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

Background: The adequatemanagement of dairy effluent is of prime importance tomitigate environmental damages. In addition, its adequate treatment could enable its reuse inside the dairy industry, contributing to a sustainable economy. Results: The 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. Conclusion: When the wastewater was pre-treated using the natural coagulant, the nanofiltration stage was improved because themembrane presented a lower fouling (similar to 10%), lower total resistance and less calcium build-up compared to direct nanofiltration of the wastewater (similar to 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.

Automated summary

The proper management of dairy effluent is crucial to mitigate environmental damages and enable its reuse in the dairy industry, contributing to a sustainable economy.