Primary treatment with a natural coagulant improved the nanofiltration stage to recover dairy wastewater

Abstract

AbstractBackgroundThe adequate management of dairy effluent is of prime importance to mitigate environmental damages. In addition, its adequate treatment could enable its reuse inside the dairy industry, contributing to a sustainable economy.ResultsThe optimization of the coagulation/ flocculation/ sedimentation stage through a Box–Behnken Design was proposed using real dairy effluent and natural coagulant of Moringa extracted with CaCl2. Then, nanofiltration with a NF 270 membrane was applied, using the raw wastewater and the wastewater pre‐treated with coagulation/ flocculation/ sedimentation, enabling apparent color and turbidity removals of >98% in the three studied conditions. A satisfactory chemical oxygen demand (COD) removal of 88.9% was obtained only with the combination of the pre‐treatment by coagulation/ flocculation/ sedimentation followed by nanofiltration. When the effluent was subjected to nanofiltration directly, the COD removal did not reach 61%. Besides improving the removal values, the pre‐treatment improved the transmembrane flow, reducing the fouling and the membrane total resistance when compared to the dairy wastewater directly subjected to nanofiltration.ConclusionWhen the wastewater was pre‐treated using the natural coagulant, the nanofiltration stage was improved because the membrane presented a lower fouling (~10%), lower total resistance and less calcium build‐up compared to direct nanofiltration of the wastewater (~60%). This indicates that the membrane lifespan can be extended when the pre‐treatment is applied. The quality evaluation of the treated effluent demonstrated that it presents the potential to be reused inside the dairy industry, which could greatly contribute to a sustainable and economic scenario. © 2023 Society of Chemical Industry (SCI).