The increasing demand for sustainable water treatment technologies has driven the development of advanced ceramic membranes with tailored properties. This study explores the fabrication of ceramic membranes using phosphate tailings and clay lithologies as alternative raw materials, offering a sustainable and cost-effective approach to membrane production. The focus is on tailoring membrane porosity through the deposition of multilayered alkali-activated coatings, leveraging geopolymerization chemistry to enhance structural and functional performance. The manufactured ceramic membranes were investigated using X-ray fluorescence spectrometry, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and a filtration test pilot. Results revealed the suitability of both phosphate tailing and the clay for membrane processing, while alkali activation effectively modulates the membrane’s porosity (from 1–10 μm to 0.1–1 μm) and mechanical strength (up to 20 MPa). Both tailored and untailored membranes demonstrated favorable performance. Key findings include the formation of a well-interconnected pore network and improved compressive strength, which resulted in sustained filtration performance under challenging operational conditions. The membranes demonstrated their suitability for environmental and industrial applications by achieving high efficiency in industrial effluent filtration tests.