Abstract: The invention at hand relates to a micro-filter disc based on kieselguhr, also known as diatomaceous earth, particularly for a complete sterilization of water. The micro-filter disc contains at least two kinds of silicately bonded kieselguhr at least one of which is pre-calcined and later burnt or sintered. The micro-filter disc has pore sizes in preferred magnitudes of 0.1 to 0.3.mu. whereby bacteria are mechanically and safely retained. A method is disclosed making possible the use of three kinds of kieselguhr and kaolin in connection with a careful drying and sintering thereafter. Thereby, it is possible to produce discs having diameters larger than 35 cm and a thickness of 1 to 1.5 cm. Such discs can be cleaned by way of rotating brushes slightly scraping off the discs. This enhances a simple construction of self-cleaning filter installations. The thus constructed filter installations require very little service and can be serviced by inexperienced operators.