Isothermal membrane distillation using omniphobic membranes for enhanced ammonia recovery from anaerobic digestion sludge leachate

초록

Membrane distillation (MD) offers a promising approach for recovering ammonia from wastewater by selectively permeating gaseous ammonia through a hydrophobic porous membrane. However, conventional hydrophobic membranes, such as those made from polyvinylidene fluoride (PVDF), encounter wetting issues when the feed water contains surfactants and low surface tension contaminants. This study demonstrates the fabrication and application of omniphobic MD membranes for the effective recovery of ammonia from anaerobic digestion sludge leachate. The omniphobic MD membrane was developed by spray coating a perfluorinated urethane polymer on a PVDF substrate. Comprehensive membrane characterization confirmed the efficacy of the omniphobic surface coating and its resistance to wetting by both water and low surface tension liquids. The developed omniphobic membrane was employed to evaluate the ammonia recovery from anaerobic digestion leachate using conventional membrane distillation (CMD) and isothermal membrane distillation (IMD) processes. While CMD operation exhibited membrane wetting, fouling, and consequently low ammonia productivity, the omniphobic membrane demonstrated stable and efficient ammonia recovery during IMD operation. In long-term IMD operation, a stable ammonia flux between 18.8 and 20.2 g/m2/h was maintained for 5 days, illustrating the promising potential of omniphobic membranes for recovering high concentration of ammonia from anaerobic digestion sludge leachate. © 2025 Elsevier B.V.

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