Sacrificial CaCO3 Precoating Preserves Fouling Reversibility of Ceramic Nanofiltration During Filtration of Real Wastewater Treatment Plant Effluent

Fouling of ceramic nanofiltration (NF) membranes becomes difficult to reverse when complex wastewater constituents accumulate directly on the selective layer. Sacrificial precoating may spatially separate foulant deposition from the membrane surface, but its effectiveness under real wastewater conditions remains insufficiently understood. A single CaCO3 precoating step was evaluated over three consecutive filtration–cleaning cycles using municipal wastewater treatment plant (WWTP) effluent. During three consecutive 6-h filtration cycles, precoating substantially improved the reversibility of hydraulic fouling. Permeability recovery reached 92% after the first cleaning and was 80% after the second cleaning, whereas the uncoated membrane recovered only 34% after the first cleaning and subsequently showed little effective recovery. The precoated system also exhibited markedly lower irreversible hydraulic resistance. In addition to fouling control, the mineral precoat altered solute removal in the complex wastewater matrix: DOC removal remained approximately 90%, while apparent phosphate removal increased from 38% for the uncoated membrane to 90% for the precoated system. These findings demonstrate that CaCO3 precoating acts as a sacrificial interfacial layer that preserves fouling reversibility during ceramic NF treatment of real WWTP effluent, while mineral–solute interactions may additionally contribute to the apparent removal of selected inorganic solutes.