewater from sugar industries after initial AnMBR treatment. The wastewater treated by an anaerobic AnMBR pilot plant, fed with wastewater from a sugar cane production unit, was used for the tests. Various formulations of <i>Moringa oleifera</i> were tested, including its defatting and dehulling products with hexane and ethanol. For nanofiltration and reverse osmosis, pressures of 4 and 8 bars respectively were applied. For the coagulation-flocculation phase, granular alum and powdered <i>moringa oleifera</i> seeds were compared as coagulants. Thus, the coupling of the coagulation-flocculation system with nanofiltration and reverse osmosis membranes effectively reduced both organic and inorganic matter. The use of aluminum sulphate proved more effective at high pollution concentrations, while <i>Moringa oleifera</i> extracted with hexane achieved removal rates exceeding 70 % for heavy metals (Cd, Cr, Cu, Zn). Purification efficiencies of over 90 % were obtained after filtration with the reverse osmosis membrane, while the nanofiltration membrane showed retention rates of 90 % for color, but less than 50 % for monovalent ions. The treated effluent at the outlet of the nanofiltration and reverse osmosis systems complies with Burkina Faso's discharge standards, with superior quality allowing for direct reuse in the industry.