Dairy wastewater treatment with direct-contact membrane distillation in Oman

Direct contact membrane distillation (DCMD) process was implemented for treating dairy wastewater (DWW) from an Omani dairy industry. Commercial polytetrafluoroethylene (PTFE) and polypropylene (PP) membranes were tested under different temperatures. The aim of this study in to investigate the potential of pure water production rejecting salts, volatile and non-volatile organic compounds present in DWW. Using laboratory techniques such as gas chromatography, we inspected permeate composition, identifying both volatile and non-volatile organic matter. Comprehensive characterization of membrane surface properties via Fourier-transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Thermal Gravimetric analysis (TGA) provided critical insights. Findings revealed the denaturation of proteins at 60 °C, leading to significant pore blockage and a consequential 50.3 % reduction in flux. Impressively, the membranes achieved rejection rates of 89–99 % for non-volatile organic matter, while completely rejecting D-limonene. However, traces of volatile fatty acids were detected in the permeate. Elemental analysis exposed the presence of various dairy-derived elements at the membrane surface. FTIR peaks highlighted distinct functional groups of dairy components, while TGA affirmed the accumulation of dairy aggregates with rising temperature. These findings underscore membrane distillation's competence in dairy wastewater treatment, presenting a compelling case for its widespread application in environmental remediation endeavors.